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Global Climate Change
Global Climate Change
Ayers, John C
Global warming is too serious for the world any longer to ignore its danger or split into opposing
factions on it. TONY BLAIR, speech, Sept. 27, 2005
Perhaps the greatest challenge to sustainability is Global Climate Change (GCC). Burning fossil fuels
releases carbon dioxide (CO2), a known greenhouse gas, into the atmosphere. This has led to a steady rise in the
atmospheric concentration of CO2 and in global surface temperatures. That humans can change the earth on a
global scale is shocking, but greenhouse gas pollution is just the type of “sink” problem that the Limits to
Growth study predicted in 1972 (Meadows, Meadows et al. 1972). It results from too many people producing
too much waste for the environment to absorb. Human release of greenhouse gases into the atmosphere has
caused the average global temperature to rise 0.8°C (1.4°F) since 1850, a phenomenon known as
Anthropogenic Global Warming (AGW).
My generation grew up believing that nuclear bombs were the greatest threat to our existence. It has
taken some time for the realization to sink in that AGW has replaced nuclear bombs as the greatest threat to
humanity. This shift is mirrored by a shift in the focus of groups like the Union of Concerned Scientists from
the threat of nuclear war to the threat posed by AGW. AGW is a better threat to face than nuclear annihilation
because it is not disempowering and even presents some opportunities. We felt powerless during the Cold War;
there was nothing an individual could do to decrease the threat of nuclear annihilation, and people other than
defense contractors couldn't make money by finding ways to combat the threat. In contrast, every person can
make a difference in the fight against AGW, and some entrepreneurs will become rich by creating and selling
green products or by trading in the carbon market.
“Business as usual” models project global temperatures to rise an additional 3°C (5.4°F) by 2100. The
consequences of such rapid and dramatic global change are largely unknown, but preliminary estimates
suggest that sea level will rise a little over 3 feet by 2100, and that weather hazards will become more severe.
Estimates are that by the year 2100 climate-related deaths will be in the hundreds of millions and economic
losses will be trillions of dollars. A 3°C rise in average global temperature could also put 30-50% of plants and
animals at risk of extinction (IPCC 2007). Passing a tipping point that leads to irreversible change would
amplify climate-related risks. The high level of uncertainty about the effects and consequences of GCC
demands that we apply the precautionary principle and reduce carbon emissions. However, uncertainty over
the economic costs of climate change mitigation, opposition from powerful fossil energy interests, and the
difficulty of attaining international agreements have led to an inadequate global response to the threat of AGW.
The rising costs of GCC will demand a combination of mitigation, regulation, and adaptation measures.
Sustainability thinking can reduce opposition to these measures and make them more effective.
In this chapter we will review the theory behind AGW, the supporting evidence, future projections of
GCC, and potential consequences. We will also examine the public debate in an attempt to understand why
close to half the American public doubts the scientific consensus. Finally, we will introduce proposed solutions
to the problem of GCC.
Background
* Earth's climate has been inhospitable more often than hospitable to life, ever since multicellular
organisms appeared roughly 600 million years ago. During that time earth's climate has wobbled between
inhospitable and hospitable. Sudden climate changes have led to mass extinction events. Our actions could
push earth's climate back into the inhospitable zone, and the rapid transition would accelerate the rate of
extinctions during the current mass extinction event that we precipitated.
Humans have adapted to the earth's surface environment over ~200,000 years since Homo sapiens
originated before migrating out of Africa ~70,000 years ago. Since the beginning of the Holocene epoch
10,000 years ago, earth's climate has been stable. In fact, “it is the longest stable and warm period in the entire
108,000 years of the Greenland ice core record (Mathez 2009).” Some argue that it was this climate stability
that allowed for the invention and spread of agriculture. It has allowed humans to make large investments in
the infrastructure, knowing that essential resources like water are unlikely to disappear because of sudden
climate change. Humans have built cities along coastlines, confident that no rapid sea level rise would
inundate them. However, the days of climate stability are coming to a close, and humans are responsible for
the shift to an unstable, rapidly changing climate. We have entered the Anthropocene period, when humans
have started to change the earth on a global scale (Zalasiewicz, Williams et al. 2010).
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To understand these changes, we must make clear the meaning of “climate.” Climate is what you
expect, but weather is what you get. Climate is the "long-term characterization of the 'average' weather.” It
changes over decades, while weather changes on a daily and even hourly basis. Humans often overgeneralize,
in space and time, the short-term changes in weather (Pollack 2005). An example of overgeneralizing in a
geographic sense is "we had a wet summer, so everyone in the US had a wet summer." We overgeneralize in a
temporal sense by saying "this week is the coldest I can remember; we must be entering a new Ice Age.” We
make both types of mistake when we generalize short term changes in local weather to long-term changes in
global climate, e.g., "this summer in Nashville is the hottest I can remember; it must be global warming.”
GCC has happened often during earth’s long history. Much of what we know about these changes
comes from the study of ancient climates as preserved in rocks, sediments, and ice cores. These changes
resulted from natural processes such as variation in solar output, in the earth’s orbit around the sun, in the
spatial distribution of the continents, in oceanic circulation patterns, and the rates of volcanic activity.
However, never has climate change resulted from human activity, until now. Scientists believe that the
greenhouse gas carbon dioxide (CO2) emitted during the burning of fossil fuels is responsible for a sudden
rapid increase in average global surface temperatures in the last century. We emitted 8.4 Gt C in 2006; about
half stays in the atmosphere, and about 2 Gt C/y dissolves in seawater. The ocean holds most of the CO2 in the
surface environment; because the oceans overturn about every thousand years, excess CO2 will influence
climate for about one thousand years (*check, MacKay 2009).
*Globally we emitted 38 billion tonnes (1 tonne – 1 metric ton = 1000 kg) of CO2 and 49 billion tonnes
CO2e in 2004 (Dawson and Spannagle 2009). Why the discrepancies?
Average global temperature has risen by 0.76°C (1.4°F) since 1850 and is projected to increase another
0.5-1.0°C (0.9-1.8°F) due to greenhouse gases we have already added to the atmosphere (Dawson and
Spannagle 2009). These changes are irreversible over a timescale of 1,000 years because it would take longer
than 1,000 years for the artificially warmed oceans to overturn and cool off (Solomon, Plattner et al. 2009).
Atmospheric CO2 concentration and its influence on global temperature changed faster in the 20th century than
any natural factors that affect global temperatures have changed over the last 22,000 years (Joos and Spahni
2008). Thus, we infer that a new, non-natural process, Anthropogenic Global Warming (AGW), is responsible
for these changes. A similar change in atmospheric CO2 concentration occurred naturally at the beginning of
the Eocene period 56 million years ago, and though the rate of change was lower than today, it caused
widespread extinctions (Zalasiewicz, Williams et al. 2010). Thus, AGW is a major problem because the rate of
change is unnaturally high. It will further speed up if we continue business as usual, as human population will
increase to ~9 billion by mid-century (Richter 2010).
The idea of global warming is really quite simple. Energy in sunlight passes through earth’s atmosphere
and heats the surface, which warms and gives off heat. Without greenhouse gases like CO2 in the earth’s
atmosphere, that heat would radiate into space and be lost. The average surface temperature of the earth would
be only -20°C (-4°F), meaning that all water on the earth’s surface would be frozen (Faure 1998; Richter 2010).
Life would not be possible. Fortunately, the greenhouse gases in our atmosphere absorb and trap the heat,
increasing the average observed surface temperature of the earth to a very hospitable 15°C (60°F). We are
fortunate to have greenhouse gases in our atmosphere. However, like Goldilocks we need it not too cold and
not too hot, but just right. If the concentration of greenhouse gases gets too high, it will be too hot for us.
Recognition of the greenhouse effect goes back to Joseph Fourier in the early 19th century. John Tyndall
identified the role of carbon dioxide (CO2) as a greenhouse gas in 1859. No scientists dispute that CO2 is a
greenhouse gas: scientists have repeatedly verified that through experiment. It was Svante Arrhenius in 1896
who predicted that human activities could contribute to the greenhouse effect, but it wasn’t until the 1970’s that
scientists like Roger Revelle and Wallace Broecker began to raise the alarm. Their concern was based on
measurements by Charles Keeling, who showed that CO2 concentration in the atmosphere was increasing at an
alarming rate. Atmospheric concentrations of CO2 (Figure 1) show both seasonal fluctuations related to plant
growing seasons, and a long-term trend of steadily increasing CO2. So how is this related to human activity? In
the Peak Oil chapter, we described how oil contains the energy of sunlight that fell on earth millions of years
ago, trapped in organic molecules manufactured by plants using photosynthesis. The simplified chemical
reaction is:
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Figure 1. Atmospheric concentration of carbon dioxide at Mauno Loa, Hawaii, USA (ppm) and average
annual global surface temperature anomaly (°C) between 1958 and 2010. Temperature data from {Hansen, 2010
#3876}, atmospheric CO2 concentration data from {Keeling, 2009 #3875}.
Eq. (1) CO2 + H2O + energy from sunlight = CH2O + O2
The molecule CH2O represents the organic matter that stores the energy in fossil fuels. When we use
fossil fuels, we undo the work of photosynthesis, promoting the reverse reaction by heating the organic matter
in the presence of atmospheric oxygen so that they react and liberate the stored energy, a process called
combustion. The troubling product of this combustion is CO2, which accumulates in earth’s atmosphere,
leading to the observed steadily increasing atmospheric CO2 concentration (Figure 1).
Equation (1) illustrates the delicate balance between plant photosynthesis (forward reaction) and
combustion (reverse reaction) that determines the concentrations of oxygen and carbon dioxide in the earth’s
atmosphere. From Eq. 1 above we can see that combustion consumes O2 while producing CO2. Thus, we would
predict that increasing CO2 concentration will cause decreasing O2 concentration in the atmosphere, which is
what we observe (IPCC 2007).
The current atmospheric O2 concentration of 21% is just right for trees: If O2 rose to 25%, forests would
burn after every lightning strike, but if it fell to 13%, we could not start a fire. In fact, it is life that regulates the
composition of the atmosphere, as illustrated vividly by James Lovelock’s Gaia hypothesis, which posits that
earth behaves like an organism because its components act in concert to maintain life-support systems at
optimal levels. Just as our body maintains a constant temperature of 98.6°F, the earth can maintain global
temperatures within a narrow range that is conducive to life. How does it accomplish this? Eq. (1) gives us
some insight. Because CO2 is a greenhouse gas, when atmospheric CO2 concentration increases, temperature
increases, and these changes combine to create a greenhouse that promotes plant growth through
photosynthesis (Eq. 1). This causes plants to extract greater amounts of CO2 from the atmosphere, decreasing
atmospheric CO2 concentration and therefore temperature. In this way life helps to regulate the composition of
the atmosphere and maintain an optimal temperature, and the earth system of which life is a part is selfregulating (homeostatic). Essentially, the atmosphere and biosphere have co-evolved and maintained a balance
that has kept global climate stable.
The rapid increase in human population coupled with the rapidly rising rate of combustion of fossil
fuels since the Industrial Revolution has destroyed the balance. Where atmospheric concentrations of CO2 and
O2 were in a steady state before the Industrial Revolution, they are now rapidly changing. As noted by E.F.
Schumacher in “Small is Beautiful (1973),” “The system of nature, of which man is a part, tends to be selfbalancing, self-adjusting, self-cleansing. Not so with technology.”
The concentration of CO2 in the atmosphere increased much faster than researchers such as Arrhenius
anticipated at the end of the 19th century. This was for several reasons: During the 20th century population
increased roughly four times, from 1.5 to 6 billion, and per capita income more than doubled, so the economy
increased tenfold. Since energy fuels the economy and consumption, the rate of energy consumption and CO2
emissions also increased tenfold. Furthermore, Roger Revelle found in the 1950s that the rate at which the
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oceans absorbed CO2 was only 1/10 of what early researchers thought. These factors combined to reduce the
estimated doubling time of CO2 in the atmosphere from 1,000 years in 1896 to 50 years today (Richter 2010).
Atmospheric CO2 concentration has already increased about 40%, from 270 parts per million (ppm) in preindustrial times to ~380 ppm today. This would not be a problem if natural processes rapidly removed excess
CO2 from the atmosphere, but that is not so; the removal time (the time it would take nature to remove
anthropogenic gas if we stopped emitting it) of CO2 is >100 years and as much as 1000 years (Richter 2010).
Carbon dioxide in the atmosphere is one part of the global carbon cycle. The carbon cycle is critical to
understanding the greenhouse effect and global warming (see Chpt. 5). Understanding the role of feedbacks in
the climate system is essential for predicting the environmental effects of anthropogenic activity. For example,
photosynthesis counteracts anthropogenic CO2 emissions (Eq. 1). As we pump increasing amounts of CO2 into
the atmosphere and temperature rises, the earth acts more like a greenhouse and plants grow faster. In Eq. (1)
we see that plant growth should remove CO2 from the atmosphere and store it in plant tissue, acting as a sink
for CO2. Increased atmospheric CO2 concentration also causes more CO2 to dissolve in seawater to form
carbonic acid, leading to ocean acidification:
Eq. (2) CO2(g) + H2O = H2CO3(aq) = H+ + HCO3Thus, photosynthesis (Eq. 1) and CO2 dissolution in seawater (Eq. 2) counteract the addition of CO2 to
the atmosphere (similar to LeChatlier’s principle in chemistry). These two negative feedbacks counteract
increased CO2 emissions and slow the rate of accumulation of CO2 in the atmosphere. Negative feedback loops
reduce, but do not eliminate, changes to the system. The CO2 content of the atmosphere is still increasing, as
shown in (Figure 1), but not as fast as it would without these negative feedback loops.
Increasing atmospheric CO2 concentrations does more than increase global temperatures. Dissolution
of CO2 in seawater (Eq. (2)) causes the pH of seawater to decrease. Ocean acidification is a major problem
for organisms that extract Calcium Carbonate (CaCO3) from seawater to build shells, because Calcium
Carbonate dissolves readily in acidic water. Coral reefs are the backbone of coastal marine ecosystems that
have very high biodiversity, yet these reefs are rapidly dying across the world’s oceans, in part due to ocean
acidification. How sad that these corals, which have been some of earth’s most successful creatures, having
survived for hundreds of millions of years, now face extinction because of anthropogenic CO2 emissions. If the
world’s coral reef ecosystems collapse, so will most of the world’s coastal fisheries, leading to the loss of the
primary protein source for most low-income coastal communities.
How do scientists know that the excess CO2 in the atmosphere did not come from decaying plant matter
or burning of modern vegetation? The proportion of atmospheric carbon that is radioactive 14C has been
declining steadily because we are adding ancient carbon from fossil fuels to the atmospherei. How do we know
that the CO2 didn't come from volcanoes? Because the 13C/12C ratio of the atmosphere is steadily decreasing.
Volcanic CO2 has high 13C/12C, and only plant matter has low 13C/12C, so the decrease in atmospheric 13C/12C
must come from burning plant matter ii .
So we can agree that CO2 is a greenhouse gas, and that human activity has increased the CO2
concentration in the atmosphere. This should lead to warming of the atmosphere, which will thermally
equilibrate with the land surface and oceans through heat transfer, causing them to warm also. Thus, the
entire earth will warm, as is evident in (Figure 1). The rate of heating was higher in the last 25 years than over
the previous 150 years. This acceleration of warming to unnaturally high rates is what has scientists concerned
(Richter 2010).
In (Figure 1) we also see that average annual surface temperatures jump up and down, above and below
the trendline, due to random variations called system "noise." All natural processes have a random element,
which is why scientists must always state the uncertainty in their measurements and predictions. Some years
just turn out to be hotter than expected, and some cooler. This variation is roughly 0.2°C (0.4°F), i.e., most
years fall within ± 0.2°C of the trendline. However, some years the temperature difference from the trendline
due to random variation is less, and sometimes more (Richter 2010). This noise causes confusion, as many
people don't understand how one year could be cooler than the previous year if global warming is occurring.
Many global changes attest to global warming. Climatologists use globally distributed weather stations
that continuously monitor temperature and other parameters; this instrumental record extends back to about
1850 (Figure 2). They also use remotely sensed data collected by satellites to estimate temperatures of various
layers of the atmosphere. These direct observations show that the earth’s surface has warmed 0.4-0.8°C (~1°F)
during the 20th century (Figure 2). Consistent with these measured changes are observed shrinking and
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thinning of Arctic ice, loss of Antarctic ice shelves, receding of most Alpine glaciers globally iii, lengthening of
growing seasons, and migration of animals and plants to higher latitudes.
Figure 2. Views of temperature change in the next century are informed by temperature changes in the past.
For illustrative and educational purposes, three sets of surface temperatures have been assembled: 1000-year
reconstructions of past temperature change based on proxies (tree rings, corals, etc.), glacier lengths, and borehole
temperatures; the instrumental record; and Intergovernmental Panel on Climate Change (IPCC) projections for
temperature change from 2000 to 2100. From Chapman and Davis (2010).
Paleoclimatologists estimate surface temperatures that predate modern instrumental records using
many temperature proxies, which are indirect methods of estimating past temperatures. They can date a
growth ring in a living tree simply by counting the number of rings that grew around it, and estimate the
average temperature during the year that ring grew from its thickness (Richter 2010). The isotopic
composition of layers in ice cores and corals extend the continuous temperature record much farther into the
past than the most ancient trees, as do layers of sediment in lakes and oceans iv. Changes in temperature with
depth within boreholes are a reflection of past surface temperatures, so borehole temperature measurements
can be mathematically “inverted” to estimate surface temperatures in the past. (Figure 2) shows results from
some of these paleoclimate proxies extending back to 1000 A.D.. The average global surface temperature was
stable from 1000 A.D. until roughly 1800 A.D., when it began to rise rapidly because of the Industrial
Revolution.
It’s important to know that CO2 is not the only important greenhouse gas; others include methane CH4
and Nitrous Oxide N2O (Table 6-1). Together, these gases increase the average global surface temperature by
34°C (61°F). The heating power of a greenhouse gas (radiative forcing) is proportional to the reduction of
infrared radiation leaving earth caused by a unit increase in concentration of gas in the atmosphere. The
cumulative effect of a greenhouse gas depends on its radiative forcing and its residence time. The total Global
Warming Potential therefore depends on both the radiative forcing and residence time of a greenhouse gas
in the atmosphere (scale normalized to CO2): CO2 = 1, CH4 = 21, N2O = 290, and Chlorofluorocarbons (CFCs) =
3000-8000. Scientists usually report greenhouse gas emissions as CO2 equivalents CO2e. So, for example,
emission of 1 kg of CH4 would have the same Global Warming Potential as 21 kg of CO2, so CO2e = 21 kg. The
Global Warming Potentials of CFCs are large because their atmospheric concentrations are near zero, they
absorb infrared radiation between 8000-12,000 nm where CO2 is ineffective, and they have long atmospheric
residence times (Faure 1998) v.
Table 6-1: Greenhouse Gases in Earth’s Atmosphere*
GAS
Pre-1750
Recent
GWP(100-yr Atmospheric
Increased
tropospheric
tropospheric
time horizon) lifetime(years) radiative forcing
concentration
concentration
(W/m2)
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Concentrations
in parts per
million (ppm)
Carbon dioxide
(CO2)
Global Climate Change
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280
386
1
~ 100
1.66
Methane (CH4)
700
1742-1866
25
12
0.48
Nitrous oxide
(N2O)
270
322
298
114
0.16
Concentrations
in parts per
billion (ppb)
Tropospheric
25
34
n.a.
hours-days
ozone (O3)
*From http://cdiac.ornl.gov/pns/current_ghg.html, updated February 2011.
0.35
Figure 3 compares the relative importance of greenhouse gases to global warming by plotting the
percentage of total CO2e associated with each type of greenhouse gas emission. Although CO2 is the weakest of
the greenhouse gases, it has the largest effect on global warming because we emit such large volumes of CO2
during fossil fuel burning. Thus, AGW mitigation measures should first focus on reducing CO2 emissions.
Figure 3. Global anthropogenic greenhouse gas emissions in 2004 expressed as the percentage of total CO2e.
Data from IPCC 4th Assessment Report: Climate Change 2007: Synthesis Report,
http://www.epa.gov/climatechange/emissions/globalghg.html
Of course anthropogenic greenhouse gas emissions are not the only cause of GCC. Natural causes of
GCC include variable sunlight intensity, the El-Nino Southern Oscillation (ENSO), and volcanic aerosols
(Figure 4). Measurements show that these natural drivers alone cannot account for the observed increase in
global temperatures. Volcanic aerosols cause global cooling for a few years after major eruptions like Mount
Pinatubo in 1991. The effect of solar intensity is small, and is sometimes in the opposite direction of expected
temperature changes (global temperature increases when solar intensity decreases). Furthermore, if the sun
were responsible for global warming then the atmosphere would be uniformly heated from top to bottom.
However, heating of the atmosphere has been concentrated in the lowermost layers, consistent with
greenhouse gases trapping infrared radiation emitted from the earth's surface. ENSO events seem to
determine the location of temperature peaks and troughs but cannot explain the long-term increase in global
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temperature. Since none of the natural climate drivers can explain global warming, we conclude that human
burning of fossil fuels has increased the concentration of the greenhouse gas CO2 in the atmosphere, causing
global surface temperatures to increase. (Figure 1) shows an excellent positive correlation between
atmospheric CO2 concentration and average surface temperature and from 1880 to the present, consistent with
the idea that increased CO2 is associated with increases in temperature. Data from ice cores collected in
Antarctica show that this correlation stretches back 420,000 years (Figure 5) (Petit, Jouzel et al. 1999).
Plotting CO2 concentrations versus temperature anomalies recorded in the ice cores shows that the trend for
the “Anthropocene” is distinctly different from the natural trend, suggesting that human activities have highly
perturbed the atmosphere-climate system (Figure 6, from (Etkin 2010)). The positive correlation between
temperature and atmospheric CO2 concentration shown in (Figure 1) and (Figure 6) suggests, but does not
prove, a cause and effect relationship vi. However, we can say with a high level of confidence that when
atmospheric CO2 concentration is high, average global surface temperatures are high.
Figure 4. In (a) average global surface temperatures are compared with a model that accounts for the four
primary influences on global temperature: the El-Nino Southern Oscillation (ENSO), volcanic aerosols, solar
radiation intensity (insolation), and anthropogenic effects including greenhouse gas emissions and deforestation.
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Figure 5. Plot of CO2 (Green), temperature (Blue), and dust concentration (Red) measured from the Vostok,
Antarctica ice core as reported by Petit et al. (1999). From http://serc.carleton.edu/eslabs/cryosphere/7a.html
Figure 6. State–space (phase space) view of Antarctic ice-age cycles. From Etkin (2010).
We are currently in the Pliocene-Quaternary ice age that started about 2.6 million years ago. Since then,
the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year
time scales called glacial and interglacial periods. The earth is currently in an interglacial known as the
Holocene, which started about 10,000 years ago. All that remains of the continental ice sheets are the
Greenland and Antarctic ice sheets and several isolated smaller glaciers. These ice sheets have given us the ice
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core records that have been so useful for reconstructing the history of climate and atmospheric composition
over the last 600,000 years.
The Greenland ice cores taught us that climate can change not only gradually, but also abruptly, with
average surface temperatures changing by several degrees in a matter of decades. Each ice layer in the
Greenland ice cores gives us information about the climate in Greenland at the time it formed. Plotting
temperature measured from the ice cores as a function of time (Figure 5) shows peaks and troughs
corresponding to ice ages (glacials) and warm periods (interglacials). The timing of these peaks and troughs
coincide with cyclical changes in earth’s orbit called Milankovitch cycles. The agreement of the timing of the
ice core temperature peaks and troughs with Milankovitch cycles gives credence to the isotopic and dating
methods used for analyzing the ice cores. Ice ages occurred roughly every 100,000 years, which is the longestperiod Milankovitch cycle where the earth’s orbit shifts from circular to slightly elliptical (Richter 2010). The
temperatures varied from +3°C (+5°F) to -8°C (-14°F) relative to today’s average surface temperature. The
atmospheric CO2 concentration varied between 190 and 300 ppm. Today’s atmospheric CO2 concentration of
386 ppm is higher than any time in the last 420,000 years. Since the ice core record shows that temperature
closely tracks CO2, we can expect temperature to reach the highest level in 420,000 years.
Contrary to the expectation that global warming should be preceded by an increase in the atmospheric
concentration of the greenhouse gas CO2, in the ice core record changes in atmospheric CO2 concentration lag
800 years behind changes in temperature. This was predicted by James Hansen and others ten years before the
ice core data were published. They reasoned that Milankovitch climate forcings are weak, and therefore they
could only initiate changes in global temperature (glacials and interglacials). Their effects would have to be
amplified by positive feedbacks in order to cause the observed changes in global temperature. For example,
when Milankovitch cycles cause a small decrease in solar insolation, growing glaciers reflect more sunlight,
causing further cooling vii. Milankovitch-triggered increases in solar insolation cause warming that is amplified
when warming oceans and soils release greenhouse gases. This also explains how increased sunlight in the
northern hemisphere could cause warming in the southern hemisphere. According to Milankovitch theory the
next cooling event would occur in ~20-30,000 years. But Milankovitch cycles (changes in solar insolation)
cannot explain the last century’s increases in atmospheric CO2 and global temperature.
Unfortunately the high resolution ice core records do not cover a time period with CO2 concentrations
and surface temperatures as high as we are experiencing today. Further increases in CO2 levels and
temperature will bring us increasingly outside the range of well-understood climate conditions. Earth's history
includes long periods with CO2 levels and temperatures similar to and even higher than we have today. For
example, Paleoclimatologists say that during the Paleocene-Eocene Thermal Maximum (PETM) 56 million
years ago repeated, and sudden releases of carbon compounds to the atmosphere caused warming of 5°C at the
equator and 9°C at the poles over a period of roughly 170,000 years (National Research Council 2011). Melting
of methane clathrates stored in shallow marine sediments and release of the greenhouse gas methane is the
most widely accepted cause of the PETM, although other factors must have been involved since models suggest
this factor alone was insufficient to produce the observed increase in atmospheric carbon (Panchuk, Ridgwell et
al. 2008). Warming during the PETM was associated with disruption of the carbon and hydrologic cycles,
ocean acidification, and widespread species extinctions. These changes occurred within a few thousand years,
but the climate system did not fully recover for ~100,000 years (National Research Council 2011). Scientists
must use the rock record to learn more about "deep time" climate episodes such as this so they can reduce
uncertainty about what will happen as global warming intensifies today. Melting of methane clathrates stored
in modern marine sediments is one potential positive feedback that may push modern climate past a tipping
point and cause catastrophic climate change.
A tipping point is a point in time when global climate changes from one stable state to another stable
state. Flannery (2008) says that Hansen distinguishes between climate tipping points and irreversible and
catastrophic climate change. We are currently suspended between the two. We passed the tipping point of 350
ppm CO2 in the atmosphere, but the full effect of our massive addition of CO2 to the atmosphere has not yet
been realized. In effect, we are in climate overshoot, and will have climate collapse if we don't reverse the trend.
We can still avoid catastrophe if we act soon to bring the concentration down to 350 ppm or less viii.
Because climate change occurs over decades and centuries, and because it took scientists decades to
perfect proxy methods and collect enough data to be confident in their conclusions, it took several decades for
the scientific community to reach a consensus. They agreed in the late 1990’s that global warming is occurring,
and then in the early 2000’s that warming is primarily human-induced. Currently 97% of actively publishing
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climate scientists agree that data clearly show the earth is warming and that human activity is contributing to
rising temperatures ix. The development of this consensus is illustrated by the increasing levels of confidence
and estimated risks in statements issued by scientific organizations (for a more detailed history see (Weart
2008)). In 2001 the Intergovernmental Panel on Climate Change (IPCC) concluded that warming was
occurring, that “There is a discernible human influence on global climate,” and that the mean surface
temperature will increase 1.5° to 6.0° during the 21st century. President Bush was skeptical and asked the US
National Academy of Sciences (the most prestigious scientific organization in the US) for an independent
report. That report, published later in 2001, fully supported the conclusions of the IPCC report x . In 2003 the
American Geophysical Union published its position paper. It stated that “In view of the complexity of the Earth
climate system, uncertainty in its description and in the prediction of changes will never be completely
eliminated…AGU believes that the present level of scientific uncertainty does not justify inaction in the
mitigation of human-induced climate change and/or the adaptation to it.” In 2004 the American Association
for the Advancement of Science concluded that “even if measures to reduce global warming are put into place
today, some increase will still occur and ways will be needed to adapt to it; that adapting will be challenging,
costly and imperfect; that ecosystems around the world are already being affected by global warming; and that
acting in advance of problems is necessary to reduce damage.”
Finally, in 2007 the IPCC released its fourth report (IPCC 2007), for which the committee received the
2007 Nobel Prize. The report concludes that "Warming of the climate system is unequivocal . . . Most of the
observed increase in global average temperatures since the mid-20th century is very likely due to the observed
increase in anthropogenic greenhouse gas concentrations,” where “very likely” means a greater than 90%
probability.
The probability that modern global warming is real is > 99% (IPCC 2007). Since 1850 the 24 warmest
years have been as follows, from warmest to coolest: 2010 and 2005 (tied), 2009 and 2007, 2002 and 1998,
2003, 2006, 2004 and 2001 (tied), 2008, 1997, 1995 and 1990 (tied), 1991, 2000, 1999, 1988, 1996, 1987 and
1983 and 1981 (tied), 1994, and 1989 (Hansen, Rued et al. 2010). In the last 161 years the 24 warmest years
have all occurred since 1980. It is nearly impossible for these observations to occur by chance.
Given that our actions are causing the earth to heat up, what can we expect for the future? First we will
examine projections of future atmospheric CO2 concentrations and surface temperatures, and then we will
explore the potential consequences.
More info: Is there a scientific consensus on global warming?
Projections of Future Atmospheric CO2 Concentrations and Temperatures
The story of AGW is more interesting and scarier than any plot devised by science fiction writers. The
human race is actively changing the planet without knowing the consequences. Science fiction writers used to
write about humans terra-forming other planets to make them suitable for human habitation. Those writers
never dreamed we would change our own planet, possibly in ways that would make it unsuitable for human
habitation.
Estimates of how much CO2 we will emit in the near-future range widely. The actual amounts of
greenhouse gas emitted will depend on the future strength of the global economy (greenhouse gas emission
rates are higher when the economy is strong) and on the success of international climate mitigation
agreements. Accurately estimating future atmospheric concentrations of greenhouse gases is even harder
because the concentrations depend not only on emission rates (source terms) but also removal rates (sink
terms) that are difficult to quantify. The existence of many recognized, and probably some unrecognized,
feedback loops in the carbon cycle complicate the relationship between emission rates and actual atmospheric
concentrations. Negative feedbacks such as increasing plant productivity will likely dampen the increases in
atmospheric CO2 concentration and surface temperatures resulting from an increase in CO2 emission rates. On
the other hand, positive feedback loops could cause the concentration of CO2 in the atmosphere to rise to levels
higher than predicted by increased emissions alone. For example, an increase in atmospheric CO2
concentration resulting from an increase in CO2 emission rate would cause global surface temperatures to rise,
continental ice sheets to melt and expose permafrost to sunlight, and organic matter in the permafrost to
decompose and release additional amounts of the greenhouse gases CO2 and CH4. "Helium dating of trapped
bubbles in the permafrost shows that we’re melting permafrost now that hasn’t been melted in 40,000 years.
And there’s enough CO2 and methane (another greenhouse gas) trapped in the permafrost to have the
greenhouse gas levels not go up by a factor of two but by a factor of 10 xi." Another positive feedback in this
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scenario results from a decrease in the surface albedo, the proportion of sunlight reflected back into space.
Melting continental ice sheets and exposing underlying soils would decrease the surface albedo (soil would
absorb more sunlight than ice), resulting in increased absorption of sunlight and increased surface
temperatures. Still another positive feedback loop results from increased temperatures causing increased
evaporation and higher levels of water vapor, a greenhouse gas, in the atmosphere. The number of recognized
positive feedback loops outnumbers the known negative, balancing feedback loops. If the net effect of feedback
loops is positive, the climate system is unstable and the risk of a catastrophic temperature increase is high. The
presence of many feedback loops in the climate system introduces significant uncertainty into climate
scenarios. We need more research to reduce these uncertainties.
The effects of future greenhouse gas emissions on climate are estimated using General Circulation
Models (GCMs). Scientists use GCMs to construct future climate scenarios based on different sets of
assumptions. The first assumption is the growth rate of the economy, which determines the energy usage rate
and the carbon emission rate. Adopted values range between 2 and 3% annual growth, which may not seem like
a big difference. However, that extra 1% of economic growth over 100 years more than doubles the size of the
economy, energy used, and carbon emissions (Richter, 2010). A primary goal of sustainability is to decouple
economic growth and carbon emissions by using energy conservation and by transitioning to renewable energy
sources, which would help to mitigate GCC.
The GCMs break the very complex global climate problem down into many manageable parts. They
divide the oceans and atmosphere into multiple layers, and then divide those layers into cells that are typically
about 25 miles on a side. The model starts with current conditions, and then adds the expected carbon
emissions for the next year to the atmosphere. After "perturbing" the atmosphere in this way it models the
effect on climate by using physical laws to model atmospheric and oceanic circulation. The model calculates
energy and mass fluxes between cells, allowing the atmosphere and ocean to relax in response to the
perturbation. After calculating the average surface temperature at the end of that time step, the model injects
the next batch of carbon into the atmosphere and repeats the calculations. The model continues step by step,
iterating the calculations at each step. As you can imagine, the errors in calculated values accumulate from step
to step, so that the first time step, the time closest to the present, will have the lowest uncertainty. The
uncertainty increases as the model progresses further into the future.
GCMs are very complex, and can only be run on the fastest supercomputers. They have many adjustable
parameters analogous to knobs on an electronic device. Observation of the real world constrains most of the
adjustable parameters to a narrow range of values. For example, a scientist may feed into the model measured
ranges of economic growth and surface albedo. Scientists tweak the knobs and then model the effect of those
changes on climate. They adjust the sets of parameters until the model can reproduce past climates. They then
run the resulting sets of calibrated parameters through the model to calculate realistic estimates of future
surface temperatures and other climactic parameters.
The IPCC uses seven sets of parameters to model future scenarios. They run each scenario through
many different GCMs, resulting in a range of estimated average surface temperatures. For example, according
to the IPCC 2007 report scenario A1B predicts that by the end of the 21st century average surface temperature
will increase between 1.7 and 4.4°C (3.1-7.9°F). We won't know which temperature is most likely to be correct,
and therefore which model is most accurate, for at least 30 years, but the higher estimates are more likely than
the lower estimates (Richter, 2010).
All future scenarios produced using GCMs, using a wide range of input parameters and various
combinations of feedback loops, show global temperatures increasing over the next century (Figure 2).
"Nobody had been able to build a model that matched the historical record and that did not show significant
warming when greenhouse gases were added xii." The “middle of the road” model A1B in the IPCC Fourth
Assessment report (IPCC 2007) assumes a balanced use of both fossil and non-fossil fuels. The IPCC often uses
the A1B scenario as a basis of comparison. In the A1B scenario, atmospheric CO2 concentration increases from
386 ppm in 2008 to ~550 ppm in 2050. How much would temperature increase in this scenario? To answer
that question, we need to know the climate sensitivity, i.e., how much would global temperature increase if
atmospheric CO2 concentration doubled? To measure the sensitivity of climate to changes in CO2
concentration, climate scientists use the modern instrumental record and temperature proxies in the ancient
ice core record. When combined with GCM calculations, the resulting equilibrium climate sensitivity is 2-3°C
(Mann and Kump 2009). These results mean that a doubling of atmospheric CO2 concentrations will lead to a
roughly 2-3°C warming of the globe ((Chapman and Davis 2010), Figure 2).
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How high can temperatures get before humans start dying from heat stress? The upper temperature
limit for human habitability is expressed as the wet bulb temperature measured by wrapping a thermometer in
a wet cloth and ventilating it (Sherwood and Huber 2010). The second law of thermodynamics states that an
object cannot lose heat to an environment with a wet bulb temperature greater than the object's temperature.
The human body generates about 100W of heat and has an internal temperature of 37°C (98.6°F). The body
regulates skin temperature at a lower level, 35°C (95°F), so that it can conduct heat from the interior to the
exterior of the body. The air must have a wet bulb temperature lower than the skin temperature so that the skin
can lose heat to the air through conduction or evaporation of sweat. If the air's wet bulb temperature is higher
than the skin temperature of 35°C, the skin and then the internal body will heat up, causing hyperthermia or
heat stress. Wet bulb temperatures exceeding 35°C for extended periods are considered intolerable. Currently
the highest wet bulb temperature on earth is 31°C. A 7°C increase in global surface temperatures will cause
some regions of the world to have wet bulb temperatures > 35°C, making them uninhabitable. A warming of 1112°C would affect larger areas than rising sea level, and make areas containing most of the world's current
population uninhabitable (Sherwood and Huber 2010). Models suggest that such extreme warming could occur
by the end of the 21st century. "In principle humans can devise protections against the unprecedented heat such
as much wider adoption of air conditioning, so one cannot be certain that TWMax > 35 °C would be
uninhabitable. But the power requirements of air conditioning would soar; it would surely remain
unaffordable for billions in the third world and for protection of most livestock; it would not help the biosphere
or protect outside workers; it would regularly imprison people in their homes; and power failures would
become life-threatening. Thus it seems improbable that such protections would be satisfying, affordable, and
effective for most of humanity (Sherwood and Huber 2010)."
Problems (Potential Consequences)
If you asked me to name the three scariest threats facing the human race, I would give the same
answer that most people would: nuclear war, global warming and Windows. - Dave Barry
*Discuss threat to human health - see Karl et al. (2009)
We have reviewed what we know about GCC based on study of modern and ancient records. We have
also explored the more uncertain future projections of CO2 concentrations and temperatures. What effects will
these higher temperatures have? This question is very difficult to answer because we have not done this
experiment before. Furthermore, the atmosphere and oceans form a very dynamic, complex climate system
with countless feedback loops and rapid, nonlinear responses, making it very difficult to predict how climate
will change. For example, as the earth gets warmer, more water evaporates from the oceans; since water vapor
acts as a greenhouse gas, it contributes to the greenhouse effect and promotes further warming (Mann and
Kump 2009). GCM estimates of global climate change are improving, but much uncertainty about the effects
of increased atmospheric greenhouse gas concentrations remains. However, even if we stopped emitting
greenhouse gases now, the greenhouse gases we have already emitted will continue to warm the earth for more
than 1,000 years. This is because some greenhouse gases such as CO2 have long atmospheric residence times
(Archer, Eby et al. 2009) and because the oceans will retain for centuries the heat they have already absorbed
(Solomon, Plattner et al. 2009). Thus, increases in temperature and the environmental changes they cause will
be irreversible, and we will be forced to adapt to them. Here we will examine potential consequences of AGW
and attempt to give some measure of associated uncertainties.
One effect on which scientists agree is sea level rise. Warming causes ice on land to melt and enter the
sea, increasing the water in the world’s oceans. This effect is well documented: nearly all of the world’s glaciers
are receding and thinning. The loss of ice volume on land becomes a gain in seawater volume. Warming also
causes seawater to expand, further increasing the volume of seawater. In the IPCC 2007 “middle of the road”
model A1B atmospheric CO2 concentration doubles by 2100, from a pre-industrial concentration of ~270 ppm
(Richter 2010) to ~550 ppm. For this scenario GCMs predict that global temperature will increase 2-3°C (3.65.4°F). A 3°C increase in global average temperature would raise sea level ~0.8 m = 2.6 ft., causing the global
loss of 2223 km2 of land and $944 billion (Mann and Kump 2009). Thus, by the end of this century cropproducing river deltas in countries such as Bangladesh and Viet Nam will likely be partially inundated (Brown
2011). Many inhabited small islands and some coastal cities like New Orleans will likely be partially or
completely abandoned. The resulting environmentally-caused human migration would be costly and would
stress social support systems.
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Inundation is not the only threat presented by seal level rise: salinization of coastal aquifers may have
an even greater impact in the short term, and is already a chronic problem in mostly low-lying countries like
Bangladesh. As sea level rises, salt water advances into coastal aquifers, and less-dense freshwater floats on the
denser salt water. Pumping from wells near the coastline pulls the saltwater toward the surface, eventually
contaminating the well water, surface aquifers, and soils. Salinization makes soil useless for agriculture because
salt is poison to plants. Thus, a sea-level rise would displace coastal farmers, who would move inland to
compete with other farmers for precious land.
Agricultural productivity may decrease in response to rising temperatures. A 1°C increase in
temperature during the growing season translates into a 10% drop in crop yields (Brown 2009). Since average
global temperatures may increase 2-3°C by the end of this century, agricultural productivity may decrease 2030%, causing widespread starvation. In some regions agricultural productivity is already decreasing and will
further decrease due to longer, more intense droughts and resulting desertification (Karl, Melillo et al. 2009).
Scientists estimate that 1.4-6.7 million adult Mexicans will emigrate from Mexico to the US because of declines
in agricultural productivity in response to warming associated with GCC (Feng, Krueger et al. 2010).
Another concern is that weather events may become more intense. Higher temperature means a greater
amount of stored energy. Gigantic storms can unleash this energy. Flooding, drought, and heat waves are all
likely to become more frequent and intense in certain parts of the world. The 2010 extreme heat wave in Russia
and record flooding in Pakistan and Australia are examples of the extreme weather events we can expect from
GCC, and are signs of instability in the global climate system (Brown 2011). During the Russian heat wave in
July-August 2010 the average Moscow July temperature was 8°C (14°F) above normal. The heat wave started
many forest fires with economic losses estimated at $300 billion, and the resulting pollution combined with the
high temperatures caused more than 56,000 deaths. This event was also a global disaster because Russia, a
grain exporter, lost 40% of its wheat crop, causing world wheat prices to increase 60% over two months (Brown
2011).
Our understanding of the effects of GCC on ecosystems is very limited. Because the rate of GCC is
unnaturally high, species will have difficulty adapting. Some probably could not migrate to higher latitudes or
higher altitudes fast enough to stay within a livable range of temperatures. Others will migrate into ecosystems
to which they have not adapted and will therefore fall victim to predators or starvation. Some migrating
species will displace other species in ecosystems they enter; the increasingly common problem of invasive
species has caused a variety of problems around the globe. GCC will undoubtedly increase species extinction
rates, with a 3°C rise in average global temperature estimated to put 30-50% of plants and animals at risk of
extinction (IPCC 2007). The resulting disruption of ecosystems would decrease the flow of ecosystem services
to humanity. Lands that are currently marginally inhabitable will become uninhabitable. In those regions the
death rate will surely rise. The World Health Organization (WHO) estimates that climate change already causes
more than 150,000 deaths each year ((Steffen 2006), p. 513). This number will increase as population
increases and global warming intensifies.
The global climate system may pass a tipping point where catastrophic and irreversible changes occur.
The Greenland and Antarctic ice cores reveal abrupt changes in climate over the last 600,000 years in. Deeper
back in time, catastrophic climate change during the PETM 56 million years ago caused ocean acidification and
mass extinction (Zalasiewicz, Williams et al. 2010).
What possible climate system tipping points do we face today? A catastrophic change in the climate
could result when AGW passes a tipping point and shuts off the Atlantic conveyor belt. This would lead to
abrupt cooling in northern Europe and other irreversible changes that are difficult to predict. Complete
collapse of the Greenland and west Antarctic ice sheets could rapidly raise sea level by 12 m (39 feet). Other
potential tipping points could involve positive feedback loops such as warming-induced melting of methane
clathrates in shallow marine sediments causing the sudden release of the greenhouse gas methane, as
discussed previously. If we pass a climate tipping point, adaptation will become much more difficult and costly.
In summary, GCC will affect coastal areas, agriculture, water supply, human health, and many other
aspects of society and the natural environment (Karl, Melillo et al. 2009). There will winners and losers: some
areas may become more hospitable, while others will become less so. These changes will trigger large-scale
climate migrations that will be highly disruptive to society. Having reviewed the science of GCC, let’s examine
the recent development of this issue in the public arena. We will examine the phenomenon of “climate
contrarians,” and show that corporate interests have waged a public relations battle with the scientific
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community. Unfortunately, because they have more money and public relations experience than scientists,
corporations are winning the battle in the public arena.
The Lack of Public Consensus
“All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is
accepted as being self-evident.” Arthur Schopenhauer, German philosopher (1788 - 1860).
persist.
So why is there public disagreement about AGW? Here we examine why lingering public doubts
The scientific community took several decades to reach a consensus on AGW. As expected for an issue
this complex, it is taking longer for the public to reach a consensus. This is not surprising, as the culprit is
fossil fuel use, and extremely powerful and wealthy business concerns have campaigned against this consensus
to protect their profits. This situation closely parallels that of the tobacco companies in the 1970’s, who paid
lobbyists and scientists large sums of money to spread falsehoods about the link between smoking and
cancer xiii. Unfortunately, this has led to a politicization of the global warming issue.
The politicization of AGW was partly due to the involvement of Democratic politician Al Gore. Although
Gore did an admirable job of raising public awareness on this issue xiv, his political associations led many to
close their minds to the possibility that he was right. However, Al Gore did not invent the theory of global
warming, nor did he participate in any of the scientific investigations; he was merely publicizing the issue.
The politicization of AGW has polarized the debate over the reality of AGW. On one side of the debate
are climate contrarians, a group mostly driven by opposition to any type of government regulation. I choose the
term “contrarian” over “skeptic” because healthy skepticism is necessary for good science, but contrarians
ignore all evidence except that which supports their beliefs, and that evidence usually turns out to be anecdotal
(Hansen 2006). Climate contrarians are usually exemptionalist (anthropocentric), old, and arrogant, with a
strong belief in the ability of a free market to solve all problems. However, as pointed out by Nicolas Stern in
the famous “Stern Review,” GCC is the largest example of market failure (Stern and Treasury 2007). We can’t
rely on the market alone to mitigate AGW.
On the other side of the global warming debate are the “ultra-greens” who often exaggerate the threat of
global warming and other environmental problems. They tend to advocate solutions that are impractical from
a monetary or societal perspective but that fit their prejudices against possible solutions like nuclear power.
Ultra-greens will make claims such as “we can solve the energy problem through conservation alone,” not
mentioning that would require that everyone give up their cars, move into much smaller homes, and grow their
own food. Ultra-greens make it harder to reach a public consensus on environmental problems because of
their extreme and unrealistic positions on the issues.
People who fall into these two extreme groups cannot be reasoned with. No amount of evidence will
make them shift their positions, which are irrational. For example, Richter (2010) observes that climate
contrarians “agree that the greenhouse effect is real, and that greenhouse gases in the atmosphere are the main
control on the average temperature of the planet. Why they do not agree that changing the greenhouse gas
concentration changes the temperature is beyond me.”
For the AGW issue the biggest obstacle to reaching a public consensus is several politically conservative
scientists opposed to government regulation. This group of climate contrarians has had a disproportionately
strong influence on public opinion and the formation of public policy, as documented in the book “Merchants
of Doubt” by science historians Naomi Oreskes and Erik M. Conway (2010). The book focuses on the physicists
Fred Singer and Fred Seitz, who long ago were prominent scientists. Singer worked in rocket science, and Seitz
worked on the atomic bomb. However, over time they started acting more like lobbyists than scientists,
attacking the work and reputations of scientists while doing almost no original research of their own. Singer
and Seitz are right-wing libertarians opposed to all forms of government regulation. Both disputed claims that
tobacco causes lung cancer, both have formed conservative foundations that receive corporate money, and both
are well-known climate contrarians. Neither of them are climate scientists, but they have loudly disputed the
findings of climate scientists. Because of their conservative political connections, they have served at high levels
in federal science administration and played a large role in shaping public policy. Oreskes and Conway
((2010), pg.8) state “They used their scientific credentials to present themselves as authorities, and they used
their authority to discredit any science they didn't like.”
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Over time, Singer and Seitz have become experts at fooling the public on issues like the health effects of
tobacco smoke, the role of CFCs in formation of the ozone hole (see below), the environmental effects of acid
rain, and now the effect of anthropogenic greenhouse gases on GCC. “In each case the tactics are identical:
discredit the science, disseminate false information, spread confusion, and promote doubt. xv” On every issue
time has shown them to be wrong, yet they still wield considerable influence. Singer and Seitz are not
interested in the truth, and neither are the people who continue to listen to them after they have repeatedly
been wrong. They have led the public to believe that the climate science community lacks a consensus on
AGW. Nothing can be further from the truth: A recent poll of earth scientists found that 97% of actively
publishing climate scientists agree that data clearly show the earth is warming and that human activity is
contributing to rising temperatures xvi. Yet this tiny group gets more press than all of those climate scientists,
regularly testifying in Congress about a topic they are not experts on. Their belief that individual liberties are
more important than any other cause may end up causing countless less privileged people in the world to suffer
the consequences of AGW xvii.
In the future there will likely be finger pointing, anger, and lawsuits directed at those perceived to be
responsible for problems associated with AGW. Already groups like ExxonSecrets.org are documenting how
organizations and oil companies paid contrarian scientists to spread misinformation and talking of charging
these people with crimes against humanity ((Steffen 2006), pp. 512-13). However, given that Seitz and Singer
caused delays in tobacco regulations that likely caused the loss of thousands of lives without suffering any
consequences, it seems unlikely that they will receive the punishment they deserve for delaying action on
climate change mitigation.
The politicization of AGW has caused many people to base their opinions and decisions on emotions
rather than facts and logic. Unfortunately, slandering individuals or groups who say things they don't want to
hear is easier than listening to the messages carefully and building an informed opinion. This explains the
popularity of conservative talk shows, and the public reaction to climate scientists' theory of global warming:
kill the messenger xviii!
The politicization and denial of AGW, especially by conservatives, is sickening even to some Republican
career politicians. For example, on 11/17/2010 Representative Bob Inglis (R-SC) felt free to speak his mind
because he was not returning to the House of Representatives for the following term. He said, “Because 98 of
the doctors say, “Do this thing,” two say, “Do the other.” So, it’s on the record. And we’re here with important
decision to be made. And I would also suggest to my Free Enterprise colleagues — especially conservatives here
— whether you think it’s all a bunch of hooey, what we’ve talked about in this committee, the Chinese don’t.
And they plan on eating our lunch in this next century. They plan on innovating around these problems, and
selling to us, and the rest of the world, the technology that’ll lead the 21st century. So we may just press the
pause button here for several years, but China is pressing the fast-forward button. And as a result, if we wake
up in several years and we say, “geez, this didn’t work very well for us. The two doctors didn’t turn out to be so
right. 98 might have been the ones to listen to.” [...] Meanwhile we've got the people who make a living and a
lot of money on talk radio and talk TV pronouncing all kinds of things. They slept at a Holiday Inn Express last
night, and they’re experts on climate. And those folks substitute their judgment for people who have Ph.D.s and
work tirelessly [on climate change] xix.”
A recent development is certain to further slow progress on fighting climate change. Correspondence
between some British climate change researchers was leaked to the Internet in late November of 2009.
Statements in the leaked emails seem to suggest that some researchers may have been trying too hard to make
their case. Included were "discussions of how to keep critical work out of peer reviewed journals and efforts to
shield scientists' data and methodology from outside scrutiny xx.” One researcher claimed to have used a "trick"
to "hide the decline" in a time plot of global temperatures (which is unnecessary - see discussion in the
Technical Chapter "Climate Change - Testing Hypotheses"). Climate contrarians, looking for evidence of what
they believe to be a cover-up, started calling this incident “Climategate” (an obvious reference to the Watergate
cover-up).
For advocates of a global climate change agreement, Climategate couldn't have come at a worse time,
right before the international climate conference in Copenhagen. Republican Senator James Inhofe of
Oklahoma, a leading climate change contrarian, stated in a letter to Barbara Boxer, the California Democrat
who chairs the Senate environment committee, that "the e-mails could have far-reaching policy implications
for the US.” Climategate is what Inhofe and other contrarians had been hoping for. In 2008 he instigated a
congressional investigation of climate change research in the US, charging The Pennsylvania State University
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researcher Michael Mann with fraud after Mann published the famous "hockey-stick" diagram (Figure 2).
However, Inhofe's investigation, which many characterized as a "witch-hunt" intended to intimidate scientists,
found no evidence of wrongdoing. Now that Inhofe has found evidence of potential fraud by one research
group, out of hundreds worldwide, he can cast aspersions on all of the remaining researchers. Imagine an
investigation in the US that found one corrupt cop and concluded that all cops are corrupt, and that we should
release all of the criminals from prison because corrupt cops wrongfully apprehended them. That's the type of
logic that Inhofe is using.
In Britain the House of Commons' Science and Technology Committee announced that they found no
evidence of data tampering or perverting the scientific review process by the University of East Anglia's
Climatic Research Unit or its director, Phil Jones xxi. Although they absolved the unit of scientific wrongdoing,
the Committee criticized Jones and his colleagues for stonewalling their critics by withholding data and for
conspiring to shield their data from public records laws. The hope is that this criticism will persuade the
climate science community to make the scientific process more transparent.
I could spend time trying to convince you that the scientists involved in Climategate did nothing wrong,
and that they are only guilty of bad judgment. The science they have published is sound, and climate
contrarians took the phrases attributed to them out of context. However, that would miss the main point.
Even if it appears that a research group distorted the facts, that is only one group out of scores that have
studied this narrow topic (mostly focused on dendrochronology, the study of tree rings) and come to similar
conclusions, and that is only one type of evidence out of scores that are consistent with global warming.
Contrarians are hoping that the public will "throw the baby out with the bathwater.”
With Republicans taking control of the US House of Representatives in the November 2010 elections,
some Republican representatives are vowing to start another investigation of Climategate, even though five
independent panels have already cleared the scientists of wrongdoing and validated the science. xxii Do they
really think a sixth investigation will come to a different conclusion? Their objective is to keep the "scandal" in
the headlines and keep doubts in the mind of the American public as long as possible by continuously
questioning the veracity of climate scientists’ claims, even when all evidence supports those claims.
Climate contrarians also trumpeted recent findings that the IPCC 2007 report contained a few errors.
Considering that the report consisted of three massive volumes totaling more than three thousand pages, and
that hundreds of scientists contributed to this massive effort, it is not surprising that they made a few mistakes.
The biggest error was stating that Himalayan glaciers may disappear by 2035, when the correct estimate is
2350. This inaccurate statement raised many alarms because the Himalayan glaciers are the primary source of
water for the world’s two most populous countries, China and India. Recognition of the errors led the UN to
begin a review of IPCC procedures before the release of its fifth report in 2014. However, it bears repeating
that this is one piece of scientific evidence of AGW out of hundreds. If you believe that the theory of AGW is a
hoax perpetrated by scientists throughout the world, perhaps as part of a bid for the UN to take over the world,
then that error will support your bias and provide enough evidence for you to dismiss all of the other evidence,
in which case you shouldn’t bother reading any more of this book.
Scientists are growing increasingly frustrated by the distortions of contrarians, which have created
public confusion and greatly slowed and even reversed public acceptance of the reality of AGW. For example,
Lord Christopher Monckton claims that scientists are lying about global warming. Monckton testified to
Congress as a climate change expert, but his degrees are in classics and journalism and he has not published a
single peer-reviewed paper. Climate scientist John Abraham researched Monckton’s many public claims and
effectively refuted every claim xxiii. A statistician named Grant Foster who posts blogs under the name Tamino
has tested the many different claims of fraud made by contrarians, especially meteorologist and blogger
Anthony Watts. Foster has taken the raw data and analyzed them himself to see if climatologists drew the
correct conclusions. Every time he tested the claims of contrarians he found they were false. According to
Foster xxiv, “Anthony Watts and Joe D’Aleo published a document claiming that the GHCN data, and the way it
was processed, exaggerated estimates of how much the globe has warmed over the last century or more. They
even claimed that the scientists who managed, and who processed, these data had deliberately manipulated
both the data (by selectively removing or retaining data locations) and the analysis (by their methods of
applying “adjustments”) to exaggerate the warming trend. I discovered that both claims by Watts & D’Aleo
were wrong. Station dropout did not exaggerate the warming at all (it had almost no effect), and the
adjustments didn’t exaggerate warming either (in fact they reduced it). I challenged Watts to apologize, not for
getting it wrong but for accusing the scientists involved of fraud. His only response, as far as I know, has been
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to plead ignorance because he didn’t do the analysis — nor did D’Aleo. They published a document claiming
fraud, but they hadn’t even done the analysis.” What is frustrating is that non-experts like Watts
(remember that meteorologists study weather, not climate) can repeatedly slander scientists and harm their
reputations through baseless accusations without it hurting their reputations or shrinking their audience.
Climategate and errors in the IPCC 2007 report have increased public doubt about the reality of AGW.
For example, a Rasmussen Reports poll in February 2010 showed that the percentage of likely voters who
believed humans are primarily responsible for global warming decreased from 47% in April 2008 to 35% xxv.
Why does the public refuse to accept the scientific evidence of AGW? The reasons include long-standing antiintellectualism in the US, which has roots in the long battle between science and religion; the public’s low
regard of science caused by scientists inability to communicate to the public effectively; scientific “waffling,”
such as the constantly changing claims about the health effects of eating foods like red meat; the perception
that scientists are politically biased; a shortage of transparency in the science enterprise; the lack of public
understanding of complex issues with a scientific component; the inability of humans to detect slow changes,
which is related to their inability to distinguish climate and weather; the public opposition of a handful of
contrarian scientists funded by oil companies; distrust of the U.N., which has been brokering an international
climate treaty; the view that emission limits are an infringement on personal freedom; and the “secret war”
waged by corporations who stand to lose money if America adopts emissions standards. These biases prevent
the public from reaching the correct conclusion about AGW. Even without these biases, persuading Americans
to change their lifestyles to stop something they cannot detect with their own senses to prevent an undefined
threat in the future is a steep, uphill battle.
Unfortunately the American public has been bamboozled by ideologues like Singer and Seitz and by the
corporations that fund them, namely big oil companies like Exxon-Mobil. The subtlety and effectiveness of the
oil companies’ campaign against global warming science is frightening. The general belief in the US is that you
can accomplish anything if you have enough money, and the oil companies have proved it. Evidence suggests
that lobbying by oil companies delayed political action on global warming by at least ten years, allowing them
to earn record profits. They also eliminated competition. xxvi Governments around the world could learn a lot
from the disinformation campaigns of big oil. Unfortunately, the world will not be a better place if they do. If
you think that oil companies do not have such power, consider that Exxon Mobil is larger than the economies
of 180 nations ((Speth 2008) p. 62). It has great power, and uses it to fight government regulation and
oversight.
In contrast to oil companies, the insurance industry has accepted the reality of GCC and is actively
lobbying Congress to enact legislation to fight AGW. They recognize that AGW can increase the frequency and
intensity of tropical storms, cause loss of shore-front homes due to a sea level rise, increase the spread of
disease, and reduce agricultural productivity, all which represent financial risk to insurers. Insurance
companies are currently hurting financially due to increase in the number of failed states and the effects of
AGW (Steffen 2006).
Because insurance companies will be among the first to pay the consequences of change, they are less
likely to let ideology compromise the accuracy of their risk assessments. Insurance is a hedge against
unexpected change, so when unexpected change occurs insurance companies lose. Thus, insurance companies
want to reduce uncertainties in their models of the future and prevent the probability of catastrophic events
from increasing by eliminating or reducing the rate of AGW. AGW presents high risk to insurance companies
due to loss of coastal properties resulting from sea level rise, and possible increased losses due to more severe
weather events.
The approach that government and many people take to climate change is similar to the approach they
take when driving in a lane that is about to close. Prudent people change lanes when they see a warning sign.
The probability that they can change lanes without slowing is high because they have much time and therefore
opportunities to change lanes. However, some people won't change lanes until they are forced to when their
lane ends. Because they didn’t use the warning sign, they have only one chance to change lanes. The
probability of their being able to change lanes without slowing or stopping is low. They may find it very
difficult to change lanes and get back up to speed. They may even get into an accident. By ignoring warnings
they miss most of the opportunities to make change easy. Likewise, if we keep driving down the same path and
don't heed the warning signs about AGW, we will miss most of the opportunities to make change easy. As a
result, we may be forced to slow drastically (greatly decrease our consumption rates and quality of life) to make
the necessary changes.
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The lack of an adequate response to the threat of AGW is similar to the response to the early warnings
of environmentalists. For example, the authors of the Limits to Growth series of books have warned the public
every decade about the dangers of ecological overshoot and the potential for societal collapse by the middle of
the 21st century. Critics responded that we don’t need to worry, but as evidence mounted supporting the claims
of environmentalists the critics changed their reasons not to worry (see Chpt. 1). It is the same story with
climate contrarians, who have stated:
(Late 1990s): GW is not happening.
(Early 2000s): GW is happening, but humans are not responsible.
(Late 2000s): Humans are responsible, but AGW is not a serious problem.
Soon they will say:
(Early 2010s): AGW is a serious problem, but it’s too late to do anything.
People who say that we don't have to worry about making changes to the earth, or that the changes we
make may even prove beneficial, should think of this analogy: the earth is a complex system that we don't
understand. Making changes to it without knowing the consequences is like an untrained mechanic bashing
the working engine of a flawless Ferrari with a wrench in hopes of improving its performance. The Ferrari is a
complex system of working parts, and almost any change will have deleterious effects. In fact, breaking one
part of the engine can lead to other parts breaking down if it is kept operating (and we can't stop the earth
system from operating to repair it). Our tweaking of the much more complex earth system, with its many
working connected parts, could lead to the failure of individual parts or complete subsystems (atmospheric or
oceanic circulation patterns, ecosystems, etc.). The precautionary principle states that we would be unwise to
make global-scale changes without having any idea of what the consequences will be. As Donald Rumsfeld
said, “there are the known knowns, the known unknowns, and the unknown unknowns.” For global climate,
we know there are known unknowns, and almost certainly there are unknown unknowns.
It’s time to end the denial and take action. An April 2006 poll showed that 70% of Americans are
willing to make sacrifices to stop global warming, but the federal government did nothing. Due to inaction by
the federal government during the Bush administration, state and local governments stepped in to fill the
leadership vacuum. In 2005 Seattle mayor Greg Nickels committed the city of Seattle to the Kyoto protocol's
goal of reducing emissions to 1990 levels, and challenged the mayors of other cities to make the same
commitment. As of May 2006, 230 cities made this commitment, and "the US Conference of Mayors
unanimously endorsed the concept" ((Steffen 2006), p. 512). Our federal government needs to invest in
insurance against global warming. We spend trillions of dollars per year for national defense as an insurance
policy against external aggression, but we spend zero dollars to insure ourselves against the threats posed by
global warming (Pollack 2005). Here, the old adage “An ounce of prevention is worth a pound of cure” is
appropriate: it is usually a lot cheaper to prevent a problem than to deal later with its consequences. The
sustainability perspective says that we should apply the precautionary principle when making decisions
involving global risks. Decisions to take preventive actions sometimes can’t wait for conclusive scientific proof.
Each of us needs to educate the public about the threat of GCC. If a contrarian challenges your view on
AGW a good response is “my opinion on AGW is based on science. What is your opinion based on?” Many
good talking points are presented on the web site “How to Talk to a Climate Skeptic: Responses to the most
common skeptical arguments on global warming” at http://www.grist.org/article/series/skeptics/. For a
comprehensive set of video rebuttals of climate contrarian claims see videos posted to www.youtube.com by
greenman3610.
Example of a False Controversy Generated by Contrarians
In early 2010 two snowstorms hit the US east coast, and climate change contrarians touted them as
proof that the theory of global warming is incorrect. The focus was on Washington, D.C., because that's where
media people and contrarian politicians are concentrated. Here I examine the many errors associated with
this line of thinking.
First, contrarians argued that snow equals cold, and therefore that an unusually large amount of snow
means unusually cold. Of course this is a logical fallacy: anyone who has lived in a snow-prone area like my
hometown of Buffalo, N.Y. knows that unusually cold means less snow, because very cold air holds less
moisture. Large snowfalls are usually associated with warm, moisture-rich air. Washington, D.C. is usually
cold enough in January and February to snow, so what was unusual was how much snow fell, not how cold it
was. Thus, people were confusing precipitation and temperature. In fact, the theory of global warming
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predicts more intense storms, because the atmosphere has more energy, and greater amounts of precipitation,
because the atmosphere is warmer and therefore can hold more moisture. One study concluded that most
snowstorms in the US between 1901 and 200 occurred in warmer-than-normal years (Changnon, Changnon et
al. 2006). The storms on the east coast resulted from warm moist air from the Gulf of Mexico moving
northeast and hitting cold dry air from Canada xxvii. This caused the warm moist air to cool, and because cold air
can hold less moisture than warm air, the excess moisture fell as snow. Scientists expected this because El
Nino, which was active off the US west coast, typically causes more precipitation in the southern and eastern
US xxviii.
Contrarians were also confusing local and global. They were committing the logical fallacy of
overgeneralizing when they inferred from observations on the US east coast the condition of weather globally.
They don't seem to understand that it's possible to be unusually cold in some areas but unusually hot in the
rest. In fact, in December 2009 it was unusually cold in the US and Siberia, but unusually warm in the rest of
the world.
Finally, contrarians were confusing weather and climate. On the short term of weather, having
unusually cold temperatures for days or weeks is entirely possible; warming just makes it less probable. Yet
over the long term of climate (years, centuries, millennia) the trend is toward increasing average global
temperatures. So when arguing that snowstorms on the US east coast refute global warming, contrarians were
confusing precipitation and temperature, local and global, weather and climate. Is it possible to get more
confused about global climate change xxix?
Solutions
"We can evade reality, but we cannot evade the consequences of evading reality." — Ayn Rand
The lack of agreement on cause and effects of global warming has slowed society’s response to a
potentially terrible threat. We have known for decades that AGW is a potentially serious global threat, but we
have not stopped its cause, emission of CO2 during burning of fossil fuels. Instead we have increased the rate of
CO2 emissions. Lack of action on climate mitigation has reduced our security and the security of future
generations.
Humanity’s carbon footprint makes up about half the world’s ecological footprint (Hill and O'Neill
2008). Our carbon emissions are disrupting climate and damaging ecosystem services. Now we are
approaching what scientists believe are dangerously high levels of CO2 in the atmosphere. We must consider
from a sustainability perspective the potential impacts to future generations before we choose to continue
emitting greenhouse gases. The sooner we act to reduce greenhouse gas emissions, the less severe the
consequences will be, and the less expensive the solutions will be.
Public opposition to the scientific consensus on AGW is rooted in the fear that mitigation measures will
be costly and therefore harmful to the economy. Sustainability thinking is useful for putting this potential
roadblock into perspective. Sustainability requires that we meet present needs without compromising the
ability of future generations to meet their own needs, and that we do so by preserving economic, social, and
environmental capital. Let’s examine whether we currently meet these requirements on the issue of AGW.
Because of AGW, global temperature is changing faster than any time in the earth’s past. If continued,
changes in global temperature will outpace the ability of plants and animals to adapt by migration and
evolution. AGW is altering global ecosystems and causing increasing rates of species extinctions. The resulting
loss of species and ecosystem services will make it harder for future generations to meet their needs.
Sustainability thinking suggests that we must act to preserve environmental capital and protect ecosystem
services.
AGW is putting millions of the world’s most vulnerable citizens at risk. Residents of low-lying coastal
communities face having to abandon their ancestral homes due to sea level rise and groundwater salinization.
Humans can probably adapt through use of technology. However, most cannot afford the costs of these
technologies, so the death rate in poor undeveloped countries is and will likely continue increasing. Americans
can afford air conditioners, imported food, bottled water, and seawalls. This is a great injustice of global
warming: those most responsible for global warming (e.g., US citizens) are likely to suffer the least from it.
Distributional equity requires that we preserve social capital by reducing these risks and compensating those
affected.
Finally, the consequences of AGW will be felt most strongly by future generations. Intergenerational
equity compels us to combat AGW to protect the interests of our descendants. We may be making many areas
of the earth uninhabitable for our offspring. Almost certainly, life will be more difficult for the next generation.
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We will burden them with the consequences of global warming, an enormous financial debt (witness the
exploding budget deficit of the federal government), and shortages in key resources such as oil. The current
generation must look for ways to soften the blow to our offspring from our actions and decisions. Most parents
make sacrifices for their children’s welfare. Truly responsible parents also make sacrifices for their children’s
future (e.g., saving money for them to go to college). We must now make other kinds of sacrifices, ones that
will make our lifestyles more sustainable and therefore easier for our children to maintain in the future. To
reduce the effects of climate change, we must decrease emissions of CO2.
We must act to preserve social and environmental capital and protect present and future citizens of the
earth by taking drastic steps to mitigate AGW, even if it means losing some economic capital. However, many
steps that we can take to mitigate AGW can save money. Clearly these are the steps we must first focus on.
To reduce climate impacts in the future we will need to use three primary approaches: mitigation,
regulation, and adaptation. It doesn't matter whether humans caused global warming; we still have to deal
with the consequences through mitigation, regulation, and adaptation. The risk of underreacting to the threat
of global warming is much greater than the risk of overreacting.
Mitigation
In this book we will look at a variety of methods to combat AGW. We are already actively intervening in
the earth's climate system. At first our intervention was unknowing, but now we know that we are adding
greenhouse gases to the atmosphere, and we are starting to manage or regulate the composition of the
atmosphere so that earth's climate will stay within the narrow range of conditions that have allowed us to
prosper as a species. Through its 4.5 billion year history earth was inhospitable to us more often than not, so
we must make every effort to keep it hospitable by stopping AGW. The terminology in this area is still evolving,
so we will carefully explain our use of terms. Climate change mitigation approaches reduce radiative
forcing, the amount of solar energy per unit area that enters and gets trapped in the atmosphere. Radiative
forcing can be reduced by reducing atmospheric concentrations of greenhouse gases and by reducing the
amount of solar energy that enters the atmosphere. Geoengineering is a climate change mitigation approach
that actively intervenes in the climate system by using greenhouse gas remediation methods to remove
greenhouse gases from the atmosphere or by using solar radiation management (SRM) to reflect sunlight.
Remember that geoengineering is a specific type of climate change mitigation, and includes the even more
specific SRM and greenhouse gas remediation methods.
The most effective climate change mitigation approaches that reduce greenhouse gas sources include
reversing the trend of deforestation, increasing energy efficiency, and transitioning from conventional fossil
fuel power plants to low greenhouse gas emission plants that use either renewable energy sources (WWS) or
fossil fuels coupled with CCS. Greenhouse gas remediation increases greenhouse gas sinks, extracting
greenhouse gases from the atmosphere using trees, chemical pumps, ocean nourishment, or enhanced
weathering of rocks. Of these, afforestation and fertilization of the ocean with iron to grow CO2-eating plankton
are the most promising methods xxx. SRM is a more intrusive approach that can only be performed globally and
has higher costs and risks. It is considered a method of last resort because it is likely to have unintended
consequences, but it has the advantage that it can mitigate AGW faster than greenhouse gas remediation, so it
could be used in the case of a planetary emergency. The leading candidate for SRM proposed by Nobel laureate
Paul Crutzen would use stratospheric aerosol particles to reflect sunlight (Flannery 2008). Injecting sulfur
dioxide into the stratosphere would form sulfate aerosols that reflect sunlight. When Mt. Pinatubo erupted in
1991, it injected 20 million tons of SO2 into the atmosphere, causing the earth to cool 0.5°C (0.9°F) for a year or
so. An unwanted side effect is that sulfates destroy stratospheric ozone, which increases ground levels of
harmful ultraviolet radiation.
Climate change mitigation represents a huge business opportunity. Research in the public and private
sectors is needed to develop new, effective geoengineering technologies. The federal government has put the
US at a disadvantage by not creating a domestic carbon market. European countries adopted the Kyoto
protocol and created a carbon trading system that puts a price on carbon emissions. Carbon-emitting
companies and countries are purchasing technological tools for greenhouse gas remediation in order to offset
their emissions. Domestic entrepreneurs and companies are much less likely to develop new technologies
without the incentive of a domestic market. The US must adopt a carbon trading scheme to become a player in
this new market sector. We are rapidly falling behind while members of Congress argue about a scientific issue
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that has already been resolved. Opponents argue that adopting a carbon trading system will hurt the economy,
but in reality we are missing the opportunity to add a whole new sector to our economy.
In 2009 the US Global Change Research Program (USGCRP) published an important report titled
"Global Climate Change Impacts in the United States" (Karl, Melillo et al. 2009). This report evaluated the
potential effects of climate change on various regions and economic sectors in the US. It also evaluated current
and potential future responses to climate change, which fall under the categories of mitigation and adaptation.
As noted in the report, "these two types of responses are linked in that more effective mitigation measures
reduce the amount of climate change, and therefore the need for adaptation."
Mitigation aims to reduce GCC by reducing greenhouse gas emissions and removing greenhouse gases
from the atmosphere (Karl, Melillo et al. 2009). Scientists believe that a temperature increase of more than
2°C above preindustrial levels may greatly increase risk. Thus, the objective of mitigation is to keep greenhouse
gas concentrations from increasing above 450-500 ppm CO2e (CO2e reached 455 ppm in 2005). This goal is
similar to preventing the doubling of atmospheric CO2 concentration from the preindustrial level of 280 ppm
to 560 ppm. However, if we continue Business As Usual (BAU) and don’t take steps to reduce greenhouse gas
emissions, CO2e is likely to reach 550-650 ppm by 2050, corresponding to a 3°C increase (Dawson and
Spannagle 2009; Mann and Kump 2009). Thus, we must start reducing greenhouse gas emissions now.
Mitigation steps taken early have a greater effect in reducing climate change than comparable reductions made
later (Karl, Melillo et al. 2009). Economist Nicolas Stern estimated the cost of mitigating climate change to be
~2% of GWP xxxi, corresponding to a total cost of $1.3 trillion or $210 per capita in 2008. Stern warned that this
was much less than the cost of inaction. Reducing emission of greenhouse gases other than CO2 will help, but
CO2 has the largest climate impact of the greenhouse gases (Figure 3), so we will focus on mitigation of CO2.
Reducing Carbon Emissions
What are the most effective mitigation options for reducing CO2 emissions? Energy use is responsible
for 70% of greenhouse gas emissions (Richter 2010). To reduce energy-related greenhouse gas emissions we
must reduce the use of fossil fuels, particularly coal, that emit large amounts of CO2 per unit energy. Old,
polluting coal-fired power plants should either be retrofitted for Carbon Capture and Storage (CCS) or replaced
with power sources that emit little CO2 such as wind, solar, geothermal, and possibly nuclear. Second, we must
reduce overall energy use through conservation and increased efficiency, not just in homes, which only emit
17% of greenhouse gases in the US, but also in industry (30%), transportation (28%), commercial (17%), and
agriculture (8%). Third, we must discourage deforestation, as it changes a carbon sink into a carbon source
and is responsible for ~30% of greenhouse gas emissions (Richter 2010).
Socolow and Pacala (2004) devised a popular graphical approach to formulating policies for carbon
mitigation xxxii. In the recent past, BAU annual increases were 1.5% for carbon emissions, 2% for primary energy
consumption, and 3% for Gross World Product (GWP). The stated objective is to keep atmospheric CO2 from
doubling in concentration from the preindustrial level of 280 ppm to 560 ppm (the current level is 386 ppm).
The plan they present would hold carbon emissions at the current level of 7 billion tons of carbon per year
(GtC/y) for the next 50 years and stabilize atmospheric CO2 concentration at 500 ppm. Socolow and Pacala
(2004) divided the growing gap between future BAU emissions and the desired flat emissions trajectory (7
GtC/y) into stabilization wedges (Figure 7). They offered 15 possible mitigation steps or “wedges” that use
existing technologies to fill the gap (Table 5.1). They are not the only options, but are presented as examples.
Each emission reduction wedge starts at zero in 2005 and increases linearly until it reaches 1 Gt C/y of reduced
carbon emissions in 2055. Over that 50-year period each wedge would prevent the emission of 25 Gt of carbon.
We need at least eight wedges to achieve the desired reduction in carbon emissions (Friedman (2008) pp. 211213). Adding those wedges we obtain a “stabilization triangle,” located between the desired flat trajectory and
BAU, that removes exactly one third BAU emissions between 2005 and 2055 and one half BAU emissions in
the year 2055. Some wedges represent carbon-free or reduced carbon energy sources, and others are "invisible
energy," i.e., reduction of carbon emissions through conservation and efficiency measures. The reduction in
carbon emissions must add up to at least 200 billion tons by mid-century. We would use new technologies in
the second half of the 21st century to decrease net emissions, eventually to zero. If we delay action and
continue BAU, annual carbon emissions will double by 2055 and atmospheric CO2 concentration will be triple
the preindustrial value.
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Figure 7. The carbon emission stabilization wedges of Socolow and Pacala (2004).The stabilization triange
shaded green is comprised of eight stabilization wedges. From https://www.eeducation.psu.edu/egee401/content/p10_p3.html
Table 5.1: Carbon Emission Stabilization Wedges xxxiii
Energy efficiency and conservation:
1.
Efficient vehicles: Increase fuel economy for 2 billion cars from 30 to 60 mpg.
2.
Reduced use of vehicles: Decrease the number of car miles traveled by half.
3.
Efficient buildings: Use best efficiency practices in all residential and commercial buildings.
4.
Efficient baseload coal plants: Produce current coal-based electricity with twice today’s
efficiency.
Fuel substitution:
5.
Replace 1400 coal electric plants with natural gas-powered facilities.
CO2 Capture and Storage (CCS):
6.
Capture AND store emissions from 800 coal electric plants.
7.
Produce hydrogen from coal at six times today's rate AND store the captured CO2.
8.
Capture carbon from 180 coal-to-synfuels plants AND store the CO2.
Nuclear fission:
9.
Add double the current global nuclear capacity to replace coal-based electricity.
Renewable electricity and fuels:
10.
Wind: Increase wind electricity capacity by 15 times relative to today, for a total of 2 million
large windmills.
11.
Solar: Install 350 times the current capacity of solar electricity.
12.
Solar: Use 40,000 square kilometers of solar panels (or 4 million windmills) to produce
hydrogen for fuel cell cars.
13.
Biofuels: Increase ethanol production 15 times by creating biomass plantations with area equal
to 1/6th of world cropland.
Natural sinks:
14.
Eliminate tropical deforestation.
15.
Adopt conservation tillage in all agricultural soils worldwide.
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The study of Socolow and Pacala (2004) did not estimate the cost of each carbon emission stabilization
wedge. Studies by McKinsey and Company xxxiv have shown that many greenhouse gas abatement options have
negative costs, meaning we can save money by adopting them. The most recent version of the now famous
“global greenhouse gas abatement cost curve” shows that 35% of identified greenhouse gas abatement
strategies have negative costs (Figure 8). For example, switching residential lighting from incandescent or
halogen to CFL or LED has large negative costs, meaning that by switching we can save money while reducing
greenhouse gas emissions. Furthermore, it’s easy to switch from incandescent to CFLs, making this a good
example of the “low hanging fruit” that our society must focus on first if we are serious about reducing
greenhouse gas emissions (Dietz, Gardner et al. 2009). A total of 75% of abatement strategies cost less than
€20 ($27 USD.) per ton CO2e (Enkvist, Dinkel et al. 2010). This is close to the Obama administration’s current
(and very low) estimate of the social cost of carbon xxxv, which is the marginal cost of emitting one ton of CO2e.
Over time the social cost of carbon will rise as temperatures rise, and even more abatement strategies will
become profitable when considering social costs. Since 35% of abatement strategies are already economically
profitable, the US has no excuse to continue dragging its feet on climate change mitigation measures. We
should adopt abatement strategies with cost savings quickly to reduce climate change risks and save money.
McKinsey and Company estimate that it would take only 0.6% of the world’s GDP to reduce greenhouse gas
emissions so that CO2e never rises above 450 ppm (Creyts 2007).
Figure 8. The cost of various greenhouse gas abatement (mitigation) strategies per ton of CO2e in euros in
2010 compared to business as usual "BAU." From Enkvist et al. (2010), Global GHG abatement cost curve v. 2.1,
McKinsey & Company.
We can also take steps as individuals to reduce carbon emissions and mitigate GCC. The following steps
reduce carbon emissions through conservation and increased efficiency:
• Use mass transit, bike, walk, roller skate.
• Buy water-saving appliances and toilets; installing low-flow shower heads.
• Tune up your furnace.
• Caulk, weatherstrip, insulate, and replace old windows.
• Unplug appliances or plug into a power strip and switch it off.
• Buy products with a US EPA Energy Star label.
Removing Carbon from the Atmosphere: Geoengineering
An alternative to preventing carbon emissions is to remove carbon from the atmosphere. Because this
would involve global-scale changes in the earth system, we call this approach geoengineering. The problem
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with geoengineering is that we are experimenting with a complex system that we don’t fully understand. Each
geoengineering option is likely to have unintended consequences, and it’s possible that none of them may be
effective. In 2010 Congress debated expanding research on geoengineering, though most of the representatives
don’t think AGW is serious enough to reduce carbon emissions. They will do nothing to mitigate climate
change, but now they want to skip that step and go straight to remediation. As observed by Richter (2010)
“…large-scale technical intervention in the climate system can have large-scale unintended consequences; it is
not smart to count on introducing new effects you don’t fully understand to cancel another effect you do not
fully understand. Doing two dumb things rarely gives a smart result.”
Capturing carbon from thin air is very expensive, but it may be our last line of defense (MacKay 2009).
The laws of Physics say that to remove CO2 from the air, concentrate and compress it requires at least 0.2
kWh/kg CO2 xxxvi. Given an average efficiency of 35%, the required amount of energy increases to 0.55 kWh/kg
CO2. Americans emit ~60 kg CO2/d, so removal of CO2 from the atmosphere would require a minimum of 33
kWh/d per person, about 13% of our average energy consumption of 250 kWh/d per person.
Geoengineering approaches for removing CO2 from the atmosphere fall into the following four
categories (MacKay 2009):
1.
Chemical pumps: As of 2005 it cost 200 kWh/d to remove each American’s output of 60 kg
CO2/d, equivalent to 80% of the average amount of energy we use.
2.
Trees are “carbon-capture facilities powered by built-in power stations.” However, burning or
decomposition usually returns the carbon stored in trees to the atmosphere. Trees can only
sequester carbon permanently if we bury them in the ground. This would require country-sized
facilities.
3.
Enhanced weathering of rocks: Silicate weathering and subsequent carbonate precipitation
in the oceans sequesters about 0.7 Gt CO2/y. Human emit about 28 Gt CO2/y, about 40 times as
much CO2. We could increase the rate of geologic sequestration by pulverizing rocks with
appropriate mineralogy xxxvii and spreading the powder on the ground. This would require about
0.04 kWh/kg CO2 to pulverize the rock, so it is an energy-efficient process, but again it would
require country-sized facilities.
4.
Ocean nourishment: Fertilize the fish-poor parts of the oceans with nitrogen as urea (or
iron?) to feed marine plankton, expanding the base of the food chain and producing more fish as a
by-product. Carbon would be removed from the atmosphere because much of the plankton gets
buried in marine sediments. Inexpensive.
Options (1) and (2) rely on burying organic matter before it has a chance to decompose and return CO2
to the atmosphere. Paper shredding is an example of a “green” practice that misses a chance to mitigate GCC.
Paper shredding is sold as being green because it helps paper decompose faster. However, we don't want paper
to decompose fast; we want to store organic matter like paper in the ground for as long as possible because it
sequesters carbon. Instead we should use pyrolysis to convert as much organic matter as possible into inert
biochar for use as a soil amendment. A permanent pyrolysis machine should be set up at every wastewater
treatment facility to convert sewage into biochar; this avoids the problem of biohazards in sewer sludge
because all living organisms are killed during the high-temperature pyrolysis process. All municipalities should
buy portable pyrolysis machines to collect and convert yard biomass into biochar.
Because all geoengineering choices are likely to have unintended consequences, society should only use
them when a climate catastrophe strikes, such as when the global climate system passes a tipping point. We
must mitigate carbon emissions before we consider geoengineering options. However, we should be
researching geoengineering options now so that we will be prepared if a climate catastrophe strikes.
Regulation
Domestic regulation
The two principal market-based policy instruments for mitigating greenhouse gas emissions are
emissions trading (cap and trade) and carbon taxes (Dawson and Spannagle 2009). Market-based
instruments, particularly emissions trading, have become favored over traditional regulatory approaches such
as command-and-control. They provide flexibility, allowing the market to decide the most cost-effective
approaches to reducing emissions, and therefore achieve emissions reductions at lower cost. Emission trading
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involves setting an upper limit to emissions (the cap), and then giving emitters tradable emissions allowances.
Traders buy and sell allowances as commodities, and the commodity market determines the price of an
emission allowance. Those who emit more must purchase emission allowances from those who emit less,
providing a financial incentive to reduce emissions. This approach was first shown to work effectively in the
1990's by the US Sulphur Dioxide (SO2) Allowance Trading System. The European Union Emissions Trading
System began operating in 2004, and is now part of a global carbon-trading market.
In an emission trading scheme, the government sets the allowable emissions amount, and the market
sets the emissions cost. In an emission tax system the government sets the emissions cost, and the market
determines the emissions amount. Since the objective of greenhouse gas emission regulations is to hold
atmospheric CO2 concentration to below 450 ppm, which sets an upper limit to CO2 emissions, an emission
trading scheme is preferable. It is also preferable because emission trading is more effective when regulating a
few large emitters (power plants). Carbon taxes work better for many small emitters, which makes imposing
high gas taxes a good approach to limiting CO2 emissions from automobiles.
As of March 2011 the US Congress has failed to pass any cap and trade legislation. Sensing that the
legislative process had stalled, President Obama directed the EPA to start regulating CO2 as a pollutant. The
Supreme Court considered a challenge to this policy and ruled that CO2 is a pollutant, and therefore the EPA
has the power to regulate CO2 emissions. Having failed in the judicial branch, House Republicans are now
trying to pass legislation to prevent EPA from regulating CO2 emissions. Carbon dioxide is invisible, tasteless,
and odorless, which is partly why some people object to calling it a pollutant. However, we define a pollutant
as any compound that human activities cause to increase above the natural background level and that is
potentially harmful to humans or other species. Carbon dioxide clearly meets these criteria.
It's urgent that we begin a carbon cap and trade system now. Soon the price of oil and gas will rise, and
consumers will turn to cheaper forms of energy. If we don't eliminate industry subsidies and incorporate
externalities so that the price of coal accurately measures its cost, then consumers will turn to coal as the cheap
but dirty alternative, and AGW will spiral out of control xxxviii.
Richter (2010) notes that “the consequences (of AGW) are in the future while action has to begin in the
present, and that creates difficult political problems for all nations because the costs are now, whereas the
benefits will come later…The longer we wait (to reduce emissions), the harder it will be to solve the problem,
because the emissions will be larger and reductions will have to be larger, faster, and more expensive." Most
economists agree that AGW will harm not only ecology but also the economy, and therefore that society must
make investments to prevent future harm. They also agree that the cost is paid most fairly and effectively by
internalizing the external costs of activities that emit greenhouse gases. What is debated is how fast we should
act. Should we accept responsibility for our actions now, or leave that burden to future generations? How much
should we spend now on climate change mitigation? These questions have led to the development of two
competing schools of thought led by William Nordhaus from Yale University and Sir Nicholas Stern of the
London School of Economics. Both use very complicated models that produce the same results if given the
same assumptions. The two groups arrive at different conclusions largely due to their subjectively using
different values of the discount rate, which is the present value of a future cost. Both Nordhaus and Stern
estimate the cost of future harm from AGW, and then use their preferred discount rate to estimate how much
money we should invest now to offset that cost and break even. The discount rate actually consists of two parts,
a wealth factor that accounts for changes in per capita income over time and can be extrapolated from
historical data, and the social discount rate, which is a subjective measure of how important it is to ensure the
well-being of future generations. Sustainability requires that we use a low discount rate to ensure
intergenerational equity, which is the approach Stern takes. A low discount rate requires that we spend more
money now to reduce harm to future generations. In contrast, Nordhaus effectively discounts future
generations by using a high social discount rate of 4%. As an example of how choosing a high discount rate
makes a large problem appear small, to have $1 in 100 years with a 5% discount rate you need only invest $0.01
today. Thus, the Nordhaus school concludes that we don’t have to act now because we will have so much
money in the future that we will easily be able to deal with AGW. This is the conclusion that free market
enthusiasts in the Republican party like, and it is the primary reason that they are employing every conceivable
means to avoid paying the costs now, including denying the existence of global warming. Proponents of the
Nordhaus school are betting that the economy will grow faster than the cost of climate change mitigation, and
that we will always be able to counteract the effects of AGW. If we lose that gamble, it will be future generations
that will pay the consequences. I believe that discounting the needs of our offspring in this way is
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irresponsible, immoral, and inconsistent with the principles of sustainability. Nate Lewis, a Chemistry
Professor at Caltech, puts the economist’s approach into perspective: “I haven’t talked much about economics,
but I will say that it’s easy to prove, thinking 100 years out, on a risk-adjusted net-present-value basis, that the
earth is simply not worth saving. It’s a fully depreciated, four-billion-year-old asset. Unless you have policy
incentives that reflect the true cost of doing this experiment, the economically efficient thing to do is just what
we are doing now xxxix.”
International Regulation
The US government has only recently acknowledged that human activity is the main cause of global
warming, but has done little to address the problem. Members of the US Congress have been unable to agree on
a climate mitigation plan, or even on whether we need one. It is that much harder to get all of the world’s
major countries to sign an international agreement to reduce carbon emissions. Most governments agree we
have a problem, but don’t agree on how to deal with it.
Citizens of most countries in the world burn fossil fuels for energy. All countries profit economically
from burning fossil fuels and emitting carbon. So how can they all agree to limit carbon emissions? We call
one barrier to agreement the Tragedy of the Unmanaged Commons. It says that profit-seeking individuals use
shared resources unsustainably by completely consuming them or hopelessly polluting them. Because each
individual earns a greater profit if they put the resource to greater use, and society penalizes no one for using
more than their neighbors, there is no incentive to preserve the resource. Countries do not want to sign an
international agreement that limits their ability to make profits from putting CO2 into the atmosphere. Yet
every country knows that unregulated CO2 emissions will likely harm future generations. How much are we
willing to discount the needs of future generations? Humanity must use smart management of shared
resources like the atmosphere to prevent individuals from consuming or destroying them in an economic “free
for all.”
The United Nations Framework Convention on Climate Change (UNFCCC) took the first step toward
smart management of the atmosphere as a shared resource by adopting the Kyoto protocol in 1997. This
protocol called for a reduction in emission of four greenhouse gases, carbon dioxide, methane, nitrous oxide,
and sulfur hexafluoride, and two groups of gases, hydrofluorocarbons and perfluorocarbons. The 1987
Montreal protocol and subsequent stricter amendments already restricted emission of chlorofluorocarbons,
another group of greenhouse gases. By July 2010 191 countries had signed the Kyoto protocol. Although the US
was the world’s largest emitter of greenhouse gases in 1997, it never signed the protocol.
Disputed between developed and developing countries have prevented further progress in international
negotiations to adopt a successor to the Kyoto protocol. Developing countries like China argue that developed
countries have historically emitted greater amounts of CO2, and therefore they should be primarily responsible
for mitigating GCC. Burning fossil fuels made the developed countries wealthy, and now the developing
countries want to follow the same path. Developing countries rightly claim that restricting their ability to
develop and achieve the prosperity attained by developed countries is unfair. However, this argument has
several problems. First, developing countries don’t need to burn fossil fuels to reach the same level of wealth as
the developed countries. They can skip the “fossil fuel” stage of development and go directly to the future of
energy production by building power plants that use renewable energy sources (solar, wind, and geothermal)
and by building smart grids. Technological leapfrogging can give developing countries a big advantage over
developed countries that now have outdated energy infrastructures.
Another problem with developing countries’ argument that they should not have to restrict their carbon
emissions is that “according to projections, the developing world will add as much greenhouse gas to the
atmosphere in this century as the industrialized nations will have contributed in the 300 years from 1800 to
2100 (Richter 2010).” We will have a global climate disaster if the developing world doesn’t take steps to slow
growth in carbon emissions.
These arguments have led to the development of an impasse between developing countries with
growing economies, primarily China, and developed countries. China argues that as a developing country it
should not have to restrict carbon emissions, but developed countries like the US say it would not be fair to ask
the developed countries alone to be responsible for climate mitigation. China’s argument no longer makes
sense because it is now the largest carbon emitter in the world. The developed countries cannot solve this
problem alone, so developing countries must be part of the solution. A potential compromise is to have
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developed countries do more initially since they have the resources, and over time have the developing
countries adopt emission standards that increase until they are equal to those of the developed countries.
Developed countries should use their wealth now to develop needed technologies and share them with
countries in the developing world to help them meet these standards (Richter 2010).
Adaptation
If mitigation is insufficient to prevent the harmful effects of AGW, we will be forced to adapt to a new
environment. The further temperature increases, the harder it will become to adapt. Large, rapid climate
changes are likely to affect humans and ecosystems adversely and possibly catastrophically. According to
Dawson and Spannagle (2009), “the extent and severity of climate change impacts rise nonlinearly with global
temperature increases.” Here we will focus on a few potential examples of adaptation by humans, recognizing
that all species will be forced to adapt, and that most species will not adapt as well as humans and may
therefore become extinct.
The objective of adaptation is to reduce risk associated with climate change. Anticipating all of the
potential types of adaptation that humans will employ in the future is impossible. Perhaps the most common
form of adaptation will be migration. Rising sea level and increasing storm strength will force seaside
communities to migrate landward. People will also migrate away from regions that experience severe drought
or food shortages. Environmental refugees will become commonplace across the world.
The type of adaptation will depend on how climate change is manifested in a specific region. Thus,
adaptation responses will vary by region. Currently warming is currently strongest at high latitudes, where
agricultural yields will likely increase as growing seasons lengthen (Dawson and Spannagle 2009). However, at
low latitudes temperatures may increase to levels beyond the capacity of ecosystems, agricultural systems, and
humans to adapt. Reduced crop yields may result in widespread starvation. Farmers will need to adapt by
switching to heat-resistant crops, and in areas of drought they will need to adopt rainwater harvesting, drip
irrigation, and drought-resistant crops.
As noted by Karl et al. (2009) “there are limits to how much adaptation can achieve. Humans have
adapted to changing climatic conditions in the past, but in the future, adaptations will be particularly
challenging because society won’t be adapting to a new steady state but rather to a rapidly moving target.
Climate will be continually changing, moving at a relatively rapid rate, outside the range to which society has
adapted in the past." Societies and communities will adapt more effectively if they adopt an effective decisionmaking process (Figure 9). The main phases of the decision-making process include understanding the
problem, planning adaptation actions, choosing the best action, and managing the application of the chosen
action (Moser and Ekstrom 2010). This process is most likely to be effective if it involves affected stakeholders,
requires a consensus on chosen actions, and considers all dimensions of the problem including economic,
social, and environmental. Individuals and communities that anticipate the risks associated with climate
change and respond by becoming more sustainable and self-reliant will be better prepared to adapt when it
becomes necessary.
Figure 9. Phases and subprocesses throughout the adaptation process. From Moser et al. (2010).
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Parallels between the greenhouse gas -AGW and chlorofluorocarbon (CFC) - ozone hole problems
The development of the greenhouse gas - AGW problem closely parallels that of the chlorofluorocarbon
(CFC) - ozone hole issue (see Meadows et al. (2004) Chpt. 5 for a full account). Initially industry and the
government disputed the scientific claim that CFCs destroy ozone, saying scientists and environmentalists were
being alarmists. Publication in 1987 of the smoking gun proving the link between CFCs and ozone destruction
finally silenced the skeptics xl. Due to industry opposition, the government didn't ban CFCs in aerosols, so the
public voted with their wallets and stopped buying aerosol cans, which greatly decreased the production of
CFCs in 1974. Industry said it would be too expensive to find and deploy substitutes. In the end phasing out
CFCs was much less expensive and disruptive than predicted by skeptics and industry (about $40 billion
globally). Only when a crisis was reached, the discovery of the ozone hole in 1985, did the government take
action and sign the Montreal Protocol in 1987. They acted even though our knowledge of how CFCs created the
ozone hole was imperfect. Perfect knowledge or scientific proof are not necessary for action. This crisis was
scary because it was the first time that the public recognized that we could change the earth on a global scale,
and that those changes could endanger us. Developing countries such as China refused to sign the protocol
unless developed countries shared technical knowledge and established an international fund to ease the
transition away from CFCs. The US initially balked, but then signed a stricter protocol in London in 1990. The
industrializing countries (China, India) later signed on. Finally, when the ozone hole problem grew beyond
expectations, governments revised the Montreal protocol with stricter limits in London (1990), Copenhagen
(1992), Vienna (1995), and Montreal (1997). Scientists later found that the 1987 and 1990 emission limits were
inadequate, i.e., the stratospheric concentrations of chlorine and bromine would have continued to increase
without the stricter emission limits adopted later. Scientists now expect the ozone hole to disappear by the
middle of the 21st century.
How did we solve the CFC - ozone problem? By reducing the need for CFCs, adopting temporary
substitutes such as HCFCs, and shifting to alternatives that do not harm the ozone layer (Meadows et al.,
2004). In the process governments learned some valuable lessons about atmospheric pollution and the need
for international regulatory agreements. First, continuous environmental monitoring with quick and honest
reporting of results is essential. Second, the ozone hole and other issues involving environmental regulations
show that industry often exaggerates or overestimates the economic consequences of meeting new
environmental regulations. According to Meadows et al. (2004), the reason is most likely because they
"systematically underestimate the capacity for technological advance and social change." Finally, when
knowledge is incomplete, stakeholders must write environmental agreements flexibly and review them
regularly (Meadows, Randers et al. 2004).
The situation with greenhouse gas emissions is similar. First, scientists learned that CFC emissions
cause stratospheric ozone depletion and that greenhouse gas emissions cause AGW. Fearing that regulations
limiting emissions of CFCs and greenhouse gases might decrease profits, industry disputed the science. The
government caters to industry, so in both cases it ignored the warnings of scientists. Government inaction
caused environmentalists and a concerned public to become increasingly vocal; activists started to organize
protests and boycotts. To date, attempts by the U.N. to forge an international agreement to limits emissions of
CFCs and greenhouse gases have made little progress. Developing countries like China insist that they deserve
lenient or delayed emission limits. They also demand increased access to, and subsidies for, green technologies.
At the U.N. climate conference held in Cancun, Mexico in late 2010 delegates abandoned efforts to negotiate
carbon emission limits due to opposition of developing countries like China, and now are discussing
approaches to setting up a climate fund. Potential solutions include levies on greenhouse gas sources such as
airline travel and gasoline xli.
This is where we are today with the greenhouse gas -AGW problem. I expect that the parallels with the
CFC-ozone hole problem will continue. A crisis will force delegates back to the negotiating table, where they
will hammer out a weak international agreement to limit greenhouse gas emissions. Intensifying AGW will
repeatedly force delegates back to the negotiating table to adopt increasingly strict emission limits.
Conservation, substitution, and shifting to alternatives will reduce greenhouse gas emissions. Transitioning
away from greenhouse gas emitting technologies will be less disruptive and expensive than the business sector
predicted. The successful international response to the CFC-ozone hole problem gives us hope that we can
tackle the greenhouse gas -AGW problem before it is too late.
The only problem is that it's not clear what type of crisis would convince people that AGW is a global
threat. The ozone hole was a visible, global phenomenon that we could not attribute to natural variation or any
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cause other than anthropogenic ozone destruction. In contrast, natural processes could cause all of the
predicted consequences of AGW. The difference is because anthropogenic ozone destruction was caused by a
synthetic chemical that does not occur in nature, that initiated a process (Cl-catalyzed stratospheric ozone
destruction) that does not occur naturally, and that produced an effect (the ozone hole) that does not occur
naturally. Carbon dioxide, on the other hand, occurs naturally, and the process it initiates (greenhouse effect)
and the resulting effects (rising global temperatures, sea level rise, etc.) have occurred naturally in the past.
What effect of AGW could we unambiguously ascribe to AGW rather than natural processes?
Summary
Humans are warming the earth by releasing greenhouse gases during fossil fuel burning and
deforestation. Even ignoring global climate change, these practices are unsustainable and should be phased
out. Atmospheric concentrations of greenhouse gases are now reaching potentially dangerous levels. We must
take global action now to mitigate global climate change and reduce risk to future generations. As an example
of a complete global plan to stabilize climate, Lester Brown’s Plan B (Brown 2011) calls for cutting global net
CO2 emissions 80% by 2020 to keep global atmospheric CO2 concentrations from exceeding 400 ppm, which
would keep temperatures within manageable limits. According to Brown we can accomplish this by raising
energy efficiency, restructuring transportation, replacing fossil fuels with renewable energy sources, ending net
deforestation, and planting trees to sequester carbon (Figure 10).
Figure 10. Plan B Carbon Dioxide emissions reduction goals for 2020.
If we don’t take strong mitigation steps now, anthropogenic global warming will severely compromise
the ability of future generations to meet their needs. The sustainable solution is to stop deforestation and
carbon emissions from fossil fuel burning. In the next chapter we will examine alternatives to fossil fuels and
outline steps to transition to carbon-free renewable energy sources that are sustainable.
Resources: For more information about climate change and global warming see:
RealClimate: Climate Science from Climate Scientists: http://www.realclimate.org/
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i 14C has a half-life of 5700 years, so plant matter that is older than roughly 6 half-lives or 8*5700=45600 years
has essentially no 14C.
ii Note that it is the changing 14C content of the atmosphere that makes accurate 14C dating of material less than
100 years old impossible.
iii see http://www.ted.com/talks/lang/eng/james_balog_time_lapse_proof_of_extreme_ice_loss.html
iv See http://palaeo.gly.bris.ac.uk/communication/Willson/isotopeevidence.html for a good explanation.
v Some confusion about GWP values exists because they are sometimes quoted for different timescales. Some
studies only look at a 100 year timescale and find that the GWP of CH4 is 73, i.e., methane is 73 time more potent than
carbon dioxide. However, if we take the longer term view required by sustainability of, say, 1000 years, the GWP of CH4
drops to 23 because CO2 persists in the atmosphere longer than methane. See Archer, D., M. Eby, et al. (2009). The
Atmospheric Lifetime of Fossil Fuel Carbon Dioxide. Annual Review of Earth and Planetary Science. 37: 117-134.
One complication is that, when viewed at high temporal resolution, ice cores show that atmospheric
CO2 increases lag behind temperature increases by several centuries, possibly suggesting that increased
temperatures cause high atmospheric CO2 rather than the reverse. However, there is a good explanation for
this relationship, one that relies on increases in solar insolation to trigger warming episodes that then become
amplified by increases in atmospheric CO2. Variations in insolation (solar intensity) due to Milankovitch cycles
are not sufficient to explain the large (6° C) temperature variations of the ice ages. However, they can trigger
temperature excursions. If insolation increases, then atmospheric temperature will increase slightly. This
causes the solubility of CO2 in seawater to decrease; the ocean begins to add CO2 to the atmosphere, which
further increases temperature due to the greenhouse effect, which leads to more degassing, creating a positive
feedback loop. This is reinforced by another positive feedback loop in which continental ice sheets melt and
recede, exposing land with a lower albedo, leading to increased absorption of solar radiation and heating. The
oceans take about a thousand years to overturn and degas, so the CO2 concentration in the atmosphere will not
peak until roughly a thousand years after the heating episode began.
vi
vii
http://www.youtube.com/watch?v=8nrvrkVBt24&feature=uploademail
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See http://www.350.org/en/about/science
EOS v. 90 Number 3, p. 22 — those who don’t have access to Eos, see this CNN story
x Note that in his second term Bush admitted that the earth was warming and that we were probably contributing,
but he chose to do nothing about it.
xi Nate Lewis, 2007, http://www.ccser.caltech.edu/outreach/powering.pdf
ix
xii
http://www.aip.org/history/climate/summary.htm
See Buckley, C. (2006). Thank You For Smoking, Random House. for an insightful and amusing illustration of
how corporations conspire to hide the truth.
xiv For which he shared the Nobel Prize with the IPCC committee in 2007.
xv http://www.guardian.co.uk/commentisfree/2010/aug/01/climate-change-robin-mckie, retrieved 2/24/2011
xvi EOS v. 90 Number 3, p. 22 — those who don’t have access to Eos, see this CNN story
xvii ibid.
xviii And to Wikileaks' diplomatic cable leaks in 2010-2011.
xix http://www.youtube.com/watch?v=gRVlIT__w6A
xx Raphael G. Sater, Associated Press, 12/2/2009.
xxi Raphael G. Satter, Associated Press, March 31, 2010.
xxii Neela Banerjee, Tribune Washington Bureau, 11/8/2010.
xxiii http://www.stthomas.edu/engineering/jpabraham/
xxiv http://tamino.wordpress.com/2010/11/23/all-that-data/
xxv Brian Winter, USA Today, March 11, 2010.
xxvi see the movie “Who Killed the Electric Car” Paine, C. (2006). Who Killed the Electric Car?, Sony: 93 min..
xxvii Jonathan Gilligan, Pers. Comm., 2/16/2010
xxviii Note that climatologists expect El Nino events to become more frequent and intense as warming continues.
xiii
For more information see http://www.npr.org/templates/story/story.php?storyId=123671588
For more humorous takes see http://www.thedailyshow.com/watch/wed-february-10-2010/unusuallylarge-snowstorm and http://www.colbertnation.com/the-colbert-report-videos/264085/february-102010/we-re-off-to-see-the-blizzard
xxix
"Scientists ponder risks of manipulating climate: Warming intensifies talk on saving planet," Charles J. Hanley,
AP, 4/4/2011
xxxi Jowit and Wintour in The Guardian, June 26, 2008,
http://www.guardian.co.uk/environment/2008/jun/26/climatechange.scienceofclimatechange
xxxii See http://cmi.princeton.edu/wedges/intro.php for more information.
xxx
http://cmi.princeton.edu/wedges/intro.php and Pacala, S. and R. Socolow (2004). "Stabilization
Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies." Science 305(5686):
968-972. http://www.sciencemag.org/content/305/5686/968.abstract.
xxxiii
http://www.mckinsey.com/clientservice/electricpowernaturalgas/US_energy_efficiency/
http://www.grist.org/article/2010-04-23-what-is-the-social-cost-of-carbon/
xxxvi Note that one ton of CO contains 12/44 or ~1/4 ton of carbon.
2
xxxvii Mg-silicates like olivine in ultramafic rocks weather rapidly.
xxxviii How can coal replace oil and gas when autos don't run on coal? Autos can run on electricity generated by
burning coal. After peak oil people will not stop driving cars, they will just stop driving autos with gas-fueled internal
combustion engines. Most likely people will switch to electric cars, and burning coal produces most electricity today.
xxxix http://www.ccser.caltech.edu/outreach/powering.pdf
xl Unnaturally high chlorine monoxide concentrations were found to be inversely correlated with ozone
concentrations in the stratosphere. *Reference? See Meadows et al. (2004).
xli Charles J. Hanley, AP, 12/9/2010
xxxiv
xxxv
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5/31/2011