Download Climate Change Primer - Brian Fisher

Global Climate Change
P. Brian Fisher
College of Charleston
POLS 405
Class 1: Climate Change Primer
Earth’s Limits
“The earth is finite. Its ability to
absorb waste and destructive
effluents is finite. Its ability to provide
food and energy is finite. Its ability to
provide for growing numbers of
people is finite…”
“Moreover, we are fast approaching many of
earth’s limits. Current economic practices that
damage the environment, in both developed and
underdeveloped nations, cannot be continued
without the risk that vital global systems will be
damaged beyond repair”
--GEG, pp. 14-5 (from Natural Resources Journal 2001)
Kiribati Video
• Life on the Edge: The President’s
Dilemma
Affecting Climate?
Definitions
• Climate Change: long term change to earth’s climatic
system—not necessarily uniform or equal
• Global Warming: Increases in global mean temperature
• Weather: all phenomenon in earth’s atmosphere at a given
time (e.g. temperature, precip, etc.).
• Radiative forcing: essentially, the difference between the
incoming radiation energy and the outgoing radiation energy
in a given climate system, measured in Watts per square
meter.
– Use by the IPCC: changes in climate from changes in earth’s energy
budget
• IPCC: Intergovernmental Panel on Climate Change
IPCC: Unequivocal Warming
“Warming of the climate system is
unequivocal, as is now evident from
observations of increases in global
average air and ocean temperatures,
widespread melting of snow and ice, and
rising global average sea level”
Global Warming
• Global Mean Temp: 1.5°F increase in average global
surface temperature in the past century.
• Rate Increase: The rate of this increased warming has
accelerated as the warming over the last fifty years is
0.13°C, almost double for the previous 50 years, and this
rate has increased to 0.17°C per decade in the last twentyfive years.
• SOUTHEAST US: Since 1970 annual avg temperature has
risen about 2°F (greatest increase in winter). The annual #
of freezing days has declined by four to seven days for most
of the region.
Global Warming, IPCC Findings
• Eleven of the twelve years in the period (1995-2006) rank
among the top 12 warmest years in the instrumental record
(since 1850).
• Urban heat island effects were determined to have negligible
influence (less than 0.0006 °C per decade over land and
zero over oceans) on these measurements.
• "Average Arctic temperatures increased at almost twice the
global average rate in the past 100 years."
• It is likely that greenhouse gases would have caused more
warming than we have observed if not for the cooling effects
of volcanic and human-caused aerosols.
• “Warming in the last 100 years has caused about a 0.74 °C
increase in global average temperature.” (up to 2007)
Observed Changes in Climate
• SLR (sea level rise) is consistent with warming. Global average SLR
has risen about 2mm/yr since 1961 and is accelerating (now at
3.1mm/yr since 1993)
• Decreases in Ice and snow are also consistent with warming. Avg
Arctic sea ice has shrunk 2.7% per decade, with larger decreases in
Summer 7.4% per decade
• Mtn glaciers and snow cover have declined in both hemispheres
• Lengthening growing seasons (northern hemisphere) and shifting
biodiversity (moving to higher altitudes)
• Mean global sea surface temp (SST) of oceans have warmed from
0.10°C (1961 to 2003), with some estimates of SST are higher,
suggesting a 0.31°C increase since 1950.
Global Effects from GCC
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Ice Melt/Deglaciation
Rising sea levels (ice melt, increase in water)
Changes in extremes of temperature
Salination of Water and Soil
Increase in Extreme weather (storm surges,
precipitation, hurricane/cyclone intensity)
Changes in Wind patterns and intensity
Wind and SLR lead to coastal erosion
Droughts and flooding
Increase in Ocean temperature
Increase in insects (particularly mosquitoes)
Changes to growing seasons
3 Ways to Change Climate
There are three fundamental ways to change the
radiation balance of the Earth:
1) by changing the incoming solar radiation (e.g., by
changes in Earth’s orbit or in the Sun itself);
2) by changing the fraction of solar radiation that is
reflected (called ‘albedo’; e.g., by changes in cloud
cover, atmospheric particles or vegetation); and
3) by altering the longwave radiation from Earth back
towards space (e.g., by changing greenhouse gas
concentrations).
Climate, in turn, responds directly to such changes, as
well as indirectly, through a variety of feedback
mechanisms."
Anthropogenic
Climate Change
Fingerprint-modeling of global
surface temperature change
(Adapted from Meehl et al. 2004).
(A) Model results with all forcings
included. The combined forcings
provided the best match to the
fingerprint of climate change in
the observed record. (B) Natural
forcings alone explained much of
the temperature change in the
first half of the century. (C) Manmade forcings strongly dominated
the temperature change after
1975.
Note: The 20th C warming trend at the earth’s surface
progressed in a distinct pattern, with a large warming
during 1910-1940, moderate cooling during 19401975, and a large warming from 1975 to today.
Biophysical Climate Change Process
Anthropogenic
Drivers
Biophysical Climate Cycle
(human activities)
Natural Drivers
(solar processes,
earth’s orbit,
volcanoes)
Biogeochemical Feedback
GHG Emissions
(∆CO2; ∆CH4;
∆N2O; ∆ HCs)
Atmospheric
Concentrations:
“Climate Drivers”
(GHGs, aerosols,
clouds, solar irradiance)
Radiative
Forcing
(GWP Metric)
Biophysical
Climate
Responses
(global/regional ∆ temps & ∆
precip, ∆ vegetation, extreme
weather)
Increasing Uncertainty
Anthropogenic drivers augment natural levels of GHGs and together with natural processes trigger climate
drivers (e.g. clouds, GHG concentrations). These changes result in specific radiative forcing, positive or
negative (along with some non-radiative effects like evaporation). This radiative forcing then creates
biophysical responses in the climate system, such as changes to regional or global temperature and
precipitation, and extreme weather events. Biogeochemical processes then operate as feedbacks from
climate change back to its drivers. Finally, with each step further into the process, there is greater scientific
uncertainty.
Ice reflects solar radiation very well; water absorbs most of it. So if you have some of
the ice melt and it is replaced by water, then there is a lot less radiation being
reflected back because you have replaced the albedo of ice with the albedo of water.
That means more absorption, and tends to warm up where the ice is melting.
NOT Solar Output/Irradiance
• Since 1750, the average amount of energy coming from the
Sun either remained constant or increased slightly. Since
1978, with actual measurements, show decrease in activity
• If the warming were caused by a more active sun, then
scientists would expect to see warmer temperatures in all
layers of the atmosphere. Instead, they have observed a
cooling in the upper atmosphere, and a warming at the
surface and in the lower parts of the atmosphere. That's
because GHGs are trapping heat in the lower atmosphere.
• Climate models that include solar irradiance changes can’t
reproduce the observed temperature trend over the past
century or more without including a rise in GHGs.
• NASA Warming Climate Explained
Not Natural Cycles
• Earth’s atmosphere has indeed gone through many
changes in climate over its 4.5b history
• Natural cycles are created in earth’s climate from
earth’s orbit, tilt (21.8-24.4°), and its axis rotation
(precession).
• Earth’s orbit (eccentricity) operates in 100k cycles
which roughly mirrors the cycles of ice ages
• Many factors suggest we should be cooling from
natural cycles not warming
• **If warming from natural cycles, we’d expect daytime
temps to represent much of the increase (more solar
radiation), but we see more increase in nighttime
temps
Albedo 0-1 (0=no reflection) on Multi-Angle Imaging SpectroRadiometer
See: eosweb.larc.nasa.org/HPDOCS/misr/misr_html/global_seasonal_albedo.html
Feedbacks mechanisms, such as albedo, play a major role in driving climate change. The
reflectivity of various surfaces is shown on the chart (right side) above. The seasonal and annual
changes in the earth’s northern hemisphere albedo are shown on the image above (100%
reflectivity is denoted as 1.0 on the scale). The two images on the lower right are infrared satellite
images of Lake Tahoe, CA taken during winter (left) versus late spring (right).
Causes of GCC
(IPCC 2007)
•
Global GHG emissions (from human activities) have exploded with an increase of 70% just
since 1970. Humans pump 30 million metric tons of CO2 into atmosphere every year. 2%
increase every year, and double CO2 every 30 years.
•
“Carbon dioxide is the most important anthropogenic greenhouse gas (see Figure SPM.2).
The global atmospheric concentration of carbon dioxide has increased from a pre-industrial
value of about 280 ppm to 379 ppm in 2005.”
– 387 ppm (July 2009); 390 (Dec 2010). See CO2 Now
•
“The primary source of the increased atmospheric concentration of carbon dioxide since the
pre-industrial period results from fossil fuel use, with land-use change providing another
significant but smaller contribution.”
•
Methane and Nitrous Oxide have both increased significantly, and current levels “far
exceed any previous levels for last 650,000 yrs.”
•
The combined radiative forcing due to increases in carbon dioxide, methane, and nitrous
oxide is +2.30 [+2.07 to +2.53] W m–2, and its rate of increase during the industrial era is
very likely to have been unprecedented in more than 10,000 years
•
The understanding of anthropogenic warming and cooling influences on climate has
improved, leading to very high confidence that the global average net effect of human
activities since 1750 has been one of warming
Main Greenhouse Gases (GHGs)
• Carbon Dioxide (CO2)
– Steady at 270ppm until Ind Rev
• Methane (CH4)
–
1/3 impact of CO2
• Nitrous Oxide (N2O)
• Ozone (O3)
• Water Vapor
(largest part)
GHG Emissions Flow Chart
GWP (Global Warming Potential)
• ( concentration ) X ( the appropriate GWP multiplier
(2) (3) of each gas relative to CO2 ) = GWP
• CFCs banned (Montreal Protocol) substituted HFCs
which do contribute to GW
% of GHGs
% Rise since 1750
Sources
Time in Atmosphere
GWP
Carbon (CO2)
~63%
~ 31%
Autos, fossil
fuels,
deforestation
100-200 years
1
Methane (CH4)
~ 18%
~ 151%
Livestock, rice,
landfills, coal
mining
12 years +-3 yrs
25
Nitrous Oxide (N2O)
~ 6%
~17%
Auto exhaust,
fertilizers,
waste
120 years
300
Flourocarbons (CFCs;
HFCs)
~ 12%
Rising sharply
AC, Fridge
Varies
~1k-22k
(CFC11-12: 45-100 yrs)
Atmospheric CO2
concentrations
Mauna Loa, Hawaii
Charles Keeling
CO2 Concentrations
(Mauna Loa)
IPCC Findings, Industrial Revolution
“Global atmospheric
concentrations of
carbon dioxide,
methane and nitrous
oxide have
increased markedly
as a result of human
activities since 1750
and now far exceed
pre-industrial
values”
Proxies for Evaluating Climate
How do we establish long-term assessments
of climate change?
1.
2.
3.
4.
5.
Temperature records
Tree Rings
Ice Core Samples
Sediment samples
Observations/Traditional Knowledge
Findings, IPCC
(2007)
The amount of
carbon dioxide in
the atmosphere in
2007 (385 ppm)
exceeds by far
the natural range
of the last 650,000
years (180 to 300
ppm).
Co2 over last 400k years
Figure 4
Al Gore Explains ”temperature changes”
Barnola et al.
Projected Increases in Global Temperature
• NASA 2009 Video on Warming
• Climate Modeling (NASA)
• Global projections on Temperature
(1974-2099)
Projected surface temperature changes for the early and late 21st century relative to the period 1980–1999. The
central and right panels show the Atmosphere-Ocean General Circulation multi-Model average projections for the
B1 (top), A1B (middle) and A2 (bottom) SRES scenarios averaged over decades 2020–2029 (center) and 2090–
2099 (right). The left panel shows corresponding uncertainties as the relative probabilities of estimated global
average warming from several different AOGCM and EMICs studies for the same periods. Some studies present
results only for a subset of the SRES scenarios, or for various model versions. Therefore the difference in the
number of curves, shown in the lefthand panels, is due only to differences in the availability of results.
Temperature Projections in
2100 (A1B)
Peak Temp in Southeast US
SLR: New Projections
New studies find that warmer temperatures and changes in precipitation
caused by CO2 emissions from human activity are largely irreversible.
Atmospheric temperatures are not expected to decrease for many
centuries to millennia, even after human-induced greenhouse gas
emissions stop completely (Solomon et al. 2009; Eby et al. 2009).
New Findings Since IPCC 2007
• The link between fossil fuel emissions and GCC is
increasingly clear
• Ocean acidification severely threatens marine
ecosystems and fisheries
• Better understanding of ice sheets has raised
projections of 21st C global SLR
• Surface melting of the Greenland Ice Sheet is
accelerating & Arctic sea ice and permafrost melting
more rapidly than projections
• Antarctic ice shelves are collapsing more rapidly
than expected
• Warming will be higher than IPCC projections (based
on current emissions trends)
Main Features of GCC
1.
2.
3.
4.
5.
6.
7.
8.
Human Induced: current climate changes are largely human caused
Positive Feedbacks: thermal expansion, lessening albedo, and
increasing melting, increasing water vapor, all feedback into system
accelerating GCC
Climate variability: both at different spatial and temporal scales,
which often leads to climate extremes.
Local/Regional Phenomenon: because of variability, GCC is best
characterized as a regional or local phenomenon.
Inertia: The GHGs all have half-lives that will keep them in the
atmosphere from 10-1000+ years.
Adaptation is necessary. Because of inertia, climate effects will
continue for centuries and adaption is needed even if stopped today
Irreversible: GCC is irreversible.
Poor Most Affected: The impoverished areas, those more dependent
on natural resources, will be most affected (Injustice??)
UNFCCC and Kyoto Protocol
• UNFCCC: United Nations Framework
Convention on Climate Change
– US signed ratified.
– Core framework int’l agr on GCC
• Kyoto Protocol
– Addendum to UNFCCC
– Calls for developed countries to limit their GHG
emissions by certain dates.
– Full compliance would “only make a small dent in the
world’s ever-increasing output of GHGs.” (RG)
• Copenhagen and Cancun