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Global warming and climate change
This lecture will help you understand:
• Earth’s climate
• Human influences on the
atmosphere and climate
• Current and potential
impacts of climate change
• Scientific, economic, and
political debate on
climate change
• Potential responses
Climate and climate change
• Climate: a region’s long-term pattern of atmospheric
conditions, results from all the combined elements of
– General atmospheric circulation patterns and precipitation
– Wind and weather systems
– Rotation and tilt of Earth, which creates seasons
• Global climate change: changes in Earth’s climate, including
temperature, precipitation, and other variables
• Global warming: an increase in Earth’s average surface
temperature
• Climate changes naturally, but the recent rapid warming of
the planet and its change in atmospheric composition are
widely thought to be due to human activities.
How do we know what temperatures were
in the past?
• Scientists analyze tiny air
bubbles trapped in ice
cores learn about past:
– Troposphere composition
– temperature trends
– Greenhouse
gas
concentrations
– solar, snowfall, forest fire
activity
Ice cores
• Analyzing ice cores from Greenland and the Antarctic
shows global climate can change within decades.
– Uses CO2 and CH4 (methane) and isotopes of O and H
• Climate oscillates between ice ages and warm periods.
– Ice ages tie up water in glaciers, lowering sea levels
– 8 glacial periods occurred over the past 800,000 years
• Ice ages have lower green
house gases
temperatures.
– CO2 levels ranged between 150 and 280 ppm
and
• Milanovitch cycles: climate oscillations due to Earth’s
orbit
– Periodic intervals of 100,000, 41,000, and 23,000 years
Changes
in
Earth’s
temperature during the
past million years
Milankovitch cycles
• Over thousands of years, changes in Earth's orbit cause changes in
the amount of the Sun's energy that gets to the planet. Over the
past several million years these changes have caused cycles of
global warming and cooling.
• There are three ways that Earth's orbit changes over time.
– Eccentricity: The shape of Earth's orbit around the Sun becomes
slightly more and then less oval every 100,000 years.
– Precession: Earth wobbles on it axis as it spins, completing a full
wobble every 23,000 years.
– Tilt: The angle of the Earth's axis relative to the plane of its orbit
changes about three degrees every 41,000 years.
• Once the Sun's energy reaches the Earth, several things can happen.
The energy can be absorbed by the planet, reflected back into space,
or become trapped in the atmosphere.
Milankovitch cycles
These 3 types of cycles also affect climate in the long term.
Variation
of
Earth’s
orbit → a cycle of about
100,000 years
Wobble
of
Earth’s
axis
→
a
periodicity of
23,000 years.
Variation of
Earth’s tilt →
a periodicity
of
41,000
years
Fluctuation in natural climate
Milankovitch theory of climate change
Glacial
Ice Growth Configuration:
High eccentricity
High Tilt
Small Earth-Sun Distance
in Summer
Net Effect:
More seasonal contrast
Interglacial
Ice Growth Configuration:
Low eccentricity
Low Tilt
Large Earth-Sun Distance in
Summer
Net Effect:
Less seasonal contrast
Factors that influence climate
Three factors influence Earth’s climate more than
all others combined:
• The sun, which provides most of Earth’s
energy
• The atmosphere, which both absorbs energy
from the sun and reflects it back into space
• The oceans, which stores and transports heat
and moisture
The Earth as a greenhouse
• Factors that influence climate
– Internal components: oceans, atmosphere, snow, ice
– External factors: solar radiation, Earth’s rotation and
orbit, gaseous makeup of the atmosphere
• Radiative forcing: unit used to compare the relative
contribution to the IR absorption per molecule added
to the atmosphere
 Positive and negative forcing: leads to warming
or cooling
• Forcing is measured in Watts/m2
– Solar radiation entering the atmosphere = 340 W/m2
– Radiation is acted on by forcing factors
Radiative forcing
Greenhouse effect: warming process
• Greenhouse gases (GHGs): water
vapor, CO2, other gases (NOx, CH4,
CFC)
• Light energy goes through the
atmosphere to Earth.
– Earth absorbs and converts
energy to heat
– Infrared heat energy radiates
back to space
• GHGs (but not N2 and O2) in the
troposphere absorb some infrared
radiation.
– Direct it back to Earth’s surface
• The greenhouse effect was first
recognized in 1827.
– It is now firmly established.
Properties of anthropologic greenhouse gases
GHGs insulate Earth
• GHGs delay the loss of infrared heat (energy)
– Without insulation, Earth would be -19°C instead
of +15°C.
– Life would be impossible.
• Earth’s global climate depends on the concentration
of GHGs.
– Changing amounts of GHGs change positive
forcing agents, which would change the climate.
• Tropospheric ozone has a positive forcing effect.
– Varying with time and location
Cooling processes
• Planetary albedo: sunlight reflected by clouds
– Contributes to overall cooling by preventing
warming
– Low-flying clouds have a negative forcing effect
• High-flying, wispy clouds have a positive forcing effect
– Absorb solar radiation and emit infrared radiation.
• Snow and ice contribute to albedo by reflecting
sunlight
– Black carbon soot darkens snow and ice
– Dark snow/ice absorbs radiant energy instead of
reflecting it and reduces albedo
Global warming and cooling
Net effect of forcing reagents
on atmosphere
• Global atmospheric temperatures are a balance
between positive and negative forcing from natural
causes (volcanoes, clouds, natural GHGs, solar
irradiance) and forcing from anthropogenic causes
(sulfate aerosols, soot, ozone, increased GHGs)
• Forcing agents result in climate fluctuations
– It is hard to say any one event or extreme season
is due to humans
– But climate has shifted enough to generate
international attention
Major greenhouse gases
• Increases
in
average
concentrations
of
three
greenhouse
gases
in
the
troposphere between 1860 and
2004, mostly due to fossil fuel
burning,
deforestation,
and
agriculture.
Global warming potential
•
Carbon dioxide: primary greenhouse gas
•
•
•
methane traps 23 times the heat of CO2
nitrous oxide traps 296 times the heat of CO2
HFC-23 traps 12,000 times the heat of CO2
Rising greenhouse gases
• The Intergovernmental Panel on Climate Change (IPCC)
AR4 report states that global GHG emissions from
humans have grown 70% between 1970 and 2004
– The most important GHG is carbon dioxide (CO2)
• Carbon dioxide:
– Over 100 years ago, Swedish scientist Arrhenius
suggested that burning fossil fuels may increase CO2
– But he was not concerned about the impacts
• Carbon dioxide monitoring: CO2 levels have been
monitored on Mauna Loa, Hawaii since 1958
– Atmospheric CO2 levels have increased 1.5–2 ppm/yr
Average concentration of atmospheric
carbon dioxide, 1500-2000
In 2005, an ice core showed that CO2
levels in the troposphere are the
highest they have been in 650,000
years.
Carbon dioxide levels
• CO2 concentration has increased 33% in the past 200 years.
• It is now at its highest level in 400,000 years, and probably 20
million years.
• CO2 levels oscillate 5–7 ppm, reflecting seasonal changes in
photosynthesis and respiration.
– Fall through spring: respiration increases CO2 levels
– Spring through fall: photosynthesis decreases CO2
• By 2011, atmospheric CO2 levels = 390.5 ppm
– 40% higher than before the Industrial Revolution
– Higher than in the past 800,000 years
• Fossil fuels increase CO2 levels.
– 1 kg of fossil fuel burned releases 3 kg CO2
– Eight billion tons (gigatons, Gt) of fossil fuel carbon/year
Sources of carbon dioxide
• Half of fossil fuel carbon comes from industrialized nations
– Burning forests adds 1.6 GtC/year
– Over the past 50 years, release of carbon has tripled
– Half of the carbon is removed by sinks
• Sinks: burning fossil fuels should add 8 GtC/year to the air
– But only 3.3 GtC/year are actually added
– Carbon sinks (the ocean, biota, CaCO3 formation) absorb CO2
• Oceans take up CO2 by phytoplankton or undersaturation
– But there are limitations to uptake
• Forests are valuable for their ability to sequester carbon
Global carbon cycle
Other GHGs
• Water vapor: the most abundant GHG
– Its tropospheric concentration varies, but is rising.
– Higher temperatures increase evaporation and water vapor
(humidity).
– Higher humidity traps more heat, causing more warming
(positive feedback).
• Methane: 20 times more effective than CO2 in heating
– From microbial fermentation (in wetlands), green plants
– Two-thirds of emissions are from human sources: animal
digestion, wet lands, landfills, coal mines, natural gas, rice
cultivation, manure
– Rising at 0.8 ppb/year, it is more abundant than in the
past 800,000 years
• Nitrous oxide: has increased 18% over the last 200 years
– From agriculture, oceans, biomass burning, fossil fuel
burning, industry, anaerobic denitrification (fertilizers)
– Warms the troposphere and destroys stratospheric ozone
• Ozone: a short-lived but potent GHG in the troposphere
– From sunlight acting on pollutants
– Has increased 36% since 1750
– From traffic, forest fires, agricultural wastes
• CFC and other halocarbons are entirely anthropogenic.
– Long-lived GHGs causing warming and ozone destruction
– From refrigerants, solvents, fire retardants
– They absorb 10,000 times more infrared energy than CO2
– Levels are slowly declining but will remain for decades.
Thermohaline circulation
• High-latitude North Atlantic ocean flows from the Gulf Stream north
on the surface and is cooled by Arctic air.
• North Atlantic Deep Water (NADW): the cool water increases in
density, so it sinks (up to 4,000 m)
– The current spreads to Africa’s southern tip
– It is joined by cold Antarctic waters
– The two streams spread north into the Indian and Pacific Oceans
as deep current
• The currents slow and warm and rise to the surface
– Move back to the North Atlantic
Polar (ice)
Warm temperate
Highland
Subarctic (snow)
Dry
Major upwelling zones
Cool temperate
Tropical
Warm ocean current
Cold ocean current
River
Heinrich events
• Heinrich events: fresh water from melting icebergs from the polar
ice cap dilutes salt water
– Six times in the past 75,000 years
– Diluted water doesn’t sink
– The conveyor system is shifted southward to Bermuda (instead
of Greenland)
– The climate cools in a few decades
• Return of the normal pattern abruptly warms the climate
• The Younger Dryas event involved dammed-up water from
glacial Lake Agassiz entering the St. Lawrence
• Extended global warming will
– Increase precipitation over the North Atlantic
– Melt sea ice and ice caps
• The conveyor will decrease over the 21st century
• The Achilles’ heel of our climate system: weakening of the
conveyor and a changed climate
– Especially in the northern latitudes
Ocean-atmosphere oscillations
These processes produce globally erratic climates.
• The North Atlantic Oscillation (NAO): atmospheric
pressure centers switch back and forth across the
Atlantic
– Switching wind and storms
• El Niño/La Niña Southern Oscillation (ENSO): shifts in
atmospheric pressure over central equatorial Pacific
Ocean
– Dominates global climate for over a year at a time
– 1997–2000 ENSO cost $36 billion and killed
thousands
• Interdecadal Pacific Oscillation (IPO): a warm-cool cycle
that swings over the Pacific over several decades
El Nino and La Nina
In normal conditions, winds push warm waters (red) to
the western Pacific Ocean. This allows cold water to
well up from the deep in the eastern Pacific.
In an El Niño event, winds weaken, warm water sloshes
to the east, and prevents the cold upwelling.
La Niña is the opposite: Cold water spreads west.
History of El Niño
• El Niño, as a oceanic phenomenon along the coasts
of northern Peru and Ecuador, has been
documented since the 1500s.
• Originally, the term El Niño was used to describe
the annual appearance of warm waters along the
coast of northern Peru around Christmastime.
• In some years the warm waters appeared earlier
and lasted longer. Eventually, the term El Niño was
applied to the periods of anomalous warming.
• The stronger events disrupted local fish and bird
populations.
History of the Southern Oscillation
• Beginning in the late 1800s scientists began to
describe large-scale pressure fluctuations.
• Dr. Gilbert Walker and colleagues extended the
early studies and determined that a global-scale
pressure fluctuation (the Southern Oscillation, SO)
is related to rainfall anomalies in many areas of the
Tropics (e.g., India and South America).
• The SO was used as the basis for seasonal rainfall
predictions (ca 1930s).
Discovery of the “El NiñoSouthern Oscillation (ENSO)”
• El Niño and the Southern Oscillation were studied as separate
phenomena until the 1950s-1960s.
• Important works by Berlage (1956) and J. Bjerknes (late 1960s)
demonstrated a link between the two phenomena.
• Studies at that time also showed that the anomalous warming of
the waters during El Niño extended over a large portion of the
equatorial Pacific.
The ENSO cycle
• Naturally occurring phenomenon
• Equatorial Pacific fluctuates between warmer-thanaverage (El Niño) and colder-than-average (La Niña)
conditions
• The changes in SST (Sea surface temperatures) affect
the distribution of tropical rainfall and atmospheric
circulation features (Southern Oscillation)
• Changes in intensity and position of jet streams and
storm activity occur at higher latitudes
Properties of El Niño/ La Nina
Signals in Tropical Pacific:
•
•
•
•
•
Sea surface temperatures (SSTs)
Precipitation
Sea Level Pressure
The Southern Oscillation (High vs. Low Phases)
Low-level Winds and Thermocline Depth
Sea Surface Temperatures(SST)
• Equatorial
cold
tongue is weaker
than average or
absent during El
Niño, resulting in
positive
SST
anomalies.
• Equatorial
cold
tongue is stronger
than
average
during La Niña,
resulting
in
negative
SST
anomalies.
Precipitation
Enhanced
rainfall
occurs over warmerthan-average waters
during El Niño.
Reduced
rainfall
occurs over colderthan-average waters
during La Niña.
Sea Level Pressure(SLP)
• El Niño: Positive SLP anomalies over the western tropical Pacific,
Indonesia and Australia. Negative SLP anomalies over eastern
tropical Pacific, middle and high latitudes of the North Pacific, and
over U.S.
• Opposite pattern for La Niña. The pressure see-saw between the
eastern and western tropical Pacific is known as the Southern
Oscillation.
Low-Level Winds & Thermocline Depth
El Niño: weaker-thanaverage
easterlies
lead to a deeper
(shallower)-thanaverage thermocline
in
the
eastern
(western) eq. Pacific.
La Niña: strongerthan-average
easterlies lead to a
deeper (shallower)than-average
thermocline in the
western (eastern) eq.
Pacific.
ENSO: A Coupled Ocean-Atmosphere Cycle
ENSO is a “coupled” phenomenon: atmosphere drives
the ocean and the ocean drives the atmosphere.
“Positive Feedback” between ocean and atmosphere.
Example:
Weaker equatorial trade winds  cold water upwelling
in the east will decrease  surface warming of the
ocean  reduced east-west temperature gradient 
Weaker equatorial trade winds
Normal(Average) condition
Winds and Sea Surface
Temperature are COUPLED.
The SSTs influence the winds
and vice versa.
Warm
Warm
Cold
Cold
(1) Easterly
trade-winds
help push warm water to
the western Pacific and
upwell cold water along
the equator in the
eastern Pacific Ocean.
(2) Warm water heats the
atmosphere, the air rises,
and
low-level
trade
winds converge toward
the
warm
water.
Subsiding air occurs in
the eastern Pacific basin.
“El Niño”
Warm
Warm
Cold
NOTE: Location of the
warmest SSTs (>~28°C)
determines
where
tropical convection will
be located.
• Convection
shifts
eastward
over
the
central and/or eastern
Pacific
Ocean.
Convection
becomes
suppressed over the
far western Pacific/
Indonesia.
• Easterly
weaken
trade
winds
• Thermocline deepens
and the cold water
upwelling decreases in
the eastern Pacific.
Warm
Cold
Global El Niño Impacts
Impacts
are
generally
more
extensive during
the
northern
winter.
“La Niña”
Enhanced
More
Convection
Stronger
Stronger
Upwelling
Warm
ColdCold
becomes more shallow
• Convection becomes
stronger over the far
western
Pacific
Ocean/ Indonesia and
more suppressed in
the central Pacific.
• Easterly trade winds
strengthen
• Thermocline becomes
more shallow and the
cold water upwelling
increases
in
the
eastern Pacific.
Warm
Cold
Global La Niña impacts
Mid-latitude
impacts generally
occur during the
winter
season
(NH–DJF;SH- JJA).
Typical evolution of the ENSO cycle
• Irregular cycle with alternating periods of warm (El
Niño) and cold (La Niña) conditions
• El Niño tends to occur every 3-4 years and generally
lasts 12-18 months
• Strongest El Niño episodes occur every 10-15 years
• La Niña episodes may last from 1 to 3 years
• Transitions from El Niño to La Niña are more rapid
than transitions from La Niña to El Niño.
Evidence of climate change
• Weather varies naturally year to year
– Local temperatures may not follow global averages
• But the 10 warmest years on record were 1997–2008.
– 2005 set a record high—the warmest since the late
1800s
– The average global temperature has risen 0.6°C since
the mid-1970s (0.2°C/decade)
• Warming is happening everywhere.
– Most rapidly at high latitudes of the Northern
Hemisphere
• The warming is a consequence of an “enhanced
greenhouse effect”.
Intergovernmental panel on
climate change (IPCC)
• Founded in 1988 by the UN Environmental Program and
the World Meteorological Society to provide accurate
and relevant information leading to understanding
human-induced climate change
• Working Group I: assesses scientific issues of climate
change
• Working Group II: evaluates impacts and adaptation to it
• Working Group III: investigates ways to mitigate its
effects
• The AR4 report had over 2,000 experts from 154
countries
– Risk assessment: is the climate changing?
– Risk management: how do we adapt and mitigate
effects?
Synopsis of global climate change
• In 2007, scientists from the IPCC sifted through thousands of
studies and published the Fourth Assessment Report (AR4).
• The report concluded that warming of the climate is unequivocal
– The atmosphere and oceans are warmer.
– Sea levels are rising and glaciers are melting.
– There are more extreme weather events.
The IPCC’s report
• The report concluded that it is very likely (90%
probability) that warming is caused by human
factors
– Increased greenhouse gases (GHGs) trap infrared
radiation
• GHGs come from burning fossil fuels
– Along with deforestation
– The major GHG: CO2
• Responses to climate change
– Mitigation: reducing GHG emissions
– Adaptation: adjusting to climate change
Ocean warming
• Recently, the upper 3,000 meters of the ocean have warmed.
– Dwarfing warming of the atmosphere
– 90% of the heat increase of Earth’s systems
• Over the last decade, oceans have absorbed most of the nonatmospheric heat.
• A long-term consequence: the impact of this stored heat as it
comes into equilibrium with the atmosphere.
– It will increase atmospheric and land heat even more.
• A short-term consequence: unprecedented rising sea levels
– Thermal expansion and melting glaciers and ice caps
Shrinkage of the Muir glacier
Decline of Arctic sea ice
1979
2003
Ice cover decreased by
9% during this period
and then 20% at 2005
Arctic sea ice thinned
10–40% in recent
decades.
Changes in average sea level
Today’s sea level
0
–130
250,000 200,000 150,000 100,000 50,000
Years before present
0
–426
0
Present
Height above or below
present sea level (feet)
Height above or below
present sea level (meters)
Average sea level increased 10–20 centimeters (4–8 inches) during
20th century.
World sea level will rise 15-90 cm.
Mean Sea-Level Rises (centimeters)
Estimated global
sea level
100
90
80
70
60
50
40
30
20
10
High Projection
Shanghai, New Orleans,
and other low-lying cities
largely underwater
Medium Projection
More than a third of U.S.
wetlands underwater
Low Projection
0
2010 2020 2030 2040 2050 2060 2070 2080 2090 2100
Year
Potential global temperature and
precipitation change by 2050
Global warming impacts on biological systems
Causes and consequences of climate change
Achieving stabilization of global warming
• The Framework Convention on Climate Change (FCCC)
– We must stabilize GHG levels on a time scale that
prevents interfering with climate.
– 3°C rise: rising sea levels of 80 feet
– 2°C rise: irreversible melting of the Greenland Ice
Sheet
• We have a target of 1–1.5°C more warming.
– CO2 = 400–500 ppm
– Al Gore’s inconvenient truth: carbon emissions
must fall from 8 GtC/year to 2 GtC/year
What has been done?
• The Framework Convention on Climate Change
(FCCC) agreed to stabilize GHG emissions to 1990
levels by 2000 in all industrialized nations.
• This voluntary approach failed
– All developed countries (except the EU) increased
GHG emissions by 7%–9%.
– Developing countries increased theirs by 25%!
• Kyoto Protocol: the third Conference of Parties to
the FCCC met in 1997 in Japan to craft a binding
agreement on reducing emissions
International climate negotiations
The Kyoto protocol
• 38 industrial nations agreed to reduce GHG emissions
5% below 1990 levels by 2012.
– Annex I parties: signatories to this agreement
– Non-Annex I parties: developing countries
• Developing nations refused any reductions
– They said they have the right to develop using fossil
fuels, just as developed nations had
• FCCC
principle
of
“common
but
responsibilities”
– Each nation must address climate change
– But its priorities and efforts could differ
different
Ratifying the Kyoto protocol
• Treaty on global warming which first phase went into
effect January, 2005 with 189 countries participating.
– The U.S. is the only Annex I party that has not.
• Signers of the protocol have flexibility in how they
will achieve their GHG reductions
– Renewable fuels, nuclear, conservation, planting
trees
– Emissions trading, helping other nations
• There are penalties for failing to meet commitments
• Many Annex I countries are on target
– But not the U.S., Australia, Canada, Japan
Weaknesses of the Kyoto protocol
• The protocol’s targeted reductions will not stabilize
GHGs
– It would take immediate reductions of 60% globally
– There is no chance of this happening, so emissions
will continue to rise
• The world’s largest GHG emitters are not participating
– India, China, the U.S.
• A 2007 UN-sponsored climate conference occurred in
Bali
– The U.S. and some developing countries opposed
emission cuts and targets
– Negotiations on emissions occurred in Copenhagen
(2009)
Mitigation tools
• Reducing GHG emissions (several are already in place)
• Cap-and-trade, renewable energy, carbon capture and
storage, nuclear power, reforestation, efficiency
• Mileage standards, subsidies, carbon tax
• Stabilization triangle: carbon savings by reducing GHGs
– It is broken into seven wedges (mitigation strategies)
– Each wedge reduces 1 billion tons of carbon
emissions
• 15 wedge strategies in four categories: efficiency/
conservation, fossil fuels, nuclear, renewables
– Only seven are needed to bring about the desired
future
Stabilization wedges
Preparation for global warming
Carbon capture and storage (CCS)
Several
problems
approach
with
this
• Power plants using CCS
More expensive to build
None exist
• Unproven technology
• Large inputs of energy to
work
• Increasing CO2 emissions
• Promotes the continued use
of coal (world’s dirtiest fuel)
• Effect
of
government
subsidies and tax breaks
• Stored CO2 would have to
remain sealed forever: no
leaking
Carbon capture and storage (CCS)
We can capture
at least 90% of
emissions from
fixed emitters
We have been
transporting CO2
for decades
CO2 can be stored
safely and permanently
using natural trapping
mechanisms
CO2 Capture
There are 3 technologies to capture CO2 :
• Pre-combustion:
Where CO2 is captured before fuel is burned
• Oxy-fuel:
Where CO2 is captured during fuel combustion
• Post-combustion:
Where CO2 is captured after fuel has been burned
(This technology can also be retrofitted to existing
power and industrial plants)
Pre-combustion
CO2 is captured
before fuel is burned
Oxy-fuel
CO2 is captured during
fuel combustion
Post-combustion
CO2 is captured
after fuel has been burned
73
CO2Transport
• Once captured, the CO2 is compressed into a liquid
state and dehydrated for transport and storage.
• CO2 is preferably transported by pipeline.
• …or by ships when a storage site is too far from
the CCS capture plant
Safely storing CO2
• We use a natural mechanism that has trapped CO2,
gas and oil for millions of years.
• Liquid CO2 is pumped deep underground into one of
two types of reservoirs:
– deep saline aquifers (700m-3,000m)
– depleted gas and oil fields (up to 5,000m)
• Both types of reservoirs have a layer of porous rock
to absorb the CO2 and an impermeable layer of cap
rock to seal the porous layer
Safely Storing CO2
The liquid CO2 is pumped deep
underground into one of two types of
CO2 storage reservoir (porous rock)
Cap rock
Deep saline aquifer
700m - 3,000m
Cap rock
up to 5,000m
Depleted oil and gas fields
76
The safety of stored CO2 increases
over time
... due to 3 natural mechanisms
1
2
3
Residual trapping
CO2 is trapped in tiny rock pores
and cannot move
Dissolution trapping
CO2 dissolves into surrounding
salt water
Mineral trapping
CO2-rich water sinks to the bottom
of the reservoir and reacts
to form minerals
Monitoring CO2 storage sites
• To ensure that a CO2 storage site functions as it should,
a rigorous monitoring process begins at the reservoir
selection stage and continues for as long as required.
• Monitoring continues even after a CO2 injection well is
closed and EU legislation requires that stored CO2 is
kept safely and permanently underground
ouldGeoengineering?
• Paul Crutzen (Nobel Prize in Chemistry) and Tom Wigley (NCAR)
suggested that we consider temporary geoengineering as an
emergency response.
• Some Proposed Geoengineering Schemes:
A. Space
Modifier of solar radiation
B. Stratospheric
Stratospheric aerosols (sulfate, soot, dust)
Stratospheric balloons or mirrors
C. Tropospheric
Modifying total reflection from marine stratus clouds
D. Surface
Making deserts more reflective
Modifying ocean albedo
Reforestation (CO2 effect, but albedo effect causes warming)
Direct absorption of CO2
Ocean fertilization
Keith, David, 2001: Geoengineering, Nature, 409, 420.
Geoengineering
• Futuristic schemes to fight climate change may not
work
– Fertilizing
oceans
with
iron
to
stimulate
photosynthesis
– Scrubbers to remove and store CO2
– Sulfate particles or satellites to block solar radiation
• These schemes
consequences.
have
huge
costs
and
unintended
• We are conducting an enormous global experiment in
geoengineering
– Our children and their descendants will have to live
with the consequences.
Conclusions
• Much if not all recent increases in global temperatures are due to
anthropogenic sources.
• Global temperatures and CO2 concentrations in ice cores are
strongly correlated.
• Only certain vibrations of molecules will absorb infrared radiation
and be effective greenhouse gases.
• The relative importance of various greenhouse gases is given by
their relative abundance and global warming potential.
• Controlling population growth and economic development,
energy conservation, alternate energy sources, and CO2
sequestration are key elements in mitigating climate change.