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ESYS 10 Introduction to Environmental Systems
March 7, 2006
Reading: Chapter 16 Global Warming and Technical Summary for the IPCC
Chapter 16 problems: review questions 2, 3, 10, due Tuesday March 14
Problems from chapter 8 due today
Case Study 3 due next Tuesday March 14
Term papers due Thursday March 16
Discussion time: Complete Case Study 3, handout for C.S. 4http://realclimate.org site contributed to by climate scientists
http://www.marshall.org/ somewhat objective site, but funded by Exxon, some good links
Global Change
• “Change” a synonym for anthropogenic climate change, as opposed to “variability” which is a synonym for natural climate variation.
• Evidence of global change– CO2 rise - documentation and evidence that it is
anthropogenic – Temperature change– Sea level change– Permanent ice cover changes in Arctic and Antarctic
• Climate modeling using expected CO2 rise, predictions for climate change
• Temperature rise - documentation and evidence that it is anthropogenic
Natural climate “modes” (patterns)
• What are the dominant natural modes of climate that impact us on decadal to millenial scales (short of glaciations)?
• El Nino Southern Oscillation• Pacific Decadal Oscillation• North Atlantic Oscillation (or Northern Annular Mode)• Southern Annular Mode• Atlantic thermohaline circulation changes
• Go to separate powerpoint for these patterns
CO2, CH4 and T changes through history
Age (kyr B.P.)PASTPresent
Various greenhouse gas histories
CO2 rise
“Keeling” CO2 curve at Mauna Loa
Fossil fuel reserves
Fossil Fuels
Fossil fuel reserves
• Reservoir Size Gton Burning rate Gton/yr
• Coal 3500 2.4
• Oil 670 2.7
• Natural gas 500 1.3
• Total 4570 6.4
Deforestation also produces about 1.5 per year
Thus 670 years reserve if all fossil fuels in all forms were used up.
Who is doing the burning?Where does the total of 7.5 to 8 Gton/yr of carbon go?
Fossil fuel consumption (Gtons C/yr)(1 Gton = 1 billion metric tons
1 metric ton = 1000 kg)
• N.America 1.832• Central and S. America 0.269• Western Europe 1.000• Eastern Europe 0.844• Middle East 0.288• Africa 0.240• Far East 1.970
• Total 6.443 GtC/yr
ESYS 10 Introduction to Environmental Systems
March 9, 2006
Reading: Chapter 16 Global Warming and Technical Summary for the IPCC
Chapter 16 problems: review questions 2, 3, 10, due Tuesday March 14
Case Study 3 due next Tuesday March 14
Term papers and presentation due Thursday March 16
Discussion time: Term paper presentations and handout for C.S. 4http://realclimate.org site contributed to by climate scientists
http://www.marshall.org/ somewhat objective site, but funded by Exxon, some good links
Is Earth’s climate changing? The problem of attribution
Attribution and consistency
Detecting that some climate change has taken place does not immediately imply that we know the cause of the detected change. The practical approach to attribution that has been taken by climatologists includes a demand for consistency between the signal amplitudes projected by climate models and estimated from observations (Hasselmann, 1997). (IPCC, 2001)
Detection and attribution of climate change is a statistical “signal-in-noise” problem, it requires an accurate knowledge of the properties of the “noise”. Ideally, internal climate variability would be estimated from instrumental observations, but a number of problems make this difficult.
Lots of great websites
Particularly:
U.S. EPA on global warming http://yosemite.epa.gov/OAR/globalwarming.nsf/UniqueKeyLookup/SHSU5BUN59/$File/gw_faq.pdf
“Keeling” CO2 curve at Mauna Loa
What is the evidence that the CO2 rise is anthropogenic?
1000 million metric tons = 1GTon
Is the increase in atmospheric CO2 and other greenhouse gases anthropogenic in origin?
Yes:
(1) The observed increase is consistent with fossil fuel burning
(2) The isotopic composition (type of carbon) in the air today is very different from air from 100 to 1000 years ago, based on analyses of air from ice and firn (snow layer) cores. The present-day composition indicates fossil fuel burning is responsible for the CO2 increase. (the “Suess effect”, another UCSD/SIO carbon great)
“Keeling” curve and same in southern
hemisphere.
Oxygen in atmosphere
(Manning and Keeling, 2005)
13C/12C isotopic ratio in CO2 at
Mauna Loa, showing increase that matches with
global emissions of carbon
CO2 rise in the atmosphere: about 3 GtonC/yr of the 6-7 GtonC/yr. This is the portion that fuels greenhouse gas-
induced climate change.
60 62 3 Gton/yr stays in atmosphere
2 Gton/yr into ocean
0.5 Gton/yr into vegetation
Remainder: 2 Gton/yr - mystery???
Textbook version - pre-industrial revolution
numbers for atmosphere-ocean CO2 exchange
90 92
Sink of anthropogenic CO2?
Fossil fuel burning and changing land use create about 6-7 GtC/yr excess. Of this, about 1/2 stays in the atmosphere, 1/3 goes into the ocean, and 1/6 goes into new terrestrial vegetation.
OK - CO2 rise is anthropogenic, but are observed changes in temperature, ice cover,
sea level, etc. caused by the rise in greenhouse gases?
Look at temperature observations, and then at large computer simulations of climate.
Earth’sgreenhouse effect
Earth’s global mean energy balance
Kiehl and Trenberth, 1997
Earth’s surface temperature variations
Last 2000 years
Moberg et al (2005) reconstruction
Last 120 years
Earth’s surface temperature variations:trend from 1901 to 2004
Smith and Reynolds, 2005
Arctic warming and ice retreathttp://www.nasa.gov/vision/earth/environment/Arctic_Warming_ESU.html
1990 1999
Impacts of ice melt: (1) sea level rise, (2) low salinity cap on North Atlantic that would impeded deep water formation and change circulation/climate of North Atlantic region/world.
The year 2002 showed lowest level of sea ice on record (NASA)
Arctic warming and ice retreathttp://www.nasa.gov/vision/earth/environment/Arctic_Warming_ESU.html
1999 2002
At the rate of melting in last 15 years, could disappear entirely by the end of the century. Melt period begins earlier than 10 years ago. Strong feedback with climate (ice-albedo)
Greenland ice caphttp://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4035
Time magazine Feb. 27, 2006
Has the Meltdown Begun?The discovery that Greenland's glaciers are melting faster than anyone expected has experts worried anew about how high the seas will rise
By MICHAEL D. LEMONICK
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Greenland ice cap
http://cires.colorado.edu/science/groups/steffen/greenland/melt2005/
Greenland ice velocities, Rignot and Kangaratnam, Science Feb. 17, 2006
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Antarctic ice shelf melting
Larsen ice shelf on the Antarctic peninsula: piece larger than Rhode Island broke off
Jan. 31, 2002 March 5, 2002
Mechanism for breakup: warmer weather creates melt water ponds on the surface that seep down and weaken the ice
http://nsidc.org/iceshelves/larsenb2002/index.html
Antarctic ice shelf melting
Big concerns (media scares) seem to center on breakup of the West Antarctic Ice Shelf. Very large - if it were to go, then sea level would rise 10 meters.
Very unlikely to happen for several centuries but …
March 3, 2006, 1:30AM
Antarctica's ice melts faster than snowfall can replace itSatellite survey indicates that the continent is steadily shrinking
By ROBERT LEE HOTZLos Angeles Times
(based on paper appearing in Science, March 3, 2006)
Observed temperature changes: are they due to anthropogenic forcing?
Temperature increases can be due to:
(1) Solar radiation changes (cools or warms) - 11year cycle0.6 to 0.7 W/m2. All reconstructions indicate that the direct effect of
variations in solar forcing over the 20th century was about 20 to 25% of the change in forcing due to increases in the well-mixed greenhouse gases (IPCC, 2001)
(2) Volcanic eruptions (more particles, sulphates, cools the planet) -3 W/m2
(3) Anthropogenic greenhouse gases (warms climate)
(4) Anthropogenic aerosols (mostly cools climate)
How to tell the difference between (1) and (3)?
Natural versus anthropogenic Temperature change? Reason 1
(1) Observed warming is stronger at high latitudes than low latitudes ---> anthropogenic cause because:
(a) If due to solar radiation forcing, then water vapor would increase, and most warming would be in the wet lower latitudes.
(b) If anthropogenic CO2 increase is the cause, warming would be at higher latitudes since CO2 is more uniformly spread through all latitudes, and CO2 is a much higher relative part of greenhouse gases in the dry high latitudes
Earth’s surface temperature variations:trend from 1901 to 2004
Smith and Reynolds, 2005
Earth’s surface temperature variations:trend from 1979 to 2004
Smith and Reynolds, 2005
Natural versus anthropogenic Temperature change? (high latitudes warm more)
The spatial pattern of the simulated surface temperature response to a steady increase in greenhouse gases is well documented (e.g., Kattenberg et al., 1996; Chapter 10). The warming is greater over land than over ocean and generally small during the 20th century over the Southern Ocean and northern North Atlantic where mixing extends to considerable depth. The warming is amplified in high latitudes in winter by the recession of sea ice and snow, and is close to zero over sea ice in summer.
Natural versus anthropogenic Temperature change? Reason 2
(2) Warming is more evident in nighttime temperatures (difference between day and night temperatures is decreasing)
---> anthropogenic change because:
greenhouse gases trap heat at night as well as during the day, so there would be relatively more warming at night
Earth’s surface temperature variations:
maximum and minimum
temperatures and diurnal range
Vose et al., 2005
Minimum = night temperatures
Maximum = day temperatures
Difference - shows night is warming more
Natural versus anthropogenic Temperature change? Reason 3: Stratospheric cooling
“The vertical response to solar forcing (Figure 12.5) includes warming throughout most of the troposphere. The response in the stratosphere is small and possibly locally negative, but less so than with greenhouse gas forcing, which gives tropospheric warming and strong stratospheric cooling. The dependence of solar forcing on wavelength and the effect of solar fluctuations on ozone were generally omitted in these simulations. Hence, the conclusion that changes in solar forcing have little effect on large-scale stratospheric temperatures remains tentative.” (IPCC, 2001)
Natural versus anthropogenic Temperature change? Reason 3
(3) Stratospheric cooling: a signature of anthropogenic warming
Figure 12.5: (a) solar forcing.
(b) greenhouse gas-induced temperature change
Natural versus anthropogenic Temperature change? (observations of stratospheric cooling)
Results of warming
Change in precipitation patterns
Rise in sea level - melting of land ice, increased temperature of oceans causing them to expand, (rebound of land from last ice age)
Change in extreme weather (greater variability - bigger extremes)
Observed trends in
precipitable water (warmer
world has more water
vapor)
Trenberth et al. 2005
Sea level - what causes it to change?
1. Add more water to the oceans: melt glaciers and landfast ice (Antarctic ice cap and Greenland ice cap are the biggest).
2. Warm the ocean: thermal expansion of water will cause sea level to rise. This has been the main effect in observed sea level rise
3. (NOTE: melting sea ice does not cause sea level to rise)
How fast is sea level rising? 2 to 3 mm/year, about 2/3 due to thermal expansion, 1/3 due to land ice melt.
Observed global mean sea level rise (Barnett, 1988)
14 cm
(2 mm/year)
(other estimates are up to 20 cm)
Sea level rise: world sea level has risen up to 20 cm in the past century (60 years of data required to discern trends)
Sea level rise - vulnerable areas
National Academy of Sciences 2001
Sea level rise
From NAS workshop, 2001
Major impacts are on deltas with low sediment input
Chesapeake Bay already impacted (crabbing industry)
Delaware Bay, Outer Banks, other regions of east coast
Expected accelerating impacts on Mississippi Delta (New Orleans and barrier islands - about 1/3 lost since 1880), Venice
Sea level impacts in eastern U.S. (U.S. EPA global warming - publication)
Predicting the future: from Intergovernmental Panel for Climate Change (2001) Technical
summary
Climate models for
global change
Climate models
IPCC (2001) uses results from 20 Atmosphere-Ocean Global Climate Models (AOGCMs). These come from world modeling centers. In the U.S., some of the centers that participate are the National Centers for Environmental Prediction (NOAA), the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, the National Center for Atmospheric Research in Boulder, Los Alamos (DOE).
Each modeling center is given the forcings for the IPCC scenarios and then runs its climate model with these forcings. The IPCC committees then compare the results, evaluate the models, and average the results to yield a prediction and error bar.
The models differ from each other - sometimes significantly
Modeling CO2 rise in atmosphere and
associated climate change
IPCC 2001 Scenarios
A: strong steps to curb emissions
B: medium steps to curb emissions
C: rapid growth, multiple energy sources
D: “business as usual” continue as we are going today, most energy from fossil fuels
Modeling CO2 rise and global change
Old scenarios for IPCC (prior to 2001 report, which was the “Third”):
Doubling CO2 in the atmosphere creates about 2.5°C change
So each doubling causes change: “business as usual” scenario prediction is 5°C change over next 100 years.
Conclusion of the previous 2 reports that (1) greenhouse gases were increasing, and (2) that observed temperature changes might or might not be attributable to greenhouse gas increases.
------------------------------------------------------------------------
IPCC 2001 (“Third Assessment Report”): definitive conclusion that observed temperature changes result from anthropogenic forcing.
Expressing greenhouse gases as “radiative forcing”
4.4 W/m2 <---> double CO2 levels <---> 2.5°C change
Predicting temperature change by 2300
Prediction is 5-fold increase in CO2 --->
about 10°C change by year 2300 before decrease
Decrease in atmospheric CO2 is due to the processes we have
discussed: ocean uptake, sea-floor sedimentation
and dissolution, weathering
Temperature change in climate models with anthropogenic CO2 forcing
Patterns of predicted
temperature change:
Model results from IPCC.
Scenario D (business as usual)
Scenario B (modest growth, some measures to curb emissions)
Global sea level projections
Modeled changes in biomass for doubled
CO2
Is the Earth’s climate changing?
“The answer is unequivocally “Yes”.”
IPCC 2001 Technical Summary
“Arctic-dwelling Inuit have a word for their crazy weather - Uggianaqtuq. Pronounce it "oog-gi-a-nak-took." It means "to behave unexpectedly”. The Arctic, (scientists) say, is undergoing profound ecological change. It's become the poster child for global warming. Not only are average air temperatures rising, ice sheets thinning, and permafrost melting, the whole complex interconnected network of arctic life and its environment are changing in ways not reflected in the geological record or Inuit lore. This no longer is a forecast of what might happen in future decades. It is happening right now.”
Robert C. Cowen, Christian Science Monitor, Jan. 6, 2005
Term paper presentations
The purpose is to inform the class about the topic - useful takeaway information, resources, etc.
6-7 groups total
1 hr 20 minutes -> about 10 minutes per topic
Each group - coordinate your information and decide how to present. You can delegate to 1 or 2 people to present everyone’s information, or have a tightly choreographed presentation with everyone getting up and doing 1 slide/overhead.
Organization suggestions:
Science first - what happens, how does it happen
Impacts second - what is affected, who is affected