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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
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ESYS 10Introduction 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. 4 http://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.) Present PAST
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 tons1 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 10Introduction 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. 4 http://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
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: The observed increase is consistent with fossil fuel burning 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.
Textbook version - pre-industrial revolution numbers for atmosphere-ocean CO2 exchange 3 Gton/yr stays in atmosphere 2 Gton/yr into ocean 0.5 Gton/yr into vegetation Remainder: 2 Gton/yr - mystery??? 60 62
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. 90 92
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’s global mean energy balance Kiehl and Trenberth, 1997
Earth’s surface temperature variations Last 120 years Last 2000 years Moberg et al (2005) reconstruction
Earth’s surface temperature variations:trend from 1901 to 2004 Smith and Reynolds, 2005
Arctic warming and ice retreat http://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 retreat http://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 cap http://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
Greenland ice cap http://cires.colorado.edu/science/groups/steffen/greenland/melt2005/ Greenland ice velocities, Rignot and Kangaratnam, Science Feb. 17, 2006
Antarctic ice shelf melting Mechanism for breakup: warmer weather creates melt water ponds on the surface that seep down and weaken the ice Larsen ice shelf on the Antarctic peninsula: piece larger than Rhode Island broke off Jan. 31, 2002 March 5, 2002 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 it Satellite survey indicates that the continent is steadily shrinking By ROBERT LEE HOTZ Los 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: Solar radiation changes (cools or warms) - 11year cycle 0.6 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 • Observed warming is stronger at high latitudes than low latitudes ---> anthropogenic cause because: • If due to solar radiation forcing, then water vapor would increase, and most warming would be in the wet lower latitudes. • 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 Maximum = day temperatures Minimum = night temperatures Difference - shows night is warming more Vose et al., 2005
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? • Add more water to the oceans: melt glaciers and landfast ice (Antarctic ice cap and Greenland ice cap are the biggest). • Warm the ocean: thermal expansion of water will cause sea level to rise. This has been the main effect in observed sea level rise • (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
Predicting the future: from Intergovernmental Panel for Climate Change (2001) Technical summary