Ozone

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Methane levels - 7.66 mm absorption band -
about 2.5-fold increase since 1800 - leveling
off since 1999 is not well understood
(Bousquet et al., Nature 443, 439 (2006)
Wuebbles Hayhoe, Earth-Sci Rev. 57,
177-210 (2002))
Chief atmospheric sink for methane CH4 ?OH
? ?CH3 H2O (residence time 12 years)
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Sources of methane anthropogenic and natural
marsh gas
Natural sources
Anthropogenic sources
Approximate overall estimates Natural 140-235
Tg CH4/yr Agriculture 141 Tg CH4/yr Anthro,
non-Ag 217 Tg CH4/yr What is the ultimate
origin of CH4?
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• Methanococcus jannaschii
• Strict anaerobe
• Optimal growth temperature 85C
• Autotrophic, nitrogen fixer
• 4H2 CO2 ? CH4 2H2O (?G -131 kJ/mol)
• Exclusively hydrogenotrophic
• Central role in global carbon cycling

Methanogens account for 70 of the total
global methane source
black smoker chimney East Pacific Rise
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Methanogenesis
Hmd/Mtd
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Link between methane production rates and
industrial sulfur emissions
Schimel J, PNAS 101, 12400 (2004)
industrial emissions
microbial ecology
Competition between methanogens and sulfate
reducing archaebacteria, for nutrients in
anaerobic environments, is affected by sulfur
emissions. In turn, levels of atmospheric
methane are affected.
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Nitrous oxide, N2O Bond stretch at 7.8 mm Angle
bend at 8.6 mm
Relative levels of warming CO2 9 CH4 3 N2O
1 Implicates the global nitrogen cycle in
climate change as well
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3
-1
5
0
-3
3
2
1
3
4 reactions constitute the nitrogen
cycle Nitrogen Fixation (diazotrophy) Nitrificati
on Nitrate Assimilation Denitrification All are
catalyzed by enzymes in microorganisms Favorable
free energy changes are exploited for growth
and metabolism of the microorganism N2 fixation
nitrogenase is highly O2 sensitive (evolution,
root nodules) N2 fixation kinetically difficult,
requires ATP hydrolysis
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• Impacts of Climate Change
• Feedbacks versus forcings
• Temperature rise
• Water resources
• Melting of glaciers - snowpack
• Sea level rise
• Rainfall
• Ocean currents
• Tropical rainforests
• Methane hydrates
• Disease vectors
• Biodiversity
• Economic impacts

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Variations of Earths Surface Temperature

• Baseline for comparison
• 1961 -1990 average
• Temperature rise 0.74 C
• 0.56 0.92C IPCC4
• Difficulties in measurement
• Average seasons, day/night
• Urban heat island effect
• (less latent heat carried off)
• bucket effect on sea
• surface temperatures
• Proxy data for longer times
• tree rings
• glacier extent
• isotopic data/sediment cores

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Higher latitudes warm more quickly due to ice
albedo feedback
From IPCC4
Jim Hansen slide
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Long-term temperature trends (from sediment cores)
6C increase since last glaciation gives a
standard to compare effect on habitable surface
with temperature change
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• Data from trapped gases in Antarctic ice cores
  allows reconstruction of
• atmospheric composition over the 106 -107
  year period
• Both CO2 and CH4 levels are higher now than at
  any time in the last
• 600,000 years long-term variations due to
  glacial cycles
• Temperature changes over time track with CO2 and
  CH4

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Temperature rise in the ocean is mitigated by the
large size of the basin
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Generally smaller temperature rises in the
Southern hemisphere This is the geographic limit
of the models predictive capacity
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Predictions depend on the future world
scenarios
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Predictions depend on the future world
scenarios
A2 heterogeneous world self-reliance, local
identities preserved, population growth stays
high basically business as usual B1
convergent world, population peaks by 2050
clean technologies and global solutions, no
further climate initiatives A1B very rapid
economic growth, balance of energy sources All
scenarios equally sound.No successful
implementation of Kyoto Accords
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Prediction for 2090-2099, A1B scenario, IPCC4
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From 1995-2006, 11/12 years are among the top
12 years since 1850
Present rate of sea-level rise 3.1 mm/year
(IPCC4)
7-10 loss in Northern hemisphere snow
cover in last 50 years
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Water resources
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Water Cycle
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Water usage and wasteAgriculture dominates
usage waste in all sectors
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Freshwater availability in 2000
stress
scarcity
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US Ogallala Aquifer Depletionlargest
undergroundaquifer in US

• underlies 174,000 square miles in parts of eight
  States (CO, KS, NE, NM, OK, SD, TX, and WY)
• represents 20 irrigated land in the US
• represents 30 of ground water used for
  irrigation
• 332 Million gallons/day withdrawn in 1990 for
  irrigation

Irrigation in Kansas water from the Ogallala
aquifer center pivot irrigation systems
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Colorado River Flow at US/Mexico border
Decreased snowpack ? CO river flow impacts CA
water supply, as does sea level rise (effect on
SWP (State Water Project))
Gleick, 2003 (Science)
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San Joaquin Delta

• REDUCED SNOWPACK
• HIGHER SEA LEVEL
• LESS RAINFALL

CA aqueduct