Carbon Dioxide and Long-Term Climate Change Sept 2

Doran and Zimmerman (2009). Examining the Scientific Consensus on Climate Change. EOS 90(3): Have mean global temperatures risen compared to pre-1800s levels? - 90% of 3,146 Earth Scientists agreed 2. Has human activity been a significant factor in changing mean global temperatures? - 82% agreed - 97% of Research Climatologists agreed - 64% of Meteorologists - 58% of general public - 46% of Petroleum Geologists What do Scientists Think about Global Warming?

Doran and Zimmerman (2009). Examining the Scientific Consensus on Climate Change. EOS 90(3): “The more you know about the field of climate science, the more you’re likely to believe in global warming and humankind’s contribution to it”. “The debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes”.

Carbon Dioxide and Long-Term Climate Greenhouse Era – times when no ice sheets are present Icehouse Era – times when ice sheets are present

Albedo - % of incoming radiation reflected back to space 96% of atmosphere is carbon dioxide Longwave radiation

Why is Venus hotter than Earth? 1 – Both planets have nearly equal amounts of carbon, but they store it differently 2 – Greenhouse effects differ

Faint Young Sun Paradox

Hydrolysis – CO 2 removed from atmosphere → incorporated into groundwater to form carbonic acid in soil → used in chemical weathering of silicates → deposited into shells of marine organisms Chemical Weathering

Dissolution – rainwater combines with CO 2 in the soil → limestone bedrock dissolved → most of the CO 2 returned to the atmosphere Chemical Weathering

Climate Controls on Chemical Weathering

The Chemical Weathering Thermostat The global rate of chemical weathering depends on Earth’s climate So the amount of carbon dioxide removed from the atmosphere by chemical weathering depends on climate

Organic Carbon Subcycle

Gaia Hypothesis Life regulates climate on Earth for its own good - carbon is the basis of the carbon dioxide cycle - land plants photosynthesize carbon dioxide transferring it to litter increasing chemical weathering - shell-bearing plankton removes carbon dioxide from the ocean and stores it in their shells