PowerPoint Presentation - GHGs in EarthŐs atmosphere

Changing CO2 concentrations

ĄCO2 concentrations have varied naturally by ~30-50% over the past few hundred thousand years (ice ages)

ĄFossil fuel burning since the industrial revolution has created a recent sharp increase in CO2 concentrations

ĄCO2 concentrations are now higher than at any time in past few hundred thousand years

ĄAnd concentrations are increasing faster with time

Last 4 Ice Age cycles:

400,000 years

See http://epa.gov/climatechange/science/recentac.html

Man made

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