Global Change_2

Global Change_2 - Hypothesis: Increasing anthropogenic...

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Hypothesis: Increasing anthropogenic greenhouse gases in the atmosphere will cause global temperature to increase. How can we test this hypothesis? Very difficult to test Many factors influence global temperature Impossible to vary only one factor at a time Computer models have been used to account for factors thought to be most important Is there a correlation between CO 2 and temperature? (not necessarily cause-effect relationship)
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CO 2 concentration has increased from mid-1800’s through the present time Mean global temperature has increased from mid-1800’s through the present
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Air bubbles trapped in ice contain tiny samples of gases present in the atmosphere when the ice formed. Measuring CO 2 in bubbles provides record of CO 2 concentration in atmosphere through time. Determining past carbon dioxide levels from ice cores
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(Antarctica) Present day
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Temperature and Carbon Dioxide Correlations Temperature and CO 2 are positively correlated over time Major variations in CO 2 content in atmosphere have occurred over time Cause of the CO 2 variations prior to 1800’s could not have been due to human activities Something else caused CO 2 (and temperature) variations prior to 1800’s. What Caused Past Climate Change? Must identify source of cooling/warming Must account for cyclical changes over time
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Possible causes for climate change (forcings): Solar radiation forcing Sun’s energy output varies periodically Volcanic forcing Eruptions introduce aerosols that block incoming solar radiation Orbital forcing Periodic change in Earth’s orbit resulting in changes in solar radiation received Anthropogenic forcing Human activities alter greenhouse gases and introduce aerosol particles (only possible since 1800’s)
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Solar Radiation Forcing Energy output of the sun is not constant 11-year sunspot cycle Longer-term cycles 11-year sunspot cycle Number of sunspots
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This note was uploaded on 05/13/2011 for the course GEO 101 taught by Professor Hanson during the Spring '08 term at SUNY Stony Brook.

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Global Change_2 - Hypothesis: Increasing anthropogenic...

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