EVSC10001 Lecture 18: Greenhouse Effect and Climate feedbacks
11 Jun 2018
School
Department
Course
Professor
Greenhouse effect
Solar radiation enters from the sun
Some solar radiation is reflected by Earth + atmosphere
About half solar radiation is absorbed by Earth's surface and warms it
IR is emitted from Earth's surface
Some IR passes through atmosphere but most is ABSORBED and REEMITTED in all
directions by GHGs and clouds -> this warms the Earth's surface + lower
atmosphere
GHGs: gases with 3 atoms or more - H2O (short life - stays in atmosphere for 10
days), CO2, CH4, NO (long-lived)
Concentration of H2O determined by temp
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Global temps determined by balance b/w absorbed solar (shortwave)
radiation and infrared (longwave) radiation emitted from surface
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IR emitted from object increases and decreases very rapdily as temp varies
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If earth had no atmosphere -> global avg. temp about -15
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GHGs absorb IR and re-emit -> warming surface
Temp about 15
○
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What determines global climate?
Elevation1)
Temp decreases and precipitation increases with height
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Latitude2)
Solar intensity decreases with latitude + rainfall varies
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Land surface and vegetation3)
Distance from ocean4)
Larger temp range inland
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WARMING IS MODERATED IN OCEANS - mixing in mix layer spreads heat -> coastal
areas have moderate climate
Internal climate forces:
Atmosphere and weather variability w/ oceans, land surface, snow/ice
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External climate forces:
Volcanic eruptions
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Changes in solar forcing
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Ice ages: periods of cold temp at regular intervals
Stable climate states
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Higher albedo
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Greenhouse Effect and Climate feedbacks
Wednesday, 6 June 2018
5:20 pm
Document Summary
Some solar radiation is reflected by earth + atmosphere. About half solar radiation is absorbed by earth"s surface and warms it. Some ir passes through atmosphere but most is absorbed and reemitted in all directions by ghgs and clouds -> this warms the earth"s surface + lower atmosphere. Ghgs: gases with 3 atoms or more - h2o (short life - stays in atmosphere for 10 days), co2, ch4, no (long-lived) Global temps determined by balance b/w absorbed solar (shortwave) radiation and infrared (longwave) radiation emitted from surface. Ir emitted from object increases and decreases very rapdily as temp varies. If earth had no atmosphere -> global avg. temp about -15. Ghgs absorb ir and re-emit -> warming surface. Solar intensity decreases with latitude + rainfall varies. Warming is moderated in oceans - mixing in mix layer spreads heat -> coastal areas have moderate climate. Atmosphere and weather variability w/ oceans, land surface, snow/ice.
