AP Environmental — Unit 9: Global Change

26% of Incoming Solar Radiation

Is reflected back into space by clouds and the atmosphere

19% of Incoming Solar Radiation

Is absorbed by the atmosphere and clouds, radiating out into space and Earth

55% of Incoming Solar Radiation

Reaches Earth’s surface where it can be absorbed/reflected depending on the albedo of the surface it strikes

Low Albedo

Darker surfaces absorb sunlight and release infrared radiation

High Albedo

Lighter surfaces reflect sunlight directly back out into space or clouds/green house gases that absorb it

Greenhouse Effect

Gases in the Earth’s atmosphere trap heat from the sun and radiates it back down

• Without this, Earth would be too cold to support life

• Solar radiation strikes Earth’s surface, heating it

• Earth’s surface releases infrared radiation

• Greenhouse gases absorb infrared radiation and radiates it both out and into space and back towards Earth

CO₂

• FF comb

• Decomposition

• Deforestation

• Volcanoes

• GWP: 1

• Residence time: 300-1000 years

CH₄ (Methane)

• Natural gas extraction and combustion

• Animal agriculture

• Anaerobic decomposition

• GWP: 28-84 years

• Residence time: 12 years

N₂O (Nitrous Oxide)

• Agricultural soils

• Denitrification (releasing nitrogen from soil)

• GWP: 300 years

• Residence time: 115 years

CFCs/HCFCs/HFCs/SF₄

• Refrigerants

• Blowing agents in aerosol products

• Industrial things

• GWP: 600-3000 years

• Residence time: 50-500 years

H₂O

• Evaporation

• Transpiration from plants

Global Warming Potential (GWP)

Measure of how much a given molecule of gas can contribute to the warming of the atmosphere over a 100 year period relative to CO₂

What is GWP based on?

• Residence time

• Infrared absorption

Residence Time

How long a molecule stays in the atmosphere without breaking down

Infrared Absorption

How well the gas absorbs and radiates infrared