APES Unit 9.3 (Greenhouse Gases)

Where does solar radiation go when it hits Earth’s surface?

26% reflected back into space by clouds & atm.

19% absorbed by atm. & clouds & radiated out into space & down to earth

The rest reaches earth’s surface where it can be absorbed or reflected (depending on the albedo of the surface it strikes)

Greenhouse effect

Gases in earth’s atmosphere trap heat from the sun & radiate it back down to earth

How does the Greenhouse effect work?

Solar radiation strikes earth’s surface, heating it

Earth’s surface releases infrared radiation

GHGs absorb infrared radiation & radiate it both out into space and back towards earth

Portion coming back to earth is the “greenhouse effect”

What are the most important GHGs?

CO2, Methane, Nitrous Oxide, CFCs/HCFCs/HFCs

Why isn’t water vapor a GHG?

It doesn’t drive atmospheric temperature change

What is 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 factors is GWP based on?

Residence time and Infrared Absorption