The Greenhouse Effect

Some atmospheric basics

• The greenhouse effect • Radiant energy that is absorbed heats Earth and

eventually is reradiated skyward–Radiation is in the form of longwave infrared

radiation

–Atmospheric gases, primarily H2O and CO2, are more efficient absorbers of longwave radiation– This selective absorption, called the greenhouse

effect, results in warming of the atmosphere

The greenhouse effect

IPCC 2007

Why Focus on CO2?

• Only 390 ppm (0.039%) of the atmosphere

The total number of CO2 molecules above our heads in the atmosphere is more important than their percentage in the atmosphere

What are the greenhouse gases?(excluding H2O)

• Carbon Dioxide: 49%• Methane: 18%• “CFC’s from coolants, solvents, etc”: 14%• Nitrous Oxides: 6%• Others: 13%

Most outgoing Earth radiation is intercepted and absorbed by greenhouse gases like water vapor, methane, and carbon dioxide.