Climate Change Overview

The United States is the source of a quarter of the world’s greenhouse gas emissions, with the average U.S. household generating more than 80 tons of toxic carbon dioxide gases every year – that’s 22.5 tons of greenhouse gases per person, per year.  In addition, the average American family uses 102,000 gallons of water and creates 3.3 tons of landfill waste every year. (1)

Weather vs. Climate (2)

Weather describes short-term atmospheric conditions in a specific place, such as a sunny day in Los Angeles or a snowstorm in Boston. Climate, on the other hand, refers to average atmospheric conditions over an extended period of time, such as decades or centuries. Using the cities of Los Angeles and Boston as examples again, these two locations have very different climates, even though their weather can possibly be similar on any one day.

Atmosphere (2)

The atmosphere is the gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium, radiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio), and ozone. In addition the atmosphere contains water vapor, whose amount is highly variable but typically 1% volume mixing ratio. The atmosphere also contains clouds and aerosols.

Greenhouse Gases & Greenhouse Effect

The greenhouse effect is a natural phenomenon that helps regulate the Earth’s temperature. Greenhouse gases (e.g., carbon dioxide, methane, nitrous oxide, chlorofluorocarbons) act like an insulating blanket, trapping solar energy that would otherwise escape into space. Some of the heat flowing back toward space from the Earth's surface is absorbed by water vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then reradiated back toward the Earth’s surface. (2) Without this natural "greenhouse effect," temperatures would be about 60ºF lower than they are now, and life as we know it today would not be possible. (3) However, as atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere gradually increases.  Human activities, primarily the burning of fossil fuels and clearing of forests, have enhanced the natural greenhouse effect, causing the Earth’s average temperature to rise. (2)

Click here for information about using solar energy instead of electric to reduce your household greenhouse gas emissions. (Solar Energy section of this website)

Reference Sources: back to top

1. Bonnin, Jenny and KimMcKay.
   True Green
   Washington, D.C.: National Geographic Society, 2006.
2. “Frequently Asked Questions: Science.”
   www.epa.gov.
   2007. Environmental Protection Agency. 12 Aug. 2008 http://www.epa.gov/climatechange/fq/science.html#1
3. “Climate Change – Science.”
   www.epa.gov.
   20 Dec. 2007. Environmental Protection Agency. 12 Aug. 2008
   http://www.epa.gov/climatechange/science/