Basic Information

The Earth's climate has changed many times during the planet's history, with events ranging from ice ages to long periods of warmth. Historically, natural factors such as volcanic eruptions, changes in the Earth's orbit, and the amount of energy released from the Sun have affected the Earth's climate.

Life on earth is possible because the sun's energy warms the earth and its atmosphere. As this warmth radiates back into space, a portion is absorbed by a delicate balance of heat trapping greenhouse gases in the atmosphere, thus creating an insulating layer functioning similar to a conventional greenhouse. This "greenhouse effect" is a necessary natural global mechanism.

In the last 100 years, however, research indicates that the concentration of greenhouse gases, particularly carbon dioxide (CO2), has seen an unprecedented increase primarily due to the combustion of fossil fuels and urbanization of natural areas. Adding more heat-trapping gases to the atmosphere is causing global temperatures to increase. This increase in global temperatures is causing changes to the earth's climatic system resulting in more variable and extreme weather conditions in various parts of the world.

• DES Fact Sheet ARD-23 on Global Climate Change and Its Impact on New Hampshire
• Global Warming in New Hampshire – Our Climate, Economy, and Health (Union of Concerned Scientists, 2006)
• Global Warming and New Hampshire (National Wildlife Federation, October 2007)
• EPA's Basic Information Webpage