pics of global warming

Basic Information

Climate Change or Global Warming?

The term climate change is often used interchangeably with the term global warming, but according to the National Academy of Sciences, "the phrase 'climate change' is growing in preferred use to 'global warming' because it helps convey that there are [other] changes in addition to rising temperatures."

Climate change refers to any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer).

Climate change may result from:

Natural factors, such as changes in the sun's intensity or slow changes in the Earth's orbit around the sun;

Natural processes within the climate system (e.g. changes in ocean circulation);
human activities that change the atmosphere's composition (e.g. through burning fossil fuels) and the land surface (e.g. deforestation, reforestation, urbanization, desertification, etc.)

Global warming is an average increase in the temperature of the atmosphere near the Earth's surface and in the troposphere, which can contribute to changes in global climate patterns. Global warming can occur from a variety of causes, both natural and human induced.

In common usage, "global warming" often refers to the warming that can occur as a result of increased emissions of greenhouse gases from human activities.

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.

Beginning late in the 18th century, human activities associated with the Industrial Revolution have also changed the composition of the atmosphere and therefore very likely are influencing the Earth's climate.

The EPA climate change Web site has four main sections on climate change issues and another section on "What You Can Do" to reduce your contribution.

A "Frequent Questions" section is available, and EPA has provided a frequent questions database where users can search for more specific questions and answers on climate change.

An eight-page brochure entitled Frequently Asked Questions About Global Warming and Climate Change: Back to Basics (PDF) (8 pp, 1.6 MB, About PDF) provides illustrated answers to frequent questions.

Science

For over the past 200 years, the burning of fossil fuels, such as coal and oil, and deforestation have caused the concentrations of heat-trapping "greenhouse gases" to increase significantly in our atmosphere. These gases prevent heat from escaping to space, somewhat like the glass panels of a greenhouse.

Greenhouse gases are necessary to life as we know it, because they keep the planet's surface warmer than it otherwise would be. But, as the concentrations of these gases continue to increase in the atmosphere, the Earth's temperature is climbing above past levels.

According to NOAA and NASA data, the Earth's average surface temperature has increased by about 1.2 to 1.4ºF in the last 100 years. The eight warmest years on record (since 1850) have all occurred since 1998, with the warmest year being 2005. Most of the warming in recent decades is very likely the result of human activities. Other aspects of the climate are also changing such as rainfall patterns, snow and ice cover, and sea level.