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The American Geophysical Union and the American Meteorological Society contributed to the information contained in the TV portion of this report.

BACKGROUND: A new study by researchers at the University of Wisconsin-Madison and the University of Wyoming predicts that by the year 2100, many of today’s familiar climates will be replaced by climates unknown in today’s world, if current rates of carbon dioxide (CO2) and other greenhouse gas emissions continue. The new global climate models for the next century forecast the complete disappearance of several existing climates currently found in tropical highlands

and regions near the poles, while large swaths of the tropics and subtropics may develop new climates unlike anything seen today.

ABOUT THE STUDY: The climate modeling study translates CO2 and other greenhouse gas emission levels into climate change. It uses average summer and winter temperatures and precipitation levels to map the differences between climate zones today and in the year 2100. The most severely affected parts of the world span both heavily populated regions, including the southeastern United States, southeastern Asia, and parts of Africa, as well as known hotspots of

biodiversity, such as the Amazonian rainforest and South American mountain ranges. The predicted changes also anticipate dramatic ecological shifts, with extensive effects on large segments of the

Earth’s population.

CARBON IN THE AIR: Carbon, in the form of CO2, is a greenhouse gas continually released into the atmosphere as a direct result of human activities. This in turn raises the temperature of the earth, leading to global climate change. The concentrations of atmospheric

CO2 has already increased by about 30% since the dawn of the industrial revolution in the 19th century. Most of this increase comes from the use of fossil fuel — coal, oil and natural gas — for energy, but approximately one-quarter of it can be attributed to changes in land use, such as the clearing of forests and the cultivation of soils for food production. Natural sources of atmospheric carbon include gases emitted by volcanoes, and respiration of living things. We breathe in oxygen,

and breathe out CO2.

ABOUT GLOBAL WARMING: Global warming refers to an increase in the earth’s average temperature — which has risen about 1 degree F over the past 100 years. A warmer earth may lead to changes in rainfall patterns, and a rise in sea level, for example, as polar glaciers melt. Some of this rise is due to the greenhouse effect: certain gases in the atmosphere trap energy from the sun so that heat can’t escape back into space. Without the greenhouse effect, the earth would be too cold for humans to survive, but if it becomes too strong, the earth could become much warmer than usual, causing problems for humans, plants and animals.

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