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Earth's average temperature over the past 100 years is shown in the black line. Predictions of the amount of warming in the future are shown by the red, green, and purple lines. These predictions, developed with computer models, make different assumptions about how many greenhouse gases we release into the atmosphere in the future. Values beyond 2100 are for stabilization scenarios.
A Windows to the Universe image based on a graph from the IPCC 4th Assessment Report

Global Warming: Scientists Say Earth Is Heating Up

Earth’s climate is warming. During the 20th Century Earth’s average temperature rose 0.6° Celsius (1.1°F). Scientists are finding that the change in temperature has been causing other aspects of our planet to change. The effects of global warming are far reaching.

The warming is causing air and oceans to warm, more snow and ice in Earth’s polar regions to melt, and sea level rise. Many different effects of global warming have been seen at continental scales, as well as at smaller regional scales. Arctic temperatures have risen at twice the rate of the global average in the past century. The amount of precipitation in different regions of the world has changed, and so have aspects of extreme weather events such as droughts, heat waves, and the intensity of hurricanes and typhoons.

Things that we humans are doing are causing Earth to warm according to the Intergovernmental Panel on Climate Change (IPCC), a group of hundreds of scientists organized by the United Nations to summarize our current understanding of climate. Human activities that are currently causing global warming include burning fossil fuels like coal, oil, and gas. Burning these fuels releases greenhouses gases into the atmosphere and more greenhouse gases causes Earth's greenhouse effect to grow stronger, warming the climate. Changes in the way land is used also have an impact on climate. Climate also warms when trees and other plants are cut down to make way for new buildings or parking lots. Without the plants, more of the greenhouse gas carbon dioxide stays in the atmosphere. Plus, the asphalt and buildings tend to absorb more heat than forests and fields. Agriculture also releases greenhouse gases like methane and nitrous oxide into the air.

What does the future hold? There will be more global warming is in our future according to the results of computer models summarized in the Forth Assessment Report of the IPCC (released in 2007). For the next two decades warming of about 0.2° Celsius is projected. If we continue to emit as many, or more, greenhouse gases, this will cause more warming during the 21st Century than we saw in the 20th Century. During the 21st Century, various computer models predict that Earth’s average temperature will rise between 1.8° and 4.0° Celsius (3.2° and 7.2° F) depending largely on how humans change the ways they live on the planet.

Although there is a certain amount of global warming that we are going to have because of our activities during the past century, there are many ways to help slow the rate of warming. Recently, many people and companies have been trying to be "Carbon Neutral" to prevent more greenhouse gases from entering the atmosphere.

Last modified July 22, 2008 by Lisa Gardiner.

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