University of Illinois Extension
Environmental Awareness: Knowing Your World

Global Warming - Questions & Answers

What is Global Warming?

Scientists believe the Earth's average temperature has risen slightly in the last few decades.

For about the last 10,000 years, the average temperature the Earth has been about 15°Celsius (59°Farenheit). During this time, the Earth's average temperature has not changed by more than 1°C (1.8°F). Scientists can now document that the average temperature of the Earth has risen about 0.5°C (0.8°F) since 1850. Additionally, the 1990's was the warmest decade ever recorded. Scientists predict that the Earth will warm 1.0° to 3.5°C (1.8° to 6.3°F) in the next 100 years. This appears to be the more rapid and greater warming of Earth's temperature than has ever occurred.

What is causing Global Warming?

Many factors contribute to the Earth's temperature, including the shape of the Earth's revolution around the Sun, the Earth's tilt on its axis, the way the Earth wobbles on its axis, solar activity such as sun spots, and the chemical composition of Earth's atmosphere. Scientists believe that human activities are affecting the chemcial composition of Earth's atmosphere.

How are human activities affecting Global Warming?

Earth's atmosphere is 78 percent nitrogen and 21 percent oxygen. Less than one percent of the atmosphere is carbon dioxide, water vapor, methane, nitrogen oxides, and ozone, which are known as greenhouse gases. Greenhouse gases act like the panes of glass in a greenhouse. They keep some of Earth's heat from escaping to space. Until about 100 years ago, the concentration of greenhouse gases in Earth's atmosphere was stable. Scientists believe that human activities are changing the concentration of greenhouse gasses in Earth's atmosphere. Specifically, they are concerned about how much carbon dioxide, methane, and nitrogen oxides are being added to the atmosphere as a result of human activities. Just like adding an extra blanket to your bed will keep you warmer, more greenhouse gases will keep the planet warmer.

What might be the consequences of Global Warming?

Minor changes in Earth's temperature have resulted in dramatic changes for life on Earth. As little as a 3° to 5° C (5.5° to 9.0° F) decrease in Earth's temperature have resulted in Ice Ages. Scientists are concerned because they do not know what a similar change in the opposite direction might cause. They do feel confident that a warmer planet may not necessarily mean a more comfortable planet. Some changes that may occur include: a rise in sea level, stronger storms and where they occur, a change in where foods can be produced, and stress on plants that will not have had enough time to adapt.

How can we reduce the impact of Global Warming?

The most important thing people can do to reduce the impact of global warming is to reduce the amount of greenhouse gases they add to the atmosphere. This means we must reduce our use of fossil fuels. This means driving less and using the most energy efficient appliances available. We must also wisely choose what land will be developed for houses and other construction. Land that is developed reduces the amount of vegetation present. Vegetation takes carbon dioxide out of the air, so less vegetation means more carbon dioxide will remain in the atmosphere.

Where can I learn more about Global Warming?

Look up the following web sites: (Union for Concerned Scientists) (United Nations Environment Programme) (United States Environmental Protection Agency


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