Will Global Warming Push Trees to Extinction?

Scientists work with uncertainty everyday. That doesn't mean that everything in science is equally uncertain. Some parts of science are based on well-known laws and documented trends. Other parts of science are almost certainly true. Other parts are big unknowns.

What do we know for certain about global warming?

Scientists know for certain that people are changing the chemicals in the atmosphere. People are adding large amounts of greenhouse gasses like Carbon Dioxide to the air. Scientists also know that these greenhouse gasses trap heat in the atmosphere. Some of the heat of the earth radiates out to space. The greenhouse gasses block some of this heat from escaping. When more heat stays on the earth the temperature rises.

In the last 100 years the earth's temperature has risen on average about 1°F. Scientists have found this increased temperature above ground, below ground, in the northern and southern hemisphere.

What is likely but not certain?

Greenhouse gasses have contributed to the rising temperature. Scientists aren't certain exactly how much of the increase is a result of the greenhouse gasses. The sun's energy output varies a little from year to year. Volcanoes periodically put greenhouse gasses and ash into the atmosphere. These and other natural variables also affect the earth's temperature. Scientists aren't certain exactly how much of the temperature rise is from natural causes and how much is from man's contribution.

Scientists are certain that the Earth's temperature will continue to rise if people continue to add greenhouse gasses to the atmosphere. Scientists aren't sure exactly how fast the temperature will rise. Scientist can't predict the exact rise in temperature but they can predict limits. In the next 100 years scientists predict that the Earth's temperature will rise at least 2.2°F. The upper limit is set at 10°F.

2.2°F to 10°F is a big range! Why can't scientists be more accurate? Scientists can't predict how many volcanoes will erupt or exactly how much pollution people will put into the air. Dust, ash, and pollution like smog block some of the sunlight from reaching the ground. Some kinds of pollution will slow the Earth's temperature rise.

Scientists know that even a 2.2°F increase will be greater than any seen in the last 10,000 years.

Scientists have a better understanding of the global effects of this predicted temperature increase. They can predict that the sea level will rise, and ice sheet will melt. Scientists' models aren't as good at predicting local climatic changes. They aren't sure if Atlanta will have more or less rain. Climate models like weather models are better at predicting national and state weather conditions than the weather over your house.

Scientists also know that complex systems can change in non-linear ways. The lesson "Melting the Arctic Ice Cap" shows this kind of surprising change.

This lesson helps you explore the impact of a range of temperature increases on the trees in a community.

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