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Why Should We Care About Climate Change?
El Nino... image courtesy of NCAR, click for www location. If there is one thing that the paleoclimatic record shows, it is the that the Earth's climate is always changing. Climatic variability, including changes in the frequency of extreme events (like droughts, floods and storms), has always had a large impact on humans. A particularly severe El Niņo, or relatively short drought, can cost US citizens billions of dollars. For this reason, scientists study past climatic variability on various time scales to gain clues that will help society plan for future climate change.

Unfortunately, records of past climate change from satellites and human measurements (thermometers, rain gauges) generally cover less than 150 years. These are too short to examine the full range of climatic variability. For this reason, it is critical to examine climate change going back hundreds and thousands of years using paleoclimatic records from trees, corals, sediments, glaciers and other natural or "proxy" sources.

Image: natural climate forcings The study of paleoclimates has been particularly helpful in showing that the Earth's climate system can shift between dramatically different climate states in a matter of years and/or decades. Understanding "climate surprises" of the past is critical if we are to avoid being surprised by abrupt climatic change.

The study of past climate change also helps us understand how humans influence the Earth's climate system. The climatic record over the last thousand years clearly shows that global temperatures increased significantly in the 20th Century, and that this warming was likely to have been unprecedented in the last 1200 years. The paleoclimatic record also allows us to examine the causes of past climate change, and to help unravel how much of the 20th century warming may be explained by natural causes, such as solar variability, and how much may be explained by human influences.

Lastly, most state of the art climate prediction is accomplished using large sophisticated computer models of the climate system. A great deal of research has been focused on ensuring that these models can simulate most aspects of the modern, present-day, climate. It is also important to know how these same models simulate climate change. This can be accomplished by comparing simulations of past climate change with observations from paleoclimatic records. Thus, paleoclimatology helps us improve the ability of computer models to simulate future climate.

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16 July 2002