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The accuracy of the CCSM

How do we know that CCSM-2 is capturing Earth’s climate accurately?

One way to check a model is to see whether it can recreate known climate patterns. When scientists tested CCSM-2, they aimed to reproduce Earth’s climate from 1870 to 2000. They also recreated the irregular cycle of the El Niño phenomenon in the Pacific Ocean and the ebb and flow of sea ice in the polar regions. In each instance, the model produced simulations that closely resembled known climate data. In the case of sea ice, for example, CCSM-2 matched satellite observations of ice pack movements over the cycle of seasons—a major achievement because of the many forces that drive the formation of sea ice, including temperatures, ocean currents, and precipitation.

Another way to check a model is to examine whether it can simulate Earth’s climate over centuries without drifting from actual world conditions. To conduct this test, scientists ran a 1,000-year simulation with hypothetical conditions based on the current-day atmosphere remaining unchanged. The results: CCSM-2 produced realistic climate patterns without requiring scientists to correct for any drift. This is known as "flux-free" modeling, and it is unique to CCSM-2.

Now that the model has passed its tests with flying colors, scientists are using it to explore major climate issues. If carbon dioxide levels in the atmosphere continue to increase, for example, should certain farmers construct more irrigation systems or should coastal residents brace for more storms? Another line of research will explore whether past climate patterns, such as the Little Ice Age that cooled temperatures in the 17th, 18th, and early 19th centuries, are likely to reoccur in some form.

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