Earth and Sky科普英語：Climate Puzzles 氣候之迷

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Scientists who predict Earth's future climate wish they knew how climate has changed in the past few thousand years. Learn more about modeling global climate -- today on Earth and Sky.

JB: This is Earth and Sky. Most scientists agree that humans are having an impact on Earth's climate. But they're also still discovering natural ways that global climate changes.

DB: For example, the sun doesn't give us exactly the same amount of heat each year -- and the sun's heat is just one factor, what scientists called one "parameter" -- needed to create computer simulations that show how climate changes -- and how it might change in the coming century. Drew Shindell models climate at the NASA Goddard Institute for Space Studies in New York City.

Drew Shindell: We had some observations showing that the wind speeds had increased when the sun got brighter in a particular region of the atmosphere. And then they decreased as the sun dimmed. And we'd never really been able to reproduce this in the model. We'd put in a brighter sun and nothing really happened to the winds in this region. . . We finally were able to add in ozone chemistry, so that as the sun got brighter you also created more ozone in the sunlit regions, and immediately the winds got faster exactly in the region where it happened in the data. So to us that was really thrilling.

JB: Shindell said that, even with supercomputers, it took his team about a month to simulate how Earth's climate changes over 50 years.

DB: For more about predicting climate change with computer models -- come to today's show at earthsky.org. Our thanks to the National Science Foundation -- where discoveries begin. We're Block and Byrd for Earth and Sky.