The Science of Climate Change

November 24, 2011

Climate negotiators are meeting in Durban, South Africa beginning from November 28-December 9 to discuss the planet's changing climate

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The first decade of this century was the hottest on record.

Polar ice is melting.

Global sea levels are rising.

And the vast majority of scientists attribute the changes to greenhouse gases, both natural from water vapor and man-made from burning fossil fuels, that trap heat in the lower atmosphere.

"Since roughly the 1850s or so, we've seen an increase globally of about eight-tenths of a degree Celsius, so that's roughly 1.4 degrees Fahrenheit," said Todd Sanford, a climate scientist at the Union of Concerned Scientists in Washington.

A one-degree difference is not noticeable in daily temperatures, but a one-degree change in global average temperature is significant.

"One way to put that in perspective is that in the last Ice Age when there was, you know, a mile of ice above much of North America, the temperature difference between then and now was only roughly five or six degrees Celsius," Sanford said.

Alden Meyer, the director of climate strategy and policy at the Union of Concerned Scientists, says global warming affects weather and water cycles.

"You have increased flooding and extreme downpours combined with droughts and desertification in some regions of the world. So there's tremendous variability here, and we're seeing that with extreme weather events on the increase, not only here in the U.S. but around the world," Meyer said.