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Shifting Rain Band Threatens Pacific Islands

Emily Sohn, Discovery News

Their results, which they reported in Nature Geoscience, suggested that the band of thick clouds and rain that circles the globe hovered right near the equator during the 1600s.

During that time, Sachs said, sunspots were rare, and the sun was putting out about 1/10th of one percent less solar radiation than today.

Over the centuries, as the Sun heated back up ever so slightly, the band (also called the intertropical convergence zone) moved northward as much as 500 kilometers (300 miles) -- turning dry regions into wet ones and wet regions into dry ones.

The rain band moves towards whichever hemisphere is warmer, said Wallace Broeker, an earth scientist at Columbia University's Lamont Doherty Earth Observatory. As global warming continues, he said, the Northern Hemisphere will warm more quickly because it has more land than does the Southern Hemisphere, where large stretches of ocean buffer some of the heat. That will likely push the intertropical convergence zone even further north.

"I think Julian's finding is just one more indication that rainfall on our planet is extremely responsive to changes in Earth's temperature," Broeker said.

What's more, shifts in the tropical rain band coincide precisely with precipitation and climate changes in other areas around the globe, including China and the United States.

"We're starting now to get a feeling for what's going to happen as the planet warms," Broeker said. "From what we're seeing, the changes are going to be dramatic, and they're going to have large consequences."

Discovery News: Earth

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