Increase in CO2 and Warmer Temperatures May Cause More Extreme Droughts in the Tropics

First Posted: Mar 10, 2015 09:19 AM EDT
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It turns out that an increase in carbon dioxide in the atmosphere may just increase drought in the tropics. Scientists have taken a closer look at what effects CO2 might have on the environment and have found that it has the potential to intensity extreme droughts.

In this case, the resrearchers looked at the Hadley Circulation. This atmospheric air current centered around the equator is associated with the prevailing trade winds in the tropics. It affects areas between the latitudes of about 30 degrees north and 30 degrees south.

The Hadley Circulation doesn't just impact trade winds; it's also responsible for influencing the distribution of rainfall, clouds and relative humidity over half of Earth's surface. It can expand or contract in a warmer or colder global climate, leading to substantial changes in regional rainfall. In fact, these changes in rainfall have been linked to the collapse of the ancient Maya civilization.

During the past decade or two, the Hadley Circulation has become stronger and expanded toward the two poles at a rate faster than predicted by global climate models. This, in turn, has contributed to increased droughts over many subtropical regions and increased rainfall in equatorial regions. While past studies have attributed intensification to natural climate variability, this latest research points to another reason.

It's possible that the Hadley Circulation has intensified due to a warmer climate caused by more CO2 in the atmosphere. With computer climate modeling, scientists have found that warmer temperatures intensify this system.

"This is the first study that suggests a possible intensification of droughts in the tropic-subtropical margins in warmer climate," said Rong Fu, one of the researchers, in a news release. "This finding is critical to understanding what the world will be like as the climate continues to change. Will the Hadley Circulation continue to expand? Could the intensification of droughts over the tropics and subtropics be a new norm? These are questions that need to be answered."

The findings are published in the journal Proceedings of the National Academy of Sciences.

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