Abrupt global warming could shift monsoon patterns, hurt agriculture: study

WASHINGTON, June 11 (Xinhua) -- At times in the distant past, an abrupt change in climate has been associated with a shift of seasonal monsoons to the south, causing more rain to fall over the oceans than in the Earth's tropical regions, and leading to a dramatic drop in global vegetation growth, a new study concludes.

If similar changes were to happen to the Earth's climate today as a result of global warming -- as scientists believe is possible -- this might lead to drier tropics, more wildfires and declines in agricultural production in some of the world's most heavily populated regions, according to a report to be published Friday in the Science journal.

The findings by researchers from Oregon State University (OSU), the Scripps Institution of Oceanography and the Desert Research Institute in Nevada, were based on oxygen isotopes in air from ice cores, and supported by previously published data from ancient stalagmites found in caves. The research was supported by the National Science Foundation.

The data confirming these effects were unusually compelling, researchers said.

"Changes of this type have been theorized in climate models, but we've never before had detailed and precise data showing such a widespread impact of abrupt climate change," said Ed Brook, an OSU professor of geosciences. "We didn't really expect to find such large, fast environmental changes recorded by the whole atmosphere. The data are pretty hard to ignore."

The researchers used oxygen measurements, as recorded in air bubbles in ice cores from Antarctica and Greenland, to gauge the changes taking place in vegetation during the past 100,000 years. Increases or decreases in vegetation growth can be determined by measuring the ratio of two different oxygen isotopes in air.

They were also able to verify and confirm these measurements with data from studies of ancient stalagmites on the floors of caves in China, which can reveal rainfall levels over hundreds of thousands of years.