CAVES IN CHINA REVEAL CLUES TO EARTH’S CLIMATE

Reported by Kristofor Husted/MEDILL
Geochemist Larry Edwards discusses the connection between monsoon patterns and carbon dioxide.

by Kristofor Husted
Jan 11, 2011

Cave deposit samples from China are helping scientists resolve the timeline of the whole Earth’s climate history.
 

Knowing this history means better predictions of what’s to come with human-driven global warming speeding up the clock of climate change, scientists maintain.
 

“It’s not that previous workers got the age wrong. They got the age for the most part right,” said University of Minnesota geochemist Larry Edwards. “But we’re able to now really fine-tune that age in a big way.”

Courtesy of Larry Edwards Geochemist Larry Edwards' map shows caves in China where he finds clues about ancient monsoon patterns and climate change.
Courtesy of Larry Edwards
Geochemist Larry Edwards’ map shows caves in China where he finds clues about ancient monsoon patterns and climate change.

 
Edwards presented his newest findings at the recent Comer Conference on Abrupt Climate Change in Wisconsin.
 

Edwards and his team collect stalagmite samples and use isotopes to accurately date them. 

With this information, they can figure out where the monsoons brought wet weather centuries ago. These monsoon patterns in turn correlate to methane levels and cycles of climate change.
 

Methane that formed thousands of years ago got trapped in air pockets in ice sheets in places such as Greenland and Antarctica. Researchers can pull out ice cores, also used for dating our planet’s climate history, and measure the amount of methane found in the air pockets. 

Also sitting in the air pockets with methane is ancient carbon dioxide, a greenhouse gas that rises and falls in near lockstep with Earth’s rising and falling temperatures. 

Monsoon intensity has been linked to increased levels of atmospheric methane concentrations. Natural decomposition and animal digestion produce methane as well. But landfills, natural gas leaks, coal mining and agriculture produce lots more and are contributing to current levels of global warming.

Methane traps 20 times more heat in the atmosphere than carbon dioxide over a 100-year period, according to the U.S. Environmental Protection Agency.
 
 

From these connections between monsoons and methane, and methane and carbon dioxide, researchers can more accurately determine how much carbon was in the Earth’s atmosphere in ages past and link it to climate.


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