Wednesday, December 03, 2014

How Agriculture Effects the Atmospheric Carbon dioxide Level

The intense farming practices of the "Green Revolution" are powerful enough to alter Earth's atmosphere at an ever-increasing rate, boosting the seasonal amplitude in atmospheric carbon dioxide to about 15 percent during the last five decades.

That's the key finding of a new atmospheric model that estimates that on average, the amplitude of the seasonal oscillation of carbon dioxide in the atmosphere is increasing at the rate of 0.3 percent every year.

A report on the results of the model, called VEGAS, is published today in the journal Nature.

"What we are seeing is the effect of the 'Green Revolution' on Earth's metabolism," says Ning Zeng, an atmospheric scientist at the University of Maryland and the lead developer of VEGAS, a terrestrial carbon cycle model that, for the first time, factors in changes in 20th and 21st century farming practices.

"Changes in the way we manage the land can literally alter the breathing of the biosphere."

Scientists have known since the 1950s that carbon dioxide levels in the atmosphere hit an annual low during late summer and early fall in the Northern Hemisphere, which has a greater continental landmass than the Southern Hemisphere and therefore has more plant life.

The atmosphere's carbon dioxide level falls in spring and summer as the hemisphere's plants reach their maximum growth, taking in carbon dioxide and releasing oxygen.

In the autumn, when the plants are decomposing and releasing stored carbon, the atmosphere's carbon dioxide levels rapidly increase.

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