The World’s Carbon Sinks May Be Running Out of Room

The Earth’s biosphere may be absorbing less carbon than it used to

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David Orias/Water Rights/Corbis

The amount of carbon dioxide that's in the air is growing. But it doesn't just matter that CO2 levels are increasing—it matters how fast that's happening. And, according to a new analysis from the World Meteorological Organization, the rate at which CO2 levels are climbing is increasing, too. 

“The changes we’re seeing are really drastic,” said Oksana Tarasova, the head of the WMO's atmospheric monitoring department to the Washington Post. “We are seeing the growth rate rising exponentially.”

That rate also rises and falls. But the overall trend is upwards. And from 2012 to 2013, says the WMO, the world saw the largest single-year jump in the gas in nearly 30 years. This is hardly the turn around in the trend that scientists are looking for. (An overall drop in CO2 levels would be the best-case scenario, but even if levels of CO2 in the atmosphere are still increasing, it'd be better if they were increasing more slowly.)

The soaring carbon dioxide concentration stems from “ever-rising emissions from automobiles and smokestacks but also, scientists believe, a diminishing ability of the world’s oceans and plant life to soak up the excess carbon put into the atmosphere by humans,” says the Washington Post. It's this second part that, if true, is potentially more troubling than the rising concentration itself.

The amount of carbon dioxide in the air is controlled, generally speaking, by two factors: the amount of the gas being emitted—by carbon dioxide sources—and the amount being drawn out of the air—by carbon dioxide sinks. Cars, factories, forest fires, and farms put carbon dioxide into the air. Plants, the ocean and the soil pull it back out.

The natural balance of sources and sinks works as a buffer against rapid changes in the composition of atmosphere. When everything is working normally, a huge burst of carbon dioxide sent into the air from a forest fire will be absorbed by other parts of the system, such as the ocean. The findings from the World Meteorological Organization suggest that this system may be losing some of its ability to deal with the excess.

If the system's buffering capacity is hampered, smaller carbon emissions will lead to bigger rises in the atmospheric concentration of the gas than if the buffer were working normally.

"It could be that the biosphere is at its limit but we cannot tell that at the moment,” said Tarasova to the BBC.

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