Will the Amazon's Ability to Soak Up Carbon Survive Warming?

2010 data from the Amazon ... indicated that the sinks that are helping to cool the Earth may not survive more extreme weather.  From January to May in 2010, half of the days saw temperatures well above long-term averages.  Air samples showed the forests were giving off CO2, not absorbing it, and the flow of CO2 into the air was accelerated by smoke from many forest fires that spread quickly as the forests dried.

In August, during the Amazon's dry season, the CO2 emissions intensified.  Relatively suddenly during 2010, the Amazon had shifted from becoming a sink to becoming one of the globe's CO2 sources.  Scientists believe the smoke, the added heat stress, and the drought slowed the photosynthesis that normally stored CO2 in trees, sending substantial quantities of it back into the atmosphere instead.

A later Stanford University study of the 2010 Amazon drought, using the Brazilian data, found the shifts from sink to source were "very large" and "surprisingly fast."

Although the drought and the heat eased the following year, air samples continued to show "large pulses" of CO2 were still being emitted into the air above the eastern Amazon throughout 2011.  Caroline Alden, a University of Colorado scientist who worked with John Miller, a NOAA scientist also working on global monitoring data here, warns that this could be a "legacy" effect that means that tropical jungles could take several years to recover from more severe droughts.

To be sure, jungles also resume their plant growth very quickly, beginning with grass fields that can start to become wooded areas in three to four years.  These are sometimes called "secondary forests," but the losses from a more extreme weather event like the 2010 drought — as it was measured in the glass flasks filled in 300 flights over the jungles in three years — showed that the renewed growth of a traditional carbon sink may not start quickly enough to offset losses from its sudden and severe collapse.

Or, as Miller puts it:  "It can return to being a sink, but to recapture all of the carbon that was taken away in the initial step, that takes a long time."

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