Saturday, July 14, 2012

Are soils the missing sink? More evidence

Scientists have discovered an abrupt increase in the uptake of atmospheric carbon dioxide by the land biosphere (which comprises all of the planet's plant and animal ecosystems) since 1988. The increase in uptake is about one billion tonnes of carbon per year. Equal to 10 per cent of the global fossil fuel emissions for 2010. Without this natural increase in uptake, the amount of carbon dioxide in the atmosphere would probably have increased even more rapidly over the last two decades. 
These new results have been reported in a recent paper in the journal Global Biogeochemical Cycles, written by an international team of researchers at Princeton University (USA), NIWA (New Zealand), and the University of Missouri (USA). They applied a suite of statistical techniques to objectively determine the timing, size, and statistical significance of this shift. They explored whether it could be explained by volcanic eruptions or the El Nino Southern Oscillation (ENSO) – it can't.
"The scientific community has known for a long time that the land biosphere takes up CO2. What's new about this study is that we have discovered an abrupt shift towards more uptake by the land biosphere since 1988. Our team applied mathematical techniques that haven't been widely used in this field to detect the shift," says NIWA's Dr Mikaloff-Fletcher.
"While the increase was shown to be significant, the physical processes driving it remain a mystery. It poses big questions for us. What caused this shift? What can it tell us about how land's ability to take up CO2 is going to change in the future, and the sensitivity of the land carbon sink to climate? How is that going to feed back into climate conditions in the future?" says Dr Mikaloff-Fletcher 

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