Tropics Feel the Heat of Climate Change
Tropical ecosystems may be responding to global warming more energetically than anyone had expected.
Scientists from China, Germany, France, the United Kingdom and the United States report in the journal Nature that the tropical carbon cycle – the uptake and release of carbon dioxide from and back into the atmosphere – has become twice as sensitive to temperature change in the last 50 years.
A one degree rise in average tropical temperature leads to a release of around two billion more tons of carbon per year from tropical forests and savannahs, compared with the 1960s and 1970s.
This is unexpected. Climate scientists had foreseen the ability of land-based ecosystems to store carbon declining through the coming century as average global temperatures rise, but not on this scale.
Positive feedback loop
To arrive at their conclusions, the researchers looked not at the crude rise in carbon dioxide levels in the atmosphere, but the year-to-year variations of traces of the gas recorded both at the top of the Mauna Loa volcano in Hawaii and at the South Pole, and then matched these with mean annual temperature variations over the same timescale.
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