Tropical ecosystems can produce significant carbon dioxide when temperatures rise, unlike systems in other parts of the world, research by NASA scientists and an international team of researchers suggests.
An increase of just 1°C in near-surface air temperatures in the tropics leads to an average annual growth rate of atmospheric carbon dioxide equivalent to one-third of the annual global emissions from combustion of fossil fuels and deforestation combined, the research reveals.
Carbon uptake is reduced at higher temperatures in tropical ecosystems. This finding provides scientists with a key diagnostic tool to better understanding the global carbon cycle.
“What we learned is that in spite of droughts, floods, volcano eruptions, El Niño and other events, the Earth system has been remarkably consistent in regulating the year-to-year variations in atmospheric carbon dioxide levels,” said Weile Wang, a research scientist at NASA’s Ames Research Center in Moffett Field, California, and lead author of a paper published in the Proceedings of the National Academy of Sciences.
Carbon-climate feedback hypothesis
The study supports the “carbon-climate feedback” hypothesis many scientists have proposed. According to the hypothesis, soils and vegetation in a warming climate will lead to faster growth of carbon dioxide in the atmosphere. Multiple Earth system processes, such as droughts and floods, also contribute to changes in the atmospheric carbon dioxide growth rate.
The new finding demonstrates observed temperature changes are a more important factor than rainfall changes in the tropics.
For the study, the researchers used a high-performance computing and data access facility called NASA Earth Exchange (NEX) at Ames to investigate the mechanisms underlying the relationship between carbon dioxide levels and increased temperatures.
The NEX facility enabled scientists to analyse data of atmospheric carbon dioxide concentrations and global air temperatures between 1959 and 2011, while studying outputs from several global dynamic vegetation models.