Soils may be less of a carbon sink than previously thought, with new research indicating that the earth is likely to release more carbon as the planet heats up.

The role of soil in the carbon cycle is crucial because the near-surface earth contains as much as 2000 billion tonnes of carbon – or roughly four times as much as the plants sprouting from it. By comparison, the atmosphere contains about 800 billion tonnes of carbon dioxide.

Tests were conducted on a range of vegetation, including from broadleaf forests.

A study of 22 soil types, mostly from the northern hemisphere, has found that with warming temperatures, microbes in the soil give off more carbon dioxide, a process that would amplify climate change.

"All the models at the moment have underestimated the loss of carbon under the elevated temperatures with global warming," said Brajesh Singh from the University of Western Sydney, one of the authors of the report, published in Nature on Thursday.