Experiments by US researchers suggest that most of the carbon sequestered in northern hemisphere peatlands may be immune to temperature rises.

The findings, published overnight in the journal Nature Communications, constitute a rare piece of good news in climate science. A complete purge of the northern peatlands, which cover close to 3 per cent of the world’s land surface and contain about one-third of the carbon in the Earth’s soil, could roughly double the amount of carbon in the atmosphere.

Experiments have indicated that when these bogs are heated, their highly organic contents break down and expel carbon dioxide and methane. But this research has only examined what happens on the surface.

The new study was conducted in an “experimental forest” in Northern Minnesota, where huge chambers have been constructed to enclose natural slices of peatland. The researchers heated the bogs to a depth of two metres and found that the deeper peat — where the bulk of the carbon is stored — did not degrade.

Co-lead author Rachel Wilson, an environmental chemist with Florida State University, said surface peat contained carbon molecules that were vulnerable to microbes. Buried peat held far less of this “easily degraded” carbon.

“What is left appears much harder for microorganisms to break down,” Dr Wilson told The Australian. “The deep peat appears to be kind of like the leftovers that no one really wants to eat.”

The researchers ran four temperature simulations, heating the peat by between 2.25C and 9C, so that the study covered the full range of Arctic climate changes scenarios predicted for this century. All four approaches found that the carbon remained stable at depths of more than 30cm.

“If all other things remain as they are, the deep peat carbon remains in the soil,” said Joel Kostka, a professor of microbiology at Georgia Institute of Technology.

But Dr Wilson said the greenhouse threat from peatland carbon could not be completely dismissed, because temperature was not the only variable of concern. “Changes in rainfall could cause drying, increasing oxygen exposure which could help decompose the peat.”

She said wetter conditions could also be problematic, shifting the balance to more methane production. As a far more potent greenhouse gas than CO2, methane could trigger runaway climate change.