Given the large amount of carbon stored in permafrost soils, this re-affirms that the climate warming feedback from the Arctic may be larger than projected. The researchers, from the U.S. and Sweden, combined global data on soil properties, ecosystem productivity and climate to quantify the long-term temperature sensitivity of Earth's soil carbon.

Co-author Gustaf Hugelius, from Stockholm University, explains: “By analyzing these broad-scale ecosystem properties, we can assess if the Earth System models we use to study climate work in the same way as the actual Earth system.”

The study goes on to show that while many Earth System models do not fully capture the observed patterns, there are ways to resolve this. The high temperature-sensitivity of the northern soils is mainly due to permafrost processes and it is captured by the models that are able to resolve soil temperature and carbon cycling with depth. The unexpectedly low temperature sensitivity of tropical soils is attributed to interactions with clay minerals, and models that represent these processes are able to recreate the observations.

These results show that projections used in international climate negotiations, such as the COP21, are based on a generation of Earth System models that likely underestimates the sensitivity of global soils to warming. Given these uncertainties, strong actions to reduce greenhouse gas emissions are ever more urgent.

Thawing permafrost in Arctic Canada (note person in photo for scale). Photo: Gustaf Hugelius.
Thawing permafrost in Arctic Canada (note person in photo for scale). Photo: Gustaf Hugelius.
Thawing permafrost in Siberian polygonal tundra. Photo: Gustaf Hugelius.
Thawing permafrost in Siberian polygonal tundra. Photo: Gustaf Hugelius.