Circum-Arctic Map of Permafrost and Ground Ice Conditions

The soil carbon feedback concerns the releases of carbon from soils in response to

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

. This response under

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

is a positive

climate feedback Climate Feedback (CF) is a web-based content annotation tool that allows qualified scientists to comment on stories online, adding context and noting inaccuracies. It is one of three websites under the Science Feedback parent organization that ...

. There is approximately two to three times more carbon in global soils than the Earth's atmosphere, which makes understanding this feedback crucial to understand future climate change. An increased rate of

soil respiration Soil respiration refers to the production of carbon dioxide when soil organisms respire. This includes respiration of plant roots, the rhizosphere, microbes and fauna. Soil respiration is a key ecosystem process that releases carbon from the ...

is the main cause of this feedback, where measurements imply that 4 °C of warming increases annual soil respiration by up to 37%.

Impact on climate change

Impact of elevated CO2 on soil carbon reserves

An observation based study on future climate change, on the soil carbon feedback, conducted since 1991 in Harvard, suggests release of about 190 petagrams of soil carbon, the equivalent of the past two decades of greenhouse gas emissions from fossil fuel burning, until 2100 from the top 1-meter of Earth's soils, due to changes in microbial communities under elevated temperatures. A 2018 study concludes, "Climate-driven losses of soil carbon are currently occurring across many

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s, with a detectable and sustained trend emerging at the global scale."

Permafrost

Thawing of permafrost (frozen ground), which is located in higher latitudes, the

Arctic The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), Finland, Iceland, N ...

and sub-Arctic regions, suggest based on observational evidence a linear and chronic release of

greenhouse gas emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and ...

with ongoing climate change from these carbon dynamics.

Tipping point

A study published in 2011 identified a so-called compost-bomb instability, related to a tipping point with explosive soil carbon releases from

peatland A mire, peatland, or quagmire is a wetland area dominated by living peat-forming plants. Mires arise because of incomplete decomposition of organic matter, usually litter from vegetation, due to water-logging and subsequent anoxia. All types ...

s. The authors noted that there is a unique stable soil carbon equilibrium for any fixed atmospheric temperature. Despite the prediction that the carbon balance of peatlands is going to shift from a sink to a source this century, peatland ecosystems are still omitted from the main Earth system models and integrated assessment models.

Uncertainties

Climate models Numerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the c ...

do not account for effects of biochemical heat release associated with microbial decomposition. A limitation in our understanding of carbon cycling comes from the insufficient incorporation of soil animals, including insects and worms, and their interactions with microbial communities into global decomposition models.

References

External links