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 Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

. This response under

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

is a positive climate feedback. 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 so ...

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) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

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

Permafrost

Thawing of

permafrost Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...

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

Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...

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

greenhouse gas emissions Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...

with ongoing climate change from these carbon dynamics.

Tipping point

A study published in 2011 identified a so-called

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by Decomposition, decomposing plant and food waste, recycling organic materials, and man ...

-bomb instability, related to a tipping point with explosive soil carbon releases from

peatland A peatland is a type of wetland whose soils consist of Soil organic matter, organic matter from decaying plants, forming layers of peat. Peatlands arise because of incomplete decomposition of organic matter, usually litter from vegetation, du ...

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 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