Permafrost: European scale
Frozen soils and permafrost currently hold about 1700 PgC, more than twice the carbon than the atmosphere, and thus represent a particularly large vulnerability to climate change (i.e., warming) (1).
It is virtually certain that the area of Northern Hemisphere permafrost will continue to decline over the first half of the 21st century in all climate change (RCP) scenarios (2). In the lower-end (RCP2.6) scenario, the permafrost area is projected to stabilize at a level approximately 20% below the 20th century area, and then begin a slight recovering trend. In the moderate (RCP4.5) scenario, the simulations that extend beyond 2100 show permafrost continuing to decline for at least another 250 years. In the higher-end (RCP8.5) scenario, the permafrost area is simulated to approach zero by the middle of the 22nd century in simulations that extend beyond 2100 (1).
Vulnerabilities - The permafrost carbon feedback
In high-latitude regions of the Earth, temperatures have risen 0.6 °C per decade, twice as fast as the global average (4). The resulting thaw of frozen ground exposes substantial quantities of organic carbon to decomposition by soil microbes (3). The permafrost region contains twice as much carbon as there is currently in the atmosphere (5). A substantial fraction of this material can be mineralized by microbes and converted to CO2 and CH4 on timescales of years to decades. At the proposed rates, the observed and projected emissions of CH4 and CO2 from thawing permafrost are unlikely to cause abrupt climate change over a period of a few years to a decade. Instead, permafrost carbon emissions are likely to be felt over decades to centuries as northern regions warm, making climate change happen faster than we would expect on the basis of projected emissions from human activities alone (5).
Abrupt permafrost thaw occurs when warming melts ground ice, causing the land surface to collapse into the volume previously occupied by ice. This process, called thermokarst, alters surface hydrology. Water is attracted towards collapse areas, and pooling or flowing water in turn causes more localized thawing and even mass erosion. Owing to these localized feedbacks that can thaw through tens of metres of permafrost across a hillslope within only a few years, permafrost thaw occurs much more rapidly than would be predicted from changes in air temperature alone. Abrupt thaw is an important mechanism of rapid permafrost degradation, yet abrupt thaw is not included in large-scale models, suggesting that important landscape transformations are not currently being considered in forecasts of permafrost carbon–climate feedbacks. This is in part due to the fact that we do not know at this stage what the relative importance of abrupt to gradual thaw across the landscape is likely to be (5).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Europe.
- IPCC (2014)
- Caesar et al. (2013); Koven et al. (2013), both in: IPCC (2014)
- Schuur et al. (2015)
- IPCC (2013), in: Schuur et al. (2015)
- Zimov et al. (2006); Tarnocai et al. (2009), both in: Schuur et al. (2015)