Tipping Point for Permafrost Peatlands Sooner Than Expected

Nature Climate Change, 14 March 2022

Large expanses of northern Europe and western Siberia may become too warm and wet within a few decades to sustain frozen permafrost peatlands, even under moderate emissions. These frozen peatlands, an especially vulnerable portion of permafrost lands, span 1.4 million square kilometers in Europe and Siberia, and contain 40 billion tons of carbon that accumulated over tens of thousands of years. As global temperatures rise, these peatland soils rapidly warm and release part of that thawed carbon into the atmosphere as both carbon dioxide and methane. Under a moderate emissions scenario, with global mean temperature passing 2°C, more than 75% of these peatland regions in northern European and western Siberian will become too warm or too wet to maintain permafrost already by the 2060s. Under high emissions, this grows to 93%. Strong action to reduce emissions by the end of the century may allow suitably cold and dry conditions in western Serbia to partially recover. Even under a low-emissions scenario, however, these models do not project a return to suitable climates in Norway, Sweden, Finland, and parts of Russia – suggesting that these permafrost peatlands are close or have already passed a tipping point. Authors emphasize the importance of following a low-emissions scenario to slow the irreversible loss of carbon from these thawing peatland soils.