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    "en": "Permafrost degradation"
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    "en": [
      "Permafrost thaw",
      "Permafrost degradation,"
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    "en": "Permafrost is defined as the ground that remains frozen under 0°C for a minimum of two consecutive years. Permafrost loss, also known as permafrost thaw is the progressive loss of ground ice in permafrost, usually due to input of heat. Thaw can occur over decades to centuries over the entire depth of permafrost ground, with impacts occurring while thaw progresses. During thaw, temperature fluctuations are subdued because energy is transferred by phase change between ice and water. After the transition from permafrost to non-permafrost, ground can be described as thawed (IPCC, 2019). <br /> <p>IPCC, 2019 . <a href=\"https://www.ipcc.ch/srocc/chapter/glossary/\">Annex I: Glossary [Weyer, N.M. (ed.)]. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. Intergovernmental Panel on Climate Change (IPCC)</a>. Accessed 21 October 2020.</p>"
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      "source:IPCC Glossary AR6",
      "source:UNDRR HIPS"
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      "Permafrost includes the mineral part of the ground (rocks) as well as any organic matter and ice if it is present (IPCC, 2019). The active layer is the uppermost part of permafrost, which thaws during summer and re-freezes during winter. Permafrost currently covers around 15 million km2, or approximately 24% of the land in the Northern Hemisphere, mostly in the Arctic region, and is very sensitive to climate change (Chadburn et al., 2017). Under future climate change scenarios, the Coupled Model Intercomparison Project Phase 6 (CMIP6) models project a gradual loss of permafrost of between 0.3 and 3.4 million km2 per °C increase in global surface air temperature (5th to 95th percentile; Burke et al., 2020). This is equivalent to a reduction of between 10% and 40% per °C in the annual mean frozen volume in the top 2 m of soil. These estimates are slightly lower than the 4.0 [-1.1; +1.0] million km2 per °C equilibrium sensitivity projected by Chadburn et al. (2017) who derived this using an observational-based relationship. The permafrost region represents a large, climate sensitive reservoir of organic carbon with approximately twice as much carbon in the soil as is currently contained in the Earth’s atmosphere. The top 3 m of permafrost soils contain 1035 ± 150 Pg C (Tarnocai et al., 2009; Hugelius et al., 2014) and could become vulnerable to decomposition under climate change. Schuur et al. (2015) suggested that between 5% and 15% of this permafrost carbon pool may be decayed and released as either carbon dioxide or methane during the 21st century, contributing to further global warming. This feedback could cause an additional warming of between 0.2% and 12% of the change in global temperature by 2100 (Burke et al., 2017). About half of below-ground carbon is stored in thermokarst landscapes vulnerable to abrupt thaw (Olefeldt et al., 2016) and has not been considered in these estimates. Therefore, these estimates may well be a substantial underestimation of carbon emissions from thawing permafrost (Turetsky et al., 2020)."
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