Melting Permafrost: Limiting Warming to 1.5º C

A new study, covered in Carbon Brief, looks at the differences in the melting of the permafrost considering a warming of 1.5ºC vs 2ºC. Permafrost, or ground/soil which is frozen below 0ºC for two or more consecutive years, will be one of the casualties of climate change. Essentially, the  study says that limiting warming to 1.5ºC against 2ºC may save an area equal to two million square kilometers.

The Paris Agreement of 2015 was an instrumental international agreement in the fight for limiting climate change, agreeing on a goal of stabilizing temperature rise to 2ºC from the baseline temperature of 1780, with an ambitious goal of 1.5ºC. Achieving half a degree of lower warming will aid in reducing the impacts of climate change such as a sea level rise, which is 10 cm less than what may be caused by a warming of 2ºC.

So why should the melting of this frozen soil should be limited? Firstly, a number of human settlements are located on permafrost, such as in Alaska.The infrastructure is built on and below the ground. Its melting will jeopardize these infrastructure systems and undermine the stability of structures as the ground will start sinking unevenly and possibly may become unstable. The soil erosion is then also accelerated, as there is nothing holding it frozen and safe from the elements. Communities, which live in and depend on the environment around the permafrost, are being severely affected. Figure 1 shows three cities with more than 100,000 inhabitants located on permafrost which is currently a continuous and homogenous piece.

Secondly, as permafrost melts, the organic material (see Figure 2) that has been frozen for a number of years is exposed. The organic matter starts decomposing and releases methane along with carbon dioxide. Permafrost has more carbon than what is present in the atmosphere. So this melting may end up releasing more carbon over the long period of melting.


Figure 1: Changes in area covered by permafrost for a warming of 1.5ºC (a) vs 2ºC (b). Colored area shows the area covered by permafrost based on observations from 1960 - 1990. The color scale is from blue to green to grey. Blue represents a continuous area of permafrost, while grey represents areas with isolated patches of permafrost. Source: Chadburn et al. (2017).


Figure 2: Amount of organic soil carbon in the top three meters of permafrost. Black dots represent field sites where data was collected. Source: Schuur et al. (2015)

The red lines in Figure 1 represent the likely outlines for the maximum and minimum areas covered by the continuous permafrost for the respective warming levels. Both the outlines for the minimum area covered for a warming of 1.5ºC and 2ºC, represented by dotted red lines, put the cities outside it. This means that the permafrost they are on is likely to melt. Thus, they are exposed to the impacts of melting permafrost. However, for the outlines for maximum area covered, represented by the solid red lines, they are likely to be inside it for 1.5ºC and outside for 2ºC. This means that it may be possible for the cities to be on continuous permafrost if the warming is limited to 1.5ºC. Along with the reductions in emissions from limiting the melting, the cities and other settlements will continue to be on stable ground.

Written by: Prathmesh Gupta
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Michelle

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