Arctic permafrost emits more carbon than it absorbs

15% of the surface of the Northern Hemisphere is covered by Arctic permafrost

The perpetually frozen ground that covers 15% of the Northern Hemisphere has become a net emitter of greenhouse gases. The Arctic permafrostmelting due to global warming, is releasing more methane (CH4) and nitrous oxide (N2O) into the atmosphere than it can absorb, while the balance is still essentially equal for carbon dioxide (CO2).

It is the result of the first scientific assessment of the greenhouse gas balance conducted over the entire Arctic region. Very important data because they give the most precise measurement so far – even if the margins of uncertainty remain high – of the exchange of the main climate-changing gases at those latitudes. But above all because the study manages to quantify the role of global warming in both its main aspects: the melting of the Arctic permafrost, which favors the release of greenhouse gases, and the increase in vegetation, which increases the absorption of CO2.

The Arctic permafrost contains within it double the carbon present in the atmosphere today and in the last 50 years its extension has already reduced by 7%. Many studies conducted recently argue that limiting global temperatures to +1.5°C above pre-industrial times will slow down this phenomenon but will not be able to stop it. Knowing the real net emission balance, therefore, is essential to establish whether the Arctic is a “climate bomb” that could explode even in the best emission scenario. And understand how many greenhouse gases could actually be released, impacting the size of our carbon budget for the Paris Agreement goals.

The study, recently published on Global Biogeochemical Cycles, concludes that the net balance is positive for both methane and N2O. The analysis was carried out starting from a database that collects field measurements between 2000 and 2020. In these 20 years, the Arctic permafrost has emitted on average 12 million tonnes (Mt) of carbon deriving from CO2 every year, 38 Mt of carbon from methane and 0.67 Mt of nitrogen from nitrous oxide. By subtracting absorptions from these values ​​and also including lateral fluxes of greenhouse gases (which depend on changes in the surface of ecosystems and exchanges between ocean and land), permafrost emerges as a net emitter. The final balance is +144 Mt of carbon and 3 Mt of nitrogen every year.