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Bankrupting the carbon budget Part III: melting permafrost

The global carbon budget tells us how much more carbon we can emit or ‘spend’ before we risk temperatures passing 1.5°C. On the current trajectory, we have about 316 Gigatonnes left before we run out around May 2029. This is why there is such an urgent push to reduce emissions by 2030.

But this budget is based on emissions from fossil fuels and agriculture. It doesn’t include emissions from ferocious forest fires, or even more concerning, melting permafrost (Fig. 1).

“Permafrost emissions are really hard to capture in global models, so even in the [new climate models] being used to project climate in the future and the behaviour of the planet and the global climate system, these emissions are not included…climate modellers don’t want to include it; permafrost modellers really think they should.” – Video (top) State of the Cryosphere Report, COP26

Fig. 1: Estimated permafrost changes 2003-2017. Images: International Cryosphere Climate Initiative at COP26. See the video at the top of this page for the full presentation.
Presently, emissions from permafrost are about the same as Japan’s; around 1.15 Gigatonnes. Not accounting for these emissions is like knowing that someone is withdrawing money from your bank account, but ignoring it. As temperatures continue to rise, more permafrost melts, so there’s even less available to ‘spend’. To compound the problem, the Arctic is warming as much as four times faster than the rest of the planet.
 
The global carbon budget does include a savings plan to draw down the excess from the atmosphere through ‘negative emissions’ technology and planting trees. But this dubious plan doesn’t include drawing down all these additional emissions from permafrost, placing an even greater burden on many future generations:

“Suppose we do reach net zero emissions by 2050, permafrost is going to continue emitting for at least a couple of centuries. So, in addition to the negative emissions that are in the models to keep temperature below 1.5°C, we also have to have negative emissions to offset permafrost. And we’re going to have to continue doing that for a couple of hundred years until the permafrost stabilises,” – Op cit.

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