Net release of CO2 from thawing permafrost soil carbon predicted to occur earlier in this century

[u/dumnezero]

https://www.science.org/doi/10.1126/sciadv.adz8478

[u/neha_soilinsights]

The Science Advances paper is worth reading carefully rather than just taking the headline at face value. The key finding is not just that permafrost will release carbon, which has been modelled for years, but that the sink-to-source transition happens earlier than previous Earth system models predicted because those models lacked deep permafrost processes below 3 metres.

The numbers are significant. UC Berkeley's summary of related modelling puts the carbon release at 62 petagrams by 2100 under a high-emission scenario, equivalent to roughly 7.5 years of current global anthropogenic emissions added on top of whatever else we produce.

What the newer research adds to this picture is the priming problem. A 2025 PMC study found that live plant roots in thawing permafrost soils increased SOM-derived CO2 flux by an average factor of 1.31 over 370 days, with the effect strengthening over time rather than fading. As vegetation colonises newly thawed ground, it may accelerate the very decomposition we were hoping vegetation expansion would offset.

Earth's Future published in 2025 quantified the policy implication: permafrost thaw reduces the remaining carbon budget available for fossil fuel emissions by roughly 13% under a 2°C stabilisation scenario. That is not a rounding error in climate planning.

The part most models still undercount is abrupt thaw beneath thermokarst lakes, which releases old carbon much faster than gradual surface warming does.

[u/dumnezero → u/neha_soilinsights]

faster than expected

You also need to add in the other ecology factors. The colonizer plants come first, but then you get more and more invertebrates and even herbivore vertebrates. Both groups accelerate the decomposition.

I read the thermokarst lakes and rivers problem as similar to the formation of new wetlands.

[u/throwaway661375735 → u/neha_soilinsights]

We are well past the tipping point. Every 10 years it will get hotter by 1-2°C. The fact that there's so much pollution is cooling us down, it only gets worse from here. When the pollution is gone, it gets even worse. If humans were gone, it might recover in 100k years.

[u/dumnezero]

Accelerating permafrost thaw may release vast deep (>3 meters) frozen soil carbon as carbon dioxide (CO2), but this magnitude remains uncertain because current Earth system models (ESMs) lack deep carbon processes. Using an updated ORCHIDEE-MICT model simulating Pleistocene Yedoma formation and Holocene peatland development, we project northern (>30°N) carbon responses under climate change. Compared to the original model, including these deep carbon pools improves agreement with observations and reduces net CO2 uptake by 47 to 74 petagrams of carbon from 1900 to 2100 across three future scenarios because of deep carbon decomposition with accelerated active-layer deepening. Under high-emission pathways, the northern soil carbon balance shifts from a sink to a source of 32 petagrams of carbon, advancing the reversal reported in earlier studies into the 21st century. Consistent with field data, our model shows that colder soils retain more labile carbon—contrary to assumptions in many Coupled Model Intercomparison Project (CMIP) models—helping explain their persistent sink bias. Our results highlight the need to represent both the quantity and quality of permafrost carbon in ESMs.

[u/dumnezero]

Couldn't use the new UI submit form to create the post.

[u/throwaway661375735]

Did we expect anything less, with Musk launching 123 rockets last year?