


- Emissions of greenhouse gases from permafrost will be larger than earlier projections because of abrupt thaw processes, which are not yet included in global climate models.
- These abrupt thaw effects could as much as double the emissions from permafrost thaw under moderate and high emissions scenarios.
- Emissions from permafrost thaw could be yet higher due to effects on plant root activity, which increases soil respiration.

- Emissions of greenhouse gases from permafrost will be larger than earlier projections because of abrupt thaw processes, which are not yet included in global climate models.
- These abrupt thaw effects could as much as double the emissions from permafrost thaw under moderate and high emissions scenarios.
- Emissions from permafrost thaw could be yet higher due to effects on plant root activity, which increases soil respiration.

Thawing permafrost in the Arctic is expected to release significant quantities of greenhouse gases over the coming decades, enough to merit consideration in climate negotiations. Recent research shows it will be larger than earlier projections due to abrupt permafrost thaw processes.
Permafrost is a perpetually frozen layer beneath the seasonally thawed surface layer of the ground, covering 18 million square kilometers in the northern hemisphere and storing 1,460–1,600 petagrams of carbon (PgC) – one third of the world’s soil carbon. The Arctic is responding quickly to climate change, with air temperatures warming more than twice as fast as the global average. Unusually warm summers – such as the record-breaking 2020 heatwave in Siberia and Svalbard – are happening more often. This is causing Arctic permafrost to thaw in some northernmost regions almost a century earlier than some climate models projected.
Peatlands have year-round waterlogged conditions that slow plant decomposition, allowing peat to accumulate – one of the largest natural carbon stores on land. Nearly half of northern peatlands are underlain by permafrost. Abrupt thaw could shift the entire northern hemisphere peatland carbon sink into a net source of global warming, dominated by methane, lasting several centuries.
An ecological feedback associated with permafrost thaw that is not yet included in global climate models is a priming effect on soil respiration, caused by an increase in root activity. This amplifies soil carbon loss, with an additional 40 Pg carbon loss (corresponding to 147 Gton CO2) projected from Arctic permafrost by 2100 for RCP8.5.
In the Special Report on 1.5°C, the IPCC assumed that permafrost thaw will release 100 Gton of CO2 equivalents cumulatively to year 2100. Abrupt thaw processes could, under moderate to high emissions scenarios, approximately double the cumulative carbon emissions compared to gradual thaw alone. This may also apply to emissions scenarios consistent with 1.5°C or 2°C warming targets, which would impose tighter restrictions on the remaining anthropogenic carbon emission budgets.

Thawing permafrost in the Arctic is expected to release significant quantities of greenhouse gases over the coming decades, enough to merit consideration in climate negotiations. Recent research shows it will be larger than earlier projections due to abrupt permafrost thaw processes.
Permafrost is a perpetually frozen layer beneath the seasonally thawed surface layer of the ground, covering 18 million square kilometers in the northern hemisphere and storing 1,460–1,600 petagrams of carbon (PgC) – one third of the world’s soil carbon. The Arctic is responding quickly to climate change, with air temperatures warming more than twice as fast as the global average. Unusually warm summers – such as the record-breaking 2020 heatwave in Siberia and Svalbard – are happening more often. This is causing Arctic permafrost to thaw in some northernmost regions almost a century earlier than some climate models projected.
Peatlands have year-round waterlogged conditions that slow plant decomposition, allowing peat to accumulate – one of the largest natural carbon stores on land. Nearly half of northern peatlands are underlain by permafrost. Abrupt thaw could shift the entire northern hemisphere peatland carbon sink into a net source of global warming, dominated by methane, lasting several centuries.
An ecological feedback associated with permafrost thaw that is not yet included in global climate models is a priming effect on soil respiration, caused by an increase in root activity. This amplifies soil carbon loss, with an additional 40 Pg carbon loss (corresponding to 147 Gton CO2) projected from Arctic permafrost by 2100 for RCP8.5.
In the Special Report on 1.5°C, the IPCC assumed that permafrost thaw will release 100 Gton of CO2 equivalents cumulatively to year 2100. Abrupt thaw processes could, under moderate to high emissions scenarios, approximately double the cumulative carbon emissions compared to gradual thaw alone. This may also apply to emissions scenarios consistent with 1.5°C or 2°C warming targets, which would impose tighter restrictions on the remaining anthropogenic carbon emission budgets.


