A climate-modelling study estimates that greenhouse-gas emissions triggered by rising temperatures could add 0.2–0.4°C of global warming by 2100, depending on the emissions pathway. The additional emissions come from permafrost, wetlands, freshwaters and wildfires.
Published in Environmental Research Letters on 10 September 2026, the study estimates that these processes could amplify post-2020 global warming by about 20%–30% by the end of the century. The result is a model-based projection, not a direct observation that this additional warming has already occurred.
Contents
- What the study estimated
- How warming creates more greenhouse-gas emissions
- Why the result matters
- Uncertainty and what to watch
What the study estimated
The authors assessed six emissions categories:
- carbon dioxide and methane from permafrost;
- methane from wetlands;
- methane from freshwaters;
- carbon dioxide and methane from wildfires.
They defined “warming-induced emissions” as emissions caused by warming after 2020. Emissions that had already occurred by 2020 were treated as part of the baseline rather than counted again as new feedback emissions.
The researchers derived relationships between temperature and emissions from existing process-based model estimates. They then added those emissions to three climate scenarios in MAGICC version 7.5.3, a reduced-complexity climate model calibrated against more complex Earth-system models.
For each scenario, the study compared a baseline projection without the newly added feedback emissions with a matched projection that included them.
| Scenario | Warming-induced methane rate by 2100 | Warming-induced CO₂ rate by 2100 | Additional warming by 2100 | Amplification of post-2020 warming |
|---|---|---|---|---|
| SSP1-2.6 | 50 ± 30 Tg CH₄ per year | 2 ± 3 Pg CO₂ per year | 0.2 ± 0.2°C | 30 ± 30% |
| SSP2-4.5 | 150 ± 50 Tg CH₄ per year | 10 ± 7 Pg CO₂ per year | 0.3 ± 0.2°C | 25 ± 15% |
| SSP4-6.0 | 190 ± 60 Tg CH₄ per year | 15 ± 9 Pg CO₂ per year | 0.4 ± 0.2°C | 20 ± 10% |
Tg means teragrams, or million tonnes, while Pg means petagrams, or billion tonnes. The projected extra warming is measured relative to the study’s 2020 baseline.
The combined warming-induced methane emission rate increased by an estimated 97 ± 6 teragrams of methane per year for each degree Celsius of warming across the three scenarios. For SSP2-4.5 and SSP4-6.0, combined carbon dioxide emissions from permafrost and wildfires increased by an estimated 7 ± 1 petagrams of carbon dioxide per year for each degree Celsius of warming. The paper notes that the permafrost carbon dioxide relationship is nonlinear in SSP1-2.6.
The additional warming is similar across scenarios until around 2050: the study estimates approximately 0.06 ± 0.06°C of extra warming by then. Differences between scenarios become more pronounced during the second half of the century.
The lower percentage amplification in SSP4-6.0 should not be interpreted as weaker feedback emissions. That scenario has the highest absolute additional warming and the highest projected feedback emission rates. Its percentage is lower because the amplification is calculated relative to the larger amount of post-2020 warming in that pathway.
How warming creates more greenhouse-gas emissions
These processes are examples of positive climate feedbacks. A positive feedback occurs when warming changes the climate system in a way that produces further warming.
When permafrost thaws, previously frozen organic matter becomes available for decomposition. In relatively dry and oxygen-rich conditions, decomposition tends to produce carbon dioxide. In wetter, oxygen-poor environments, it can produce methane.
Warming can also increase methane emissions from wetlands and freshwaters through processes including enhanced methanogenesis, the microbial production of methane, increased release of methane bubbles and changes in the extent of water bodies.
Warmer and drier conditions can raise wildfire activity by reducing fuel moisture and increasing fire danger. Fires release carbon dioxide and methane, although the study’s main analysis does not include all possible changes in vegetation or other processes that could offset some emissions.
The study estimates that methane accounts for about 60% of warming-induced warming in the early decades. Carbon dioxide’s contribution grows over time, reaching about 50%–60% by 2100. This reflects the different atmospheric behaviour of the two gases: methane is shorter-lived, while carbon dioxide accumulates over long timescales.
Among the sources included, the paper ranks permafrost carbon dioxide as the largest individual contributor to projected warming-induced warming. It is followed by wetland methane, permafrost methane, wildfire carbon dioxide, wildfire methane and freshwater methane.
Why the result matters
The study combines several warming-induced sources in one framework and estimates their aggregate temperature effect. The authors describe the result as a first-order assessment, rather than a complete Earth-system representation of every warming-related emission.
The paper argues that these processes are largely absent from the Earth-system models used for many climate projections. It reports that, among 11 models discussed in the cited IPCC AR6 biogeochemical-feedback context, none included warming-induced methane emissions from wetlands or freshwaters. Only some included permafrost or wildfire effects.
If the study’s central estimates are approximately correct, projections that omit these emissions could understate future warming and overstate the remaining carbon budget. The additional warming could therefore matter for long-term mitigation planning and climate-risk assessments.
The result does not mean that mitigation becomes ineffective. The model projects lower warming-induced methane and carbon dioxide emissions, as well as lower additional warming, in the stronger-mitigation SSP1-2.6 scenario. Reducing the initial warming reduces the temperature-driven emissions that create the feedback.
The study also reports that additional warming continues to increase even when some warming-induced emission rates peak and decline. This is because carbon dioxide accumulates in the climate system and the temperature response to emissions occurs with a delay.
Uncertainty and what to watch
The reported estimates have substantial uncertainty. The study gives combined emission-sensitivity and climate-response uncertainties of approximately ±0.2°C for additional warming and roughly ±10%–30% for warming amplification.
Most of the temperature-emission relationships come from one underlying study for each source, so between-model uncertainty is not systematically quantified. The paper also reports disagreement among existing estimates for some processes, including the temperature sensitivity of wetland methane emissions.
The relationships are intended for the modelled temperature range of approximately 1.3–3.3°C above preindustrial levels and for projections through 2100. The study treats the included sources independently in its main projections and does not model recursive feedback, in which the extra warming generated by the emissions produces still more emissions. The authors estimate that including this recursive effect would increase projected temperature by about 18% by 2100.
Other limitations include:
- only a subset of potential warming-induced greenhouse-gas sources is included;
- interactions among permafrost thaw, wetland expansion, wildfires and other processes are omitted from the main analysis;
- the model is not a fully coupled Earth-system model containing all of these processes;
- possible negative or offsetting feedbacks, including aerosol-related effects and compensating vegetation growth after permafrost thaw or wildfire, are not included;
- warming-induced methane from rice, forest-dieback carbon dioxide and nitrous oxide emissions remain among the omitted sources.
The next important step is comparison with other models and incorporation of these processes into fully coupled Earth-system models. Such work will help determine how much of the projected warming is robust across different representations of permafrost, wetlands, freshwaters, fires, vegetation and atmospheric chemistry.