How Can We Calculate the Rise in Temperatures Caused by Global Warming?

By Agence Science-Presse

Those who enjoy discussing nature’s role in global warming have their work cut out for them: intensifying wildfires will release more CO2 into the atmosphere — but how much? Thawing Arctic soils will release more methane — another greenhouse gas — but how much?

These are questions for which only partial answers exist, American researchers lament in a recently pre-published study. And these questions are far from trivial, as this « excess » greenhouse gas could add up to 0.6 degrees Celsius to global warming, they estimate.

These factors are not always included in climate models used by the United Nations’ IPCC (Intergovernmental Panel on Climate Change), since this data is only partial. Which means that IPCC scenarios, and those of other organizations that calculate greenhouse gas reductions between now and 2050 or 2100, are bypassing important information in the climate change puzzle.  

This issue has frequently been raised over the years. For instance, we can make a rough estimate of the quantity of organisms “dormant” in the frozen Arctic soil, but we do not know how fast it will all thaw — and, consequently, what impact this will have on the amount of greenhouse gases in the atmosphere by 2050 or 2100.

“If you don’t include all the emissions entering the atmosphere, then you are hamstrung from the start,” says climate scientist Brian Buma of the Environmental Defense Fund, a co-author of the study.

In addition to wildfires and permafrost, one of the major sources of warming-induced greenhouse gas emissions comes from wetlands. Increased precipitation accelerates the growth of these areas, which are rich in vegetation and in microorganisms that emit methane and nitrous oxide — the third most significant greenhouse gas.

But northern regions are the biggest cause for concern.

According to the 2024 Arctic report from the U.S. National Oceanic and Atmospheric Administration (NOAA), the combination of wildfires and thawing ground has turned the tundra into a source of greenhouse gas emissions, reversing its role as a carbon sink after thousands of years. The fact that 2026 is shaping up to be an El Niño year further complicates the picture.

The authors of this study are part of a multidisciplinary effort to precisely integrate available data on these wetlands, the Arctic, and wildfires into future climate models.