Calculating the temperature rise

Note that the anomalies for the top image are calculated from 1979-2000 as a base, while anomalies for the above image are calculated from 1951-1980 as a base. When calculated from a pre-industrial base, these anomalies will be much higher.

Furthermore, a recent analysis shows that land temperatures 30°N- 90°N in summer 2023 were 2.07°C warmer than 1850-1900, while a subsequent longer-range analysis shows that the mean temperature in the period 1850 to 1900 was actually 0.24°C lower than had been presumed on the basis of the data collected at the time by meteorological stations.

A larger temperature rise comes with stronger feedbacks, e.g. the February 2024 temperature could be as much as 2.75°C above pre-industrial, corresponding with almost ⅕ more water vapor in the air. This is just one out of numerous feedbacks, while there are also developments such as reductions of sulfur emissions that can push up the temperature rise, as discussed in many earlier posts such as this one.

A larger temperature rise comes with increasingly extreme weather events that cause widespread damage and threaten to cause even more loss of life of people, livestock and wildlife, crop failures and ecosystem collapse in the tropics and elsewhere.

Strong hurricanes can significantly add to the danger. More hurricanes are forecast for the 2024 Atlantic hurricane season than during 1950-2020, as illustrated by the above image, from an earlier post.

A recent analysis concludes that Arctic terrestrial permafrost now emits more greenhouse gases than it stores, and the trend is likely to accelerate as temperatures keep rising in the Arctic. The highest carbon dioxide emissions over the 2000-2020 period came from inland rivers and wildfires. The non-permafrost wetlands exhaled the most methane, and dry tundra released the most nitrous oxide.

The joint CO₂e of emissions in this analysis only cover part of global emissions, e.g. the analysis excludes emissions from Arctic subsea permafrost and from oceans in general, from many mountain areas and from the Southern Hemisphere. The study also appears to have excluded emissions caused by anthropogenic disturbances such as clear-cutting, logging and fracking activities in the region, while calculations typically use a low global warming potential (GWP) for methane (100-year horizon).

The prospect of further releases looks dire. The analysis gives estimates that the upper three meters of permafrost region soils store 1,000 Gt of soil organic carbon, while deeper deposits could store an additional amount of as much as 1,000 Gt C. The analysis concludes that the permafrost region is the largest terrestrial carbon and nitrogen pool on Earth. Miesner et al. warn that an additional 2822 Gt of organic carbon is stored in subsea Arctic shelf permafrost and Huang et al. warn that the top two meters of soil globally holds about 2300 Gt of inorganic carbon, which has been left out of environmental models, and 23 Gt of this carbon may be released over the next 30 years.

The transition from sink to source of the region is an important feedback of the temperature rise that is not fully reflected in many climate models. According to the IPCC, 14–175 Gt CO₂e (in carbon dioxide and methane) gets released per 1°C of global warming, which is likely to underestimate the situation by downplaying many feedbacks. Despite the dire situation, the IPCC keeps promoting less effective policies such as support for biofuel and fuel efficiency standards, as discussed in earlier posts such as this one.