Aug 9, 2021 - Energy & Environment

Scientific advances narrow range of scenarios for projected global warming

Man watching wildfire
A local resident reacts watches a forest fire approach the village of Pefki on Evia island in Greece. Photo: Angelos Tzortzinis/AFP via Getty Images

New climate science insights have enabled researchers to narrow the projected range of warming that would occur for a doubling of carbon dioxide in the atmosphere, which is known as the "equilibrium climate sensitivity" (ECS).

The intrigue: Some of the newer computer models used for the latest Intergovernmental Panel on Climate Change report show higher-end climate sensitivity results, and therefore, much more warming.

How it works: However, armed with better knowledge of historical climate change, and guided by additional tools, scientists narrowed the "very likely" range of global warming by the end of the century, relative to 1850-1900 levels, to between 2°C and 5°C (3.6°F to 9°F). The likely range is now between 2.5°C and 4°C (4.5°F to 7.2°F).

  • This compares to the previous report's range of 1°C to 6°C (1.8°F to 10.8°F), with a "likely" range of 1.5°C to 4.5°C.
  • The new very likely range has at least 90% confidence.
  • This means we're less likely to get by with low levels of warming by adding more CO2 to the air, but also that higher-end scenarios falling outside the range are more remote possibilities.

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