May 17, 2021 - Energy & Environment

The window to limit global warming to 1.5°C is closing

Illustration: Annelise Capossela/Axios

Illustration: Annelise Capossela/Axios

Just 20 out of 400 of the climate scenarios examined in a landmark 2018 United Nations climate report would have a realistic chance of limiting global warming to 1.5°C (2.7°F) above preindustrial levels by 2100, a new study finds.

Why it matters: The study, by more than a dozen researchers from around the world, shows that even the scenarios they identified would still need to employ at least one carbon emissions reduction technology at a level they classify as "challenging."

The big picture: Many of the scenarios used for the U.N. study relied heavily on employing technologies that pull carbon out of the air and store it permanently in the ground.

  • However, such carbon removal technology does not yet exist at scale, making relying on it as a "silver bullet," as the study says, extremely risky.

How it works: The study, led by Lila Warszawski of the Potsdam Institute for Climate Impact Research (PIK), used existing research to define whether the use of a particular emissions reduction "lever" by midcentury would be "reasonable," "challenging" or "speculative."

  • They quantified the range of emissions reduction potentials of each of these levers, which include everything from decarbonizing electricity generation to making dramatic cuts in energy demand and shifting ecosystems from net carbon sources into carbon sinks.

What they're saying: "The necessary emissions reductions are hard to achieve, technically but also politically. They require unprecedented innovation of lifestyles and international cooperation," said co-author Johan Rockström from PIK, in a statement.

  • "I understand anyone who thinks we might fail the 1.5°C target. ... Yet I think limiting warming at 1.5°C is worth just every effort because this would limit the risk of giving some tipping elements in the Earth system an additional push."
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