Thread by @JoeriRogelj

EXPLAINER: new projections for the next 5 years by @metoffice and @WMO indicate that there's a high chance that one of these years is 1.5°C warmer than average preindustrial levels.

What does this mean?
A short explainer.

#ClimateAction

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hadleyserver.metoffice.gov.uk/wmolc/

The 1.5C level in the @metoffice announcement should not be confused with the 1.5C limit in the Paris Agreement.

The Paris targets refer to global warming - that is, the temperature increase of our planet once we smooth out important year-to-year variations (see👇)
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Even in a stable climate, global temperatures differ from year to year because of noise in the climate system.

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E.g., an el Niño year will be slightly warmer than other years, or after a large volcanic eruption global temperatures will be temporarily much cooler.

In both cases the global temperature in these years does not represent the long-term warming. (see @NCAR_Science fig👇)
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In a world that has warmed by 1.5°C we expect half of the years to be warmer than 1.5°C, and the other half cooler.

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If you want to understand this better, check out a @CarbonBrief explainer I wrote shortly after the Paris Agreement with @CarlSchleussner:

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carbonbrief.org/guest-post-int…

For the scientists amongst you: we also wrote this up in a contribution to @theAGU journal Geophysical Research Letters.

Getting It Right Matters: Temperature Goal Interpretations in Geoscience Research

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agupubs.onlinelibrary.wiley.com/doi/full/10.10…

In conclusion: A single year hitting 1.5C doesn't mean the Paris limits are breached, but is nevertheless very bad news.

It tells us once again that #ClimateAction to date is insufficient and emissions need to be reduced urgently to zero to halt #GlobalWarming .

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