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What year will the 2˚C climate threshold be crossed?

At the Paris climate accord, world leaders promised to keep the global temperature increase this century (relative to pre-industrial levels) "well below 2 ˚C". Many experts were (and are) skeptical about this being feasible. Hence, it was asked whether there would be 5 consecutive years in which the global temperature was at least 2 ˚C above pre-industrial levels by 2100. As of the writing of this question, the Metaculus community assigns an 80% probability to this happening. The year of comparison chosen was 1880.

Here, it is asked: In what year will the average global temperature be at least 2 ˚C above the 1880 value for the first time?

Note that the answer to this question could be never and that a non-never resolution could occur without triggering a positive resolution to the previously mentioned binary question. In the case of a non-never resolution, December 31st of the first year to achieve 2 ˚C warming shall be used as the resolution date.

Data for resolution shall come from NASA, if possible. Note that the data in the link is normalized relative to the 1951-1980 baseline and 1880 stands at -0.19, so the critical value to look for is 1.81 (for temperature anomaly). It is possible, though, that the linked-to data source will no longer be available in a few years, in which case the best alternative (as of the judgement of Metaculus staff) shall be used for resolution.

Closing date is set to 2025, but should resolution triggering information become available earlier, the question shall close retroactively one year prior to that information becoming available. (In all cases in which the question was still open at some point within one year of the information becoming available.)


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