It is notoriously tricky to synthesize data from all the world’s weather stations into one measure of global warming, but all of the major efforts to do so for 2023 are now in, and they are also all in distressing alignment: Last year was the warmest recorded in modern history, and it broke that record by an exceedingly large margin, one that conventional climate science has not yet managed to adequately explain.
The big data sets are now all in, and one of them, published by Berkeley Earth last week, contained what counts as an eye-popping assertion even against the backdrop of the record-setting year: The global average temperature was more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) above the preindustrial level. (Other models had it just below.)
When climate scientists and advocates talk about the risks of breaching 1.5 degrees Celsius of warming — as they have somewhat obsessively at least since it was established as the ambitious climate goal of the 2015 Paris Agreement and since the Intergovernmental Panel on Climate Change described the consequences of exceeding it in its 2018 Special Report on Global Warming of 1.5°C — this isn’t exactly what they mean. That threshold describes a long-term average rather than a single-year anomaly. But because it describes a multidecade average, the measure will always be backward-looking, with the precise moment the world crossed the 1.5 mark clear only in retrospect. This year a handful of prominent scientists have suggested that when we do look back to mark that time, we may well circle 2023.
How hot was it last year?
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— New York Times Opinion (@nytopinion) January 18, 2024