The earth has been exceptionally warm of latecgebet, with every month from June 2023 until this past September breaking records. It has been considerably hotter even than climate scientists expected. Average temperatures during the past 12 months have also been above the goal set by the Paris climate agreement: to keep global warming below 1.5 degrees Celsius over preindustrial levels.

We know human activities are largely responsible for the long-term temperature increases, as well as sea level rise, increases in extreme rainfall and other consequences of a rapidly changing climate. Yet the unusual jump in global temperatures starting in mid-2023 appears to be higher than our models predicted (even as they generally remain within the expected range).

Jan 2023

Jul

Jan 2024

Jul

0.8

1

1.2

1.4

1.6

+1.8°C above preindustrial average

Average global temperature

In Sept. 2023, the observed temperature was 0.5°C higher than the previous monthly record

Record-breaking months

Projected temperature range

Source: NASA Goddard Institute for Space Studies

Note: The projected range is based on the long-term temperatures trends combined with a three-month lag from the ocean temperatures in the tropical Pacific

While there have been many partial hypotheses — new low-sulfur fuel standards for marine shipping, a volcanic eruption in 2022, lower Chinese aerosol emissions and El Niño perhaps behaving differently than in the recent past — we remain far from a consensus explanation even more than a year after we first noticed the anomalies. And that makes us uneasy.

Why is it taking so long for climate scientists to grapple with these questions? It turns out that we do not have systems in place to explore the significance of shorter-term phenomena in the climate in anything approaching real time. But we need them badly. It’s now time for government science agencies to provide more timely updates in response to the rapid changes in the climate.

Weather forecasts are generated regularly come rain or come shine. Scientists who do near-real-time attribution for extreme weather are also able to react quickly to tease out the effect of global warming on any new event.

1980

1990

2000

2010

2020

0.25

0.5

0.75

1

1.25

+1.5°C above preindustrial average

Average global temperature

Predicted 2023 temperature ranges

2023’s average temperature of +1.4°C exceeded even the high range of predictions

Source: NOAA, NASA, Berkeley, Hadley and Copernicus datasets

Note: The four predictions shown are from the Meteorological Office, Berkeley Earth, Carbon Brief, and Gavin Schmidt.

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