THE official numbers aren’t in yet, but this past year was almost certainly the hottest on record, with high temperatures driving extreme events across the planet. From record-breaking wildfires in Canada to record-low levels of sea ice in Antarctica, researchers say this year’s weather phenomena were shocking, even if they were precisely what was anticipated with climate change.
“We’re getting to a point where one year was bound to happen where [the effects of climate change] would be so pervasive we started to pay attention,” says at the University of Colorado Boulder. “Maybe it was 2023.”
The first intimations that this year would be one for the record books began with forecasts in late 2022 that the Pacific Ocean would see a shift to a warmer El Niño climate pattern the following year. This came after three years of a cold La Niña pattern that had masked the effect of steadily rising concentrations of greenhouse gases in the atmosphere, says at the US National Oceanic and Atmospheric Administration (NOAA). “During La Niñas, the ocean takes up more heat than usual,” he says. “During El Niño, that heat is released back into the atmosphere.”
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The results of this shift started to become clear in June, when global average temperatures first began setting records. Some regions, such as parts of the North Atlantic Ocean, saw unprecedented temperatures, as warming due to rising greenhouse gases exacerbated heat driven by natural variability in the climate system. June also saw heat and dry weather intensify wildfires burning in Canada. These went on to smash records for the area burned and carbon emitted, and sent suffocating smoke across the densely populated US east coast.
Briefly the hottest month on record, June was soon supplanted by July, which saw things hot up even more. A wobbly pattern in the jet stream continued to drive simultaneous heat waves on three continents. To take one scorching example, Phoenix, Arizona, suffered nearly the entire month with temperatures above 43°C (110°F). The global average temperature for July was more than 1.5°C above the pre-industrial average – the first month in which this has happened during the northern hemisphere summer. Researchers found that these temperatures would have been virtually impossible without climate change.
Record highs
The hot streak continued in the following month, which was the hottest August on record. One of the most striking events was in South America, where parts of Chile and Argentina saw what was effectively a heatwave in the middle of winter. Another alarming indicator between June and August – which was the hottest three-month stretch on record – was in Antarctica, where sea ice failed to recover during the southern winter from record low levels set earlier in the year.
The extraordinary heat didn’t let up with the seasons. September, though not as hot as the preceding months, saw the largest difference when compared with historical temperatures on record, rising to around 1.8°C above the pre-industrial average – a huge jump from any previous year. at Berkeley Earth memorably the size of this anomaly “gobsmackingly bananas”.
That put to rest nearly all doubt that 2023 would end up the hottest year on record, replacing the previous record year in 2016, which, not incidentally, also saw a strong El Niño develop in the Pacific. In its end of September climate report, NOAA had the odds at 99 per cent that 2023 would be the hottest year on record. An official determination will be made in January.
“The truth is that we are shocked by the ferocity of the extreme weather events in 2023,” at Oregon State University and his colleagues wrote in an end-of-year report on the state of the climate. “We are afraid of the uncharted territory that we have now entered.”
Between January and the end of September, the global average surface temperature was 1.1°C above the pre-industrial average, according to NOAA. That is 0.03°C above the previous record for that period from 2016. But this record may not stand for long. As El Niño reaches its peak strength early next year, McPhaden says it isn’t unreasonable to expect 2024 to be even hotter. “We’re on an escalator that’s only going one way. And that’s up.”
