The last 12 months were the hottest in 150 years of recordkeeping — and probably in the last 125,000 years — thanks to human-caused climate change, a new report finds.
From November 2022 through October 2023, the planet’s average temperature was about 1.3 degrees Celsius higher than the average temperature from 1850 to 1900, say researchers with the nonprofit group Climate Central. That’s just shy of the 1.5-degree threshold often cited as a benchmark for avoiding irreversible impacts on the climate.
And over the past year, about 1 in 4 people around the world experienced a climate change–driven heat wave that lasted at least five days, the scientists found. The report, released on November 9, comes just ahead of the 28th United Nations Climate Change Conference of the Parties, which begins on November 30. That’s intentional, says Andrew Pershing, vice president for science at Climate Central. There is no doubt that fossil fuels are driving most of this heat, and it’s to be hoped that the world’s nations will take note of these findings, he says.
Global average numbers can be hard to grasp. So the new report also quantifies temperatures that people around the world are actually experiencing day-to-day, and how much those are attributable to climate change, Pershing says. “We have these super important global numbers such as the 1.5- or 2-degree warming targets, but that isn’t the experience that people on planet Earth have,” he says. “We wanted to develop a way to really localize that experience … to talk about how climate change influenced that day’s temperatures on any given day anywhere in the planet.”
To that end, the analysis used Climate Central’s Climate Shift Index, or CSI, a system first described by the organization in 2022. CSI is a daily local temperature attribution system that uses a combination of observational data and climate simulations to determine the likelihood that local temperature variations are attributable to climate change. Extreme heat is a relative term, dependent on both place and time. So, in this report, the researchers considered extreme heat for a given location to be daily temperatures that would have been in the 99th percentile for that place from 1991 to 2020 — temperatures, in other words, that locals would recognize as insanely hot.
Using that index with data from hundreds of countries, states, provinces and major cities, the researchers found that about 90 percent of the world’s population, or 7.3 billion people, experienced at least 10 days of extreme temperatures in the last year that were very strongly affected by climate change.