This is the first time in history that Earth has broken the 1.5 C climate limit
An overview of extreme hot temperatures from July to September 2023, according to Gavin Schmidt, a climate scientist at NASA’s Goddard Institute for Space Studies
“When it started getting weird was around June and July of the summer,” says Zeke Hausfather, a climate scientist with the organization Berkeley Earth. July 2023 crushed all previous heat records from that month. August surpassed records even more. “September was the best month of my life, with gobsmacking bananas nearly a full degree above previous records,” I stated back in September.
In some ways, the extreme hot temperatures from the past two years are not surprising at all, says Gavin Schmidt, a climate scientist at NASA’s Goddard Institute for Space Studies: an increasingly hot planet is the well-forecasted outcome of burning vast amounts of fossil fuels.
He says that you shouldn’t get distracted by year-to-year variability. “As long as we’re dumping greenhouse gas into the atmosphere, the climate’s going to get warmer. And that’s going to have enormous impacts on people’s lives.”
Russell Vose, a climate scientist at the National Center for Environmental Information, says it was another really warm year.
The 2022 volcano eruption that killed a volcano may have a zero warming effect on the climate and climate system, says Andrew Gettleman
El Niño and La Niña events are part of a natural climate cycle that can influence weather across a broad swath of the planet. During an El Niño phase, which occurs every few years on average, global temperatures tend to be higher overall, while cooler global temperatures generally prevail during the La Niña phase.
Sometimes, eruptions release gases and particles into the air that reflect sunlight back into space and cool the Earth. But the volcano, which erupted in 2022, was underwater. It shot a bunch of water into the air which can trap heat.
Scientists theorize that the warming effect may have played a role in the mystery heat. The impact was probably minimal after close study.
“People talked about that a lot but our best guess is that it had an impact of zero,” says Andrew Dessler, a climate scientist at Texas A&M University.
A December study in Science focused on clouds. Overall, it found, cloud cover—and the bright white reflectivity they often bring—has dropped in several key parts of the globe over the past decade, and particularly strongly in 2023. The overall effect, the authors calculated, could add up to about 0.2 C of extra warming—almost exactly the size of the gap between climate models and actual average global temperatures.
The fuels used in the shipping industry were changed in 2020. The old fuel was heavy in sulfur; once in the atmosphere, sulfate pollution attracted water droplets, causing visible cloud plumes to trail behind a ship chugging across the ocean.
The newer, cleaner fuel causes less pollution. When scientists did the math, they realized those ship trails had been common and reflective enough to cool down the planet. The reductions in pollution that are set in motion in 2020 are not expected to have an immediate impact on the climate system because it doesn’t respond immediately.
Andrew Gettleman is a scientist at the Pacific Northwest National Laboratory. It isn’t nothing. “It’s probably about 10% of the global warming that we would expect over the next decade,” Gettleman says.
“It’s very clear that the clouds and specifically the low level clouds are playing the dominant role,” says Helge Goesseling, a climate scientist at the Alfred Wegner Institute in Germany and the lead author of the new study.
Other researchers are looking at pollution-focused possibilities. Sulfate pollution levels in China have dropped precipitously since 2013, driven by new air pollution policy in the country. Researchers theorize that with less pollution, fewer water droplets aggregate to form clouds over land and in the ocean.
The key question is not if the cloud changes are natural or human-caused, but if it is a fundamental change brought on by climate change.
“It’s both a physical reality and a symbolic shock,” says Gail Whiteman, a social scientist at the University of Exeter, UK, who studies climate risks. “We are reaching the end of what we thought was a safe zone for humanity.”
“Individual years pushing past the 1.5-degree limit do not mean the long-term goal is shot,” said UN secretary-general António Guterres in a prepared statement. “It means we need to fight even harder to get on track. … Now is the time for leaders to act.
An analysis of climate data from NASA’s Goddard Institute for Space Studies has revealed that temperatures in the world’s most extreme areas in the past two years are the warmest on record. The temperature extremes were recorded between July 1 and September 30 last year and between July 1 and September 30 2021 and July 1 to September 30 2018.