The 2023 global temperature record was 1.1 C above the average 1850-1901 period, and Earth is 1.3 C prior to El Nio
Earth switched into an El Niño phase in mid-2023 and stayed there through spring of 2024. So, Schmidt says, it likely contributed to 2023’s record. The timing was wrong and it couldn’t explain all of it. When the heat broke records in June of the year, it was in a La Nia state, but still cooler than it used to be.
The announcement was made jointly by several international organizations that independently track the global temperature. The consensus is that last year the world’s temperature hit 1.55 C above the average for 1850-1901, which is considered to be a pre-industrial period before humans began pouring large amounts of greenhouse gases into the atmosphere. Unexpectedly, the 2024 figure also shows a statistically significant increase over that for 2023, when heat records were set. Climate scientists are investigating whether the two-year temperature surge is a blip or whether it marks a change in Earth’s climate system that means global warming is speeding up.
The chief scientist for the Nature Conservancy states that humans are still in a 1.3 C world. She says most of the heat trapped by greenhouse gases is absorbed by Earth. By the time the ten-year average for the air tops 1.5 °C, the planet will have accumulated even more heat, further amplifying violent storms and fires, ecosystem damage and sea-level rise.
“The real punchline is, it was another really warm year,” says Russell Vose, a climate scientist at NOAA’s National Center for Environmental Information, the group that produces the temperature estimates.
On the heating effect of the Hunga Tonga-Hunga Ha’apai volcano in 2024: The hottest year on record
El Niño and La Niña events are part of a natural climate cycle that can influence weather across a broad swath of the planet. Global temperatures tend to be higher during El Nio phases, which occur every few years on average, while cooler global temperatures prevail during La Nia phases.
When there is a volcano, gases and particles are shot into the air to reflect sunlight back into space and cool the Earth. But the Hunga Tonga-Hunga Ha’apai volcano, which erupted in 2022, was underwater. Water can trap heat and it was shot into the atmosphere.
Some scientists hypothesized that the warming effect could have contributed to some of the mystery heat. But after close study, scientists realized the impact was probably minimal.
” people talked about that a lot but our best guess is that it had no effect,” says Andrew Dessler, a Climate scientist at Texas A&M University.
White clouds reflect off incoming sunlight. Cold clouds act as a blanket, trapping the heat on the Earth’s surface. Changes in cloud type, presence, and behavior can affect Earth’s temperatures.
Source: 2024 was the hottest year on record. The reason remains a science mystery
Cloud Changes in China as a Signature of Human-Caused Climate Change: A Study of Water Droplets, Fluxes, and Ship Trails
In 2020, international rules governing the fuels for the shipping industry changed. 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.
Sulfate pollution can be reduced by the newer, cleaner fuel. Scientists realized that the ship trails were reflective enough to cool the planet. The climate system does not respond immediately, meaning that reductions in pollution set in motion in 2020 could have an effect on heat in less than half a year.
The scale isn’t enormous, compared to the overall impact of human-driven global warming, says Andrew Gettleman, a scientist at the Pacific Northwest National Laboratory. But it’s not worthless. About 10% of the global warming will be expected over the next decade, according to Gettleman.
“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.
But some other researchers are poking around another pollution-focused possibility. The levels of sulfate pollution in China have plummeted since the introduction of the new air pollution policy. Researchers theorize that with less pollution, fewer water droplets will form clouds over land and on the ocean.
The key question, Schmidt says, is understanding whether the cloud changes are part of natural variation—something like El Niño, an effect that will revert on its own—or a deeper, fundamental change brought on by human-caused 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.”
The long-term goal is not shot when individual years push past the 1.5- degree limit, according to the UN secretary-general. We need to fight harder to get on track. Leaders must act — now.”