The year 2024 was the hottest on record

An explanation for the record temperature of Earth in the early 2023– 2024 period: The 2004–2005 data released jointly by the International Climate Association and NOAA

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. But it couldn’t explain all of it: the timing was wrong. The year began with a La Nia state and was still cooler in the summer months when the heat broke records.

The announcement was made jointly by several international organizations that independently track the global temperature. Although each group calculated a slightly different figure, averaged together the data indicate a consensus that last year, Earth’s temperature hit 1.55 C above the average for 1850–1900, known to be a “pre-industrial” period before humans began pouring large amounts of greenhouse gases into When the records were set, the figure shows a statistically significant increase. Climate scientists are trying to determine whether the two-year temperature surge is a blip or a sign that global warming is speeding up.

The single year beyond 1.5 is not considered a signal that the Paris Agreement numbers have been crossed, but it is still an ominous sign. The planet is predicted to warm up to about 2 degrees Celsius by the end of the century without significant action to cut planet-warming emissions according to a recent report.

“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.

Hottest Year: 2024 hottest year-human-history-global-warming’s contribution to the Hunga Tonga Ha’apai volcano

Climate events like El Nio and La Nia can affect weather in a wide range of places. Global temperatures tend to be higher in an El Nio phase compared to the cooler La Nia phase.

When eruptions take place, they shoot gases and particles into the air that reflect sunlight back into space, and help cool the Earth. But the Hunga Tonga-Hunga Ha’apai volcano, which erupted in 2022, was underwater. It shot tons of water into the air, which can trap heat.

Scientists theorize that the warming effect might have contributed to some of the mystery heat. Scientists realized the impact was not very significant after a close study.

Andrew Dessler, aclimate scientist at Texas A&M University, said that their best guess was that it had an impact on zero.

White clouds reflect off the sun’s rays. But cold clouds also act like a blanket, trapping heat from to the Earth’s surface. So changes in cloud type, or cloud behavior or presence, can have an impact on Earth’s temperatures.

Source: 2024 was the hottest year on record. The reason remains a science mystery

Changes in the fuels for shipping: sulfate pollution and atmospheric cloud changes are natural or caused by human-caused climate change

In 2020, international rules governing the fuels for the shipping industry changed. The old fuel was very heavy in sulfur, and once in the atmosphere it attracted water droplets, causing a cloud to trail behind a ship.

The newer, cleaner fuel produces less sulfate pollution—and fewer, smaller cloud plumes. The ship trails have been common and reflective enough to cool down the planet. Reductions in pollution set in motion in 2020 may have an impact of 0.1 C, or about half the total mystery heat, if the Climate system doesn’t respond immediately.

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. It is not nothing. “It’s probably about 10% of the global warming that we would expect over the next decade,” Gettleman says.

The clouds and the low level clouds are playing the leading role, says Helge Goesseling, a climate scientist at the Alfred Wegner Institute in Germany.

Some researchers are looking at another pollution-focused possibility. The new air pollution policy in China has led to a decrease in sulfate pollution levels. With less pollution, there are fewer nuclei on which water droplets aggregate to form clouds—and therefore fewer clouds, both over land and the ocean downwind, researchers hypothesize.

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..

Gail Whiteman is a social scientist who studies climate risks, and she says that it is both a physical reality and a symbolic shock. We thought we were in a safe zone for humanity.

The long-term goal isn’t shot when individual years push past the 1.5- degree limit, said the UN secretary-general. It means that we need to work harder to get on track. The leaders need to act now.