The ocean has now broken temperature records every day for more than a year. And so far, 2024 has continued 2023’s trend of beating previous records by a wide margin. In fact, the entire planet has been warm for months, according to many different data sets.
“There is no ambiguity about the data,” said Gavin Schmidt, a climatologist and director of the NASA Goddard Institute for Space Studies. “So really, it’s a question of attribution.”
Understanding what specific physical processes are behind these temperature records can help scientists improve their climate models and better predict future temperatures.
Last month, the average global sea surface temperature reached a new monthly high of 21.07 degrees Celsiusor 69.93 degrees Fahrenheit, according to the Copernicus Climate Change Service, a research institute funded by the European Union.
“March 2024 continues a string of climate records falling for both air temperatures and ocean surface temperatures,” said Samantha Burgess, deputy director of Copernicus, in a statement this week.
The tropical Atlantic is unusually warm, helping set the stage for a busy hurricane season, according to an early forecast by scientists at Colorado State University. Higher ocean temperatures provide more energy to fuel stronger storms.
Global temperatures have been rising for a long time because the burning of fossil fuels adds greenhouse gases, which warm the planet, to the atmosphere. To date, climate change has raised the global average temperature by about 1.2 degrees Celsius, or 2.2 degrees Fahrenheit, above the preindustrial average temperature. And because it takes more energy to heat water than air, the oceans absorb most of the planet’s warming from greenhouse gases.
But the “enormous, massive record” set last year was beyond what scientists expected to see even taking into account climate change, Dr. Schmidt.
What’s different today, compared to this time last year, is that the planet is dealing with the effects of an El Niño event that began in July. El Niño events are natural climate patterns associated with high temperatures.
“The temperatures we’re seeing now, the records that were broken in February and March, are actually more in line with what we’d expect,” compared to last year’s, said Dr. Schmidt. “We’ll see what happens in the summer.”
El Niño is weakening and is expected to disappear soon. What happens to global average temperatures then will help shed light on 2023 temperatures, he said.
In addition to climate change and El Niño, there are several other factors that may contribute to these staggering records.
One is the recent reduction in aerosol pollution from ocean-going container ships, following new international fuel standards that came into effect in 2020. Ironically, aerosols have a cooling effect on the atmosphere, and contribute to hide the true extent of climate change until now.
There was also a massive eruption of the undersea volcano Hunga Tonga-Hunga Haʻapai in 2022. Volcanic eruptions that occur on land send plumes of soot and aerosols, blocking sunlight and temporarily cooling the atmosphere. But because this volcano sank beneath the Pacific Ocean, its eruption also sprayed millions of tons of water vapor into the upper atmosphere. Water vapor is a powerful greenhouse gas.
“This is the most powerful eruption since Krakatoa, and usually next year is when you see the effects,” said Sean Birkel, an assistant professor at the University of Maine Climate Change Institute, which created a data visualization tool. of climate called the Climate Reanalyzer. He suspects that the warming effect of the volcanic eruption is greater than early estimates suggested, noting that the eruption may have affected atmospheric circulation and helped strengthen the El Niño that formed in 2023. But, added he said, more research is needed.
Taught by Dr. Schmidt that when scientists combine their estimates so far of how much volcanic eruptions, reduced shipping pollution, El Niño and climate change should warm the planet, the numbers don’t add up.
“There could be something missing,” he said, such as other sources of aerosol pollution that have improved beyond what researchers know, or Earth’s climate with more internal variability than expected, or the global warming that amplifies the effects of El Niño.
Several groups of scientists are trying to get a clearer picture, said Dr. Schmidt, and he expects to begin publishing the results in the next few months.
Nadja Popovich contributed reporting.
