Scientists are wondering if global warming and El Nino have an accomplice in fueling this summer’s record-shattering heat.
The European climate agency Copernicus reported that July was one-third of a degree Celsius (six-tenths of a degree Fahrenheit) hotter than the old record. That’s a bump in heat that is so recent and so big, especially in the oceans and even more so in the North Atlantic, that scientists are split on whether something else could be at work.
Scientists agree that by far the biggest cause of the recent extreme warming is climate change from the burning of coal, oil and natural gas that has triggered a long upward trend in temperatures. A natural El Nino, a temporary warming of parts of the Pacific that changes weather worldwide, adds a smaller boost. But some researchers say another factor must be present.
“What we are seeing is more than just El Nino on top of climate change,” Copernicus Director Carlo Buontempo said.
One surprising source of added warmth could be cleaner air resulting from new shipping rules. Another possible cause is 165 million tons (150 million metric tons) of water spewed into the atmosphere by a volcano. Both ideas are under investigation.
The cleaner air possibility
Florida State University climate scientist Michael Diamond says shipping is “probably the prime suspect.”
Maritime shipping has for decades used dirty fuel that gives off particles that reflect sunlight in a process that actually cools the climate and masks some of global warming.
In 2020, international shipping rules took effect that cut as much as 80% of those cooling particles, which was a “kind of shock to the system,” said atmospheric scientist Tianle Yuan of NASA and the University of Maryland Baltimore County.
The sulfur pollution used to interact with low clouds, making them brighter and more reflective, but that’s not happening as much now, Yuan said. He tracked changes in clouds that were associated with shipping routes in the North Atlantic and North Pacific, both hot spots this summer.
In those spots, and to a lesser extent globally, Yuan’s studies show a possible warming from the loss of sulfur pollution. And the trend is in places where it really can’t be explained as easily by El Nino, he said.
Did the volcano do it?
In January 2022, the Hunga Tonga-Hunga Ha’apai undersea volcano in the South Pacific blew, sending more than 165 million tons of water, which is a heat-trapping greenhouse gas as vapor, according to University of Colorado climate researcher Margot Clyne, who coordinates international computer simulations for climate impacts of the eruption.
The volcano also blasted 550,000 tons (500,000 metric tons) of sulfur dioxide into the upper atmosphere.
The amount of water “is so absolutely crazy, absolutely ginormous,” said Holger Vomel, a stratospheric water vapor scientist at the National Center for Atmospheric Research who published a study on the potential climate effects of the eruption.