Cleaner air could be contributing to the current warmer temperatures.
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.
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.
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.
“There was a cooling effect that was persistent year after year, and suddenly you remove that," Yuan said.
Diamond
calculates a warming of about 0.1 degrees Celsius (0.18 degrees Fahrenheit) by mid-century from shipping regulations. The level of warming could be five to 10 times stronger in high shipping areas such as the North Atlantic.
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.
Volmer said the water vapor went too high in the atmosphere to have a noticeable effect yet, but that effects could emerge later.
A
couple of studies use computer models to show a warming effect from all that water vapor.
One study, which has not yet undergone the scientific gold standard of peer review, reported this week that the warming could range from as much as 1.5 degrees Celsius (2.7 degrees Fahrenheit) of added warming in some places to 1 degree Celsius (1.8 degrees Fahrenheit) of cooling elsewhere.
Scientists look beyond climate change and El Nino for other factors that heat up Earth (msn.com)