The eruption of an underwater volcano in the Pacific Ocean in January triggered a global shockwave, releasing huge amounts of water vapor into the upper atmosphere, where it could cause a slight short-term rise in global warming, scientists said Thursday. .
Injecting what the researchers estimated to be at least 55 million tons of water vapor into the stratosphere could temporarily deplete the protective ozone layer in the atmosphere, they said.
The eruption of the Hongga Tonga-Hungga Hawapai volcano on the island of Tonga was on January 15th. The biggest in decades. The resulting tsunami devastated parts of Tonga, as well as smaller tsunamis thousands of miles away caused by changes in air pressure. The shock wave swirled around the world.
Because it occurred about 500 feet underwater, the eruption of extremely hot molten rock also caused seawater to explode explosively into steam. A plume of water vapor, volcanic gases, and ash reached an altitude of 35 miles. This increased the amount of water vapor in the stratosphere, which ends at an altitude of 31 miles, by at least 5 percent.
It’s completely unique. It didn’t happen because we were able to measure water vapor in the stratosphere, which started about 70 years ago,” said Holger Fommel, chief scientist at the National Center for Atmospheric Research in Boulder, Colo.. “ Dr. Vommel is the lead author of a research paper on the findings Published in Science.
Like carbon dioxide and other greenhouse gases, water vapor absorbs heat in the form of infrared radiation from the Earth’s surface and re-emits it. Therefore, adding a large amount of water vapor is expected to increase the warming for several years until the gas dissipates.
Large eruptions of terrestrial volcanoes do not release much water vapor, but they can inject huge amounts of sulfur dioxide into the stratosphere, which can have a short-term cooling effect. After the most recent eruption of Mount Pinatubo in the Philippines in 1991, average global temperatures dropped by 1°F, or 0.6°C, for more than a year.
Dr Fommel said that any estimate of how much additional warming the Tonga eruption would add was highly speculative at this point. “But I wouldn’t be surprised if they were the same size” as Pinatubo, he said, just in reverse. He added that the additional warming will likely last longer than cooling after Pinatubo.
Susan Solomon, an atmospheric scientist at MIT who described the temperature effects of changes in stratospheric water vapor in a 2010 study, said the Tonga eruption “could add something on the order of 0.05 degrees of warming to average global temperatures.” ‘Maybe for three to five years.
“That’s lower than we would expect from carbon dioxide, which is closer to 0.1 to 0.2 degrees per decade,” she said. Dr. Solomon was not involved in Tonga research.
All this water vapor will likely also change the chemistry of the atmosphere that destroys ozone, the oxygen molecule that protects life on Earth from harmful ultraviolet rays from the sun.
“By significantly increasing the amount of water vapor, this should reduce the amount of ozone,” Dr. Fommel said. But that would be temporary, he said, because ozone formation and destruction is a “cycle that goes on.”
Dr Solomon said that any loss of ozone near the boundary of the stratosphere and lower atmosphere would also likely lead to some surface cooling, which would counteract warming from the added water vapor.
published a study In July, the amount of water vapor injected by the Tonga eruption was estimated to nearly triple, at 160 million tons.
That study used data from a NASA satellite, which provides global water vapor measurements on a daily basis. Dr. Fommel and his colleagues took a different approach, using data from instruments in small packages called radio sensors that are held aloft by balloons. Radio probes are launched on a regular schedule, usually every 12 hours, at weather stations around the world.
This approach was only possible because there were regular balloon launches from Australia, Fiji and other locations that were close enough to the volcanic eruption that the tools were carried into the volcanic plume. It was also helped that the concentrations of water vapor in the column were very high.
“Any self-respecting scientist who knows stratospheric water vapor knows that you can’t measure it with radio probes,” Dr. Vommel said. “Don’t even think about it. However, this event was just too huge.”
He said his team’s estimate of 55 million tons was conservative, and their calculations showed the amount could be twice that. While this is still lower than the previous study, he said the difference in effect “probably wouldn’t be that huge.”
“This is just scientific rhetoric,” he said of the difference between the estimates of the two studies. “At some point we will get a better understanding, once all the dust has settled.”
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