Climate change is the primary cause of the extraordinary temperatures, not the eruption of an underwater volcano near Tonga in the Pacific Ocean in January 2022.
While the volcano's eruption is an aggravating factor, scientists say it is not having the impact that conservative critics who have dismissed the importance of climate change have claimed.
"It's probably fair to say that the influence of [the volcano] on this year's extremes is quite small," Stuart Jenkins, said in an interview.
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Volcanic eruption not a big contributor
Massive volcanic eruptions typically lower temperatures because they eject large amounts of sulfur dioxide, which forms sulfate aerosols that can reflect sunlight back into space and temporarily cool the Earth's surface, according to the researchers.
However, the Tonga eruption had an additional effect because it occurred underwater.
According to a study published in the journal Nature Climate Change, the eruption raised the water vapor level of the stratosphere by 10% to 15%, the largest rise scientists have ever measured.
This determined that water vapor might raise the average global temperature by up to 0.063 degrees Fahrenheit (0.035 degrees Celsius) using a model.
Because of this discovery and other studies suggesting a potential warming influence, several commentators linked the eruption to warming, although researchers participating in these studies have made it clear that the volcano isn't a big contributor to our unpredictable weather.
"Even though El Niño has made the global temperature higher and the Hunga Tonga-Hunga Ha'apai eruption might have affected some regions for a short time, the main culprit is climate change," Gloria Manney, a senior research scientist at NorthWest Research Associates and New Mexico Institute of Mining and Technology, and Luis Millán, a research scientist at NASA's Jet Propulsion Laboratory, said in an email interview.
Holger Vömel, a senior scientist at the National Center for Atmospheric Research, said it's too early to say whether the volcano is a contributor to the heat waves.
But, even if the eruption is playing a role, he believes it should not be used to dismiss the significance of climate change.
"Hypothetically speaking, if the volcano does warm the surface, it adds to our man-made global warming that we already have," he said.
Hunga Tonga-Hunga Ha'apai eruption
The eruption began in December 2021 and peaked in January 2022, when hundreds of tons of material were released into the surrounding air.
The volcano is located around 65 miles north of Tongatapu, Tonga's largest island, and is submerged approximately 150 meters beneath the ocean surface.
When it erupted, it not only emitted the usual volcanic mix, but it also carried a massive amount of water with it.
The ensuing cloud generated the most powerful lightning storm in recorded history.
When the volcano erupted, an estimated 146 metric tons of water were released into the stratosphere, many miles above the planet's surface.
Water vapor functions as a greenhouse gas, trapping heat and increasing the average temperature across the Pacific. That warming is just brief, but it puts more strain on an already stressed system.
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