About 74,000 years ago, Indonesia's Toba volcano exploded with a force 1,000 times more powerful than the 1980 eruption of Mount St. Helens. The mystery is what happened next.
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When it comes to the most powerful volcanoes, researchers are looking at how post-eruption global cooling (also known as volcanic winter) could potentially pose a threat to humanity after so-called supereruptions. has been speculated for a long time. Previous research agrees that some degree of planetary cooling will occur, but opinions differ on how much. Estimated temperatures range from 3.6 to 14 °F (2 to 8 °C).
In new research published NASA team published in Journal of Climate goddard space institute, an affiliate of the Columbia Climate School, used advanced computer modeling to simulate supereruptions like the Toba earthquake. They found that even with the most powerful explosion, the cooling after the eruption would probably not exceed 2.7 degrees (1.5 degrees).
„The relatively modest temperature changes that we found to be most consistent with the evidence may explain why a single supereruption did not produce strong evidence of a global catastrophe for humans or ecosystems. ” said the lead author. Zachary McGrawa postdoctoral fellow at Goddard College and Columbia University.
To be considered a supereruption, a volcano must release more than 240 cubic miles (1,000 cubic kilometers) of magma. These eruptions are very powerful and rare. The most recent supereruption occurred in New Zealand over 22,000 years ago. The best-known example may be the eruption that blew up Wyoming's Yellowstone Crater about 2 million years ago.
McGraw and his colleagues set out to understand what caused the large discrepancies in model temperature estimates. Models are a key tool for understanding climate change, which occurred so long ago that its severity cannot be clearly recorded. They settled on a variable that can be difficult to pinpoint: the size of the microscopic sulfur particles that eruptions blow miles into the atmosphere.
In the stratosphere (about 6 to 30 miles above the Earth), sulfur dioxide gas from volcanoes undergoes a chemical reaction and condenses into liquid sulfate particles. These particles can affect Earth's surface temperature in two opposing ways. One is by reflecting incoming sunlight (causing cooling), and the other is by trapping outgoing thermal energy (a type of greenhouse effect).
For many years, the known cooling effect has raised the question of how humans could stop global warming by intentionally injecting aerosol particles into the stratosphere.
Researchers in a new study showed how much the diameter of volcanic aerosol particles influences post-eruption temperatures. The smaller and denser the particles, the greater their ability to block sunlight. However, past supereruptions have left behind no reliable physical evidence, making it difficult to estimate particle size. In the atmosphere, particles change size as they aggregate and condense. Even when particles fall to Earth and are stored in ice cores, mixing and compaction leave no clear physical record.
By simulating supereruptions across a range of particle sizes, the researchers found that such eruptions may not change global temperatures as much as the largest modern eruptions. For example, the 1991 eruption of Mount Pinatubo in the Philippines lowered global temperatures by about 1 degree Celsius over two years.
Luis Milan, an atmospheric scientist at NASA's Jet Propulsion Laboratory who was not involved in the study, said the mystery of supereruption cooling requires further research. He said the way forward is to conduct more laboratory and model studies on the factors that determine particle size in volcanic aerosols, as well as conduct comprehensive comparisons of models.
Given the continued uncertainty, Millan added, „To me, this is another example of why geoengineering via stratospheric aerosol injection has a long way to go before it becomes a viable option. ” he added.
Created based on NASA press release.