ST. LOUIS – There was little doubt that the eruption of the Hunga-Tonga-Hunga underwater volcano in January 2022 would have at least some impacts on the global climate.

Most big volcanic eruptions do.

That’s because they inject large amounts of material and gas into the atmosphere. Most eruptions have a cooling effect because of the injection of ash and sulfur dioxide into the atmosphere.

The sulfur dioxide interacts with water vapor to produce tiny droplets of sulfuric acid. Clouds of sulfuric acid act as a blanket and reflect incoming solar radiation back out into space.

The drop-off in incoming solar heat translates to a cooler earth’s surface. Following the Mount Pinatubo eruption in 1991, the Earth cooled by an average of half a degree the following year, which was significant on a global scale.

The eruption of Hunga-Tonga-Hunga was much different because it was an underwater volcano.

“This was the largest volcanic eruption of the 21st century so far,” according to Dr. Michael Wysession, Professor of Earth and Planetary Sciences at Washington University.

“When HTH erupted, it spewed forth only a small amount of sulfur dioxide. Instead, it pumped huge amounts of water vapor into the atmosphere. Formed when the eruption instantly vaporized ocean water and carried it through massive plumes high into the stratosphere. From there, wind currents distributed the water vapor around the world.

“The water vapor injected [into the atmosphere] is unprecedented in our history of volcanism. Why is this so important? Because water vapor is a powerful greenhouse gas!

“Best estimates are that it injected at least 100 million tons of water vapor into the atmosphere, which increased the total atmospheric water vapor content by 5–10%, which is quite significant.”

As a greenhouse gas, water vapor allows incoming solar radiation to pass through to the earth’s surface. However, it prevents the heat from escaping back out into space, causing global temperatures to rise, according to Wysession.

Other factors have also proven to be highly disruptive to world weather patterns this year. Those include the building El Niño in the Pacific, the approaching solar maximum, and the continued influence of human enhanced global warming. Wysession says the disruptive influence of this potent combination will likely continue for several more years, which will include above normal global average temperatures.

What that means for any one location, including St. Louis, is unclear. While some parts of the planet have warmed significantly, others have cooled, and it remains to be seen if that pattern will continue and if so, to what extent.