Volcanic ash may have a greater impact on climate than scientists thought

During volcanic eruptions, huge clouds of ash and dust are thrown into the atmosphere – plumes that can block air traffic and reach an altitude of about 40 km above the Earth’s surface. A new study by the University of Colorado at Boulder suggests that such volcanic ash could also have a greater impact on the planet’s climate than scientists previously thought. The results are published in the journal Nature Communications.

A new study focuses on the eruption of the Kelut (or Kelud) volcano on the Indonesian island of Java in 2014. Based on real-world observations of the event and advanced computer simulations, the team discovered volcanic ash that remains in the air for months or longer after a major eruption.

The study began with a casual observation: members of the research team flew in an unmanned aircraft near the site of the eruption of the Kelut volcano – an event that covered most of Java in ash and forced people to leave their homes. At the same time, passengers noticed something that should not be there.

A month after the eruption, there were still large particles in the atmosphere, ”said Yunqian Zhu, lead author of the new study and a researcher at the Laboratory of Atmospheric and Space Physics (LASP) in CU Boulder. “It looked like ash.”

She explained that scientists have long known that volcanic eruptions can affect the planet’s climate. These events lead to the release of huge amounts of sulfur-rich particles high into the Earth’s atmosphere, where they can block sunlight from reaching the earth.

However, the researchers did not think that ash could play a large role in this cooling effect. Scientists have concluded that these chunks of rock debris are so heavy that most of them probably fell out of volcanic clouds shortly after the eruption.

Zhu’s team wanted to find out why this did not happen in the case of the eruption of Kelut. Based on aircraft data and satellite observations of the unfolding disaster, the team found that the volcano’s plume appears to be teeming with small, light ash particles – tiny particles that could probably float in the air for extended periods of time, like dandelion fluff.

Study co-author Brian Thun added that these pumice-like particles also change the chemical composition of the entire volcanic plume.

Thun, professor of LASP and the Department of Atmospheric and Oceanic Sciences at CU Boulder, explained that erupting volcanoes are releasing large amounts of sulfur dioxide. Many researchers have previously suggested that these molecules interact with others in the air and turn into sulfuric acid – a series of chemical reactions that could theoretically take weeks to complete. However, observations of real eruptions show that this happens much faster.

A mystery has arisen as to why these reactions occur so quickly. However, scientists have found the answer: These sulfur dioxide molecules seem to stick to ash particles floating in the air. In the process, they can enter into chemical reactions on the surface of the ash itself, potentially pulling about 43% of the sulfur dioxide out of the air.

In other words, ash can accelerate the transformation of volcanic gases in the atmosphere.

It is unclear how these ash clouds affect the climate. In theory, long-term particles in the atmosphere can darken the planet and even contribute to its cooling after an eruption. Floating ash can also be carried away from places like Kelut to the poles of the planet. There, it can trigger chemical reactions that will damage the Earth’s most important ozone layer.

But the researchers say one thing is clear: when the volcano erupts, it may be time to pay much more attention to ash and its true impact on Earth’s climate.