A powerful volcano is erupting. Here’s what that could mean for weather and climate

By Mary Gilbert, CNN Meteorologist

(CNN) — When Mount Ruang in Indonesia underwent multiple explosive eruptions last week, volcanic gases were flung so high they reached the atmosphere’s second layer, tens of thousands of feet above ground.

Ruang’s eruptions ejected a massive ash plume and sent some volcanic gases more than 65,000 feet into the air, according to satellite estimates – about 25,000 feet higher than a commercial airplane will typically fly.

The eruption’s potential impacts to weather and climate are starting to come into focus, even as the danger posed by the volcano persists and evacuations continue.

It’s possible for volcanoes to have a short-term impact on the climate – including global temperature cooling – due to the gases they inject high into the upper atmosphere. But Mount Ruang’s influence on the climate will likely be minimal, according to Greg Huey, the chair of Georgia Tech’s School of Earth and Atmospheric Sciences.

And the day-to-day weather conditions near Mount Ruang – things like temperature, clouds and rain – probably won’t be influenced by the volcano for long, Huey told CNN.

Mount Ruang, a 2,400-foot (725-meter) stratovolcano on Ruang Island in Indonesia’s North Sulawesi province, has erupted at least seven times since Tuesday night, the country’s volcanology agency said. Stratovolcanoes can produce explosive eruptions because their cone shape allows gas to build up, according to volcanologists.

Volcanic ash is typically a mixture of crushed-up solids – including rocks, minerals and glass – and gases, such as water vapor, carbon dioxide and sulfur dioxide, according to NASA.

Crushed-up solids generate a lot of static electricity within ash plumes as they bash into each other, resulting in intense displays of lighting, according to Huey.

“The ash itself is short-lived in the atmosphere because it’s heavy, it’s big and it tends to settle out quickly,” Huey told CNN. It’s the gases that are able to reach much higher in the atmosphere.

Dense ash near the surface creates hazardous air quality and causes a temporary cooling effect as it blocks out warming sunlight. Once the active eruption stops, ash starts to settle.

But ash that reaches the ground can easily be lofted back into the air by breezy winds. Water droplets often cling to ash in the air and form storm clouds that can unload rain or produce additional lightning.

Some gases from Mount Ruang’s eruptions climbed so high they punched into the stratosphere, the second layer of Earth’s atmosphere. It’s located just above the troposphere, which is where all life and weather occur.

The stratosphere is a very dry place and typically only the gases with a long lifespan –spanning decades – filter up into it, according to Huey. A volcanic eruption is essentially the only natural way for short-lived – less than a few years – gases like sulfur dioxide and water vapor to make it into the stratosphere.

Once in the stratosphere, sulfur dioxide and water vapor combine to form sulfuric acid aerosols that create a layer of hazy droplets, according to UCAR. These droplets spread far from their point of entry and remain in the stratosphere for up to three years, reflecting sunlight back into space and causing global temperatures to cool.

But the cooling effect lasts longer if more gas makes it into the stratosphere.

In 1991, Mount Pinatubo – another stratovolcano – erupted in the Philippines and produced the largest sulfur dioxide cloud ever measured. The eruption poured over 17 million tons of the gas into the atmosphere and led to a global temperature decrease of around 0.5 degrees Celsius (0.9 degrees Fahrenheit) that lasted about a year, according to the United States Geological Survey.

In comparison, satellite instruments have estimated Mount Ruang has released an around 300,000 tons of sulfur dioxide so far, though it’s unclear how much of that plume made it into the stratosphere. While that amount is quite massive in its own right, it falls well short of the most extreme case, according to Huey.

An eruption as large as Mount Pinatubo in 1991 could certainly cool the planet for a few years, though it wouldn’t be able to erase the Earth’s current climate woes caused by planet-warming pollution, and it would come at the cost of tremendous damage to life and property.

CNN’s Kathleen Magramo contributed to this report.

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