Volcanic Eruption: How it affects the Earth’s temperature

The recent eruption of the Ruang volcano in Indonesia has brought back concerns about the effect volcanic eruptions can have on weather and climate.

Ruang’s multiple eruptions in Indonesia have resulted in the spewing of volcanic gases so high that they have reached the second layer of the atmosphere, tens of thousands of feet above the ground.

In particular, the eruption of the Ruang volcano this week sent a plume of ash tens of thousands of feet into the air while volcanic gases spewed as high as 65,000 feet, about 25,000 feet above the altitude of a commercial airliner.

Another parameter that is raised in relation to volcanic eruptions, apart from the immediate danger faced by the surrounding areas, is the possible effects of the eruption on the weather and climate.

Volcanoes are likely to have a short-term impact on climate, including cooling global temperatures, due to the gases they funnel high into the upper atmosphere. However, Ruang Volcano’s effects on climate will likely be minimal, according to Greg Huey, the chair of Georgia Tech’s School of Earth and Atmospheric Sciences.

According to him, daily weather conditions near the volcano are not expected to be affected for long such as temperature, clouds and rain.

Mount Ruang, a 725-meter-long stratovolcano on the island of the same name in Indonesia’s North Sulawesi province, has erupted at least seven times since Tuesday night, according to the country’s volcanological agency. Stratovolcanoes can produce powerful eruptions because their conical shape allows gas to accumulate.

Volcanic ash is usually a mixture of crushed solids such as rock, minerals and glass and gases such as water vapor, carbon dioxide and sulfur dioxide, according to NASA.

“Ash’s stay in the atmosphere is short-lived because it’s heavy and tends to settle quickly,” Huey told CNN in contrast to gases that can reach much higher in the atmosphere.

Dense ash near the surface affects air quality, making it more dangerous and causes a temporary cooling by blocking sunlight. Once the active eruption stops, the ash begins to settle.

Some gases from Mount Ruang’s eruptions rose so high that they fell into the stratosphere, the second layer of the Earth’s atmosphere, which lies just above the troposphere, the layer where almost all meteorological phenomena occur.

The stratosphere is a very dry place, and usually only long-lived gases filter into it, according to Huey. A volcanic eruption is essentially the only natural way for short-lived gases like sulfur dioxide and water vapor to enter the stratosphere.

Once in the stratosphere, sulfur dioxide and water vapor combine to form sulfuric acid aerosols that create a layer of cloudy 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 drop.

But the cooling effect lasts longer if more gas enters the stratosphere.

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

By comparison, satellite instruments have estimated that the Ruang volcano has released about 300,000 tons of sulfur dioxide so far, though it’s unclear how much of that has reached the stratosphere. Although this is a huge amount, it is not considered an extreme price by experts.

An eruption as big as Mount Pinatubo in 1991 could certainly lower the global temperature for a few years, but it would not be able to deal with global warming at the cost of massive damage to life and property.