On Sunday (Jan. 12), the Taal volcano in the Philippines erupted, sending plumes of smoke and ash up to 9 miles (14 kilometers) into the atmosphere. Officials closed Manila’s airport and ordered the evacuation of about 8,000 residents on the island of Luzon.
The largest volcanic explosions can alter the global climate. The last time that happened was the eruption of Pinatubo in 1991, just 89 miles (144 km) from Taal’s eruption. Pinatubo ejected 1 cubic miles (5 cubic km) of material into the atmosphere, with a cloud of pulverized rock and debris stretching for hundreds of miles. But it was the 20 million tons of sulfur dioxide that reached the stratosphere—the second layer of the Earth’s atmosphere—that touched off temporary climate change. The sulfur dioxide reacted with water to form aerosols that reflected sunlight back into space, according to the United States Geological Survey. Global temperatures fell by as much as 1°F (0.5°C) for three years after the explosion.
In extreme cases, eruptions can touch off “volcanic winters,” plunging the planet into gloom. About 74,000 years ago (relatively recently in geological terms), a colossal volcano erupted in present-day Indonesia. Mount Toba’s eruption, the largest in the past 2 million years, may have touched off a volcanic winter lasting decades and threatened global ecosystems, although scientists argue over its effects.
This month’s eruption in the Philippines is far less powerful than Pinatubo, not to mention Toba, writes Allegra Nicole LeGrande, a research scientist at the Goddard Institute for Space Studies at NASA. “To impact global climate, volcanic eruptions must inject SO2 into the stratosphere,” she wrote by email, referring to sulfur dioxide’s chemical formula. “I am not seeing measurements indicating that has happened yet in 2020 at Taal Volcano.” Alan Robock, a professor in the department of environmental sciences at Rutgers University, agreed: “So far it’s not large enough.”
But a more hazardous eruption is possible within hours or days, according to the Philippine Institute of Volcanology and Seismology. The agency raised the alert level to four on a scale of five, as researchers have recorded hundreds of small earthquakes and huge lava fountains near the main crater. Sulfur dioxide levels, however, are still just 5,300 metric tons per day, a fraction of what would be needed to affect the global climate.