How the Eruption of Mount Pinatubo Changed Climate Science
Wild Science: Mount Pinatubo’s Implications for Global Warming Mitigation and Geoengineering
As our four-wheel-drive jeep grinds into a river that flows through a bizarre landscape of jagged ash mountains, we hear a deep rumbling. Not far from us, a rock slide is crashing down the side of a mountain.
“This area is still very unstable,” says the geologist accompanying me. “We are regularly monitoring earthquakes here.”
Though still unstable, the area is much quieter than in the past.
After 500 years of sleeping quietly, the non-descript mountain north of Manila in the Philippines began to rumble and shake in early 1991. By June 15, Mount Pinatubo had erupted into the second-largest volcanic eruption of the 20th century, according to the United States Geological Survey.
The top of the mountain was cratered by the eruption, lowering the elevation by an estimated 150 meters and forcing the evacuation of more than 50,000 people and the deaths of hundreds. “The eruption produced high-speed avalanches of hot ash and gas, giant mudflows, and a cloud of volcanic ash hundreds of miles across,” the United States Geological Survey notes.
After the initial eruption, massive mudflows — called lahar — continued for years. These were described as “floods with the consistency of wet cement” that “jumped river banks, and swept away or buried everything (towns, roads, bridges) in their paths,” the United States Geological Survey reports.
More than 53,000 people have been permanently displaced by the eruption, while loss of agricultural land and irrigation sources, destruction of roads and bridges, repeated floods and disease have affected more than one million.
The 1991 eruption had another interesting effect.
“Nearly 20 million tons of sulfur dioxide were injected into the stratosphere in Pinatubo’s 1991 eruptions, and dispersal of this gas cloud around the world caused global temperatures to drop temporarily (1991 through 1993) by about 1°F (0.5°C),” the United States Geological Survey noted in a report.
This cooling effect of large volcanic eruptions — long known by volcanologists who study ancient seismic events — has captured the imaginations of some scientists and inventors who are seeking a more direct approach to stopping global warming than cutting the emissions of the greenhouse gases blamed for warming the climate.
One of the leaders in this effort is Intellectual Ventures, a Bellevue, Washington-based company that develops scientific inventions. The company — backed by one of the founders of Microsoft — published a white paper which asserts that the cooling impact of a volcanic eruption could be replicated with what is called a “hose-in-the-sky” approach.
“High-flying blimps, based on existing prototypes, could support a hose no thicker than a fire hose to carry sulfur dioxide as a clear liquid up to the stratosphere, where one or more nozzles would atomize it into a fine mist of nanometer-scale aerosol particles.”
The idea might sound far-fetched, but the venerable Royal Society, Great Britain’s respected scientific organization, is taking such proposals seriously. It undertook an extensive study to examine the viability of what is known as geoengineering — or “the deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change.”
The Royal Society report found that “unless future efforts to reduce greenhouse gas emissions are much more successful than they have been so far, additional action in the form of geoengineering will be necessary if we are to cool the planet. Geoengineering technologies were found to be very likely to be technically possible and some were considered to be potentially useful to augment the continuing efforts to mitigate climate change by reducing emissions.” A Royal Society statement added: “The report identified major uncertainties regarding their effectiveness, costs and environmental impacts.”
William Rose shares these concerns. The volcanologist and Professor Emeritus of Geological and Mining Engineering and Sciences at Michigan Technological University in the United States has extensively studied the climactic effects of Mount Pinatubo and other volcanic eruptions.
“The understanding of atmospheric effects from eruptions is not very sophisticated,” he said. “Interpretation of environmental events is very tricky because there are always many uncontrolled things happening at the same time.”
“We do think that Pinatubo had a measurable effect on global temperatures for a few years, and that the agent causing this is likely to have been liquid sulfate aerosol,” he continues. “There is a range of data to support this, and there are other examples of eruptions and similar effects. This means that putting more sulfate in the stratosphere would likely also affect global temperatures and that the process is reversible.”
Rose points out that this would put scientists — and politicians — into a dangerous system of global environmental management where essentially another form of pollution is pumped into the atmosphere to offset the impact of the current pollution.
“The idea of controlling the earth system seems arrogant and flawed to me,” the volcanologist said. “Justifying this method would require convincing data which showed that threatening environmental change was nearly certain. Decreasing greenhouse gas emissions seems economically affordable, possible and logical — therefore a much better way to go. We shouldn’t give up the conservation and non-fossil fuel approach.”
Dr. Alan Robock, a Distinguished Professor of climate science in the Department of Environmental Sciences at Rutgers University in the United States, takes a harder line about drawing too much from the global cooling benefits of replicating a Mount Pinatubo eruption.
“Pinatubo teaches us that sulfate aerosols in the stratosphere can cool the climate, but will also produce drought in certain regions, destroy ozone, and significantly reduce solar power for systems using direct sunlight,” says Robock. “It actually serves as a warning about some aspects of geoengineering.”
Robock, as well as just about every other scientist and inventor involved in geoengineering, agree on one thing: there simply isn’t enough known about these massive, global projects to scientifically understand or ultimately judge them.
“We have no idea if geoengineering could be implemented or would produce more benefit than risk,” Robock notes. “That is why we all support research into geoengineering, so we can better advise policy makers whether this is even an option to consider.”
“Geoengineering, if ever used, should be in response to a planetary emergency, and only temporarily,” he says. “The solution to global warming is mitigation, reducing greenhouse gas emissions through efficiency and green energy sources, and a certain amount of adaptation,”
Back on the still rumbling volcano that triggered this debate, the Philippine volcanologist describes how he and others with the Philippine Institute of Volcanology and Seismology monitor Pinatubo for signs of another eruption so nearby residents can be warned. It’s the nitty gritty work of public service geology and it is a long way — both physically and theoretically — from grandiose geoengineering proposals.
He appears unimpressed and more than a bit skeptical about the “hose-in-the-sky” invention, and any other proposal that would attempt to replicate the effects of the devastating eruption that he experienced years ago. When asked if the global cooling data gleaned from Mount Pinatubo might one day save the planet, he has a simple answer: “No.”
Some links on this page might be part of the Amazon Associates program. This means that the page author earns a commission from qualifying purchases made through these links, at no additional cost to the buyer.
