The normally idyllic resort island of Bali in Indonesia has hogged international headlines since last month, following the eruption of Mount Agung that has driven tens of thousands of residents from their homes and disrupted countless travel plans.
But there may be a proverbial silver lining in the very real ash cloud that has forced the cancellation of hundreds of flights to and from the island — and one with implications for slowing global warming.
Swirling within the billowing ash cloud that Agung continues to spew up to 4,000 meters (13,100 feet) into the sky is a cocktail of volcanic dust and particulates, primarily sulfur dioxide (SO2), known as aerosols.
The last time scientists studied the massive dispersal of volcanic aerosols in the stratosphere on this kind of scale, following the 1991 eruption of Mount Pinatubo in the Philippines, they found that the particulates blocked some of the sunlight, and therefore the heat, reaching the Earth’s surface. The result: a temporarily cooling of the Northern Hemisphere by up to 0.6 degrees Celsius (1.1 degrees Fahrenheit).
Today, scientists are using satellites to monitor the volume of SO2 being pumped out by Agung and the dispersal of the aerosols in search of a similar pattern.
“And the climate modelers are already prepared to run simulations as soon as that information is available,” Douglas MacMartin, a senior research associate in mechanical and aerospace engineering at Cornell University, told Mongabay in an email. “I hope that we’ll be able to launch balloons to get in situ observations.”
MacMartin will work with the U.K. Met Office and the U.S. National Center for Atmospheric Research on the SO2 study.
With emissions of heat-trapping carbon dioxide on the rise again, and efforts to prevent global temperatures rising by 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels seemingly falling short, policymakers and researchers alike are increasingly looking to bold and drastic technical interventions to artificially manipulate the climate — a field known as geoengineering, or climate engineering.
One idea is to artificially reduce the amount of sunlight reaching the Earth’s surface by injecting aerosols into the stratosphere, essentially recreating the ash clouds churned out by volcanic eruptions.
“Given that the fastest we can cut our carbon emissions will likely still lead to significant impacts from climate change, it is important to at least understand climate engineering,” MacMartin said. “Climate model results suggest that it is plausible that some limited deployment of climate engineering could reduce many climate risks.”
But there’s much that scientists still need to understand — the Pinatubo data is all they really have to go on — before any informed decisions on geoengineering can be made, MacMartin said.
“We really only have good data from that one eruption, and there are various problems with that data too,” he said.
As a result, scientists don’t really know the best way to inject aerosols into the atmosphere, or the impacts of such a move.
“So it would be valuable to have additional data from Agung,” MacMartin said. “Of course, it would be far better for the people living there to not have to live through an eruption, but if it’s going to erupt anyway, we may as well learn from it.”
For all its promise as a means of slowing global warming, the field of geoengineering remains highly contentious.
Some climate scientists warn that humans shouldn’t meddle with nature on such a scale because of as-yet-unknown knock-on effects, including on the frequency of hurricanes or distribution of rain patterns.
New research by climate experts from the University of Exeter in the U.K. indicates that injecting aerosols in the Northern Hemisphere could increase the likelihood of drought in the Sahel, the area of sub-Saharan Africa just south of the Sahara desert.
MacMartin rebuffed this finding, saying scientists would not be so reckless to cause such detrimental effects.
“Of course you can do something stupid, but why would you?” he said. “We have a number of papers pointing out that you can balance the interhemispheric temperature gradient by balancing the forcing in the two hemispheres.”
‘Just an engineering problem’
There are also concerns that just the prospect of having geoengineering to fall back on will make policymakers and politicians even more reluctant to take meaningful steps to reduce carbon emissions, as already indicated by officials in the Trump administration.
US Secretary of State Rex Tillerson, for instance, has referred to climate change as “just an engineering problem.” (Tillerson was the longtime CEO of ExxonMobil, the oil giant that Harvard researchers found had misled the public about climate change.)
“You see that even in the US congressional hearing last month, that some on the Republican side were suggesting that this could be used ‘instead’ of regulating emissions,” MacMartin said. “But 100 percent of the people who understand the science are quick to point out that it doesn’t really work as an alternative, but only as a complement.”
That hearing in early November of the House Committee on Science, Space and Technology was chaired by Rep. Lamar Smith, a Republican from Texas who is a known climate change denier and whose biggest campaign contributor is the oil and gas industry.
David Keith, a solar geoengineering expert from Harvard University, said he feared the work he and his peers were doing could be exploited by those opposed to taking any action to reduce carbon emissions.
“One of the main concerns I and everyone involved in this have, is that Trump might tweet ‘geoengineering solves everything — we don’t have to bother about emissions,’” he said as quoted by The Guardian.
As scientists and policymakers continue to debate the risks and viability of climate engineering, the reality is that a mass-scale sulfur injection that could significantly cool the planet remains out of reach.
While the basic technology already exists in the form of high-flying jets capable of carrying tanks of sulfur into the stratosphere, the cost of deploying the amount of jets required to achieve 1 degree Celsius (1.8 degrees Fahrenheit) of cooling a year would reach $20 billion, according to a paper published in July by scientists from Germany’s Max Planck Institute for Meteorology and the U.S. National Center for Atmospheric Research.
MacMartin said it would be decades before the kind of mass-scale sulfur injection needed for meaningful cooling could be carried out cost-effectively.
“My guess is 20 years,” he said. “If you were desperate and willing to try it without understanding the details, you could probably do something in as short as five years, but I don’t think there’s anyone on the planet that crazy who also has a few extra billion dollars to develop a new aircraft.”
Banner photo: Mount Agung in Bali spews volcanic ash cloud into the atmosphere. Photo by alitdesign/pixabay.