Now May Be the Time to Experiment With Mother Nature—Carefully! | Opinion

When Mount Pinatubo in the Philippines erupted in 1991, the volcano propelled huge amounts of sulfur dioxide into the stratosphere and cooled the planet by a half a degree Celsius (1degree Fahrenheit) for a couple of years.
Some leading scientists think we could do the same by deliberately shooting sulfur dioxide into the stratosphere to cool our overheating planet. Now these scientists want to undertake experiments to confirm that this type of geo-engineering—called solar radiation intervention (or SRI)—would be effective at limiting temperatures and to better understand what the possible negative side-effects might be.
For example, would SRI risk undermining the stratospheric ozone layer and increase ultraviolet radiation that causes skin cancer, cataracts, and immune suppression? If so, would such increases in ultraviolet radiation also degrade forests and other terrestrial carbon sinks adding significantly more warming? Would SRI risk drying out critical habitats or cause torrential rains in areas that are not designed to withstand downpours, threatening global food security? Right now, we simply don’t know.
A strong climate case can be made for studying SRI as a temporary stop-gap strategy for shaving peak temperature while we redouble efforts to reduce the climate pollutants that are the root cause of the problem. The planet is already far too warm today and there is little time left before current climate emissions accelerate self-amplifying feedback loops in natural systems. This process now threatens to push the climate past multiple tipping points that are lurking between the 1.5 degrees Celsius we’ve already experienced the last 12 months, and the 2 degree barrier we’re heading towards in the next few decades without urgent action.
The Arctic and the Amazon are two examples of feedback loops and tipping points now underway. We’ve already lost half of the reflective ice shield in the Arctic, and once the shield is completely gone, we’ll add the equivalent of 25 years’ worth of current climate emissions in warming. This additional warming will accelerate thawing of permafrost, which will then release more methane, more carbon dioxide, and more nitrous oxide, setting off a cascade that risks triggering other tipping points and more self-amplifying warming.
In the Amazon, close to 20 percent of the carbon-absorbing forest has already been destroyed, and scientists like Dr. Carlos Nobre calculate that if 20 percent to 25 percent is destroyed by climate-fueled fires as well as being cleared for agriculture, the Amazon will reach a critical tipping point. If this happens, the forest that was formerly pulling carbon dioxide from the atmosphere and safely storing it in biomass and soil will become a new source of additional carbon dioxide emissions. On our current course of emissions both these tipping points and feedback mechanisms could be triggered in the next few decades. Indeed, parts of the Amazon are already becoming sources of carbon dioxide.
To avoid these and other tipping points that could send the climate system toward runaway super-heating and utter climate disaster, it is critical to slow current warming as fast as possible. World leaders must recognize this need for speed. Pope Francis explained this in his recent Planetary Call to Action for Climate Change Resilience, there is a critical need to win the sprint to cut the non-carbon dioxide climate super pollutants—methane, HFC refrigerants, black carbon soot, and ground level ozone. Cutting these pollutants is the only known way, apart from geoengineering, to slow warming in the next two decades.
Francis, extending the race analogy, points to the need to also win the marathon to decarbonize by 2050, and then to win the ultra-marathon by learning how to pull carbon dioxide and methane from the atmosphere faster than the natural cycle. It’s important to face up to the fact that we are not on track to decarbonize by 2050, as fossil fuel use continues to expand and emissions with it.
Nor are we making much progress learning how to pull carbon dioxide out of the atmosphere, although the Biden-Harris administration is putting significant funding into perfecting this strategy. Methane emissions are not going down, either, and there is not yet a mandatory agreement to reduce them. The U.S. National Academy of Sciences will soon release a research agenda for methane removal, which has great promise but is not close to prime time. Nor are black carbon and ground level ozone going down. The only part of the sprint we’re winning is cutting the fluorinated gases used as refrigerants, which are being phased down under the Montreal Protocol’s mandatory controls.
With the slow progress in reducing climate pollutants, current warming is likely already locking in some of the irreversible tipping points, with others getting closer as we blow past the 1.5 degree Celsius guardrail and barrel along towards 2 degree Celsius global heating and likely beyond.
Those who oppose studying SRI—and there are many who do—often argue that it presents a moral hazard that would divert funding and slow efforts to reducing climate emissions. Perhaps. But it’s getting harder to seriously argue that current efforts, even if better funded and accelerated, will be enough to stabilize the climate in the limited time before feedback loops and tipping points push the planet to climate catastrophe.
The real moral hazard is failing to prevent climate disaster, which is our undeniable current course. If we will need to limit solar radiation using sulfates as a temporary fix to shave peak temperature for a few decades, it would be very wise to study it now to understand the risks, even as we accelerate existing efforts to cut all climate pollutants as fast as possible. Otherwise, the tragic reality is all our actions may be too little, too late, to prevent climate chaos.
Paul Bledsoe is a professorial lecturer at American University’s Center for Environmental Policy. He served on the White House Climate Change Task Force under President Clinton.
Durwood Zaelke is president of the Institute for Governance & Sustainable Development and adjunct professor at the University of California, Santa Barbara’s Bren School of Environmental Science and Management.
The views expressed in this article are the writers’ own.