A first-of-its-kind climate science research program was just shut down in Alameda, California by local leaders, against the advice of city staff and experts who confirmed the safety and value of the research. The program intended to study how tiny particles called aerosols move in the atmosphere by spraying sea-salt mist on the flight deck of the USS Hornet Sea, Air and Space Museum. The research could help address one of the greatest areas of uncertainty in projecting our future climate and, potentially, inform future methods to combat heat waves.
The Earth’s atmosphere is full of naturally derived aerosols such as pollen, dust and sea salt from ocean spray — as well as aerosols from human-caused pollution. While greenhouse gas pollution warms the Earth by acting like a heat-trapping blanket, aerosol pollution can be thought of as a light parasol, partly shielding us from the sun’s rays. Aerosols cool the climate by reflecting sunlight directly and, even more powerfully, by brightening clouds. This effect can be seen from space as bright streaks trailing cargo ships, spewing pollution aerosols from burning sludgy fuels as they travel across the oceans.
Up until now, this aerosol “parasol” has masked around one-third of the warming effect from our greenhouse gas emissions. That is starting to change, however, because new laws have dramatically curbed ship pollution over the oceans and countries like China have reduced pollution on land.
Cutting aerosol pollution is a double edged sword; it has important and necessary public health benefits, but it also means the climate is set to warm even more. Exactly how much more is still unknown because quantifying how much aerosols influence clouds remains one of the largest unsolved problems in climate science.
Understanding the effects of aerosols on climate could help protect people from deadly heat. Around a billion people live in areas projected to get so hot and humid that being away from air conditioning is life-threatening.
All humans, no matter how physically fit, have limits to the heat we can withstand before internal body temperatures rise to deadly levels. Life-threatening, humid heat is becoming more common in many parts of the world, including Bangladesh, the Persian Gulf, and even parts of the US, such as Florida and Texas. In some of these places, air conditioning is scarce — and even where it is available, a power blackout or brownout could be a death sentence.
The Alameda program would have included research related to both general aerosol effects and to marine cloud brightening (MCB), an idea for brightening clouds with sea-salt spray instead of pollution. There are still key areas of research that need attention in order to determine if MCB would be feasible, which is why numerous scientific advisory reports have recommended research on rapid climate interventions like MCB, including small-scale field studies to advance our knowledge about how aerosols and clouds interact in the real environment.
The small sea salt studies that were halted in Alameda could have helped improve computer models that project how much reducing pollution aerosols will warm the climate, and in what situations MCB might save lives by cooling it.
Some might be wondering: Why bother with ideas like MCB when we know the only long-term solution is to stop emitting greenhouse gasses?
For starters, deadly heat is already here — hundreds died in Phoenix’s record-breaking heat last summer — and this summer is already hotter than last. Reducing greenhouse gas emissions has much-needed, but gradual effects on climate, meaning that even if emissions reduction efforts are highly successful, more warming will occur over the next few decades.
What’s needed is both an end to greenhouse gas emissions and protection from heat emergencies in the near-term. These aren’t conflicting goals, but two indispensable parts of climate planning.
What we’ve learned from crises like Covid-19 is that, if science isn’t yet mature when an emergency happens, we’re mired in confusion about what works and waste time grasping at straws like ineffective treatments.
In deadly heat waves — especially combined with power grid failures, which are expected in places like Texas, and in parts of the world with little air conditioning — local agencies might try MCB-like approaches in a desperate bid to reduce temperatures and save lives. But if this happens before scientists have time to properly study the science underlying MCB and similar interventions, the effects will be hard to predict — and far more likely to fail.
Undertaking the sea salt research as part of a museum exhibit and educational program in Alameda could have been a transformative opportunity to educate the public about climate science and the role of aerosols. Some Alameda residents argued against permitting the research with “not in my backyard” vigor, not because they don’t want to protect future generations from deadly heat, but out of fear of the unknown.
Many others spoke up in favor, seeing science and information as important for the community and the climate. Meanwhile, the City of Alameda performed its own environmental and health reviews and found that the studies would not be harmful to people or animals near the site. Public education on aerosols and MCB is desperately needed — and would have been one of the best parts of the Alameda program if it had gone forward.
Small-scale sea salt research like that proposed in Alameda will not affect clouds or the climate, but it will improve scientific understanding of whether it’s possible to cool down areas experiencing deadly heatwaves. It’s possible that the research might prove MCB isn’t viable — which would be good to know so resources and time aren’t wasted during a climate emergency. On the other hand, it might show how to use MCB to save lives from a human-made crisis.
With so much at stake, shouldn’t we study every possible solution, and in the most open ways possible?
- Dr. Anna Bershteyn, PhD, is an associate professor of Population Health at New York University Grossman School of Medicine. Michael S. Diamond, PhD, is an Assistant Professor in the Department of Earth, Ocean, and Atmospheric Science at Florida State University.
