"It could be a full degree of cooling being masked."
Cool Factor
Have industrial emissions been counteracting the worst effects of global warming? Scientists are starting to think so.
Burning coal, oil, and gas warms our planet by dispersing greenhouse gases, like CO2, into the atmosphere. And before the introduction of more stringent environmental regulations, these fuel sources would often contain deadly pollutants like sulfur oxide that contribute to the deaths of millions of people globally.
World governments have rightly fought to curb pollutants. But as a growing body evidence is beginning to show, these airborne particles, or aerosols, have likely mitigated rising temperatures by reflecting sunlight and boosting the reflectivity of clouds — and as a result, concealed just how bad global warming actually is.
The extent of the cooling they've caused is more contentious. Nonetheless, it's a grim irony that exemplifies the complexities of understanding — nevermind protecting — our climate.
"We're starting from an area of deep, deep uncertainty," Zeke Hausfather, a climate scientist from the University of California, Berkeley, told The Washington Post. "It could be a full degree of cooling being masked."
Abandon Ship
One of the biggest drop-offs in pollutants may come from the shipping industry, whose regulatory body in 2020 started limiting the use of the dirty, sulfur-spewing fuels its massive vessels once relied on, in favor of cleaner alternatives.
But with the resulting decrease in aerosols, recent research has shown that these cuts in shipping pollution has directly led to more solar radiation being trapped in our atmosphere, which could explain why 2023 was the hottest year on record by a margin that alarmed even scientists.
That doesn't augur well for the future: the authors of the research suggested that as we curb these deadly pollutants, we could experience double the rate of global warming compared to the average since 1880.
As WaPo notes, however, many experts think the warming will be less pronounced, contributing somewhere between 0.05 degrees and 0.1 degrees Celsius of an uptick — which, of course, is still significantly worrying.
Clear the Air
There is, perhaps, a silver lining. The same cooling principle of these pollutants could be wielded in an experimental technique called marine cloud brightening, which would involve deliberately injecting safe aerosols into the atmosphere to cause clouds to reflect more sunlight and to increase cloud cover.
This is unproven and controversial, though, and the researchers behind the shipping study have suggested that their findings are an example of the downsides of pursuing that technique: the minute we stop pumping aerosols into the atmosphere, global temperatures will soar again, perhaps even more drastically than before.
At any rate, clarifying these gray areas will be paramount for climate scientists. The picture is more complicated than we once thought, and determining how much aerosols figure into it will be essential if humanity is to keep global warming short of even more disastrous levels.
"It's not just a story of greenhouse gas emissions," Robert Wood, a professor of atmospheric science at the University of Washington, told WaPo. "Whether you clean up rapidly, or whether you just fumble along with the same aerosol emissions, could be the difference of whether you cross the 2-degree Celsius threshold or not."
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