You know how the story goes: a hypothetical butterfly flaps its wings. The air pressure changes ever so slightly. Winds shift. Fronts collide. And the next thing you know, a hurricane kicks up halfway around the world.
We fall back on the “butterfly effect” every time we mean to say that all life is connected, or that small actions can have enormous consequences. It’s what showed George Bailey the light in It’s a Wonderful Life, and it’s what Dr. Ian Malcolm was stuttering about in Jurassic Park. But new research reminds us that the theory is far more than a Hollywood trope.
In a paper published Friday in the journal Geophysical Research Letters, a team of researchers from the University of Washington shows that decades of drought in Africa were caused, at least in part, by pollutants emitted by the United States and Europe. Throughout the 60s, 70s, and 80s, coal-burning factories spewed sulfate-laden aerosols into the atmosphere with reckless abandon. These tiny particles -- which volcanoes can also emit naturally -- reflect sunlight and produce more reflective, longer-lasting clouds. The increased cloud cover caused temperatures to drop across the Northern Hemisphere, which in turn, caused rain patterns to shift away from certain areas of Africa. These shifts, the researchers argue, contributed to droughts that choked central Africa and resulted in 100,000 deaths between the 60s and 80s.
Meanwhile, with the intention of improving air quality at home, the U.S. and Europe began to restrict coal pollution in 1970 with the Clean Air Act and other legislation. It’s only now, after decades worth of precipitation observations, that researchers have been able to tie the end of the African drought to western legislation. As our factories scaled back production of sulfate aerosols, the pollution’s cooling effect slowly reversed and rainfall in Africa returned to historic levels by the mid-1980s.
If you’re suddenly feeling all warm and fuzzy inside -- “We fixed a devastating drought!” -- the story isn’t over. Aerosols weren’t the only pollutants in the atmosphere messing with the climate. Carbon dioxide has been flapping its wings, too. In a companion study, the research team argues that climate change is affecting the Northern and Southern Hemispheres at different rates, with the Northern warming faster thanks to its greater landmass. Last century's aerosol pollution masked this warming pattern, however. According to the researchers, temperatures in the north remained steady because the aerosol-related cooling balanced out the greenhouse effect created by increased carbon dioxide.
Understanding how each piece affects the whole is crucial to combatting climate change. That’s why NASA plans to launch a fleet of aircraft and satellites this summer to take exhaustive samples of the atmosphere. Their mission is to better understand how air pollution and natural emissions (like those from forest fires) play into atmospheric composition and climate. Ultimately, such information might lead to better policy decisions both for our own country and the global community to which we’re inextricably bound. More