Let me start out by saying that what you're about to read is in no way meant to be critical of scientists in general, nor the entire scientific endeavor.
What I want to emphasize right from the beginning, though, is that however supportive I am of science, it is inherently incomplete. We fill in pieces, and move toward a more thorough understanding of the universe -- it's undeniable that we know more now than we did five hundred, or a hundred, or even fifty years ago -- but there are still edges of our knowledge, and entire realms that are only partly understood. Nearly all scientists are themselves aware of this, and consider the "perimeter of our ignorance" (to use Neil deGrasse Tyson's pithy term) not to be a problem, but an impetus to further inquiry.
That said, the familiar student's complaint of "why do we have to learn this stuff when it could all be disproven tomorrow?" is nothing more than an excuse for laziness; at this point, the overturning of entire disciplines in the fashion that Copernicus, Kepler, and Newton did for physics and astronomy, Mendel (and many others) did for genetics, and Darwin did for evolutionary biology, is vastly unlikely. About the only area of science that still has enough odd and contradictory data (with dozens of competing models vying for acceptance) to qualify as a candidate for a major overhaul is astrophysics, with its dark energy and dark matter and cosmic inflation and cosmological constants, none of which have come together into a coherent whole. (Yet.)
But. It bears keeping in mind that the systems scientists study are complex, and the models they use to make predictions are often based on qualifications, assumptions, and idealizations. That doesn't mean they're worthless or unrealistic; just that they need to be used with caution.
This is why I was horror-struck by the recent suggestion of using stratospheric aerosol injection to combat anthropogenic climate change.
Because apparently the obvious solution -- investing in conversion to renewable energy sources, and phasing out fossil fuels -- is a pill too bitter to swallow for our political leaders, people are casting about for other ways to combat the warm-up while continuing to burn our way through the Earth's sequestered carbon. And one of the ideas was to copy what volcanic eruptions do, and blow huge clouds of fine particulates into the upper atmosphere, which would block sunlight and cool the Earth's surface.
There's no doubt that the idea has some factual basis. You probably know that the 1815 eruption of Mount Tambora, in Indonesia, generated so much ejecta that the following year was called "the Year Without a Summer," and temperatures dropped enough that crops failed across the globe (and here in my home of upstate New York they had snow falling in July).
The problem, though, is that climate is a complex, multi-variable system, which is why meteorologists still have difficulty making long-range forecasts. They're vastly better than they used to be; the deadliest natural disaster in the history of the United States, the 1900 Galveston hurricane, struck with almost no warning, leaving tens of thousands of people without enough time to get to high ground. But even considering how much the science has improved, using something like stratospheric aerosol injection to cool the globe is basically a climatological game of Jenga.
Fortunately, the scientists themselves are sounding the alarm. A study just released from Columbia University has shown in no uncertain terms that tweaking the climate by injecting aerosols into the stratosphere would be likely to have drastic and unpredictable effects. "Even when simulations of SAI in climate models are sophisticated, they're necessarily going to be idealized," said Faye McNeill, who co-authored the paper. "Researchers model the perfect particles that are the perfect size. And in the simulation, they put exactly how much of them they want, where they want them. But when you start to consider where we actually are, compared to that idealized situation, it reveals a lot of the uncertainty in those predictions. There are a range of things that might happen if you try to do this -- and we're arguing that the range of possible outcomes is a lot wider than anybody has appreciated until now."
The climate shows sensitive dependence on initial conditions -- a phrase that will be familiar to anyone who has read about chaos theory. The one thing that is almost certain is that something like SAI wouldn't cool the planet smoothly and uniformly, leaving other factors (like rainfall patterns) unchanged. Models showed a chaotic response to injection, often resulting in effects like disruption of tropical monsoons, alteration in the position of jet streams (thus changing storm track patterns), and uneven and rapidly-fluctuating shifts in temperature.
Not good. As Robert Burns said, "The best laid plans of mice and men gang aft agley."
Basically: we do not understand climate well enough to do this with confidence. After all, we're in the current mess because we ignored the scientists (starting with Svante Arrhenius in 1896) who said that atmospheric carbon dioxide levels were directly correlated with global average temperature, and that therefore we were going to warm the planet by burning fossil fuels. Let's not ignore the ones now who are saying, correctly, that blowing aerosols up into the stratosphere and hoping for the best is a bad, bad idea.
My fear, though, is that the current regime here in the United States has the motto "quick fixes and short-term expediency FTW," so they'll think this is just a nifty idea.
To return to my original point, despite the best work of scientists, our knowledge is still incomplete, and that applies especially to complex, chaotic systems like the climate. The climatologists themselves know this, and thank heaven a group of them have published a paper urging us to (extreme) caution.
Let's hope the people in power are, for once, listening.
