Engineering the climate

The title of this post is a shameless rip-off of Jeffrey Mazo’s recent (and excellent) review of an the National Research Council’s new survey of potential geoengineering policies.  Mazo’s review is very worth reading, and hits virtually all of the right notes, I think.  Because much of this discussion takes place behind the unfortunate paywall that sequesters much of cutting-edge science from public attention, though, I thought it would be worthwhile to mention the topic here.  Geoengineering is a topic that’s near and dear to me (it is, ostensibly, the primary subject of my current postdoctoral research), as well as one which is garnering increasing media attention.  It is sometimes also referred to as “climate engineering,” and consists in deliberately manipulating the global climate on a massive scale in order to offset some of the problems associated with climate change.

It is, generally speaking, a terrible idea.  Here’s why I think so.


Unintentional Experiments

Earth science textbooks sometimes refer to climate change as “a vast unintentional experiment” that’s been undertaken by humanity.  I’ve always liked that way of thinking about it–as if worldwide greenhouse gas (GHG) emissions were something like the “unintentional experiments” your college roommate sometimes left in the refrigerator, only on a planetary scale.  The language is evocative, and makes it clear how risky our current practices actually are, given that we happen to live in the geological Erlenmeyer flask in which this particular experiment happens to be going on.  Bruce Banner conducted an unintentional experiment on himself as well; we all know how that turned out, and our unintentional experiment is very unlikely to give anyone superpowers.  But what if we could, rather than halting the experiment, begin to take control of it?

Geoengineering represents just such an attempt to take control, and is a radical solution to an increasingly radical problem.  We know that human behavior can change the global climate, as we’ve been blithely doing just that for over a century.  Geoengineering involves attempting to exercise our global influence deliberately to undo the results of exercising that influence accidentally.  This isn’t science fiction, and it’s not a fringe movement.  Bill Nye is talking about it.  The IPCC (one of the most cautious and conservative scientific bodies in the world) is talking about it.  It’s a real live option, and the fact that we’ve come to a place where we’re getting desperate enough to start taking it seriously should scare the pants off of you.  If undertaken, a geoengineering project would be a milestone in human history–an engineering challenge that makes the construction of the Great Wall of China or the Panama Canal look like an afternoon spent playing with Lego on the kitchen floor–but it could also cause an unprecedented global disaster.  Can we do it?  Most definitely.  However (to paraphrase Jeff Goldblum’s character from Jurassic Park), we’d do well to not get so caught up in thinking about whether or not we could that we forget to think about whether or not we should.

Shirtless Jeff Goldblum lounges in Jurassic Park.

This is how all responsible science is conducted.


So, should we?  Are you ready to decide?  You need to be, because you might be asked to vote on something like this next year, or in five years, or next decade.  We all may want to start getting ready.

How exactly might we go about seizing control?  There are lots and lots of different proposals on the table, and while some of them are as eccentric as setting up giant mirrors in space, the most plausible and popular option is a version of “solar radiation management,” (SRM) which is a sciencey way of saying “cooling off in the shade.”


Pandora’s Volcano

Most people remember making paper mache volcanoes as part of a youthful science fair project by combining baking soda and vinegar (if you’ve never done it–or really even if you have–I recommend that you try it some time as an adult, because it’s just as fun now).  The leading geoengineering proposal also involves man-made volcanoes–at least in a certain sense–but on a much grander scale.  Very large volcanic eruptions (in addition to annoying international businesspeople) release a truly mind-boggling amount of volcanic stuff into the atmosphere, including compounds known as sulfate aerosols.  Sulfate aerosols are small droplets of sulfur-based chemicals that aren’t quite liquid and aren’t quite gaseous.  When they get into the upper atmosphere, they can block significant amounts of incoming solar energy, preventing it from getting down to the Earth’s surface where it would otherwise get stuck thanks to the greenhouse effect.  This has a major cooling effect: the last big volcanic eruption, 1991’s Mt. Pinatubo, reduced incoming sunlight by 10% and decreased global temperatures by about 0.5 degrees C for two years (that might not seem like much, but spread over the whole planet it’s a huge difference).  If we wanted to, we could intentionally release similar aerosols into the atmosphere.

Aftermath of the 1991 Mt. Pinatubo eruption

Aftermath of the 1991 Mt. Pinatubo eruption

High atmosphere winds would rapidly spread aerosols released near the equator to cover the globe, and with enough aerosols, we could potentially cool the planet off enough to cancel out a quadrupling of GHG concentrations.  If successful, such a plan could prevent sea level rises, save the glaciers, and prevent many other extreme weather events that we anticipate would accompany drastic temperature increases.  The total cost is projected to be something like $50 billion per year, which sounds awfully expensive until you realize that it’s only about 1% of the expected cost of transitioning to a fully sustainable world economy.  If this sounds too good to be true, that’s because it very well might be.

Global temperature increases aren’t the only consequences of climate change (that’s why we call it “climate change” instead of “global warming”).  CO2 in the atmosphere turns to carbolic acid in the oceans, endangering marine life and disrupting ecosystems on land and at sea; aerosol injection (like all SRM plans) would have no effect on ocean acidification.  Plus, all that sulfur in the upper atmosphere would start eating away at the ozone layer again, potentially undoing all the progress we’ve made toward closing the ozone hole (remember that?) since banning CFCs two decades ago.  Perhaps most worryingly of all, decreased sunlight plus a stronger greenhouse effect would wreak havoc on the water cycle across the globe by decreasing evaporation and changing rainfall patterns.  In the years after Pinatubo blew, worldwide rainfall dropped to more than three standard deviations below normal.  That’s a gigantic decrease: to use an (imperfect) analogy, a difference of three standard deviations in adult male height in the United States is the difference between someone who is five feet and eight inches tall and someone who is six and a half feet tall.  The years after Pinatubo’s eruption saw droughts over much of the world, many of them severe.  And that eruption, remember, only cooled the planet by 0.5 degrees: the effect on rainfall is expected to increase with greater aerosol concentrations, and this plan would call for enough to cool the planet by 4 degrees C or more.  The effect on agriculture the world over could very well be catastrophic–arguably just as bad (or worse) than the damage done by warming alone.  We may reach a point where the benefits outweigh the costs–particularly if we continue not reducing our GHG emissions–but who’s to say where that point lies?  There’s no way to target this plan by region: either we do it to the whole globe, or we don’t do it at all.

Are you comfortable asking farmers on another continent to sacrifice their livelihoods for the sake of other nations’ unwillingness to reduce CO2 emissions?  Should you be comfortable with that?

How much agreement among nations is enough to take this plunge?  If the citizens of every nation but one decide that the sacrifice is worth it, would we be justified in starting the program even over that single nation’s protests?  What if it’s two nations objecting?  What if it’s just under half?  These are not idle questions–not mere hypotheticals of the type that concern few but moral philosophers inside the seminar room–but real decisions we could be facing before the century’s out, and I’m very worried that we are in no way ready to handle them.  Considering the difficulty we have making tough decisions inside individual nations, I can’t even imagine how we’d even begin to deliberate about this as a species.

The really scary thing about aerosol injection (if none of the rest of this scared you) is just how easy it really is, and how difficult to stop it would be once the compound was released.  If a Peter Thiel or a David Koch (or an Exxon-Mobil) decided to initiate a program like this, it would be almost impossible to stop them if they managed to get started; we’d just have to wait for the aerosols to fall out of the atmosphere, a process that could take years even after the emissions ceased.  The same goes for a single nation that decides such a program is in its national interest and elects to go it alone, full speed ahead and damn the torpedoes–or, in this case, damn the rainfall.  Would we go to war to stop this from happening?  Would we go to war to make this happen, should we decide it’s in our national interest?  Either way, the implications are deeply troubling.

Humanity is capable of truly amazing things, but I’m not sure we’re ready to be in charge of an experiment on this scale: better by far to take steps now to prevent the damage before this path begins to look attractive.

But you’ve heard that before, I’m sure.

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