Geoengineering and the ocean

The Wonkroom's Brad Johnson takes on USA Today's Dan Vergano over geoengineering. Geoengineering is the idea that we could combat global warming by pumping sulfur dioxide into the upper atmosphere, thus blocking some solar radiation and keeping things cooler.

Vergano is a sharp science writer and his take is hardly boosterish, but Johnson dings him for having:

failed to accurately interpret the scientific literature. The only risks he has depicted â ones that involve the potential deaths of millions if not billions of people â are the âknownâ ones, the ones easily modeled by imperfect simulations of experiments never conducted before by humanity. The risks of geoengineering, particularly the ones that emulate the effects of a nuclear winter to dim the amount of sun reaching the earth, are practically unbounded. Depicting the known risks, as Vergano did, as the only risks of geoengineering, is astoundingly optimistic.

One risk I think Vergano underplays, though he does mention it, is ocean acidification. Carbon dioxide in the atmosphere doesn't just trap solar energy, heating the planet, it also gets absorbed into the oceans. And in solution, that carbon dioxide turns into carbonic acid. This is a reverse of the dynamic you see when you open a soda bottle; in that case carbonic acid comes out of solution as carbon dioxide, yielding the bubbles. The remaining carbonic acid gives the soda its bite on the tongue.

In the ocean, that acidity has catastrophic effects. Even modest shifts in acidity are enough to damage or kill coral reefs, the spawning grounds and shelter for significant amounts of ocean biodiversity. The acidity also helps dissolve the calcium carbonate that forms a coral reef, literally eating away at those vital structures. The changing ocean chemistry also harms unicellular life, plants, and animals, disrupting mating and damaging sensitive tissues.

No geoengineering solution prevents ocean acidification. As Vergano says, "simply cutting temperatures won't stop the rise in ocean acidification arising from increased carbon dioxide levels in the air, which may affect marine life underlying the ocean food web." The only way to protect our oceans is to cut down on carbon dioxide emissions. To my mind, that single sentence of Vergano's is enough to relegate this idea to the back shelf, as an emergency measure to prevent catastrophic feedbacks, but not something that has a useful place in public policy discussions at this point.

Vergano gives other reasons, too:

Simply putting a worldwide price on carbon emissions from smokestacks and letting the marketplace lead to lower carbon emissions would likely be cheaper and more sensible than geoengineering, says [Scott] Barrett, the economist [from Columbia University]. "But let's face it. We're talking about (geoengineering) because we don't have a price on carbon."

As Johnson notes:

The only reason that serious climate scientists (other than Dr. Strangelovian extremists) are discussing geoengineering is that they fear the possibility of humanityâs extinction â or merely the utter collapse of human civilization â from unchecked fossil fuel pollution is significant enough to consider doomsday survival scenarios. âWe should avoid geoengineering if possible,â Dr. Ken Caldeira, one of the climate scientists who has explored geoengineering scenarios, âbut we need it in our toolbox in case of catastrophe.â

Simply put, there are plausible scenarios in which global temperatures could begin rising so fast that they could be impossible to stop. This could be because frozen methane begins leaking into the atmosphere, thus promoting more warming, or because ice melts and stops reflecting light back into space (allowing dark rocks to absorb more heat). Given how slowly society is moving towards carbon emission reductions, the only way to avert these catastrophic feedbacks might be a carefully planned and targeted phase of geoengineering, in concert with aggressive emissions reductions.

But by injecting geoengineering into the public discourse before we've set ourselves on that emissions-reducing course, journalists and scientists risk introducing confusion about what geoengineering can possibly do. At most, it's a stopgap to cover the inevitable lags between emissions reductions and a decline in atmospheric carbon dioxide. On its own, it won't stop global warming. Without emissions reductions, we'd be, as Vergano puts it elegantly "addicted to sky-borne sulfates to keep the cooling on track." And that, too, would have harmful effects on the global climate and on life on earth, some predictable, and others that we can't yet imagine.