A British chemical engineer, Peter Davidson, presented a webinar early this morning on his strategy to combat global warming: Fog Earth’s upper atmosphere with paint particles, streamed from giant balloons, to reflect sunlight away from Earth and offset the greenhouse effects of burning fossil fuel.

Peter Davidson

Plan B, indeed.

As the years roll by with essentially no meaningful progress on cutting carbon emissions, “geo-engineering” solutions like Davidson’s attract more attention and perhaps even faith from those inclined to believe that since technology got us into this mess, technology can somehow get us out. (A piece on Davidson’s idea in The Chemical Engineer  has drawn favorable references in places as diverse as Gasworld  and Earth Times.)

And the idea of mirroring sunlight away from Earth is not, at a certain conceptual level, completely insane. But in practice it might be close.

Making like Pinatubo

Like others before him, Davidson argues for manmade mimicry of a famous natural interruption in the planet’s warming trend — the 1991 eruption of Mount Pinatubo in the Philippines, which pumped 20 million metric tons of sulfur dioxide into the stratosphere, creating a mirroring blanket of sulfuric acid vapor that caused a dramatic two-year drop in temperatures around the world. According to The Chemical Engineer:

As sulfuric acid degrades the ozone layer and is thought to cause regional changes in rainfall, Davidson sought a benign but similarly sized particle. He suggests titanium dioxide, mankind’s most commonly-used pigment. It is stable in air, non-toxic and seven times more effective at scattering light than sulfuric acid. Titanium is abundant in the earth’s crust and we produce 5 million tons per year of the pigment so Davidson does not expect manufacture and supply will be a problem.

With a candidate particle identified, the next challenge is devising a system to effectively and economically lift and disperse millions of tons of particles some 20 km up into the stratosphere, so they stay up for a couple of years and do not immediately get rained out.

His suggested delivery system: giant balloons tethered to ships, which would pump titanium dioxide dust 12 miles into the sky. Simple as that. What could possibly go wrong?

What if everything went right?

Really, though, the question is what could happen if every step in this process went exactly right, and we were somehow able to recreate a Pinatubo-type increase in Earth’s albedo, or reflectivity, by artificial means.

“When you start to reflect light away from the planet, you can easily imagine a chain of events that would extinguish life on Earth,” says David Keith, who teaches engineering and public policy at Harvard, and is said to be among the most thoughtful supporters of geo-engineering solutions like Davidson’s.

That quote is from “The Climate Fixers,” an extraordinary piece by Michael Specter that ran in The New Yorker’s May 14 issue and as of this writing is out in front of the magazine’s pay wall. Here’s the context:

For years, even to entertain the possibility of human intervention on such a scale — geo-engineering, as the practice is known — has been denounced as hubris. Predicting long-term climatic behavior by using computer models has proved difficult, and the notion of fiddling with the planet’s climate based on the results generated by those models worries even scientists who are fully engaged in the research. …

There is only one reason to consider deploying a scheme with even a tiny chance of causing such a catastrophe: if the risks of not applying it were clearly higher. No one is yet prepared to make such a calculation but researchers are moving in that direction.

In addition to cooling the planet overall, Pinatubo’s aerosols dramatically (though temporarily) depleted the ozone layer. They are also thought to have brought devastating drought to sub-Saharan Africa, and to have caused the U.S. summer of 1992 to be the third-coldest and third-wettest in some 77 years, followed by extensive flooding in the Mississippi River basin in 1993 (a detailed paper is available from the U.S. Geological Survey here).

Longer-term manipulation of Earth’s reflectivity could have larger and more persistent regional impacts. Specter’s leading hypothetical is disruption of monsoon patterns in Africa and Asia, where agriculture feeding billions of people has been adapted to cycles that could easily be knocked out of balance, creating catastrophic floods or droughts or both.

Of course, nobody would suggest creating a Pinatubo-type aerosol layer all at once. The more likely strategy would be a gradual, controlled application to add a little reflectivity and see what happens, then dial it up and down depending on the results. Which sounds quite sensible if you assume the dialing would be guided by certainty about how the whole system was responding.

Even then there is the possibility of a nasty surprise. Pinatubo, the second-largest volcanic eruption of the century, was essentially unpredicted until a few short weeks before the magma emerged — and even then the scale of the event could not be forecast.

On the bright side

Already I can hear the global-warming deniers and the incurable technology optimists saying, OK, those are obviously serious downsides – but isn’t it equally possible that science and technology could derive undeniably good outcomes, given a little more time and research?

Specter also discusses some modeling undertaken by climate scientists who were initially skeptical about the whole idea of deflecting solar energy on a global scale. To their surprise, the models suggested it might work rather well — up to a point.

They worked from two key assumptions: a doubling of current CO₂ levels in the atmosphere, which is looking more likely all the time, and a layer of sulfate aerosols sufficient to deflect about 2 percent of incoming sunlight (Pinatubo is said to have caused at maximum a reduction of 10 percent). The results:

Farm productivity, on average, went up. The models suggested that precipitation would increase in the northern and middle latitudes, and crop yields would grow. In the tropics, though, the results were significantly different. There heat stress would increase, and yields would decline. “Climate change is not so much a reduction in productivity as redistribution,’’ Caldeira said. “And it is one in which the poorest people on earth get hit the hardest and the rich world benefits” — a phenomenon, he added, that is not new.

Caldeira is Ken Caldeira of the Carnegie Institution, a principal contributor to the team that won the Nobel Peace Prize in 2007 for the Intergovernmental Panel on Climate Change (Al Gore being the marquee member). Like most scientists, he is candid about the limits of what is known; unlike many climate scientists, he is outspoken about the need for action on a large scale before all the evidence is in.

“We don’t know how bad this is going to be, and we don’t know when it is going to get bad. There are wide variations within the models. But we had better get ready, because we are running rapidly toward a minefield. We just don’t know where the minefield starts, or how long it will be before we find ourselves in the middle of it.”

There is no shortage of other high-tech ideas for solving global warming, from capture and sequestration of power-plant emissions to low-carbon fuels to covering desert landscapes with giant mirrors. Specter’s article introduced a new one, at least for me, which at a glance seemed to have some plausibility behind it.

A company called Global Thermostat has developed a way of breaking CO₂ into harmless forms of carbon and oxygen without the high temperatures that have previously made this idea infeasible. This approach would use “a five-story brick edifice specially constructed to function like a honeycomb” to draw CO₂ out of the air, then process it with waste heat from, say, factories distributed around the globe. A prototype has been built in California.

It might take as few as 20,000 of these structures, costing only $100 million each, for a total of just $2 trillion, a mere 30 years to make a difference (sarcasm added). Again, it’s a solution that looks good only because all of the others are unthinkable.

The rich and the poor

Global warming’s differential impact on the world’s rich people and poor people, and their differing capacities to adapt, is an important theme running through all serious discussion of climate change’s impacts past, present and yet to come. It doesn’t get the attention it deserves in our national discussions, which tend to center on how avert extinction while preserving our living standards without too much pain or disruption.

Two points in the Specter piece point to the folly of imagining we can truly insulate ourselves from global catastrophe.

• A ballpark estimate of climate change’s pending economic impact suggests a 5 percent drop in global domestic production, which may not seem like a lot, says Ken Caldeira, until you consider that the subprime-mortgage crisis caused approximately the same drop, whose ripples are still being felt.
• The atmospheric-aerosols solution could cost as little as a few billion bucks a year – a trifling figure compared to, say, the Global Thermostat approach – and that’s actually the bad news, because it raises the risk of a catastrophic misapplication.

“The technology is open and available—and that makes it more like the Internet than like a national weapons program,” Specter writes. “The basic principles are widely published; the intellectual property behind nearly every technique lies in the public domain.

“If the Maldives wanted to send airplanes into the stratosphere to scatter sulfates, who could stop them?”

A podcast discussion that features Michael Specter and Elizabeth Kolbert, the New Yorker colleague who wrote “Field Notes From a Catastrophe,” is online.