Geoengineering to Fight Climate Change Still More Dream Than Reality

The idea of pumping sulfur into the stratosphere to cut down on the sunlight hitting the earth — and curbing global warming — is one that’s been around for decades.

In 2006, it came to public attention when Paul Crutzen, the atmospheric chemist who won a Nobel Prize for his work on ozone depletion, said it might be an "escape route" means of dealing with out-of-control global warming.

But the idea is still far from becoming a practical reality, a panel of scientists at the American Geophysical Union's fall meeting in San Francisco said Wednesday.

The problems with “geoengineering" a cooler planet aren’t just limited to the massive engineering efforts that would be required to lift tens of million of tons of particles into the high atmosphere via plane or balloon, said Richard Turco, professor with the Department of Atmospheric and Oceanic Sciences at the University of California at Los Angeles.

It’s also limited by the lack of scientific understanding of how the processes involved would work, he said. Most research into the concept has involved using sulfur — after all, the major climate changes caused by massive volcanic eruptions like those of Mount Pinatubo in the Philippines in 1991, which pumped about 20 million tons of sulfur dioxide into the atmosphere, have given scientists real-world data to draw from.

But what would happen if humans put huge amounts of sulfur dioxide or hydrogen sulfide gas into the atmosphere isn’t yet understood, Turco said. Variables such as how the gas would interact with oxygen at those altitudes to form particles — a big question as to whether the gas would form particles light enough to stay afloat — still are open to question, he said.

Outlining experiments into the question, Turco said that models show that “you have many particles that are small and growing, you have many particles that have reached the optimum size and you have many particles that are larger than the optimum size. … In the real world, you’re going to have a highly variable situation."

“Experiments, I think that’s fine," he said. “But having a practical solution based on all this variability and uncertainty" is a risky proposition, he said.

That’s not even counting the costs of doing it, which “could literally approach tens of trillions of dollars over the times this would have to be done, which is a couple of centuries at least," Turco said.

“You’d have to construct a whole new fleet of aircraft that aren’t even designed" yet, he said. “Moreover, you’d have to have an observational system to monitor what’s going on that’s comparable to out entire weather monitoring system on earth."

Still, more research into geoengineering is a good idea, given the scope of the climate change problem facing mankind, said David Keith, a professor with the Energy & Environmental Systems Group at the University of Calgary in Canada.

“Even if we stopped [greenhouse gas] emissions instantly today — which would require a global nuclear war or something — we still have enough CO2 in the atmosphere that it’s possible we will have unacceptable levels of climate" change, he said. “And of course, we’re not going to stop today."

Given the enormous costs of reducing greenhouse gas emissions — up to $2 trillion a year, he said — and the uncertainty that starting to do so today won’t be too late to forestall climate change, geoengineering needs to come “out of the shadows and into the scientific mainstream," he said.

Keith said he envisioned research programs in the range of “$10 million class efforts" to do more computer modeling of how the processes would work, as well as a few small-scale, real-world experiments.

Still, “Nothing short of doing it will tell you what the long-scale" effects would be the final test, he said.