volcano.jpg Geo-engineering is “the intentional large scale manipulation of the global environment” (PDF) to counteract the effects of global warming, which itself was unintentional geo-engineering — although today you’d have to say global warming is intentional, since everybody now knows what we’re doing to the planet.

But I digress. We’re screwing up the planet with unrestricted greenhouse-gas emissions, and the question is, do we want to try to fix that problem by gambling on some other large-scale effort to manipulate the climate, or should we just try to restrict emissions? It’s as if the doctor says you have a disease that can definitely be cured by diet and exercise, but you opt for expensive chemotherapy — even though the doctor can’t guarantee the results but is pretty certain the side effects would be as bad as the disease.

A new study drives that home for the most discussed geo-engineering idea:

Pumping sulphur particles into the atmosphere to mimic the cooling effect of a large volcanic eruption has been proposed as a last-ditch solution to combating climate change — but doing so would cause problems of its own, including potentially catastrophic drought, say researchers.

And if we pursued the sulphur strategy but then found out, say, a decade later, that the drought prediction was correct, we’d be stuck; if we discontinued injecting the sulphur shield, global temperatures would rebound rapidly, potentially triggering catastrophic effects. (And, of course, this shield does nothing to stop catastrophic ocean acidification.)

Here is the abstract to the study, “Effects of Mount Pinatubo volcanic eruption on the hydrological cycle as an analog of geoengineering“:

The problem of global warming arises from the buildup of greenhouse gases such as carbon dioxide from burning of fossil fuels and other human activities that change the composition of the atmosphere and alter outgoing longwave radiation (OLR). One geoengineering solution being proposed is to reduce the incoming sunshine by emulating a volcanic eruption. In between the incoming solar radiation and the OLR is the entire weather and climate system and the hydrological cycle. The precipitation and streamflow records from 1950 to 2004 are examined for the effects of volcanic eruptions from El Chichón in March 1982 and Pinatubo in June 1991, taking into account changes from El Niño-Southern Oscillation. Following the eruption of Mount Pinatubo in June 1991 there was a substantial decrease in precipitation over land and a record decrease in runoff and river discharge into the ocean from October 1991-September 1992. The results suggest that major adverse effects, including drought, could arise from geoengineering solutions.

This study underscores the conclusion of John Holdren, President of the American Association for the Advancement of Science: “The ‘geo-engineering’ approaches considered so far appear to be afflicted with some combination of high costs, low leverage, and a high likelihood of serious side effects.”

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.