by Erica Rex

Despite its great potential for remedying the climate crisis, once put into practice, geoengineering may turn out the way of many panaceas. A great idea in theory, and an expensive disaster in practice.

In the 21 August 2009 issue of the journal Science, scientists Gabriele C. Hegerl of the Grant Institute in Edinburgh, Scotland, and Susan Solomon of the National Oceanographic and Atmospheric Administration in Boulder, Colorado, point out some of the downsides.

They write:

“ [By] focusing on limiting warming, the debate creates a false sense of certainty and downplays the impacts of geoengineering solutions.

Discussions of “dangerous” levels of interference with the climate system often use warming as a proxy for the seriousness of greenhouse gas–induced climate change. However, climate change impacts are driven not only by temperature changes, but also by change in other aspects of the climate system, such as precipitation and climate extremes.”

Limiting the definition of climate change to “warming,” they say, overlooks two-thirds of the problem.

While geoengineering has the benefit of allowing us to take immediate radical planet cooling action in the event of catastrophic change – such as rapidly disintegrating ice sheets, or warming that is more severe than expected – it brings with it considerable risks: among other things, a decrease in precipitation.

“Strong volcanic eruptions have in the past led to anomalously cold conditions: The year without a summer (1816) noted in North America and Europe followed the eruption of Tambora in Indonesia the year before, which was the largest volcanic event observed in recent centuries. However, volcanic eruptions also affect precipitation. The 1991 eruption of Mount Pinatubo led to substantial decreases in global stream flow and to increases in the incidence of drought. An analysis of 20th-century observations indicates that volcanic eruptions caused detectable decreases in global land precipitation.”

Reducing precipitation in already dry regions of the world, such as sub-Saharan Africa, and parts of Asia, would affect the supply of fresh water.

“[The] combination of a strong greenhouse effect [carbon dioxide and other greenhouse gases] with a reduction of incoming radiation could have substantial effects on regional precipitation, including reductions that would rival those of past major droughts. Geoengineered changes in the environment could thus lead not only to “winners and losers” but even to conflicts over water resources and the potential for migration and instability, making shortwave climate engineering internationally very controversial.”

Cooling the Earth through use of aerosols could lead to changes in water supply. What might happen in a world where people are forced to leave their homes in search of potable water?