Written by Michael Ricciardi
Published on September 27th, 2009

With the news that climate change is occurring at a faster rate than climate models have predicted, geoengineering solutions have been brought to the fore and are being taken more seriously. The main focus of these emergency geoengineering strategies is a reduction in “shortwave” radiation entering the Earth’s atmosphere via the solar wind.
The short-term goal here is an overall reduction in global atmospheric temperatures to slow, or even reverse, warming trends. These solutions include increasing the amount of reflective particles surrounding the Earth by placing reflective particles (“mirrors”) outside the atmosphere. Such a solution may be justified to quickly curtail an emergent crisis–such as the rapid disintegration of the polar icecaps. Another strategy is to blanket the upper atmosphere with sulfur particles to block shortwave energy from reaching the Earth’s surface, thus producing a pronounced cooling effect (of variable duration).
However, in a recently published paper, Climate Engineering Responses to Climate Emergencies by Blackstock et al, this and other controversial strategies are analyzed in terms of feasibility, short-term impact, and also, the potential risks and dangers. The authors are also calling for a study phase. The major criticism in the paper is that current geoengineering strategies focus on a reduction of temperature without due consideration of the impact on precipitation, which also drives climate change. The cooler the surface temperature, in general, the less overall precipitation ( due to the fact that there is less energy for evaporation). Focusing only on temperature reduction, via incoming solar radiation, could backfire, leading to a shift in global hydrology cycles and, possibly, drought. Also, sulfur in the atmosphere combines with water to form sulfuric acid–the primary source of “acid rain”–a problem dramatically reduced since the passage of the Clean Air act.
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