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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In a recent (2008) interview with W. Dean Pesnell of Goddard Space Flight Center, I posed many questions concerning current solar activity as well as some sensationalized, catastrophic news items as of late. The following are my questions and Dr. Pesnell’s responses.

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World-wide distribution of discovered or inferred gas hydrate deposits in sediments, USGS, 1996

Nature is not entirely defenseless against rising greenhouse gas (GHG) emissions. A class of elements called halogens (fluorine, chlorine, bromine, iodine, etc., often occurring in pairs) are emitted into the atmosphere via ocean spray, where they destroy ozone (O3), a significant greenhouse gas and aerosol that promotes warming.

The removal or destruction of certain gases/chemicals in the atmosphere is referred to as “scrubbing”.

Ozone in the outer ionosphere actually protects the planet’s biosphere from harmful solar radiation. But in the troposphere (as tropospheric ozone) it bonds with other particles and acts to trap heat in the atmosphere. At ground level, O3 is a main constituent of smog.

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According to the journal Nature Geosciences, “increasing concentrations of black carbon have substantially contributed to rapid Arctic warming during the past three decades.”

A paper from that journal, “Climate response to regional radiative forcing during the twentieth century,” was authored by climate researchers Drew Shindell, at the NASA Goddard Institute for Space Studies, and Greg Faluvegi of Columbia University. Shindell, Faluvegi, and many other climate scientists believe that limiting black carbon sources may “buy the world some time” in the race to control climate change as richer nations develop their climate change policies and begin taking the slow steps towards overhauling their carbon heavy energy sources.

The researchers assert that aerosols are responsible for “half or more” of Arctic warming. Unexpectedly, their paper’s claims and recommendations sparked a flurry of critical emails, perhaps due to confusion over the atmospheric roles of different aerosols.

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By turning a long line of mirrors, the first solar thermal plant in nearly two decades was launched last week in Bakersfield, California. Unlike solar photovoltaic systems that convert sunlight into electricity, this plant will focus sunlight on tubes that contains water. The light heats the water, creating steam, thus turning turbines.

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