Emergency Climate Control: Geoengineering Risks

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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. Our planet’s climate is a complex system. Many factors interact–in both “linear” and “non-linear” ways–to alter, augment, and/or reduce other climate processes. There is, for example, also longwave radiation which refers to the radiating of latent heat (such as that from condensation) from the Earth’s surface back into the upper atmosphere. A build up of greenhouse gases (GHGs) traps heat, and interferes with this natural process, which can also result in a reduction of precipitation. The action and impact of these two forms of radiation are referred to as forcing (in general, radiative forcing). However, the Earth’s precipitation cycles tend to respond greater to alterations in shortwave radiation, as opposed to “out-going”, longwave radiation forcing via GHGs. Reducing incoming, shortwave radiation changes the “energy budget” of our planet. A corresponding change in global surface temperature from any change in this budget is fairly predictable. But due to differential heating and cooling of the Earth’s surface, variations in surface water, and ice albedo (currently in decline in the Arctic), amongst other factors, accurately calculating precipitation changes is difficult. Out current computer climate models are fairly accurate in predicting temperature impacts from greenhouse gas warming (and they do reveal precipitation pattern changes over land to be correlated with human industrial growth), but they underestimate the magnitude of precipitation changes (and precipitation extremes) in response to a combination of shortwave and longwave forcing. Recent satellite data also appears to confirm these discrepancies. Such variations between observation and modeling are problematic for geoengineering schemes which, at present, cannot reliably target both precipitation and warming at the same time. This unknown adds to the overall risks.

Natural volcanic activity that blocks some incoming solar radiation (albedo) can in theory be duplicated through artificial means.

Another impacting factor contributing to climate forcing is the presence of aerosols. Aerosols are varied size particles–like dust or soot–that help form clouds, but which can also reflect sunlight or trap heat, depending on their composition/structure. Currently, much urgent study is being given to the effects of various natural and man-made aerosol accumulations on global warming and climate change (including a recently discovered contribution from plants called isoprenes, which are five-carbon, diene molecules, and, as carbon contributors, second in abundance to methane). Geoengineering with sulfur “dust” is an attempt to mimic the well-studied, atmospheric cooling effect of volcanic ash (both being types of aerosols). However, this same research also shows a decrease in global precipitation and stream flow following major eruptions. The climate impact of this approach may not be immediate, but would be far-reaching (and presumably transient). For example, the eruption of Mt. Tambora in Indonesia in 1815, it is believed, led to the “year without a summer” for North American and Europe in 1816. The effectiveness of other, less “drastic” forms of geo-engineering–like carbon sequestration, CO2 capture, and iron seeding of the oceans (to increase CO2 absorbing plankton)–have only partial, small-scale experimental confirmation. Further, their immediate impact is believed to be considerably less as the processes involved are more cumulative in nature. Environmental organizations are reluctant to condone geoengineering on a global scale as they feel that it undermines their cause, and will be seen as a “quick fix” remedy, as well as a viable alternative to cutting our carbon usage (“decarbonizing” the economy) and GHG emissions. The appeal of shortwave, geoengineering rests in its purportedly rapid, remediation impact (although no global experiments have been conducted yet). However, the combined climate impact of GHG increases with a geoengineered reduction in shortwave radiation is not known, and, it is feared, could result in environmental “winners” and “losers”–meaning some regions of the planet could experience severe drought, and even increased conflict over water resources. In such a win/lose scenario, wealthier nations–even those impacted negatively–will most likely fair better than poorer ones, as these have the  money and resources to compensate for severe agricultural losses. Emergency, geoengineering solutions for climate control will most likely make the emerging issue of “climate fairness” and “climate debt” more pressing (see my previous blog post Climate Fairness/Climate Debt – Eco Justice for Poorer Nations. For more information on Geo-Engineering, visit: Geoengineer.org Additional reference material for this article: Risks of Climate Engineering, Gabriele C. Hegerl, Susan Solomon, Science Magazine, Aug. 21, 2009 photo credits: Public domain (NASA / USGS)