• General Interest
  • Highlighted
Nature · 2010

Research on global sun block needed now

David W. Keith, Edward Parson, and M. Granger Morgan

The idea of deliberately manipulating Earth’s energy balance to offset human driven climate change strikes many as dangerous hubris. Solar-radiation management (SRM), a proposed form of geoengineering, aims to reduce Earth’s absorption of solar energy by, for example, adding light-scattering aerosols to the upper atmosphere or increasing the lifetime and reflectivity of low-altitude clouds. Many scientists have argued against research on SRM, saying that developing the capability to perform such tasks will reduce the political will to lower greenhouse-gas emissions. We think that the risks of not doing research outweigh the risks of doing it. SRM may be the only human response that can fend off rapid and high-consequence climate impacts. Furthermore, the potential of unilateral deployment of SRM poses environmental and geopolitical risks that can be managed best by developing widely shared knowledge, risk assessment and norms of governance. SRM has three essential characteristics: it is cheap, fast and imperfect. Long-established estimates show that SRM could offset this century’s global average temperature rise at least 100 times more cheaply than emissions cuts. A few grams of sulphate particles in the stratosphere could offset the radiative forcing of a tonne of atmospheric carbon dioxide. At about US$1,000 a tonne for aerosol delivery, that adds up to just billions of dollars per year. This low price tag is attractive, but it raises the risks of single groups acting alone, and of facile cheerleading that could promote exclusive reliance on SRM.

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