(P. Kenzelmann, St. Füglistaler, E. Rozanov, B.P. Luo, T. Peter)
Recent international efforts to improve air quality have led to a reduction in anthropogenic aerosols, which is expected to result in a positive development in the public health sector. However, this fortunate development also leads to an increase of incoming sunlight to earth surface and hence will accelerate global warming. Crutzen (2006) noted that attempts in reducing anthropogenic greenhouse gas emissions have been grossly unsuccessful and therefore suggested exploring and debating again cooling climate by adding sunlight reflecting aerosol in the stratosphere. He argued that in this way, an extension of the grace period for the implementation of the necessary political measures might be obtained. The scenario he suggested to consider is by emitting aerosol precursors (S2 or H2S) on purpose into the lower stratosphere where the lifetime of the resulting aerosol particles and hence their cooling potential, is high, but side effects are presumably low – as past volcanic eruptions showed (e.g. Robock, 2000).
The geo-engineering manipulation of emulating a volcanic eruption may have various effects:
(1) The intended global cooling in the lower troposphere.
(2) Acidification of the oceans due to CO2 not addressed.
(3) Reduced precipitation and resulting danger of droughts.
(4) Enhanced cirrus cloudiness.
(5) High latitude winter warming.
(6) Reduction of the stratospheric ozone layer.
(7) Presently unforeseen side effects.
Time slice runs with varying stratospheric sulfur injections help to research the consequences of such a geo-engineering project.
Figure: Change in total ozone column in % for a perpetual Mt. Pinatubo eruption (for today’s atmospheric conditions). Global annual mean change in total ozone up to 7% can be expected.
Crutzen, P. J. (2006), Albedo enhancement by stratospheric sulfur injections: A contribution to resolve a policy dilemma?, Climatic Change, 77 (3-4), 211–219.
Robock, A. (2000): Volcanic eruptions and climate, Rev. Geophys. 38, 191–219.
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