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Strong present-day aerosol cooling implies a hot future


Atmospheric aerosols counteract the warming effects of anthropogenic greenhouse gases by an uncertain, but potentially large, amount. This in turn leads to large uncertainties in the sensitivity of climate to human perturbations, and therefore also in carbon cycle feedbacks and projections of climate change. In the future, aerosol cooling is expected to decline relative to greenhouse gas forcing, because of the aerosols' much shorter lifetime and the pursuit of a cleaner atmosphere. Strong aerosol cooling in the past and present would then imply that future global warming may proceed at or even above the upper extreme of the range projected by the Intergovernmental Panel on Climate Change.

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Figure 1: Climate sensitivity required to explain the observed 1940–2000 warming as a function of the strength of aerosol radiative cooling.
Figure 2: Temperature change simulated by the simple model for the period 1850 to 2100.
Figure 3: Modelled temperature change and CO 2 increase by 2100 under different development scenarios.
Figure 4: Strength of climate-carbon cycle feedback as a function of climate sensitivity.

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C.D.J. was supported by the UK DEFRA Climate Prediction Program.

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Correspondence to Meinrat O. Andreae.

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Andreae, M., Jones, C. & Cox, P. Strong present-day aerosol cooling implies a hot future. Nature 435, 1187–1190 (2005).

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