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AEROSOL; cycle and influence on the radiation balance ; MEMORA: MEasurement and MOdeling of the reduction of Radiation by Aerosol : cluster project in the National Research Programme on Global Air Pollution and Climate Change nr. 951205: report on Phase 1: 1996-1997
Gepubliceerd door: Publicatie datum:
ECN 1-8-1998
ECN publicatienummer: Publicatie type:
ECN-R--98-015 Overig
Aantal pagina's: Volledige tekst:
48  Niet beschikbaar.

Anthropogenic aerosols reflect solar radiation and therefore act as acooling agent. The perturbation ('forcing') of the radiation balance is so large that, according to estimates by IPCC, it could off-set the longwave radiative forcing by the manmade greenhouse gases in areas like Europe. IPCC reports that the uncertainty in the globally averaged aerosol forcing is of the order of 3 W m"-2. This uncertainty exceeds the magnitude of the longwave forcing by the manmade greenhouse gases. Of national interest is the fact that the aerosol forcing is a local/regional phenomenon because of the limited residence time of aerosols in the atmosphere. The claim by IPCC that sulfate is the only relevant manmade aerosol component is highly questionable for Europe. Whereas the value of the aerosol effect is so uncertain, predictions of the coming trend are even more problematic. This is due to the fact that the most important anthropogenic ingredients of the aerosol are not directly emitted, but made in the atmosphere. A one to one relation between emission of the precursors and resulting aerosol seems rather unlikely given a non-linear historical trend. Therefore only a combined approach in which aerosol fields are modeled and modeled fields together with the calculated reduction in solar flux should be tested against measurements. This approach should provide the tools to perform, with sufficient confidence, scenario calculation for the aerosol effect. Improvement of the current large uncertainty in the forcing of the radiation balance by anthropogenic aerosol (in Europe) by a combined experimental modeling program. This is achieved by assessment of the major aerosol components involved and their sources, using detailed measurements in The Netherlands as a reference for model input and output. 36 refs.

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