Anthropogenic increases in aerosol concentrations are believed to
significantly affect climate, notably by exerting a negative radiative
forcing which counteracts, to some extent, the positive radiative
forcing of greenhouse gases (GHGs). The potential effects of aerosols
and their short atmospheric lifetimes raise issues which are critical
to climate policy This paper isolates the implications of aerosols by
treating aerosol emissions as a policy variable separate from GHG
emissions, but Linked through energy policy, Using a simple climate
model, results show that with no GHG abatement, changes in aerosol
emissions can significantly affect net radiative forcing, but that the
positive forcing of GHGs continues to dominate, Aerosols are also shown
to reduce the difference in net radiative forcing between abatement and
`business-as-usual' policies, while the ability to reduce this effect
through aerosol emissions from energy policy is limited, However, the
conclusion that aerosols are beneficial to climate because they
counteract greenhouse warming is then questioned; scenarios with high
aerosol and GHG emissions are expected to yield both greater
uncertainty in mean temperature and a greater likelihood of changes in
other climate parameters. (C) 1997 Published by Elsevier Science Ltd.
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