Even without
the complicating effects of aerosols, things aren't that simple on Earth.
Not exact matches
The net
effect of human - generated
aerosols is more
complicated and regionally variable — for example, in contrast to the local warming
effect of the Asian Brown Cloud, global shipping produces large amounts
of cooling reflective sulphate
aerosols: http://www.sciencedaily.com/releases/1999/08/990820022710.htm
The picture is
complicated because different kinds
of aerosols can have different
effects: black carbon or soot has warming rather than a cooling
effect, for instance.
@FerdiEgb — the
effect of aerosols is thought to be more
complicated than you imply.
However — a group
of scientists
of the US Department
of Energy Pacific Northwest National Laboratory, the University
of Maryland and the Hebrew University
of Jerusalem now say that
aerosol pollution does not necessarily lead to (low - lying) stratus clouds one would appreciate for climatic cooling, but that it can also be a factor in the creation
of thunderstorm clouds, clouds that have a
complicated climate
effect, but that are suspected
of being net warmers.
Karsten: So the take - home message would then be that 1) In the mid-century the NH cooled because
of anthropogenic
aerosols (especially the most polluted areas) 2) Now anthropogenic
aerosols have a larger content
of absorptive elements so directly observing this cooling in the most polluted areas is very
complicated but we can nevertheless be sure that the global
effect of these
aerosols is markedly negative.
I know that
aerosols are a
complicated issue but frankly speaking, I think that the IPCC estimate for the direct
effect of aerosols (+0.5 Wm2) is also too high.
Having said that, modelling aviation
effects is
complicated — involving ozone chemistry, strat / trop exchange,
aerosols, CO2, contrails, water vapour etc. — all
of which interact to some degree, and which have very different timescales.