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Complexity Digest 2000.36 - 02
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04-Sep-2000

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What Factors Drive Climate	 Change?, PNAS/Nature/Science
 









The complexity of the terrestrial climate system is far
from being completely understood by today's science. Just as the
role of carbon dioxide (CO2) as green house gas (GHG)
finds global acceptance new scientific results demonstrate how
much more complex the whole story is. Hansen
et al. state: "(…) we argue that rapid warming in
recent decades has been driven mainly by non-CO2 greenhouse gases
(GHGs), such as chlorofluorocarbons, CH4, and
N2O, not by the products of fossil fuel burning,
CO2 and aerosols, the positive and negative climate
forcings of which are partially offsetting. (…)We argue that
black carbon aerosols, by means of several effects, contribute
significantly to global warming."

Especially the role of aerosols seems to be of critical
importance because of their role in cloud formation. Schrope
observes: "Tiny airborne particles affect the Earth's climate,
in part by influencing the formation of clouds. But modeling the
effects of these aerosols is proving to be one of the thorniest
problems in climatology (…). One of the main complicating
factors in modeling the effect of aerosols is their short
residence times in the atmosphere. Typically, particles remain
aloft for a week or less(…). In contrast, molecules of carbon
dioxide persist for about a century, and other greenhouse gases
also have long residence times."

Hansen
et al also mention the possibility of stripping black carbon
emissions at fossil fuel power plants.which could have a big
impact since electricity plays an increasing role in future energy
systems. They also mention that "Stripping and disposal of
CO2, although more challenging, provide an effective
backup strategy." Related to this point is an article by
Abelson
who writes: "Worldwide emissions of CO2 continue to
increase, and prudence dictates that technologies be developed to
help limit this trend. One of several ways to attenuate the
increase of CO2 in the atmosphere is to sequester it.
The technology for doing so exists. The injection of
CO2 into oil fields is having economically beneficial
effects while at the same time sequestering
CO2."



Global
Warming In The Twenty-First Century: An Alternative
Scenario, James Hansen,
Makiko Sato, Reto Ruedy, Andrew Lacis, And Valdar
Oinas, Proc. Natl. Acad. Sci. USA, Vol. 97, Issue 18,
9875-9880, August 29,2000


Trouble
In The Greenhouse, Mark
Schrope, Nature 407, 10 - 12 (2000)


 Limiting
Atmospheric
CO2, Philip
H. Abelson, Science, Volume 289, Issue 5483, p.
1293



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