Aerosols: Connection between regional climate change and air quality
(IUPAC Technical Report)
and Y. Zhang
Abstract: Aerosols play an important role in all problems connected
with air pollution, ranging from very local effects and human health
problems to regional problems such as acid deposition and eutrophication
up to continental and global questions such as stratospheric ozone loss
and climatic change. In this report, an explanation of these effects
is given and an assessment is made for parts of China, based on the
aerosol data given by Zhang et al. elsewhere in this volume.
(Pure Appl. Chem.
76(6), 1227-1239, 2004)
Epidemiological research has made clear that aerosols are a cause of
enhanced mortality due to cardiopulmonary diseases (heart and lung diseases).
Based on the same mortality as found in Europe and on linear extrapolation
(with large uncertainties; no sufficient data are available to make
better estimates), an excess mortality of 5000 to 10 000 due to acute
effects and 20 000 to 50 000 due to chronic effects per year could be
expected for a city like Beijing with a population of 14.5 million.
A major cause of these uncertainties is problems in the determination
of semivolatile compounds and elemental or black carbon in aerosols.
Aerosols have a strong impact on the radiative balance of the earth,
in a direct way by reflecting solar light as well as in an indirect
way by cloud formation leading to clouds with higher albedo, which reflect
sunlight better. The total direct effect, backscatter of sunlight, including
backscatter from nitrates and organic compounds, is estimated to be
approximately 2 to 3 W m2 for Western Europe, while
the indirect effect is approximately 0 to 6 W m2.
Soot absorbs incoming solar radiation and heats the atmosphere. This
process contributes 0.1 to 0.2 W m2 on a global scale.
If PM-2.5 levels are compared with Europe, a direct effect of approximately
4 to 10 W m2 would be plausible for China,
black carbon could contribute probably about 0.5 to 2 W m2,
and the indirect effect could be about 0 to 6 W m2.
These effects could cause a net cooling over China (and over many developing
countries in the same position) of about 4 to 15 W m2.
This estimate is obviously based on many assumptions and hence is quite
One must be aware that measures reducing local aerosol concentrations
will have a large impact on the radiative balance and could, over a
few decades, have potentially at least the same impact as the build-up
of greenhouse gases since the beginning of the Industrial Revolution.
* Corresponding author.
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