Do
all the all anthropogenic/natural emissions cause global warming? This question
kept coming to me after I read about the effects of a few aerosols, especially
sulphur dioxide (sources are: fossil fuels burning, metal smeltering, volcanic
eruptions) and carbon rich aerosols (brown clouds), on solar insolations. The
focus is on SO2 in this blog.
As per an editorial essay by P.J Crutzen some atmospheric
particles (SO2 and organic carbon) act as reflectors and scatter solar
radiations and prevent it from reaching the earth’s surface. In some cases these
particles act as a nuclei for cloud droplets (forming brown clouds), where the
water droplets coalesce around the pollutants, these then affect “the micro
physical and optical properties of clouds, affecting precipitation and cloud
albedo” (e.g. Rosenfeld, 2000; Ramanathan et al., 2001; Ramaswamy et al., 2001).
These cool the earth's surface by reducing the incoming sunlight. This has been observed in volcanic eruptions e.g.,
during the volcanic eruption in June 1991,Mount Pinatubo injected some 10 Tg S,
initially as SO2, into the tropical stratosphere (Wilson et al., 1993; Bluth et
al., 1992). In this case the particles cooled the earth’s surface on average by
0.5 ◦ C in the year following the eruption (Lacis and Mishchenko, 1995). Effects
of these clouds have been found to extend thousands of kilometers from the
source. Studies reveal that reflective particles are found in the Troposphere
and the Stratosphere, and these have a residence time of a week and one to two
years respectively.
But
on the other hand these aerosols cause acid rain (SO2) and may affect the hydrological
cycle which affects agriculture (brown cloud), and also causes ecological
damage (eg yellowing of the Taj Mahal). The pollution particles also cause more
than 500,000 global premature deaths per year (as per the World Health
Organization, Nel 2005). Although there is a lot of research required in this
field, some believe that the increase in concentrations of these aerosols will
be a solution to curb global warming. But this leads to a catch 22 situation. What
is your opinion on this?
Indeed a catch 22 situation !!I guess the lesser of the two evils would make a workable solution , at least for some time.
ReplyDeleteI think SO2 may be temporarily able to reduce the rise of the temperature, but in the long run it will causes more negative effects, perturbation on other cycles (hydrology, biology, ecology, etc.).
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