Not only fighting air pollution differs from fighting climate change
(see previous post November 21st, 2014), it could imply the reverse! China
has never been so concerned with air pollution (Hong Kong starts being upset as
well, see SCMP January 25th 2015)[1]
and calls for actions have become even stronger since the “Apec blue”. General
opinion seems to view this concern as being rather consistent with the fight
against climate change and this is also what is suggested by the recent
US-China climate agreement (November 12th, 2015). As we mentioned in
our previous post, it is not that straightforward. In fact it may prove even
worse than we thought!
There is now a growing literature
on the “dimming” effect that had been observed in the period 1950s–80s: the decline in surface solar radiation due to
aerosol and particles pollution may have outweighed increasing atmospheric downwelling
thermal radiation from enhanced greenhouse gases and effectively counteracted
global warming (see Wild, 2012).[2] Notably, such an effect was already reported
in 2005 by European scientists in Nature[3] and is particularly
well-known for particles emitted through volcanic eruptions (see the figure
below[4]).
A corollary is that too much
aerosol removal generates a “brightening effect” that enhances climate change.
Such an effect has been recently documented by O’Dowd et alii., 2013 that argue (they demonstrate the direct link between
aerosol emissions, concentrations, and surface radiation) that the clean
air policies might have resulted in higher temperatures.[5]
Does this mean that we should
not worry about pollution generated by fossil fuel since it generates both GHG
and particles? It rather calls for more effort to fight climate change because IPPC predictions that do not account
for the brightening effect underestimate future climate change. And it will be
become worse. Consistent with the intuition,
there has been a renewed dimming in China after a phase of stabilization
during the 1990s (Wild, 2012). When looking at the air pollution, we can expect
-and hope- that China now reduces efficiently air pollution, that will generate
a significant brightening effect (note that this provides a fresh perspective
on US-China agreements…) which enhances the need for GHG reduction.
In the meantime, the dimming effect is clearly ignored by economists.
First, to my knowledge, they have never taken it into account explicitly.
Second, they often consider that fossil
fuel use directly generates climate change (see van der Ploeg et alii., 2012 for instance,[6]
or my work[7]). It might in fact be crucial to distinguish
between GHG and particles that both need to be reduced but affect climate
change in opposite ways.
[1] South
China Morning Post, “Every breath you take” January 25th 2015, Post
Magazine. http://www.scmp.com/magazines/post-magazine/article/1689002/air-pollution-practical-tips-how-cope-it
[2]
Wild, M. 2012: Enlightening Global Dimming and
Brightening. Bull. Amer. Meteor. Soc., 93, 27–37
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-11-00074.1
[3]Meinrat O. Andreae1, Chris D. Jones & Peter M. Cox, Strong present-day aerosol cooling implies a hot
future Nature 435,
1187-1190 (30 June 2005) | doi:10.1038/nature03671
[4]
Seminar by Prof. Johnny Chan at City University of Hong Kong, January 9th, 2015, http://www.cb.cityu.edu.hk/cityseminar/past/20150109.html
[5] Colin
O'Dowd, Darius
Ceburnis, Aditya
Vaishya, S.
Gerard Jennings and Eoin
Moran “Cleaner air:
Brightening the pollution perspective?” AIP Conf. Proc. 1527, 579 (2013); http://dx.doi.org/10.1063/1.4803337
[6]
Van der Ploeg R. and Withagen C. Is there really a green paradox? Journal of Environmental Economics and Management, Volume 64, Issue
3, November 2012, Pages 342–363
[7] Ayong
le Kama A. and Pommeret A., 2015 « Adaptation and
mitigation are not enough : turning to mitigation abroad “https://drive.google.com/file/d/0B563l-M03kqnTU9pdlI1R2dQWmc/view?usp=sharing
