Environmental Engineering Reference
In-Depth Information
Priorities for future work.
To build confidence in our understanding as represented
in chemistry-climate models, observational constraints are crucial, not only for O
3
and temperature, but also for the processes driving their strong correlation. Critical
to this effort is the availability of long-term, high quality measurements of relevant
species. Complementing routine measurements of O
3
, PM, and weather variables
with species such as formaldehyde (a proxy for isoprene), NO
x
, and PAN could
help to determine the relative importance of the various climate-driven impacts on
air quality. In particular, large uncertainties exist in our understanding of isoprene
oxidation chemistry, especially in low-NO
x
regions (e.g., Horowitz et al., 2007).
Additional work is needed to place climate-driven changes in the context of
potentially larger changes to air quality induced through trends in land use and
anthropogenic emissions, both locally and globally (e.g., Avise et al., 2009; Chen
et al., 2009). While global increases in humidity in a warmer world will likely
decrease background O
3
in surface air (e.g., Murazaki and Hess, 2006), future
increases in global anthropogenic emissions may extend the O
3
season (e.g., Fiore
et al., 2002). A lengthening of the pollution season may also occur in a warmer
climate independently of global emission changes (e.g., Racherla and Adams,
2006).
Acknowledgments
We thank S. Howard and J. Swall (EPA) for providing daily MDA8 O
3
and
temperature from the CASTNet sites, and M. Evans (U Leeds), A. Steiner (U Michigan), and
C. Wiedinmyer (NCAR) for insightful conversations.
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