Our new study on co-occurring air pollution extremes (ozone & PM2.5), led by @wx_statman & w/co-authors including @ClimateChirper, @climate_guy, & @Weather_West, is out today in @ScienceAdvances. We find large increases in co-occurrences in U.S. West.(1/n) science.org/doi/full/10.11…
Increasing air pollution co-occurrence trends are widespread across the U.S. West over the last ~20 years, and encompass almost all of the West's major population centers from the Rocky Mountain Front Range to the Pacific Coast. (2/n) science.org/doi/full/10.11… 
This increasing trend in co-occurring high levels of two key classes of air pollutants, ozone (photochemical pollution; think smog) & PM2.5 (fine particulate matter; think smoke) is almost entirely due to increasing frequency of extreme PM2.5 events. science.org/doi/full/10.11… (3/n)
"Stagnant" summertime weather patterns--those characterized by high temperatures, relatively low winds, and low precipitation--favor the development and persistence of extreme air pollution episodes. (4/n) science.org/doi/full/10.11…
We find that summertime high pressure patterns conducive to widespread extreme air pollution co-occurrence events have increased substantially in the past 20 years (at expense of summertime low pressure patterns that tend to disperse pollution). (5/n) science.org/doi/full/10.11…
We further report that the spatial extent of such extreme ozone & PM2.5 co-occurrences are strongly associated with both a) the West-wide area burned by wildfire in the preceding week, and b) the West-wide extent of unusually hot temperatures. (6/n) science.org/doi/full/10.11…
From an extensive body of existing research, we already know that both wildfire area burned as well as the extent and magnitude of summertime heat is increasing due to human-caused #ClimateChange. (7/n) science.org/doi/full/10.11…
Also, from past work, it's clear that widespread increase in PM2.5 events in U.S. West is due to increasing extent & combustion intensity of wildfires. Hence, there is a plausible link between increasing co-occurrence events & #ClimateChange. (8/n) science.org/doi/full/10.11…
We find an increase of 25 million person-days/year of exposure in just 20 years. There has been much work on human physiological effects of air pollution--& negative impacts extend well beyond lungs to broader cardiovascular system & immune system. (9/n) science.org/doi/full/10.11…
These findings have potentially major public health implications--especially since these trends are likely to continue to escalate in a warming climate with increasingly widespread/intense wildfires in the American West. (10/n) science.org/doi/full/10.11…
It's important to note, though, that this trend is not inevitable! Ozone pollution is often local or regional in nature--& even city-scale emissions reductions in pre-cursor compounds can greatly reduce photochemical side of the co-occurrence coin. (11/n) science.org/doi/full/10.11…
Wildfire smoke emissions (which causes PM2.5 pollution) is arguably a tougher problem, due prevalence of long-range smoke transport and broader challenges surrounding escalating wildfire crisis. (12/n) science.org/doi/full/10.11…
But even here, partial solutions are possible. Prescribed fire--a management strategy increasingly touted as a necessary tool in reducing risk of catastrophic fires & restoring ecosystem health--can actually reduce wildfire emissions in long run. (13/n) science.org/doi/full/10.11…
• • •
Missing some Tweet in this thread? You can try to
force a refresh
