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…

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More from @Weather_West

31 Dec 21
Some photos, footage, and commentary from yesterday's devastating #MarshallFire in Boulder County. All photos and videos taken at various points along South Boulder Road (north side of the fire, looking south, on 12/30/21). Winds were gusting around 90mph at the time. #COwx (1/4)
Fire behavior was as you'd expect in grass/brush amid extreme wind & drought conditions: rapid rates of spread, continuous spotting and periodic sheeting fire. Fire jumped 6-lane Hwy 36 like it was nothing, and there was a 2+ mile long active fireline. #MarshallFire #COwx (2/4)
Behavior and dynamics of the fire plume were fascinating...and scary. A nearly horizontal plume, tilted by extreme westerly downslope winds, transitioned into a shallow pyroCu plume at the top of a hydraulic jump within a pronounced mountain wave. #MarshallFire #COwx (3/4)
Read 5 tweets
30 Dec 21
Conditions along South Boulder Road right now. #marshallfire #COwx
Unfortunately can confirm that numerous structures are now burning, many of them homes. This is an extreme/dangerous wildland-urban interface fire. Mainly Superior/Louisville. Gusts in excess of 80mph continue.
Read 4 tweets
30 Dec 21
Serious wind driven brush fire in wildland-urban within/just south of Boulder, CO city limits. Along Marshall road. Estimating downslope wind gusts near 90 mph. #COwx @NWSBoulder @mitchellbyars
Multiple structures burning/extreme rate of spread from my vantage point.
Read 5 tweets
29 Dec 21
As a climate scientist, one aspect of #DontLookUp that resonates strongly is notion that an otherwise solvable planetary crisis will go away if we just ignore it--or that a silver bullet solution will magically present itself. Spoiler alert: it won't. @davidsirota @GhostPanther
Also highly relatable was the impassioned and exasperated rant by @LeoDiCaprio's character. There's a reason why much of the climate science community has responded to this film in a similar way--variations on a theme of "yep, that's all uncomfortably familiar."
It can become exhausting to constantly be the bearer of bad news when many folks simply don't want to hear it. "Why are you always so negative? You always focus on the harm from climate change, not the economic opportunities! Scientists are such pessimists."
Read 5 tweets
17 Nov 21
Being a climate scientist sometimes feels like being an astrophysicist in one of those 90s asteroid impact disaster movies...
except instead of coming to together to save humanity, the people in power shrug & point out how sending rockets might increase inflation. #ClimateChange
I was once, coincidentally, seated on a flight next to a @NASAJPL scientist who described his job as "taming near-Earth asteroids" from a planetary protection perspective. This is a person who would actually be called to the White House in scenarios portrayed in Hollywood films.
The JPL near-Earth object specialist made it clear that he was more concerned about #ClimateChange than an asteroid impact--not because latter wouldn't be devastating, but because the odds were low in our lifetime & "we would actually do something about it, if it ever came."
Read 4 tweets
13 Oct 21
California, on statewide basis, is now experiencing its worst drought in observational record going back to late 1800s--narrowly beating out peak of last drought in 2014-15 (as measured by PDSI, a metric that takes into account both precip & temperature). #CAwx #CAfire #CAwater
There is a clear trend toward increasing aridity in California--and yet little trend in mean precipitation. How can this be? A very strong warming trend due to #ClimateChange means same the amount of water falling from sky just doesn't go as far as it used to. #CAwx #CAwater
We explored this phenomena in research published in 2015 (finding that rising temps are the main factor behind increasing CA drought severity):

and 2018 (increasing "precip whiplash" despite little change in mean):
#CAwater #CAwx
Read 5 tweets

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