Dan Westervelt
@dwesty.bsky.social
Associate professor in climate change, atmospheric chemistry, and air pollution at Columbia-Lamont @lamont.columbia.edu
There’s more to wildfire smoke than meets the eye, and what you can’t see can hurt you. Climate scientist @dwesty.bsky.social of @lamont.columbia.edu explains. Via @cnn.com. https://www.cnn.com/2026/07/17/weather/air-quality-wildfire-smoke-chemistry-brown-carbon
Why air quality can still be bad even if the sky doesn’t look smoky | CNN
The orange haze hanging over your house is, indeed, bad. But the chemistry of wildfire smoke doesn’t have to be visible to be threatening.
cnn.com
AQI in the "Good" range finally, for the first time in many days. Just in time for the biggest sporting even in the world. Got pretty lucky on this!
After work to clean up other sources of pollution in US, “big challenge” is wildfire smoke, says @dwesty.bsky.social of @lamont.columbia.edu, as exposure to high levels of air pollution over long period of time is demonstrated to lead to premature mortality. Via @wired.com. https://bit.ly/4vxTIti
How to Protect Your Health as Skies Fill With Smoke From Canada’s Wildfires
Roughly 100 fires are raging out of control in Ontario, sending smoke streaming 1,000 miles to the south and east.
wired.com
NYC in the thick of it right now, corroborated by our observation site data and a photo from the UES/Yorkville. Supertall Park Ave apartments barely visible.
Canadian wildfire smoke triggered an air quality alert in NYC ahead of the World Cup final, but climate scientist @dwesty.bsky.social of @lamont.columbia.edu says rain should clear conditions, with no major disruptions expected to the weekend's events. Via @reuters.com. https://bit.ly/4vvM2Yn
NYC air quality set to clear for World Cup final
YouTube video by Reuters
youtube.com
Columbia Climate School@climate.columbia.edu · 3w agoAir pollution expert @dwesty.bsky.social of @lamont.columbia.edu discusses this summer’s wildfires and resulting air quality in New York City and beyond. Via State of the Planet: https://news.climate.columbia.edu/2026/07/16/wildfire-smoke-returns-what-to-know-about-this-weeks-air-quality/
Some thoughts from me on this year's edition of the extreme wildfire smoke: www.wired.com/story/northe...
Smoke From Canada's Wildfires Turns Skies Sickly Orange Across the Eastern US
Roughly 100 fires are raging out of control in Ontario, sending smoke streaming 1,000 miles to the south and east.
wired.com
The latest data from my lab observation site at @lamont.columbia.edu . Seems like we're heading towards a big event. Visibility is currently very poor as can be seen from the photo of the monitoring site.
HRRR-smoke near surface smoke forecast for 5pm EDT this afternoon. Things could get pretty gross!
A wave of dense wildfire smoke has pushed from Michigan's Upper Peninsula to the Lower Peninsula this morning, bringing an AQI in the Purple range (Very Unhealthy) to Sault Ste. Marie. Visibility on the Mackinac Bridge is very poor, as seen in these comparison photos. Smoke coming to Detroit ~4 pm.
Some initial reporting below from AP including a quote from me: apnews.com/article/wild...
Wildfires expose millions in the Midwest and Northeast US to dangerous smoke
Heavy smoke from several large wildfires blazing in Canada and Minnesota is expected to engulf large swaths of the Midwest and Northeast U.S. this week, exposing millions of people to dangerous air po...
apnews.com
NOAA's AQI model for 8 am Thu shows Brown ("Hazardous") AQI from smoke in the NYC, Detroit, Milwaukee, and Cleveland metro areas. These conditions (if they verify, remember forecasting smoke is HARD!) will likely last only for a few hours, but you don't want to be outside without an N95 mask! (7/8)
Time for the regularly scheduled eastern US smoke event. See thread below and check out the latest here: www.airnow.gov/wildfires/
Wildfires Landing Page | AirNow.gov
Wildfire smoke is a mixture of air pollutants of which particulate matter is the principal public health threat. Although a large population can be exposed to smoke during a wildfire event, most healt...
airnow.gov
Dan Westervelt@dwesty.bsky.social · last yr.Wildfire smoke is back across most of the eastern half of the US! It was this month 2 years ago that an exceptional smoke event blanketed NYC and much of the east coast, vaulting the story into national news. Here's a spotlight I did back then which is still relevant: www.curbed.com/2023/06/nyc-...
So thrilled to see this out! 🤩 The Chemistry of Aerosol Interfaces (CHAI) model was created by the brilliant @sandhyasethuraman.bsky.social while she was an undergraduate researcher with us @mcneill-lab.org. CHAI models size-dependent kinetics in small droplets (1/4) pubs.acs.org/doi/10.1021/...
Modeling and Parametrization of Size-Dependent Processes in Multiphase Aerosol Chemistry
Many atmospherically relevant multiphase reactive systems exhibit size-dependent kinetics in laboratory studies, with apparent reaction rates increasing with decreasing droplet size, suggesting an important role for interfacial processes. Here, we present CHAI (CHemistry of Aerosol Interfaces), a physicochemical modeling framework that describes these reactive systems using an additive resistance approach, considering the various mass transfer and reaction processes taking place simultaneously in the gas phase, droplet bulk, and at the droplet surface, and their relative time scales. We demonstrate its applicability to modeling and developing parametrizations for several inorganic and organic oxidation processes in microdroplets and aerosols, including S(IV) to S(VI) conversion, through simulation of experimental data. CHAI is also used to reconcile single-droplet observations with chamber and flow tube experiments and is extended to parametrization of these processes for representation in large-scale atmospheric models. Our results show that neglecting the size dependence of aerosol reaction processes can lead to inaccuracies in atmospheric chemistry modeling, motivating the CHAI approach for modeling these multiphase reactive systems and further experimental studies.
pubs.acs.org
📣 Call for abstracts closes on May 29, 2026! ASIC LATAM convenes researchers, policymakers, industry leaders, & community stakeholders from across Latin America and around the world to advance #AirQuality science & action. event.fourwaves.com/asiclatam
The article misses a key point which is that, now that the identity of these designer particles is public, it's clear they don't make much sense as an SAI material.
James Temple@jtemple.bsky.social · 3mo agoStardust has finally revealed its proprietary geoengineering particles are made from amorphous silica. Pre-prints here: stardustsrt.com/science It's also filed for a patent, the application for which should pop up in public records in coming days, I'm told. NYT got the scoop:
New paper by Dr. Sathish Swaminathan @aqtoolbox.org @mcneill-lab.org. Sathish used agent-based modeling to gain insights from mobile air pollution measurements in Chennai, India. #openaccess 🌇🚗🧑💻💡 rdcu.be/fiewz
Agent-based framework for modeling hyperlocal urban air quality
npj Clean Air - Agent-based framework for modeling hyperlocal urban air quality
rdcu.be
Now that NYC's congestion pricing program has been in place for over a year, our experts weigh in on its success: LDEO's @dwesty.bsky.social on air quality, Columbia SPS' Steven Cohen on public policy, @sabincenter.bsky.social's @michaelgerrard.bsky.social on legal challenges. https://bit.ly/4vJe6Jj
👏 Meet our inaugural Dean's Graduate Scholars, 8 MS in Climate (https://bit.ly/4u9S5Tf) students with diverse backgrounds, from engineering & policy to data science & environmental justice, who are united by a shared commitment to advancing climate solutions around the world: https://bit.ly/3OS0xWV
This week's air quality dip in NYC is connected to temperature fluctuation, says LDEO expert @dwesty.bsky.social. Recent cold/snow created a "temperature inversion" where temps near ground became cooler than those above, causing pollutants to build up. Via @nytimes.com. https://nyti.ms/3OADZty
What’s Up With New York’s Bad Air Quality This Week?
nytimes.com
New wheels! Our first EV, the Kia EV6. Plugged in at the @lamont.columbia.edu charging point conveniently located right outside of my office!
Textbook winter temperature inversion across the mid-Atlantic today impairing air quality (yellow = moderate AQI). A 20+ ºF swing in warmer temperatures today versus the last few days means warmer air aloft than at the surface (air has a lower heat capacity).
The Trump Administration's plan to dismantle the @ncar-ucar.bsky.social is senseless & dangerous. It would weaken weather forecasting, climate research, & the science that keeps people safe. We urge that this plan be abandoned. Call Congress to #SaveNCAR today. buff.ly/7ka1BQA
Save NCAR from being dismantled today!
The Trump Administration has vowed to dissolve the center that provides critical extreme weather and climate data for our nation.
buff.ly
There has been a decent amount written thus far on the air pollution response to New York City's congestion pricing policy, most of which has been overwhelmingly positive. While PM2.5 concentrations are indeed down at most locations in NYC, (1/4)
Our new article out today takes a hard look at some practical limitations on stratospheric aerosol injection and what they means for the riskiness of this approach. @mcneill-lab.org w/ @gwagner.com & @steingart.bsky.social @climate.columbia.edu @columbiaseas.bsky.social Here's the press release:
How hard is it to dim the Sun?
Solar radiation management is gaining traction as a climate intervention—but new research warns that real-world constraints make it riskier and more uncertain than most models suggest.
eurekalert.org
Columbia Dinner 🩵🩵🩵 with Westervelt Group @dwesty.bsky.social , @mcneill-lab.org past and present, @aqtoolbox.org and some additional @climate.columbia.edu friends! #AAAR2025
