James Allan
@jamesallanatmos.bsky.social
Long haired atmospheric scientist at the University of Manchester and NCAS. Opinions my own.
The reason is shown by our ceilometer, which uses a laser to see pollution above us. Here it shows that for some of the time (e.g. between 5 and 10am this morning), the smoke was mainly drifting about 500m above us, but after that it started mixing downward and affecting people on the ground. (2/2)
July 14, 2026 at 3:32 PM
The reason is shown by our ceilometer, which uses a laser to see pollution above us. Here it shows that for some of the time (e.g. between 5 and 10am this morning), the smoke was mainly drifting about 500m above us, but after that it started mixing downward and affecting people on the ground. (2/2)
Update on the fires at Manchester. Some people (like me) might be wondering why the smell has been coming and going, but all the while the sky has been persistently hazy. Our instruments see this as well, here showing PM coming and going. (1/2)
whitworth.cas.manchester.ac.uk/live/firs/ae...
whitworth.cas.manchester.ac.uk/live/firs/ae...
July 14, 2026 at 3:32 PM
Update on the fires at Manchester. Some people (like me) might be wondering why the smell has been coming and going, but all the while the sky has been persistently hazy. Our instruments see this as well, here showing PM coming and going. (1/2)
whitworth.cas.manchester.ac.uk/live/firs/ae...
whitworth.cas.manchester.ac.uk/live/firs/ae...
July 13, 2026 at 6:44 PM
A satellite picture from yesterday showing how the fires have been influencing Manchester. Note it's not affecting the whole are at the same time, which is why the smell has been coming and going all day.
Source: NASA Aqua/MODIS true colour reflectance 12/07/2026, worldview.earthdata.nasa.gov
Source: NASA Aqua/MODIS true colour reflectance 12/07/2026, worldview.earthdata.nasa.gov
July 13, 2026 at 2:48 PM
A satellite picture from yesterday showing how the fires have been influencing Manchester. Note it's not affecting the whole are at the same time, which is why the smell has been coming and going all day.
Source: NASA Aqua/MODIS true colour reflectance 12/07/2026, worldview.earthdata.nasa.gov
Source: NASA Aqua/MODIS true colour reflectance 12/07/2026, worldview.earthdata.nasa.gov
We'll need to look at this carefully, of course, but the PM2.5 composition is looking very consistent with wildfire smoke, with a very high organic and black carbon content. (2/2)
July 13, 2026 at 5:34 AM
We'll need to look at this carefully, of course, but the PM2.5 composition is looking very consistent with wildfire smoke, with a very high organic and black carbon content. (2/2)
Last night's data from the Manchester Air Quality Supersite. We had some serious influence from the fires. (1/2)
whitworth.cas.manchester.ac.uk/live/firs/ae...
whitworth.cas.manchester.ac.uk/live/firs/ae...
July 13, 2026 at 5:34 AM
Last night's data from the Manchester Air Quality Supersite. We had some serious influence from the fires. (1/2)
whitworth.cas.manchester.ac.uk/live/firs/ae...
whitworth.cas.manchester.ac.uk/live/firs/ae...
Think we're seeing the emissions from the nearby Dovestone moorland fire at the Manchester supersite. That's pretty nasty!
whitworth.cas.manchester.ac.uk/live/firs/ae...
whitworth.cas.manchester.ac.uk/live/firs/ae...
July 12, 2026 at 6:06 PM
Think we're seeing the emissions from the nearby Dovestone moorland fire at the Manchester supersite. That's pretty nasty!
whitworth.cas.manchester.ac.uk/live/firs/ae...
whitworth.cas.manchester.ac.uk/live/firs/ae...
These can contribute massively to ultrafine particles, which is a strong area of interest. These can penetrate into the bloodstream and potentially cause more damage, but we lack decent data on. This is the red line on the graph below. (5/6)
June 25, 2026 at 12:17 PM
These can contribute massively to ultrafine particles, which is a strong area of interest. These can penetrate into the bloodstream and potentially cause more damage, but we lack decent data on. This is the red line on the graph below. (5/6)
But going back to particulates, we can also see interesting stuff going on with the very small particles. The white splotch on the bottom right hand corner is likely new particle formation, again driven by chemistry. (4/6)
June 25, 2026 at 12:17 PM
But going back to particulates, we can also see interesting stuff going on with the very small particles. The white splotch on the bottom right hand corner is likely new particle formation, again driven by chemistry. (4/6)
Also ozone was high. If you convert ppb to µg m-3 (approximately double it), we maybe hit the WHO guideline limit of 100 µg m-3 over an 8-hour mean. (3/6)
June 25, 2026 at 12:17 PM
Also ozone was high. If you convert ppb to µg m-3 (approximately double it), we maybe hit the WHO guideline limit of 100 µg m-3 over an 8-hour mean. (3/6)
But I actually started drafting that article a few days ago, so I couldn't use any actual data from the current heatwave. So here it is now taken from whitworth.cas.manchester.ac.uk/live/firs/. As predicted, in Manchester we have particulate matter dominated by organics (2/6)
June 25, 2026 at 12:17 PM
But I actually started drafting that article a few days ago, so I couldn't use any actual data from the current heatwave. So here it is now taken from whitworth.cas.manchester.ac.uk/live/firs/. As predicted, in Manchester we have particulate matter dominated by organics (2/6)
So what's my point? A quote attributed to Isaac Asimov is "The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' but 'That's funny...'". This was my personal example of that.
Pic by Martin Irwin (one of the best ever taken of the 146)
Pic by Martin Irwin (one of the best ever taken of the 146)
February 26, 2026 at 11:29 PM
So what's my point? A quote attributed to Isaac Asimov is "The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' but 'That's funny...'". This was my personal example of that.
Pic by Martin Irwin (one of the best ever taken of the 146)
Pic by Martin Irwin (one of the best ever taken of the 146)
But the real kicker? An eagle-eye person (forget who, sorry) later pointed out that this rogue m/z=82 signal was there much earlier in our work, in figure 10c of this 2008 paper we did based on flying over tropical Australia. We just didn't spot it at the time. 😳
doi.org/10.1029/2007...
doi.org/10.1029/2007...
February 26, 2026 at 11:29 PM
But the real kicker? An eagle-eye person (forget who, sorry) later pointed out that this rogue m/z=82 signal was there much earlier in our work, in figure 10c of this 2008 paper we did based on flying over tropical Australia. We just didn't spot it at the time. 😳
doi.org/10.1029/2007...
doi.org/10.1029/2007...
The Aerosol Mass Spectrometer (AMS) showed a signal at m/z=82, which through sheer virtue of being even-numbered, was an anomaly. Through interrogating high resolution measurements on the ground, we figured its formula was C5H6O. The C5 bit was where things got interesting.
February 26, 2026 at 11:29 PM
The Aerosol Mass Spectrometer (AMS) showed a signal at m/z=82, which through sheer virtue of being even-numbered, was an anomaly. Through interrogating high resolution measurements on the ground, we figured its formula was C5H6O. The C5 bit was where things got interesting.
Needed an image depicting indoor air pollution for a presentation, so asked Microsoft Copilot to draw me something.
Astounded by the scientific accuracy of this. Wouldn't even know it was AI! /s
Astounded by the scientific accuracy of this. Wouldn't even know it was AI! /s
February 12, 2026 at 1:29 PM
Needed an image depicting indoor air pollution for a presentation, so asked Microsoft Copilot to draw me something.
Astounded by the scientific accuracy of this. Wouldn't even know it was AI! /s
Astounded by the scientific accuracy of this. Wouldn't even know it was AI! /s
Good news (I hope) for those of us planning to go to the International Aerosol Conference this year! (www.iac2026.cn)
January 29, 2026 at 11:13 AM
Good news (I hope) for those of us planning to go to the International Aerosol Conference this year! (www.iac2026.cn)
This is a pretty cool statistic, seen via Facebook. Indoor cooking is one of the biggest sources of exposure to air pollution in the less developed world, and the resulting health impacts are a source of gender inequality to boot.
ourworldindata.org/grapher/acce...
ourworldindata.org/grapher/acce...
January 27, 2026 at 10:57 AM
This is a pretty cool statistic, seen via Facebook. Indoor cooking is one of the biggest sources of exposure to air pollution in the less developed world, and the resulting health impacts are a source of gender inequality to boot.
ourworldindata.org/grapher/acce...
ourworldindata.org/grapher/acce...
This one for me is the most interesting bit. The second panel is what would happen to PM2.5 if people ditched the wood burners and only relied on their primary domestic heat source (usually gas). The numbers don't look huge, but in dense population centres the health impacts can add up. (2/3)
October 23, 2025 at 11:35 AM
This one for me is the most interesting bit. The second panel is what would happen to PM2.5 if people ditched the wood burners and only relied on their primary domestic heat source (usually gas). The numbers don't look huge, but in dense population centres the health impacts can add up. (2/3)
I was asked to do a talk about AI in Atmospheric Chemistry a couple of weeks ago and as part of this I presented the latest version of the Gartner Hype Cycle (h/t @loftytopping.bsky.social). Worryingly, LLMs are currently on the wrong part of the rollercoaster. Now see www.bbc.co.uk/news/article...
October 11, 2025 at 10:49 AM
I was asked to do a talk about AI in Atmospheric Chemistry a couple of weeks ago and as part of this I presented the latest version of the Gartner Hype Cycle (h/t @loftytopping.bsky.social). Worryingly, LLMs are currently on the wrong part of the rollercoaster. Now see www.bbc.co.uk/news/article...
It's interesting looking at the traffic statistics as well (roadtraffic.dft.gov.uk/summary). Traffic is kinda-almost back to where it was pre-pandemic, so a decrease in NOx will be a manifestation of cleaner vehicles on the roads, be they newer ICEs or EVs.
October 9, 2025 at 8:31 AM
It's interesting looking at the traffic statistics as well (roadtraffic.dft.gov.uk/summary). Traffic is kinda-almost back to where it was pre-pandemic, so a decrease in NOx will be a manifestation of cleaner vehicles on the roads, be they newer ICEs or EVs.
Here's the last 10 years of data, zoomed in. You can see a downward blip in 2020, which went flat afterwards. However it seems it's started going down again.
October 9, 2025 at 8:26 AM
Here's the last 10 years of data, zoomed in. You can see a downward blip in 2020, which went flat afterwards. However it seems it's started going down again.
The UK emissions inventory for 2023 has been published (naei.energysecurity.gov.uk). Been picking through the numbers and one thing that's reassuring is that it appears that the downward trend in NOx from transport is continuing post-COVID. We've still got a way to go, but it's good news.
October 9, 2025 at 8:10 AM
The UK emissions inventory for 2023 has been published (naei.energysecurity.gov.uk). Been picking through the numbers and one thing that's reassuring is that it appears that the downward trend in NOx from transport is continuing post-COVID. We've still got a way to go, but it's good news.
Some people may already know this, but I managed to make professor recently. I'm not one for blowing my own trumpet, but I wanted to extend a thanks to all my students, postdocs, colleagues and collaborators (you know who you are), without whom this wouldn't have been possible (or as fun).
August 21, 2025 at 2:30 PM
Some people may already know this, but I managed to make professor recently. I'm not one for blowing my own trumpet, but I wanted to extend a thanks to all my students, postdocs, colleagues and collaborators (you know who you are), without whom this wouldn't have been possible (or as fun).
Here's an interesting paper I've just seen (h/t @jacquirickard.bsky.social) using energy performance certificates to estimate wood burning use in England and Wales. Figure 4 comparing with Index of Mean Deprivation (IMD) and ethnicity jumped out for me.
www.sciencedirect.com/science/arti...
www.sciencedirect.com/science/arti...
June 27, 2025 at 8:30 AM
Here's an interesting paper I've just seen (h/t @jacquirickard.bsky.social) using energy performance certificates to estimate wood burning use in England and Wales. Figure 4 comparing with Index of Mean Deprivation (IMD) and ethnicity jumped out for me.
www.sciencedirect.com/science/arti...
www.sciencedirect.com/science/arti...
Setting up a field campaign and I've been using this tool far too much. IYKYK.
May 21, 2025 at 3:02 PM
Setting up a field campaign and I've been using this tool far too much. IYKYK.