James Allan
@jamesallanatmos.bsky.social
Long haired atmospheric scientist at the University of Manchester and NCAS. Opinions my own.
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.
But one of the biggest factors is just how cold and still the air is. The plot below is from our ceiliomter. The green streak in the top right is cloud, but the purple at the bottom is a thick layer of pollution trapped above Manchester. (4/4)
January 8, 2025 at 7:54 PM
But one of the biggest factors is just how cold and still the air is. The plot below is from our ceiliomter. The green streak in the top right is cloud, but the purple at the bottom is a thick layer of pollution trapped above Manchester. (4/4)
Ammonium chloride in particular is something we saw a lot of in India, but we also see it here if there's enough ammonia in the air, which we also see. This is something we associate with agriculture, but there are also urban sources, such as SCR slip from diesel vehicles. (3/4)
January 8, 2025 at 7:54 PM
Ammonium chloride in particular is something we saw a lot of in India, but we also see it here if there's enough ammonia in the air, which we also see. This is something we associate with agriculture, but there are also urban sources, such as SCR slip from diesel vehicles. (3/4)
The PM is a real mixed bag. There's probably some wood burning in there (evidenced by the UV-BC) but also lots of other stuff, including secondaries (note that the ACSM data needs multiplying by 2; we need to update the live feed code). (2/4)
January 8, 2025 at 7:54 PM
The PM is a real mixed bag. There's probably some wood burning in there (evidenced by the UV-BC) but also lots of other stuff, including secondaries (note that the ACSM data needs multiplying by 2; we need to update the live feed code). (2/4)
Update on my post the other day saying how clean it was at the Manchester Supersite (www.cas.manchester.ac.uk/restools/firs/) when it was cold and raining. Today's cold an sunny and yeah, it's not so clean now (1/4)
January 8, 2025 at 7:54 PM
Update on my post the other day saying how clean it was at the Manchester Supersite (www.cas.manchester.ac.uk/restools/firs/) when it was cold and raining. Today's cold an sunny and yeah, it's not so clean now (1/4)
But this wouldn't be a wintertime if we didn't see at least some evidence of domestic burning somewhere. Note the UV carbon being much higher than BC yesterday evening, compared to them being equal during the day today. That indicates soot from wood burning rather than traffic. (5/5)
January 6, 2025 at 11:52 AM
But this wouldn't be a wintertime if we didn't see at least some evidence of domestic burning somewhere. Note the UV carbon being much higher than BC yesterday evening, compared to them being equal during the day today. That indicates soot from wood burning rather than traffic. (5/5)
A big factor in the low PM will be the relative lack of secondary PM, which is produced partly by sunlight. But on top of that is the precipitation, which cleans out PM very well. Here's me showing off our distrometer, which can tell the difference between rain and snow. (4/5)
January 6, 2025 at 11:52 AM
A big factor in the low PM will be the relative lack of secondary PM, which is produced partly by sunlight. But on top of that is the precipitation, which cleans out PM very well. Here's me showing off our distrometer, which can tell the difference between rain and snow. (4/5)
The PM is actually quite clean; PM2.5 is even below the WHO annual guideline of 5 µg/m3. Interesting that PM10 and TSP is so high during the day though; could be surface spray from the roads? Although the crenulation pattern screams "data artefact" to me, so we'll have to check that. (3/5)
January 6, 2025 at 11:52 AM
The PM is actually quite clean; PM2.5 is even below the WHO annual guideline of 5 µg/m3. Interesting that PM10 and TSP is so high during the day though; could be surface spray from the roads? Although the crenulation pattern screams "data artefact" to me, so we'll have to check that. (3/5)
Because of the lack of sunlight, the oxides of nitrogen are almost all in the form of NO2, which is the more toxic form. Converting from ppb to µg/m3 (×1.9), we're well below the DEFRA annual limit (40) and WHO guideline daily limit (25) but not below the WHO annual (10). (2/5)
January 6, 2025 at 11:52 AM
Because of the lack of sunlight, the oxides of nitrogen are almost all in the form of NO2, which is the more toxic form. Converting from ppb to µg/m3 (×1.9), we're well below the DEFRA annual limit (40) and WHO guideline daily limit (25) but not below the WHO annual (10). (2/5)
Been a while since I did one of these, so to mark the first day back in the office I thought I should do an update from the Manchester Air Quality Supersite (www.cas.manchester.ac.uk/restools/firs/) and see how the cold weather is affecting Manchester air quality (1/5)
January 6, 2025 at 11:52 AM
Been a while since I did one of these, so to mark the first day back in the office I thought I should do an update from the Manchester Air Quality Supersite (www.cas.manchester.ac.uk/restools/firs/) and see how the cold weather is affecting Manchester air quality (1/5)
An upcoming online 'masterclass' event promoting our taught MSc programme in Pollution and Environmental Control. I'll be speaking, highlighting our recent work in India in collaboration with IIT Madras.
manchester.ac.uk/study/underg...
manchester.ac.uk/study/underg...
December 20, 2024 at 1:53 PM
An upcoming online 'masterclass' event promoting our taught MSc programme in Pollution and Environmental Control. I'll be speaking, highlighting our recent work in India in collaboration with IIT Madras.
manchester.ac.uk/study/underg...
manchester.ac.uk/study/underg...
Me talking at the Royal Society of Chemistry earlier this week. Picture courtesy of Maria Val Martin (who I don't think has a BlueSky account?)
December 14, 2024 at 7:01 PM
Me talking at the Royal Society of Chemistry earlier this week. Picture courtesy of Maria Val Martin (who I don't think has a BlueSky account?)
Not done a post showing data from the Manchester Air Quality Supersite on BlueSky yet, so may I present the first snows of winter?
www.cas.manchester.ac.uk/restools/fir...
www.cas.manchester.ac.uk/restools/fir...
November 18, 2024 at 8:28 PM
Not done a post showing data from the Manchester Air Quality Supersite on BlueSky yet, so may I present the first snows of winter?
www.cas.manchester.ac.uk/restools/fir...
www.cas.manchester.ac.uk/restools/fir...
Took a load of pictures this evening. This one's my favourite.
October 10, 2024 at 9:24 PM
Took a load of pictures this evening. This one's my favourite.
Well that sucks. Was going to do an exercise for the students tomorrow downloading weather data. Turns out the server is down, and guess why? How's that for irony...
October 10, 2024 at 7:57 PM
Well that sucks. Was going to do an exercise for the students tomorrow downloading weather data. Turns out the server is down, and guess why? How's that for irony...
The advert says "X is the world's town square." As someone who grew up in the north of England in the 80s and 90s, stuff like this gives me the image of a declining town centre that is full of graffiti, badly-policed, and failing to attract businesses and visitors. ☹️
September 23, 2024 at 10:04 AM
The advert says "X is the world's town square." As someone who grew up in the north of England in the 80s and 90s, stuff like this gives me the image of a declining town centre that is full of graffiti, badly-policed, and failing to attract businesses and visitors. ☹️