James Allan

What’s the worst that could happen with climate change? - NCAS NCAS and University of Reading researchers have explored the high impact low-likelihood climate scenarios.

Climate change conversations centre on a few degrees of warming, rising seas, more frequent heatwaves and storms. But what about the high impact low-likelihood scenarios?

Read our latest article: ncas.ac.uk/climate-scie...

Turns out net zero is cheaper than a single fossil fuel crisis. 🤷

The sooner we build on clean, home-grown energy, the sooner we stop handing the keys to foreign gas markets. But we also need market reform now - so customers, not just corporations, actually reap the benefits of renewables.

Climate change is creating new drought hotspots - NCAS New research shows that in many parts of the world, soils are drying out - even in places that are projected to get wetter.

What does climate change mean for drought in Europe, Africa, and America?

We asked NCAS climate scientist Professor Emily Black to explain: ncas.ac.uk/climate-chan...

As with the previous version, I'm kind of curious to know where the limit values have come from, given they go beyond the WHO recommendations in places. Don't suppose you know, do you?

What does Saharan dust mean for UK weather and air quality? - NCAS Find out why Saharan dust is drifting over the UK and what it means for our weather and air quality, and how scientists measure it.

Vibrant sunsets, dirty windows, and increased particulate matter - it must be Saharan dust.

Hugo Ricketts explains the what, where, and how of airborne dust in the UK: ncas.ac.uk/why-is-there...

Hello from Leeds 👋

We've just hosted our Introduction to Atmospheric Science course. Thank you to everyone who came to learn and network with our experts and with like-minded peers!

Closure of the FAAM Airborne Laboratory - NCAS The National Centre for Atmospheric Science can confirm that the FAAM Airborne Laboratory will cease operations at the end of this financial year, following the withdrawal of funding by UKRI-NERC.

Following the withdrawal of funding by UKRI-NERC, we can confirm that the FAAM Airborne Laboratory will cease operations at the end of this financial year. Our immediate priority is supporting affected staff and the wider UK atmospheric science community.

ncas.ac.uk/closure-of-t...

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)

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...

Largely underestimated production of isoprene epoxydiols (IEPOX) through high-NO oxidation pathways in urban areas - npj Climate and Atmospheric Science npj Climate and Atmospheric Science - Largely underestimated production of isoprene epoxydiols (IEPOX) through high-NO oxidation pathways in urban areas

So while I can't lay claim to the chemical mechanism, I'd like to think we got there first on the marker for observing it on an AMS. And this still proves to be important to this day, see this paper from last year.
www.nature.com/articles/s41...

This in turn had major implications for not just the tropics but the Southeastern US, where it turns out this has a major influence on PM2.5 in that part of the country. This paper by the @jljcolorado.bsky.social group did a nice round-up of the AMS work.
acp.copernicus.org/articles/15/...

Real-Time Continuous Characterization of Secondary Organic Aerosol Derived from Isoprene Epoxydiols in Downtown Atlanta, Georgia, Using the Aerodyne Aerosol Chemical Speciation Monitor Real-time continuous chemical measurements of fine aerosol were made using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) during summer and fall 2011 in downtown Atlanta, Georgia. Organic mass spectra measured by the ACSM were analyzed by positive matrix factorization (PMF), yielding three conventional factors: hydrocarbon-like organic aerosol (HOA), semivolatile oxygenated organic aerosol (SV-OOA), and low-volatility oxygenated organic aerosol (LV-OOA). An additional OOA factor that contributed to 33 ± 10% of the organic mass was resolved in summer. This factor had a mass spectrum that strongly correlated (r2 = 0.74) to that obtained from laboratory-generated secondary organic aerosol (SOA) derived from synthetic isoprene epoxydiols (IEPOX). Time series of this additional factor is also well correlated (r2 = 0.59) with IEPOX-derived SOA tracers from filters collected in Atlanta but less correlated (r2 < 0.3) with a methacrylic acid epoxide (MAE)-derived SOA tracer, α-pinene SOA tracers, and a biomass burning tracer (i.e., levoglucosan), and primary emissions. Our analyses suggest IEPOX as the source of this additional factor, which has some correlation with aerosol acidity (r2 = 0.3), measured as H+ (nmol m–3), and sulfate mass loading (r2 = 0.48), consistent with prior work showing that these two parameters promote heterogeneous chemistry of IEPOX to form SOA.

This was eventually published by Niall Robinson, a student I co-supervised, although I admit that in that paper we got the SOA mechanism wrong. It was subsequently linked to the 'IEPOX' mechanism that @surrattairchemlab.bsky.social did so much pioneering work on.
pubs.acs.org/doi/10.1021/...

But one rogue peak in a mass spectrum wouldn't prove anything. Thankfully, @jacquirickard.bsky.social had GC-MS data that when interrogated, was able to show that the molecule was methylfuran, produced from the thermal decomposition of the particles in the respective instruments.

Formation of Secondary Organic Aerosols Through Photooxidation of Isoprene Detailed organic analysis of natural aerosols from the Amazonian rain forest showed considerable quantities of previously unobserved polar organic compounds, which were identified as a mixture of two ...

But by the mid 2000s, evidence was appearing to the contrary and the implications were huge; if isoprene could make aerosol particles, this means tropical forests could be influencing clouds and thus climate.
www.science.org/doi/abs/10.1...

C5 corresponds to isoprene, which is a naturally-produced organic molecule, produced in abundance in the tropics, particularly over the palm oil plantations in Borneo. For a long time, many assumed it couldn't produce secondary aerosol in the atmosphere.
en.wikipedia.org/wiki/Isoprene

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.

But no, Borneo will stay with me for a bunch of reasons, and not just the hair-raising low level flying. That particular result was something I can claim to have spotted in flight, which was a rogue signal at a specific altitude, which turned out to be really important.

Near-field emission profiling of tropical forest and Cerrado fires in Brazil during SAMBBA 2012 Abstract. We profile trace gas and particulate emissions from near-field airborne measurements of discrete smoke plumes in Brazil during the 2012 biomass burning season. The South American Biomass Bur...

I could have picked others. Chasing plumes of forest fires in Brazil, ships in the Atlantic or the Buncefield incident were all more than a little entertaining and I could go on, but then I'd be doing the whole "tears in rain" thing.
acp.copernicus.org/articles/18/...

Still trying to process FAAM's plug getting abruptly pulled today. But among many other things, I'm thinking back on the positives, of the good science we did. If I had to pick one, it'd be this, which came out of the OP3 campaign in Borneo. 🧵

acp.copernicus.org/articles/11/...

NERC pivots investment in atmospheric research into new technologies NERC is transitioning its funding of atmospheric science infrastructure to exploit more flexible, scalable and sustainable technologies.

There's a lot of things I could say, but I should probably let this sink in a bit first.

Why climate education matters for social justice - NCAS On World Day of Social Justice, we are reminded that climate education matters more now than ever - find out why.

Every learner today will live their entire life in a climate different from the one their parents and grandparents grew up in. Find out why climate education matters more now than ever, on World Day of Social Justice:

ncas.ac.uk/turning-know...

#SocialJusticeDay #WorldDayofSocialJustice

Wood burning pollution leads to 8,600 premature US deaths a year, study finds Wood is primary heating in 2% of homes but contributes to producing 21% of country’s wintertime particle pollution

Tackling residential wood combustion "could lead to outsized improvements in air quality.”

An opportunity to reduce the toll of 8,600 premature deaths each year in the US and 2,600 in the UK.

My latest piece for @theguardian.com.

www.theguardian.com/environment/...

Think that table might be in danger of catching fire, if that helps?

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

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...

This is an interesting piece of work done at the Energy House over in Salford. With increased interest in indoor air quality in homes, there's a lot of talk about tradeoffs between that and energy efficiency.

How romanticised images of London fog shaped the way we see polluted air London’s fog literally fogged photographs with the yellowish hue of the capital’s notorious ‘pea-soupers’.

That's really interesting.

theconversation.com/how-romantic...

One for the academics: The UK Exposure Science conference 2026. A good interdisciplinary conference dealing with all kinds of exposure science (not just air pollution 😜). I've previously found it great for networking, particularly with people from outside your field.

www.rsc.org/events/detai...

What does climate change mean for cold weather? - NCAS We asked climate and weather scientists about “coldwaves”, the role of climate change, and what the UK’s winters will be like in the future.

Isn’t climate change supposed to make the weather warmer? The cold conditions in early January prompted questions about the impact of climate change.

We spoke to Ed and Weronika about “coldwaves” and global warming: ncas.ac.uk/what-does-cl...