News

Noel Nelson is a senior air quality scientist at the Met Office, and is talking here with Ben Hudson, Global Action Plan's Head of Insight and Engagement about the Great Smog of 1952, which started 70 years ago on the 5th of December, what we've learned about air quality since then, and what we need to do to protect people's health going forward.

"We Share Freely". The change we want to see in the world is bigger than we are. So, we're sharing our knowledge, resources and ideas to help more people and organisations take steps forward towards our vision of a green and thriving planet, where everyone can enjoy happy and healthy lives within the Earth's limits.

 

As part of this, we've launched our "5 Minute GAP" series, a collection of five minute conversations that will share how we work and what we're working on. We'll talk about what we're trying to achieve and why, how we function as an organisation, and the thinking behind our plans and strategy.

 

We'll be regularly sharing these conversations, which will feature different members of our team and trustee board, as well as external experts.

 

We hope you enjoy listening in to our chats, getting to know our team and finding out what makes us who we are. 

 

---

 

If you prefer to read rather than watch, the transcription is here:

Noel: I guess we’re here to talk about the smog.

Ben: That's right. I understand it had a lot to do with the weather conditions, but also the pollutants that were being burned at that time?

Noel: That's correct.

Ben: I’m sure you can tell us a bit more. 

Noel: Well, yeah. Yes, I'll try. So it's probably worth bearing in mind at this stage that practically anything really any material is released to the atmosphere, its eventual fate is sort of heavily influenced by the weather. Now with pollution that is admitted to the atmosphere, sometimes the weather is very conducive to helping that pollutant mix in the atmosphere with nice clean air so you don't get such a bad problem. But occasionally the weather works against us and it's not conducive to mixing and we get these horrible high pollution episodes we sometimes get. 

So, back in the smog days of 1952, a lot of the pollutants to the atmosphere were provided by people burning coal to keep warm because it was early December. So it was very cold. So a lot of people were burning what at that time actually was actually considered to be quite low grade coal, producing a lot of horrible nasties in the atmosphere. But on top of that, you had local factories burning a range of different material, and some of the emissions emitted from these factories were acidic in nature. So once in the atmosphere, if you were to breathe some of this in, they would actually burn the back of your throat. Or sometimes people talked about some skin irritation as well. So gives us an idea of how concentrated some of these pollutants might have been. 

Ordinarily, when these pollutants are emitted from the atmosphere they would rise up higher in the atmosphere. And the weather allows the various gasses and particles to mix. And when they do so, the concentrations are diluted and that's under good weather conditions. Sometimes, though, as was the case in 1952, we were under what we term as an anti-cyclonic weather system was at play at the time and this tends to push a lot of the air masses quite high down to the ground. And as this air mass descends, it tends to warm. So you get this odd situation where the air masses that are quite close to the ground are quite cool when compared to the warmer air above we've normally termed this as a temperature inversion. 

Now the effect this has is it suppresses the continual upward movement of some of those lower air masses. So imagine that if those air masses are polluted with all these emissions we spoke about from people's homes and from the factories, it tends to stop that from being mixed higher up in the atmosphere and everything is kept at quite low ground level. But on top of that, very early on the fifth I think of December, the sky was quite clear. So a lot of radiation that might have been emitted from the ground was lost to space. You know, basically just weren't any clouds around at all to trap that heat. So we had quite moist surface and light winds. Now, these are traditionally very good conditions for the formation of fog. 

So we had fog form quite early on and with those light winds that began to whip up a little bit of that fog, until it got to the stage where you had a fog bank that was about 200 meters high or so. But remember, this is now mixing in with all these pollutants that were being emitted from people's homes and from the factories. And you add to that the fact that these the air mass and those pollutants couldn't go anywhere because of this temperature inversion, trapping everything in. You had a terrible situation where this cocktail of pollutants were just left stagnant in a way, mixed up in the fog to cause all the problems they did cause. And, you know, of course, that's where we get the term smog from because it’s smoke infused with the fog. 

So that was the main reason why it was such a huge event at the time. And there were many deaths, not just because of the people suffocating, I guess, but also things like road accidents because people literally couldn't see across the other side of the road. It was that thick at times. So yeah, quite an event. 

Ben: And so the weather had a big part to play with this temperature inversion, as you described it. If we had levels of emissions, or pockets of emissions in maybe small neighbourhoods, could the conditions be right for another smog episode? 

Noel: Certainly we get anti-cyclonic conditions like this all the time and certainly we do get the build up of fog. The only difference, I guess, between then and now is that we don't have the same cocktail of emissions. Generally, even when people are burning coal in their homes, it tends to be smokeless fuel generally and nowhere near as poor quality as was burned then, a lot of the factories that were really very polluting then were either cleaned up and/or removed because, you know, an act was passed soon after that actually to limit the amount of that sort of emissions. Some factories were made to have much taller chimneys. So the pollutants were emitted into the atmosphere much, much higher up. And these things generally led to a far cleaner, compared to then anyway, far cleaner atmosphere. 

But as we know things, you know, we found as the science has moved on, we understand far more about what was emitted from cars, etc. We have other sort of problems now with pollution.

Ben: Yeah, as you alluded to there, the Clean Air Act that came in 1956, kind of reduced the amount people were burning at home. So that was kind of removed as an issue. Of course, we have we still have air pollution. It's just from different sources, different places. So I think transport would be our main offender and then we'd have wood burning stoves and combustion processes as well. 

But I think from what you're saying there, the actual cocktail of these emissions are not quite the same as they were in 1952. So hopefully we won't be experiencing any smogs. But there is there's still work to be done in terms of clearing it up. So the pollution we experience now is obviously very invisible. Yeah, microscopic and altogether different. But equally, we do need a strong, clean air act in order to address this. 

Noel: Definitely. I think, you know, like I say, it doesn't stop us from having the odd event. That's quite bad. Obviously not as bad as before. But you know, we all remember times on bonfire nights where we smell slightly sulphurous fireworks in the atmosphere at the time and or in winter, walking past various houses who are burning wood in their fireplaces. We can smell it outside the houses. So we know there are conditions where very locally pollution pollutants are elevated slightly because of what's going on and our various habits in our behaviour.