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Case Study: Understanding CF4 emissions

In this video, Simon O'Doherty talks about his research into greenhouse gasses, as part of the Advanced Global Gases Experiment.
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12.5
When I first started it wasn’t so much climate change we were interested in. At the time, it was more to do with ozone depletion and the two things are kind of linked but what we were doing was looking at the accumulation of ozone depleting gases in the atmosphere and they had been regulated under the Montreal Protocol and they were being replaced because they were strong ozone depleters, by a new range of gases. So these these gases were called the hydrochlorofluorocarbons, HCFCs, and hydrofluorocarbons, HFCs. And these gases were designed, if you like, such that they would react in the lower atmosphere they wouldn’t reach the stratosphere, they wouldn’t destroy ozone.
54
Which is, you know, great for the ozone layer, and it is great for the ozone layer, the only problem is that these gases are all strong climate gases, climate forcing gases or greenhouse gases. So we started measuring these gases like I say probably around the early 80s and we set up two field stations one in the northern hemisphere, one in the southern hemisphere and the idea really was to really look to see how these new gases were accumulating in the atmosphere. Well CF4’s a really interesting gas.
86.8
It’s used in the semiconductor industry and it’s used in the aluminium industry and when it’s released into the atmosphere it has what’s called a lifetime, so it’s half-life in the atmosphere, if you like, of around fifty thousand years. So it’s one of these gases that we don’t release a huge amount in the atmosphere, but once we do release it into the atmosphere it’s more or less there forever more. So if we have processes, industrial processes, releasing these gases, or this particular gas and a whole range of other CFCs, into the atmosphere over a prolonged period of time these gases are going to build up and they’re climate forcing gases, so they will cause climate warming.
128.3
The idea of a network of stations of good quality measurements are vital to the kind of work that we do. There’s two aspects to the work. The first aspect of what we do is we make physical measurements of the gases in the atmosphere. So we need to have a good network to cover the areas that we want to measure. If we have stations just related to one part of the world then we won’t really see the emissions of these gases from another part of the world very easily.
155.7
So what you want to do is, you don’t really want to be based by a factory that’s producing these gases because what you’ll be doing is, you’ll be measuring the output of these gases close to the site. What you want to be doing is taking an average, if you like, of the atmosphere where your sampling station is. We have a station at Mace Head it’s on the west coast of Ireland, in Connemara.
175.8
So if you sample on a seaboard location where the prevailing wind is coming in from the West then, basically, we’re sampling air that’s come across from America, come across the Atlantic, is really well-mixed and is really representative of the Northern hemispheric concentration of these gases as they arrive at Ireland. Mace Head is a great sight there because we have times where the air mass switches round and the air mass suddenly comes off Europe and across the UK.
203.9
And what we see in our data is suddenly, you know, a large increase in the concentrations of for example, methane or carbon dioxide or any of the other gases and that’s because these air masses are picking up emissions pollution from the UK, from Europe that are being transported to Ireland. So what we can do there is we can look at the baseline trend that we get from the Northern hemispheric average and then we can look at the differences between the baseline trend and the pollution spikes that we see and then we can use modelling techniques to work out the actual emissions of those gases in the atmosphere.
239
We need this coverage to give us the information that’s required to then go on to the second part of the work we do which is the modelling part which is the mathematical modelling. So here we take the information, we put it into these theoretical models and then we see how these models then replicate reality. The atmosphere is a complex place. Models are very gross oversimplifications of the atmosphere and what we use is these measurements to test these models. We don’t do this work solely, it’s great that we have all this work going on in Bristol, we’re not part of, we just don’t do this by ourselves.
275.4
So as part of the AGAGE Network this is a global network so the really important thing there is that we collaborate with the other people that run all of the other sites. Some of the sites are funded by NASA, some of the sites are based in the US. We collaborate with the Scripps Institution of Oceanography and they have a site at Trinidad Head in Northern California and then we have other groups around the world that have become part of the AGAGE network.
300.9
The group in Switzerland from EMPA measuring on the Jungfraujoch, we have a group from Nilu in Norway who measure similar sorts of things in the Zeppelin station in the Arctic and then we have group at Shangzheng in China. We have this whole network of international collaborators and the idea of the network really is that we all use similar types of equipment and we all work using similar protocols and we all use similar software and there’s a huge value in having long term continuous measurements as opposed to short term campaign type measurements. They both work well together but I think we do really need these long term networks to understand what’s happening over periods of decades.

Simon O’Doherty is a Professor at the Department of Chemistry of the University of Bristol. His main area of research is concerned with the global growth of Montreal Protocol gases or gases that are involved in stratospheric ozone depletion (CFCs, HCFCs and halons) and the Kyoto gases, or gases that are involved in global warming.

This internationally recognised work is funded by Department of Energy and Climate Change, the Irish Environmental Protection Agency, NASA and the National Oceanic and Atmospheric Administration. He is a member of the Advanced Global Gases Experiment, AGAGE team, as a principal scientist in charge of two of the five AGAGE research stations (in Ireland and Barbados).

AGAGE is one of only two groups in the world making ground-based global measurements of these compounds. This area of research has expanded in recent years with national and EU funded projects such as SOGE, SOGE-A, UK-SOLAS, Eurohydros, InGOS and GAUGE. Simon leads the UK DECC Network. This network incorporates a range of novel measurement approaches, and is a collaboration between the Universities of Bristol, East Anglia, and the UK Met Office. Other areas of research include the development of equipment for monitoring a wide variety of other ozone precursor compounds, which play an important role in issues of public health and both urban and rural pollution assessments.

Since recording this interview, a new site in Norfolk has been added to the AGAGE network – and has uncovered a surprising and as-yet unexplained release of PFC in March 2020. The AGAGE data is also being enhanced by combining it with locally obtained samples from other sites that are subsequently evaluated back at the University.

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