Recently I had a paper from this project published on emissions of HCFC-141b, which have been rising (published in ACP). HCFC-141b is an ozone depleting substance (but not as bad as CFCs) and also a pretty potent greenhouse gas. sWe were originally interested in HCFC-141b emissions when looking at emissions of CFC-11. CFC-11 emissions had grown, most likely following illegal production, and we wanted to know if anything peculiar was going on with HCFC-141b, which largely replaced CFC-11 – mainly for foam blowing. At the time there wasn’t anything, as far we could tell, unusual happening with HCFC-141b and we left it out of the paper.
In the following couple of years we realised that emissions of HCFC-141b had also been rising. The timing of this was suspiciously similar to when emissions of CFC-11 dropped. This might suggest that people who were using CFC-11 had switched their use to HCFC-141b instead. HCFC-141b isn’t illegal to produce, but it is being phased-down fairly quickly and so its usage should not be becoming more common.
The paper looked at both global emissions and regional emissions. Interestingly, it’s really hard to tell where these new emissions are coming from – both geographically and from what source. A complicating factor is that some models predict that HCFC-141b emissions from some parts of the world will increase around this time because lots of refrigerators (which have HCFC-141b in their insulating foams) will be disposed of, releasing a lot of HCFC-141b to the atmosphere.
In the end, the conclusion is that we don’t know for sure what’s going on. There could be illegal production, leading to increased emissions, but we by no means have any direct evidence for it happening. It may also be coming from the disposal of old refrigerators, but there are no published models on a global scale to tell us whether this is a feasible avenue. Of course, it could also be something we’ve not thought of or a combination of factors also. But what is really interesting is that it raises the possibility that emissions can still rise after a phase-down of production. This shows how the Montreal Protocol, which controls production, may not have such an immediate impact. This is particularly relevant when we rely on the Montreal Protocol for climate change purposes and aim for net zero.
The preprint of this paper got some media interest (such as this article in Science) and Christina Theodoridi, one of the co-authors, did a really great blog entry on the topic.