Susan Solomon: Climate change and the ozone layer - The Naked Scientists

Susan Solomon: Climate change and the ozone layer | Interviews

Susan Solomon: Climate change and the ozone layer

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Chris - How do we expect then that climate change will influence this? Do we think that if we push temperatures up then this makes things worse in the Antarctic or will it make things better? So we have to suffer a hotter climate, but we get our ozone back?

Susan - Boy, that is a fantastic issue. It turns out that although carbon dioxide and the other greenhouse warming agents warm the lower atmosphere, they actually cool in the stratosphere. So the sign of the impact of increasing carbon dioxide actually flips. We have great satellite data now that shows unequivocally that we have cooling of the stratosphere that is due to the greenhouse gases. So if anything, that effect would make it slightly worse. It's not big enough to have an enormous effect and, in the Antarctic, you're already way colder than you need to be to make these clouds. So the effect is not large there. Where it might have a bigger effect is actually in the Arctic because you're right on the edge in the Arctic. So ironically, the fact that climate change agents warm the lower atmosphere but cool the upper atmosphere would actually make the ozone loss potentially worse. Another thing that's come up recently is the impact of wildfires. There's pretty good evidence that wildfire smoke from the Australian fires actually impacted the chlorine chemistry at mid-latitudes over Australia in a way that's surprisingly similar to what happens only at cold temperatures on the polar stratosphere clouds that are normally there. It's just a different kind of particle that can do different chemistry. It's really amazing how clear cut the satellite data on this actually are. I think the whole community now is wondering as we go forward into this 21st century and things get a little bit warmer - hopefully before we start to turn it over and stop warming - but we probably will get a little bit warmer and we are seeing more wildfires. To what extent could that actually affect the recovery of the ozone layer is a very interesting question. One that I'm actually working on right now.

Chris - Why do we still have a hole, though? Because it will soon be four decades since it was confirmed and we launched one of the most successful environmental protocols that's ever been launched that you allude to, that people responded like we've never seen people respond before, and industry too. Why is the hole still there though? Is it that we are seeing the legacy effect of what damage we did do and it's just going to take a long time for those chemicals to disappear? Or has something else taken over as the source of the toxic chlorine that dismantles ozone?

Susan - As was said in the 1970s, these molecules that are causing the problem really do have long lifetimes in the atmosphere. These chemicals last anywhere between 50 and in some cases even as much as 500 years. The stuff that I used when I sprayed my hair when I was a teenager in the early 70's, some of it is still here and that's kind of amazing, but that's what happens when you talk about a chemical with a long atmospheric lifetime. It's still here chewing up the ozone layer and makes me think about every time that I do something that produces a long-lived chemical: what really is my impact on this planet.

Chris - Even CO2 has a long lifetime in the atmosphere doesn't, it? It's measured in centuries. When you light a match, the CO2 that's coming off the end of that match is going to be around for a lot longer than we are. It's also extraordinary, just listening to what you're saying about the legacy effect of chemicals that hang around for a long time, that really the writing was on the wall for these chlorine based chemicals, and yet we've gone ahead making what we now dub persistent organic fluorocarbons and these alcohol groups and things which make plastics feel nice and make our paper so we can put greasy things on it and not get greasy fingers. They're now being found all over the planet, yet we continue to produce them in prodigious quantities. It seems strange that we've gone from poisoning the air to poisoning the planet elsewhere.

Susan - I am always concerned when I see that we're thinking about things that are persistent because we've made so many mistakes with them in the past. It's not just chlorofluorocarbons with their 100 year lifetimes. Think about DDT for example. DDT had about a 20 year lifetime in soils and people just didn't realise that by using it as a pesticide year after year, building up and building up and causing tremendous damage to wildlife, especially the deaths of the robins back in the 60's, were what prompted people to realise that persistent pesticides were dangerous. Nowadays we're talking about persistent fluorinated compounds, PFAS compounds. We are lucky in one respect, fluorine does not deplete the ozone layer, unlike chlorine. It's not a risk to the ozone layer, but certainly these compounds are everywhere and they're building up in our bodies and the ecosystem and there's a lot of questions about how dangerous they are and they'll be with us for a long time. Plastic of course is the same problem. Plastics have lifetimes of many hundreds if not a thousand years, depending on what kind you talk about. They do break down to make microplastics and even nanoplastics, but it's pretty frightening how many little pieces of microplastic are in a plastic water bottle. This is all going into our bodies. We don't know what happens to it.

Chris - Time magazine said you had saved the planet once, now you are trying to do it again. Are they referring to the fact that we've moved beyond ozone and we realise that we have a really big problem with carbon dioxide now?

Susan - Yes. I had the honour of being part of the intergovernmental panel on climate change the year before Time magazine cited me, working with 150 wonderful scientists from around the world to produce a report for the world that had the statement 'warming is unequivocal' as its key finding. Those words I think have resonated and are still part of why people are so concerned. The evidence that we are warmer is now so clear that climate deniers don't really try to pretend that it's not warming anymore. They tried that method for a while, they could get away with it, but that's just not going to work now. Too many observations and people's own perceptions that summers are hotter and extreme heat waves are hotter than they were before in many parts of the world. Not everywhere, but in surely an overwhelming number of places.

Susan - So, yes, I've been also involved in climate change. You mentioned the issue of the lifetime of carbon dioxide in the atmosphere, which is also one that I've worked on and what the implications of that are for warming and it's really bad news, there. Most of it does go away on a timescale of maybe 150 years. That's actually comparable to the chlorofluorocarbons we've been talking about for the ozone layer. But some of it stays in the atmosphere - about 20% of it actually - for about a thousand years or more. So every time that you drive your car, your gasoline powered car that is or, as you said, light a match, you're adding stuff to the atmosphere that will be here for a very, very long time and cause warming.