With an unseasonably warm spring on the cards in Australia, atmospheric scientists are casting their eyes to the ozone hole lingering above Antarctica. Unusual events in recent years have delayed the recovery of the ozone hole, which was first discovered in 1985. Some of these events include the Australian bush fires of 2019 to 2020 and rocket launches. Laura Revell is an associate professor in environmental physics at the University of Canterbury and says full recovery will take some time.
Category
📺
TVTranscript
00:00The Montreal Protocol was signed in 1987 to remove ozone-depleting gases from the atmosphere,
00:09but these gases have very long lifetimes of up to 100 years or more.
00:14So there's still plenty of them up in the stratosphere where they cause the ozone hole
00:19to form over Antarctica each spring.
00:23And while we are seeing the early signs of recovery, which is really great news, we still
00:29have to continue making sure that it is continuing to recover as expected, especially given new
00:37technological innovations that could potentially pose a threat to ozone recovery.
00:42Yeah, so what are those new threats that are compounding the problem?
00:47Yeah, there's a bunch of things going on, but they all have in common that they involve
00:55tiny particulates being injected into the stratosphere where they can speed up the
01:00rate of ozone depletion.
01:02So these might be things like rocket launches that emit reactive gases that can contribute
01:08to ozone depletion as they launch to space.
01:12They might include the wildfires, like the Australian bushfires of 2019-2020.
01:20Of course, they produced a lot of smoke.
01:22Some of that got into the stratosphere and we did observe extra ozone depletion that
01:27year.
01:28And unfortunately, with climate change, we do expect to see those mega wildfires becoming
01:33more frequent in future.
01:35And then there's things like these really controversial proposed solutions to climate
01:42change, such as stratospheric aerosol injection geoengineering, which would involve deliberately
01:48putting particulates into the stratosphere to stop some of the sunlight from reaching
01:54the Earth's surface and try and offset global warming.
01:57Unfortunately, that would probably cause some ozone loss and slow down the rate of ozone
02:02recovery.
02:03And so what do you think of that as a suggestion?
02:05I mean, it's very controversial and there are so many things that could go wrong.
02:12There's all the ethical questions, you know, who controls the thermostat, who decides when
02:15we stop doing it?
02:17And then there's the potential for things to go very, very wrong.
02:20So causing ozone depletion, potentially changing rainfall patterns and meaning that some areas
02:26get not enough rainfall and some places get flooding.
02:30So definitely in the climate change space, it's something that would need very careful
02:35thought and consideration before it's attempted at any large scale.
02:40So what's happened to the ozone hole in terms of its size over the years?
02:45Is it still decreasing?
02:49We have started to see the very early signs of recovery since about the mid 2010s, which
02:55is great news.
02:57There have been some unusual things going on in the last few years.
03:00So about the last four years or so, we've seen unusually long lived ozone holes that
03:06have lasted into the early summertime in Antarctica.
03:10Those are for different reasons relating to things like the Australian bushfires, kind
03:14of a series of one off events.
03:17But of course, climate change is bringing lots of surprises.
03:20So we don't know how that might play out in future.
03:22But I mean, those things aside, we generally expect that as these ozone destroying gases
03:27are eventually removed from the stratosphere, that we will see that ozone recovery happening
03:33later this century, hopefully.
03:35Why does the hole generally open up around this time of year and down this way?
03:41Yeah, it's a great question because most of the gases were emitted in the northern
03:45hemisphere.
03:46So why is it Antarctica that sees the ozone hole?
03:49That's because Antarctica is very, very cold.
03:53In wintertime, it's about the coldest place you can get on Earth.
03:57And that causes these clouds to form in the stratosphere called polar stratospheric clouds.
04:04They only form at very low temperatures.
04:06And they behave a bit like those solid particulates that we were talking about earlier, in that
04:11they act as surfaces that help catalyze the rates of chemical reactions.
04:17And they help a really big buildup of chlorine to occur in the stratosphere during wintertime.
04:24And then when the sunlight returns to Antarctica in late winter, early spring, that just kicks
04:31off this explosion of ozone-destroying reactions such that this hole appears over Antarctica.
04:38Yeah.
04:39And so that Montreal Protocol was so successful in cutting chlorofluorocarbons to address
04:44this issue.
04:46What's the danger if this continues to linger over the coming decades?
04:51So, as you said, the Montreal Protocol has been incredibly successful.
04:57If it hadn't been signed, we would have been looking at possibly a collapse of the global
05:02ozone layer by about the 2060s.
05:04But instead, we expect to see a recovery.
05:07We do still expect to see that coming.
05:09It's just a case of monitoring these new emerging issues, such as the wildfires, the rocket
05:16launches and so on, and making sure that those are not going to interfere with ozone recovery.
05:21Because we certainly wouldn't want to see ozone depletion happening outside Antarctica
05:26on any great scale, because, of course, it's a vital planetary boundary layer with protecting
05:31us from the sun's harmful rays and stopping us getting sunburned and skin cancers and so on.
05:39OK, Laura Revel, thanks so much for talking to us from Christchurch in New Zealand.