How Colorado scientists are helping track the ozone hole
At least one thing in the environment seems to be improving.
The annual ozone survey, in which Boulder scientists and their instruments play a key role, tells us we are still on track to solve the problem that terrified the world in the 1990s and early 2000s. At the time, headlines and interviews with Southern Hemisphere residents warned of blind sheep, disease caused by uncontrolled ultraviolet radiation in cities like Punta Arenas, Chile, and dangers to Antarctic science stations beneath the crater.
The Boulder-based National Oceanic and Atmospheric Administration (NOAA) tells us that the worst day for the ozone layer of 2023 was only the 12th worst since it began recording in 1979, and that overall it was a “very modest ozone hole.” And remember, this is a hole in the “good” ozone, which protects us from the intensity of the sun’s rays, not the “bad” ground-level ozone pollution caused by a mixture of nitrogen oxide, volatile organic compounds, and extreme summer heat.
So the international ban on chemicals – the Montreal Protocol – that protects the ozone shield continues to work its scientific magic. Now if only we could reach the same consensus and move quickly on carbon dioxide.
The ozone hole peaks over Antarctica during the spring, bringing the September 21 reading this year to a gap of 10 million square miles. The peak season average from September 7 to October 13 was 8.9 million square miles, roughly the size of North America, according to the helpful acronym compiled by the National Oceanic and Atmospheric Administration (NOAA).
The “very modest” assessment came from Paul Newman, leader of NASA’s ozone research team based in Greenbelt, Maryland. “Declining levels of human-produced chlorine compounds, coupled with help from active stratospheric weather in Antarctica, have led to a slight improvement in ozone levels this year,” Newman said.
Did we bring all this up so we could mention the Hunga Tonga-Hunga Haapai volcano? Maybe not at all. The violent eruption of this underwater volcano in the South Pacific Ocean sent a massive plume of water vapor into the stratosphere, likely worsening ozone depletion this year.
The National Oceanic and Atmospheric Administration’s (NOAA) Global Observing Laboratory’s ozone project leader is based in Boulder, as are senior scientists and laboratory technicians who are spending the winter at the Amundsen-Scott Antarctic Station to launch a portable “ozone probe” for readouts. Balloons have one advantage over satellites: they can take direct readings of ozone across different layers of the atmosphere. The ozonesonde on US balloons was invented in Boulder in the 1960s, and is still manufactured by Boulder companies, according to National Oceanic and Atmospheric Administration spokesman Theo Stein.
The Colorado Sun spoke with Steven Montzka, a senior scientist at the National Oceanic and Atmospheric Administration based in Boulder, about how to track the ozone hole, and what the Montreal Protocol findings might tell us about international cooperation on climate change or other challenges.
sun: How do scientists track good ozone over time, and what is Boulder’s role in this?
Montezca: NOAA measures ozone locations around the world. It also measures ozone-depleting gases, the problem chemicals, emitted by human activity. So NOAA’s Global Monitoring Laboratory in Boulder measures ozone in several different ways. First, a sensor that we build in-house is attached to the balloon. It is then released like a weather balloon. A current is measured and transmitted to the ground when the balloon rises to a very high altitude. So we do that in Boulder on a regular basis. We do this in other locations around the world, including Antarctica. So here’s one way: a high-resolution vertical image of how ozone changes as a function of altitude.
The other way we measure ozone is by measuring the total column, which is basically looking at the wavelengths of light through the atmosphere. You can look at a wavelength of light that is absorbed by ozone and one that is not absorbed by ozone, and the difference there gives you an idea of how much ozone is in the total column above you. We do this in a number of locations. Fewer locations, but Boulder and definitely Antarctica. This is a measure of the density of ozone above you at any point on Earth.
sun: So maybe we were driving and saw one of you pointing something at the sky? Where are you located?
Montezca: David Skaggs Research Center on Broadway. There’s a rooftop on the south side of the building, and every once in a while, you’ll see some people carrying rather large, unwieldy white boxes and making ozone measurements in this column of air. We basically image the Sun with instruments, making measurements of the light as it passes through the atmosphere.
sun: What happened in your measurements over time?
Montezca: Spring in Antarctica is September and October, and we’ve been measuring that time every year since about 1980. We have measured significant ozone depletion that was not measured in the years before 1980. Ozone has almost completely disappeared at certain levels from the atmosphere since the late 1980s and early 1990s.
Since that time, there has been a slight rebound, although it is difficult to detect, because other factors play a role in exactly how much ozone is destroyed in the stratosphere over Antarctica each year. We have this picture where we understand that the concentration of ozone-depleting substances is gradually decreasing. So we expect that over time there will be less ozone depletion anywhere in the stratosphere. Particularly over Antarctica, we expect this general gradual trend towards improving ozone concentrations and for the hole to be smaller and less complete.
But what happens from year to year, there are other factors that play a role and have to do with meteorology and weather. The extent of the vortex’s containment over Antarctica during that spring. By vortex I mean the tightly insulated circulation of air around the South Pole and over Antarctica. If this tight circulation breaks early in a given year, we will mix with air from higher latitudes in a way that makes ozone depletion that year less severe. So the weather makes a difference. The amount of water vapor there also makes a difference.
sun: And as for water vapor, the recent eruption of a large underwater volcano didn’t help?
Montezca: Yes, it didn’t happen this year, but it was the Honga Tonga-Hunga Haapai event of the Southern Hemisphere. We have seen that the amount of water vapor in the stratosphere increased by about 10% as a result of this volcanic eruption. A large amount. Large input of water vapor. Therefore, it was expected that water vapor would eventually reach the stratosphere over Antarctica during the spring and may cause the addition of some polar stratospheric clouds. Increased drag means there is more surface area for ozone to destroy. But this year there were competing influences. Even though there was enhanced water due to this eruption, the meteorology was such that the vortex would disintegrate a little easier, and a little earlier than usual. So this mitigated the effect of the increased water.
sun: Overall, how did we do this year?
MontezcaWe estimate that concentrations of ozone-depleting gases in the stratosphere this spring are now 25% lower than they were during the worst peak year for ozone-depleting chlorine and bromine. And that was around the year 2000. So, we know that there was a decline in concentrations of ozone-depleting substances.
sun: Are there other lessons we can learn about other global environmental challenges, based on a global treaty such as the Montreal Protocols having a significant positive impact on ozone?
Montezca: Yes, there is, and it has a lot to do with the Montreal Protocol. Countries around the world came together in the late 1980s and agreed that this was the issue they wanted to address. The first studies came out that said, oh my God, the ozone over Antarctica in the spring was falling like a rock. This has made countries around the world take notice.
They came together and agreed that they would take steps to reduce the gases causing the problem. I think some things about this process and protocol are worth mentioning and talking about. The first is that the initial agreement would not have solved the problem. There was an attempt immediately to say, “Okay, we’re going to stop producing and using these chemicals.” It was very difficult for the parties to agree on it at that time.
What they did instead was say: “We will limit their use in the future.” And a few years from now we’ll be back together. They meet twice a year and have done so ever since. We will continue to meet and learn as science advances and as scientists tell us more about the problem. We will then decide whether to impose further restrictions. Delegations from around the world agreed to reconsider this issue every year. There was a mechanism through which they ensured that any new updates in science were conveyed to them so that they could make informed decisions.
They also had other advisory committees, not just scientists, they had advisory committees that had a role in helping guide the best way forward. To the chemicals that industry knew how to make, which scientists said “do not deplete ozone significantly, or perhaps at all.” The second committee is the Technological and Economic Evaluation Committee. These people also carry out analyzes of the economics of the transition, so that parties know the financial and environmental costs and benefits of the decisions they make.
sun: A skeptic might say, okay, but on climate change, you’re asking these countries to make executive decisions that have a bigger and broader impact on the economy, and so it’s harder for them to deliver and enforce their promises in these kind of international agreements. Protocols.
Montezca: This is not a skeptic. This is a fact. The amount of fossil fuel burning is or has been fundamental to our economy around the world for many years, right? And so, trying to address this problem, trying to change things in a way that reduces the emission of carbon into the atmosphere – this will likely involve fairly central aspects of our economy, our energy production system and our infrastructure. So, yeah, it’s been more difficult, there’s no doubt about that.
It is important to remember that this chemical industry in the 1980s was not a small industry. They weren’t necessarily on board right away; The people who discovered this issue, and who eventually won the Nobel Prize, faced a lot of criticism at first, and industry was part of that. But eventually, the industry saw the light, and for whatever reason, for good reasons and undoubtedly financial reasons, they eventually joined the industry. When they came on board, it made a huge difference.
sun: Are there any other connections you would like to make between these major global environmental issues?
Montezca: I think there is a relationship between ozone depletion and climate that we haven’t really talked about. It is the fact that most of the ozone-depleting gases that have been used historically have also been powerful greenhouse gases. Overall, the Montreal Protocol has resulted in significant reductions in ozone-depleting gases, as well as greenhouse gas emissions.
There has been a huge climate benefit… (from) fluorocarbons being banned. The most recent amendments to the Montreal Protocol concerned chemicals that actually did nothing to deplete the ozone layer. The only negative effect it had was that it was still a fairly strong greenhouse gas. The Kigali Amendment to the Montreal Protocol was agreed in 2016. It provided for the phase-down of the current generation of ozone-depleting chemicals as an alternative to HFCs, to ensure that the benefits provided by the Montreal Climate Protocol would be sustained.