How do you solve a problem like the ozone layer? In 1989, we thought we were well on the way with the Montreal Protocol, which directly addressed the growing hole in the ozone layer and took steps to reduce the pollution associated with it. The goal was to help the ozone layer recover, but as it turns out, this has been a slow process, and one marked by ups and downs as well. In other words, the path to recovery is far from over — in fact, scientists estimate that we’re at least 50 years away from having a fully recovered ozone layer, and that’s assuming we do everything right.
But we banned the use of ozone-depleting compounds, right? So how come the ozone layer isn’t perking back up? Well, it’s a complicated story.
For starters, it took years and in some cases decades to fully phase out harmful chemicals — asthmatics like me, for example, may remember that CFC inhalers were in use long after 1989, and in fact many tout the fact that they’re CFC-free because the change is still so new. Furthermore, some chemicals aren’t so easily dispatched (that’s why you have to be responsible when you dispose of old refrigerators and air conditioners). So although the treaty laid the groundwork for getting rid of the chemicals leading to the destruction of the ozone layer, which is a very good thing, it didn’t magically eliminate them.
Even worse, some of them lingered in the atmosphere for years, even after bans started to take effect and nations got into compliance. Pollutants have a funny way of sticking around where they’re not wanted, and the atmosphere hosts a whole slew of bad guys; part of the reason why global climate change is occurring is because of complex chemical interactions in the atmosphere, some of which are caused by pollutants or imbalances in normal chemical levels. Think of it this way: CO2 is holding a party with atmospheric mercury, and they really want to TP your house.
For that reason, NASA estimates that we won’t actually start to see solid signs of recovery in the ozone layer until at least 2025. The ozone hole is leveling out around now, thanks to the Montreal Protocol, and we’re going to start to see a downward trend around 2015, but it will take another ten years, or more, to confirm that trend, and along the way, the ozone layer may waver, because nature doesn’t always do exactly what we want it to do. NASA puts an estimate of the final recovery date between 2058 and 2090, meaning that many of us will never live to see the ozone layer restored to its former glory, and we’re counting on the work of others to follow through when it comes to protecting the environment.
NASA and other agencies keep a very close eye on the ozone hole and what it’s up to, because they want up-to-date information for purposes like issuing sunburn warnings, monitoring overall trends in ozone levels and comparing information day to day to learn more about how the atmosphere behaves. You can follow the ozone hole at a site they maintain for this purpose, where you should be able to see that the size and nature of the ozone hole has shifted over time, rather than trending steadily up or down in an easily-followed trajectory. This explains why researchers are uncertain about when, precisely, we’ll have the ozone layer under control.
Their work also must include the larger issue of global climate change, caused in part by buildups of CO2, a compound that can linger for centuries, in the atmosphere. This and other greenhouse gases are a looming threat for the planet’s long-term health as well as our own.
Image: 2010 and 2011 ozone surveys over the Arctic illustrate the fluctuation in ozone levels over time. Credit: NASA.