Science of Summer: After damage from gases, our ozone layer is 'healing'
By Tom Spears
First posted: Wednesday, July 27, 2016 02:55 PM EDT | Updated: Wednesday, July 27, 2016 05:19 PM EDT
This summer brings a happy answer, from one of the foremost ozone scientists in the wordl.
This summer, Postmedia’s Tom Spears brings you the often offbeat science behind the season that calls us to go outdoors. It’s a series we call the Science of Summer. Today he looks at an environmental disaster that is slowly turning into a victory.
I was in school back in 1974 when two California scientists published a study with the prosaic title "Stratospheric sink for chlorofluoromethanes." Sherwood Rowland and Mario Molina had discovered that the upper atmosphere is where this class of industrial gases (and a related group called chlorofluorocarbons, or CFCs) goes to die, and this rewrote our understanding of how air works.
It was revolutionary stuff. For the first time, we knew that the structure of our atmosphere itself was vulnerable.
CFCs were used everywhere in refrigerators, air conditioners and spray cans. The industrial gas had replaced ammonia in fridges because while ammonia cools well (it’s still used on the International Space Station) it can leak out and kill people.
CFCs are harmless at ground level. But not, as it turned out, to the ozone layer in the stratosphere, where the chlorine-based molecules break apart one ozone molecule, move to the next, break it apart too, and keep going for years.
The ozone layer makes life on land possible by filtering out some of the sun’s UV radiation. And when the Antarctic ozone hole appeared, there was a sense that we were in deep trouble and didn't know what to do about it.
Except we did. The Montreal Protocol of 1987 was a promise signed by most of the world’s countries to stop using CFCs, and the amazing thing is that the signatories kept their promises.
Spray cans went first, mostly even before the ban. Refrigerants went later, but today’s fridges and the AC in your car are free of CFCs.
But was it too late? Once you make a part of Earth’s atmosphere go away, can you ever get it back?
This summer brings a happy answer, from one of the foremost ozone scientists in the world, Susan Solomon of the Massachusetts Institute of Technology.
There wasn’t a lot of attention paid when she published her latest work in the journal Science in early July. But she found the “first signs of healing” in the biggest ozone hole, the one over Antarctica.
The Antarctic hole forms because of conditions down there. Ozone destruction happens at the fastest rate in deep cold where there is also sunlight.
Late in the Antarctic winter, in August, the sun returns and the southern continent's air is still at its coldest. The result is a rush of ozone destruction, and the hole grows through September and reaches its peak in October. It can be half the size of the lower 48 U.S. states.
Solomon has found that in recent years, the September growth of the hole is not as great as it used to be. The hole is still there, but it’s not the monster it was. It has in fact shrunk by more than four million square kilometres since 2000.
I like how she explained it to reporters: "We can now be confident that the things we've done have put the planet on a path to heal. Which is pretty good for us, isn't it?
"Aren't we amazing humans, that we did something that created a situation that we decided collectively, as a world, 'Let's get rid of these molecules'? We got rid of them, and now we're seeing the planet respond.”
The significance goes beyond our best defence against ultraviolet light. There is a common belief that humans will destroy the planet and that there is nothing we can do, or will voluntarily do, to prevent this. Sometimes, it seems, we really can do the right thing.
tspears@postmedia.com
twitter.com/TomSpears1
In this false-colour image, the ozone hole of 2013 is shown in blue. (NASA)
Science of Summer: After damage from gases, our ozone layer is 'healing' | World
By Tom Spears
First posted: Wednesday, July 27, 2016 02:55 PM EDT | Updated: Wednesday, July 27, 2016 05:19 PM EDT
This summer brings a happy answer, from one of the foremost ozone scientists in the wordl.
This summer, Postmedia’s Tom Spears brings you the often offbeat science behind the season that calls us to go outdoors. It’s a series we call the Science of Summer. Today he looks at an environmental disaster that is slowly turning into a victory.
I was in school back in 1974 when two California scientists published a study with the prosaic title "Stratospheric sink for chlorofluoromethanes." Sherwood Rowland and Mario Molina had discovered that the upper atmosphere is where this class of industrial gases (and a related group called chlorofluorocarbons, or CFCs) goes to die, and this rewrote our understanding of how air works.
It was revolutionary stuff. For the first time, we knew that the structure of our atmosphere itself was vulnerable.
CFCs were used everywhere in refrigerators, air conditioners and spray cans. The industrial gas had replaced ammonia in fridges because while ammonia cools well (it’s still used on the International Space Station) it can leak out and kill people.
CFCs are harmless at ground level. But not, as it turned out, to the ozone layer in the stratosphere, where the chlorine-based molecules break apart one ozone molecule, move to the next, break it apart too, and keep going for years.
The ozone layer makes life on land possible by filtering out some of the sun’s UV radiation. And when the Antarctic ozone hole appeared, there was a sense that we were in deep trouble and didn't know what to do about it.
Except we did. The Montreal Protocol of 1987 was a promise signed by most of the world’s countries to stop using CFCs, and the amazing thing is that the signatories kept their promises.
Spray cans went first, mostly even before the ban. Refrigerants went later, but today’s fridges and the AC in your car are free of CFCs.
But was it too late? Once you make a part of Earth’s atmosphere go away, can you ever get it back?
This summer brings a happy answer, from one of the foremost ozone scientists in the world, Susan Solomon of the Massachusetts Institute of Technology.
There wasn’t a lot of attention paid when she published her latest work in the journal Science in early July. But she found the “first signs of healing” in the biggest ozone hole, the one over Antarctica.
The Antarctic hole forms because of conditions down there. Ozone destruction happens at the fastest rate in deep cold where there is also sunlight.
Late in the Antarctic winter, in August, the sun returns and the southern continent's air is still at its coldest. The result is a rush of ozone destruction, and the hole grows through September and reaches its peak in October. It can be half the size of the lower 48 U.S. states.
Solomon has found that in recent years, the September growth of the hole is not as great as it used to be. The hole is still there, but it’s not the monster it was. It has in fact shrunk by more than four million square kilometres since 2000.
I like how she explained it to reporters: "We can now be confident that the things we've done have put the planet on a path to heal. Which is pretty good for us, isn't it?
"Aren't we amazing humans, that we did something that created a situation that we decided collectively, as a world, 'Let's get rid of these molecules'? We got rid of them, and now we're seeing the planet respond.”
The significance goes beyond our best defence against ultraviolet light. There is a common belief that humans will destroy the planet and that there is nothing we can do, or will voluntarily do, to prevent this. Sometimes, it seems, we really can do the right thing.
tspears@postmedia.com
twitter.com/TomSpears1
In this false-colour image, the ozone hole of 2013 is shown in blue. (NASA)
Science of Summer: After damage from gases, our ozone layer is 'healing' | World
