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Ozone Layer Protection Essay Checker

The ozone hole over the Antarctic has begun to heal, according to a new study, more than 30 years after its discovery. The findings suggest that global efforts to phase out ozone-depleting chemicals have been effective, though scientists still aren't entirely sure about what's driving the ozone hole's recovery.

The study, published in the journal Science, combines data gathered from balloons and satellites to measure the area of the ozone layer over Antarctica from 2000 to 2015. Since 2000, the paper reports, the size of the ozone hole over Antarctica shrank by about 4 million square kilometers — an area equivalent to about half of the contiguous United States. Using computer simulations to account for changes in wind and temperature, the study's authors estimate that about half of its reduction can be attributed to a decline in levels of the ozone-depleting gases chlorine and bromine.

The stratospheric ozone layer protects Earth from the sun's harmful ultraviolet (UV-B) rays, which can cause skin cancer and cataracts in humans, and physiological damage in animals and plants. Faced with growing evidence of ozone depletion, governments in 1987 ratified the Montreal Protocol, a global treaty that aimed to phase out the production of harmful chemicals known as chlorofluorocarbons (CFCs). At the time, CFCs were used in hairspray, aerosol cans, and refrigerators. A single CFC molecule can last for between 20 and 100 years in the atmosphere, and can destroy100,000 ozone molecules.


Previous studies have shown that the rate of ozone depletion has declined since the Montreal Protocol went into effect, and a 2014 United Nations report showed that Earth's ozone layer has begun to heal. But the ozone hole over the Antarctic reached a record size in 2015, casting some doubt over claims of a recovery, and the UN report said it was still unclear whether healing in the Antarctic could be attributed to a decline in ozone-depleting gases. Susan Solomon, professor of atmospheric chemistry and climate science at MIT and lead author of the study published this week, says her findings suggest that the Montreal Protocol has in fact worked.

"We are beginning to see clear signs that actions that society took to phase out chlorofluorocarbons are actually having the intended effect of beginning to heal the Antarctic ozone layer," Solomon says, stressing that the recovery is still in its early phases. "It's really a remarkable achievement for society," she adds. "It's a global environmental problem, and we have put ourselves on a good trajectory."

The ozone hole appears over Antarctica every year and is usually at its largest during October, as the continent transitions from winter to summer. Previous studies used that month as a benchmark for measuring the hole's size, but Solomon and her colleagues focused instead on September because the Antarctic weather is historically less variable, making it easier to isolate the effect of chlorine and bromine, which deplete ozone. In the process, they found that the Antarctic ozone hole is opening later in the year, another sign that it is healing. They also found that seemingly anomalous observations of very large holes, as in 2015, could be attributed to volcanic eruptions, which deplete ozone by releasing sulfates into the atmosphere.

A satellite image of the ozone hole over Antarctica in October 2015, when it was at its largest. (NASA)

Paul A. Newman, chief scientist for atmospheric sciences at NASA's Goddard Space Flight Center, says the study raises important questions about what else is driving the recovery of Antarctica's ozone hole besides the decline in chlorine and bromine. He notes that the paper's ozone measurements still show a high level of variability, which Solomon and her colleagues attribute to weather effects. The authors say there is likely some interplay between declining chlorine levels and changes in Antarctic weather, though they have yet to quantify that relationship.

"You have to be able to explain the causes of the total trend," says Newman, who was not involved in the study. "Not just the half due to the ozone depleting substances."

Still, Newman believes that the study's findings provide further proof that experts were correct in sounding the alarm over ozone levels during the 1970s and 1980s. "We predicted this way back in the day — we scientists said this would happen, and we said that if you do something, things will eventually get better," he says. "And so this is the kind of thing that we've been looking for."

But the Montreal Protocol has had some negative consequences, as well. When countries began phasing out CFCs, manufacturers replaced them with hydrofluorocarbons (HFCs). HFCs don't deplete ozone, but they are potent greenhouse gases, which contribute to global warming. The challenge going forward, then, will be to develop new alternatives to HFCs — and to have the world adopt them, once again.

"That's going to be really interesting to see if the diplomatic community can manage that," Solomon says. "And what the technology community can do in terms of developing alternatives is obviously going to be very important."

Jonathan Shanklin, a meteorologist at the British Antarctic Survey, was one of three scientists who discovered the ozone hole over Antarctica in 1985. Their discovery spurred world leaders to ratify the Montreal Protocol two years later, and every country in the UN has now signed on to it. He says Solomon's findings are further proof that the treaty has been "astonishingly successful," though he never imagined that the work he did 30 years ago would lead to it.

"At the start, I didn't really think it was a terribly significant discovery," Shanklin says. "I thought it was some obscure fact of Antarctic meteorology and it might be interesting scientifically, but that would be the end of it."

"It has been really astonishing to me that that little discovery has unified the world's countries to really produce a measurable effect. And I only wish that they could unify in the same way over the many issues that affect the climate today."

Correction 3:10pm ET: A previous version of this article stated that the Ozone hole over Antarctica had shrunk by 4 million square miles. The correct measurement is in kilometers. The piece has been updated.


Miami may be underwater by 2100

Sometimes the world really can get together and avert a major ecological catastrophe before it's too late. Case in point: A new study in Science finds evidence that the Earth's protective ozone layer is finally healing — all thanks to global efforts in the 1980s to phase out CFCs and other destructive chemicals.

This is one of the great environmental success stories of all time. Back in the 1970s, scientists first realized that we were rapidly depleting Earth's stratospheric ozone layer, which protects us from the sun's harmful ultraviolet rays.

The culprit? Chlorofluorocarbons (CFCs), a chemical widely used in refrigerators and air conditioners. These chemicals had already chewed a massive "hole" in the ozone layer above Antarctica, and the damage was poised to spread further north.

Without the ozone layer's protection, more and more people would be exposed to UV rays. Skin cancer rates would have soared in many regions, as they already have in Punta Arenas, Chile, which lies under the existing ozone hole. Those UV rays would also harm crops and the marine food chain.

Fortunately, this apocalyptic scenario never came to pass. Scientists uncovered the problem in time. And under the 1987 Montreal Protocol, world leaders agreed to phase out CFCs, despite industry warnings that abolishing the chemicals would impose steep costs. The hole in the ozone layer stopped expanding. The global economy kept chugging along.

Now comes further good news. The latest study, conducted by scientists at MIT and elsewhere, identifies several "fingerprints" suggesting that the ozone layer is on its way toward actually healing. The researchers note that the annual ozone hole that appears above Antarctica in September has shrunk by some 4 million square kilometers since 2000, although there are ups and downs each year due to volcanic eruptions.

This 2014 video from NASA illustrates the healing process, showing the minimum concentration of ozone in the Southern Hemisphere each year from 1979 to 2013. The process is sluggish: The ozone layer kept thinning in the 1980s and 1990s, even after the big agreement to phase out CFCs. In 2006, another major hole appeared. But recently, the hole has started shrinking and ozone concentrations have started rebounding:

Back in 2014, a United Nations assessment projected that the ozone layer would fully recover by 2050. "There are positive indications that the ozone layer is on track to recovery towards the middle of the century," said UN Undersecretary General Achim Steiner. "The Montreal Protocol — one of the world's most successful environmental treaties — has protected the stratospheric ozone layer and avoided enhanced UV radiation reaching the earth's surface."

Granted, just because the world banded together and saved the ozone layer doesn't ensure that we’ll also do the same for future environmental problems, like global warming. It will almost certainly be harder to reduce our reliance on fossil fuels than it was to curtail our use of CFCs. (For one thing, the DuPont chemical company developed easy substitutes to CFCs fairly quickly.) But the ozone case remains the best example of international cooperation to halt a slow-moving ecological disaster. And it worked.

We barely dodged a bullet with the ozone layer

It's worth reflecting on what a close call we had with the ozone layer. Scientists in Antarctica first began measuring stratospheric ozone levels in 1957, but it still took decades to realize how dire the situation actually was. Indeed, when researchers found signs of severe ozone depletion in the 1970s, they initially thought their instruments were faulty.

It wasn't until 1974 that chemists Mario Molina and Sherwood Rowland published a paper proposing that rising concentrations of CFCs in the atmosphere could deplete the ozone layer. These stable chemicals were widely used as refrigerants and cleaning solvents. But when CFCs wafted up into the stratosphere, they got ripped apart by UV rays, and the free chlorine atoms would catalytically destroy the ozone there.

This hypothesis was difficult to prove, and it was fiercely disputed by DuPont, the world's biggest manufacturer of CFCs, for many years. But evidence kept accumulating, and by the 1980s scientists finally had incontrovertible proof that CFCs were to blame. That's also when the massive "hole" over Antarctica received widespread attention. (This hole is a severe thinning of the ozone column throughout the atmosphere during the spring and summer.)

We were lucky that the damage wasn't even greater by that point. DuPont had been using chlorine instead of bromine to create its refrigerants. The two elements were roughly interchangeable for this purpose; it just so happened that chlorine was cheaper. Yet, as Paul Crutzen later observed in his Nobel Prize acceptance speech, bromine is 45 times more effective at destroying ozone. Had DuPont used bromine, the ozone layer might have been damaged beyond repair long before anyone even noticed.

Fortunately, that didn't happen. Under the Montreal Protocol of 1987, the world's nations agreed to phase out the use of CFCs in refrigerators, spray cans, insulation foam, and fire suppression. By and large, countries complied. Atmospheric concentrations of chlorine have stabilized and have been declining slowly over time.

In their 2014 report, the UN panel noted that without that agreement, atmospheric levels of ozone-depleting substances might have increased tenfold by midcentury. The resulting ozone loss could have led to 2 million additional cases of skin cancer by 2030 — to say nothing of crop damage or other impacts.

Today, recovery is slow, since there's still chlorine lingering in the stratosphere. The Antarctic hole still appears every spring and summer, even reaching a record size in 2006. And it's not just Antarctica: An especially cold Arctic winter in 2011 led to an ozone hole up north, too.

But the broad picture is encouraging: The ozone layer is on track to bounce back to 1980 levels by around midcentury.

Unexpected side effects of the Montreal Protocol

Meanwhile, there have been a few unexpected side effects of this whole affair.

As a result of the Montreal Protocol, companies and countries stopped using CFCs and started using HFCs (hydrofluorocarbons), which have a much more benign effect on the ozone layer. That seemed like a satisfying solution — at least until global warming became a much more pressing concern.

Both CFCs and HFCs are potent greenhouse gases that help warm the planet. And on net, swapping out CFCs for HFCs reduced the overall amount of greenhouse gases in the atmosphere (making the Montreal Protocol unintentionally one of the biggest steps we've ever taken to prevent climate change).

But now HFCs are becoming a big climate problem in their own right, especially as air conditioning becomes more popular in fast-growing countries like China and India. HFCs are up to 10,000 times as effective as carbon dioxide at trapping heat, and their use is soaring.

"Hydrofluorocarbons (HFCs) do not harm the ozone layer but many of them are potent greenhouse gases," the UN panel noted in 2014. "They currently contribute about 0.5 gigatonnes of CO2-equivalent emissions per year. These emissions are growing at a rate of about 7 percent per year. Left unabated, they can be expected to contribute very significantly to climate change in the next decades."

Many environmental groups have urged world nations to revisit the Montreal Protocol and phase out HFCs in favor of chemicals that — like HFO-1234YF — that are both harmless to the ozone layer and don't warm the planet significantly.

In June 2016, the United States and India reached a side agreement to amend the Montreal Protocol in this fashion. The hope is to get a new international agreement late this year. Many companies in the United States, such as DuPont, Coca-Cola, and Target, have already pledged to shift away from using HFCs as refrigerants and toward more benign alternatives.

Further reading:

  • Roger Pielke Jr. once wrote a nice essay about why the Montreal Protocol isn’t a great template for efforts to tackle climate change. Relatedly, I wrote a piece here about how the success of the Montreal Protocol in the 1980s arguably led UN climate negotiators astray in trying to craft a similar treaty for global warming.
  • Back in June, the US and India agreed to tackle HFCs, a little-known (but potent) climate problem.

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