stratospheric ozone
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How smoke from Australia’s megafires ate away at the ozone
Wildfire smoke can change the chemistry of the stratosphere, resulting in chlorine molecules that deplete the ozone layer
insideclimatenews.org
Recent megafire smoke has reached the stratosphere, threatening earth’s ozone shield
Scientists researching how the recent spike in extreme wildfires affects the climate say that just a few weeks of smoke surging high into the stratosphere from one intense fire can wipe out years of progress restoring Earth’s life-protecting ozone layer. Close study of Australia’s intense Black Summer fires in late 2019 and early 2020 suggests […]
www.nytimes.com
In a high-stakes environmental whodunit, many clues point to China
Scientists say new production of a banned industrial chemical is damaging the ozone layer. Investigations by The Times and an independent environmental group lead to factories in China.
Someone, somewhere, is making a banned chemical that destroys the ozone layer, scientists suspect
It's an ozone mystery, as well as a threat to one of the planet's great environmental success stories.
Liberals struggling to reverse Harper's cuts to climate science in Canada.
Scientists are questioning whether the Trudeau government's funding decisions will result in science being served to the best it could be over the long term.
Liberals struggling to reverse Harper's cuts to climate science
By Carl Meyer in News | September 5th 2017
Environment and Climate Change Minister Catherine McKenna tells reporters at an Aug. 31 event in Gatineau. Que. that the Liberal government wants to recognize the “very important work” of scientists. Photo by Alex Tétreault
Five years ago, climate change scientists said they were in the midst of a severe funding crisis.
For more than decade, they had benefited from tens of millions of dollars in federal funding, which allowed Canada’s academic leaders to build a robust research network that pioneered significant breakthroughs. An independent organization, the Canadian Foundation for Climate and Atmospheric Sciences, evaluated their project proposals and allocated the federal dollars for a wide range of research topics.
It led to many groundbreaking studies across the country on drought, extreme weather, permafrost and more. But it was all about to end, because former prime minister Stephen Harper's government had decided to turn off the financial taps.
Scientists started speaking out.
In the face of mounting public pressure, Harper’s government introduced a new program with dedicated funding for climate change research, outside of federal departments, providing a temporary solution.
But now, with that money drying up, many scientists say it’s all happening again, putting several environmental monitoring programs, including those tracking key climate change indicators, in jeopardy.
Budgets for seven key independent projects are set to expire, including the Polar Environment Atmospheric Research Laboratory (PEARL) — arguably the most important Arctic research lab in the world.
“There does seem to be a strong element of history repeating itself here,” said James Drummond, a professor from the Department of Physics and Atmospheric Science at Dalhousie University in Halifax, who has led research at the Arctic lab.
“The PEARL facility nearly went under in 2013 — in fact, we were within a few weeks of starting the shutdown when we got new funding. The problem is now repeating itself, since we will run out of funding early in 2018 and there seems to be no prospect of any additional funding.”
Prime Minister Justin Trudeau’s Liberals swept into power in the 2015 election with a promise to put scientific evidence at the heart of government decisions. But despite the rhetoric from Liberals about paying attention to science and making climate change a key priority, the Trudeau government continues to struggle in its efforts to rebuild what was lost during the Harper era.
Even if PEARL gets new funding today, there will still be gaps in data, noted Katie Gibbs, executive director of Evidence For Democracy, a non-profit group that advocates for government decisions based on evidence.
Katie Gibbs, executive director of Evidence For Democracy, said the PEARL Arctic research lab, which is powered by funding about to expire at the end of the year, is a "one-of-a-kind research facility." Photo courtesy of Evidence For Democracy on Facebook
Canada's academics are still recovering
“It’s a one-of-a-kind research facility,” Gibbs told National Observer, speaking about PEARL. “It’s the most northern Arctic research centre studying atmospheric change in the world.
"So this is not just important to Canadian science, it’s absolutely important to global science and I think it also represents the role that Canadians science can play in international research, especially around arctic science and arctic issues.”
Even so, she said, gaps in the data are still preferable to no data, and Evidence For Democracy would still like to see new funding announced immediately.
Kimberly Strong, a physics professor at the University of Toronto who has worked at PEARL validating data for a satellite ozone monitoring instrument, also said it will take another year to get a program in place.
That's in addition to the lead time between the announcement of any funding program and actually getting calls out for proposals, she said — not to mention getting peer review in place, and other typical steps in the funding process for research.
Thomas Pedersen, a professor from the school of earth and ocean sciences at the University of Victoria, intimately knows what research is now in jeopardy.
He's the chairman of the Canadian Climate Forum, which emerged from the ashes of the Canadian Foundation for Climate and Atmospheric Sciences after it was starved of its funding between 2012 and 2013. He said the Harper government’s funding choices “resulted in a decline in climate-research support of nearly 50 per cent nationwide.”
The academic community has yet to recover, he added, despite the Trudeau government “being much more progressive in facing the immense climate change challenge.”
“As a nation, we must do better in supporting research on the physics of our changing planetary climate, on adapting to what will be — and already is — a different future, and reaching out more vigorously to Canadians to make the case that dealing with the climate challenge presents us with immense new-economy opportunities.”
The PEARL lab in 2008. Christos Zerefos, president of the International Ozone Commission, said there are “uncomfortable feelings” in the ozone scientific community about the future of the polar ozone research program. PEARL photo
Scientists want long-term commitment
As PEARL and other environmental monitoring projects face their potential demise, Canada plays host this week to a prestigious gathering of the Intergovernmental Panel on Climate Change (IPCC), featuring scientists and government officials from around the world.
And later in the month, the world will celebrate the 30th anniversary of the Montreal Protocol, a monumental treaty that changed the course of history by shifting humanity’s damage to the ozone layer into reverse gear.
Environment and Climate Change Minister Catherine McKenna, who will open the IPCC conference this week in Montreal, said in an interview that the Liberal government wants to recognize the “very important work” of scientists in government as well as in academic institutions.
“It has been a top priority of mine to ensure that we have capacity, that we are rebuilding capacity of our scientists that we’re working with other groups, with other organizations, and that's certainly been a key priority," she said Aug. 31, after unveiling a new website designed to engage children on climate change.
"I spent a lot of time in the Arctic this summer, where we’re seeing the impacts of climate change. We opened a new laboratory, research station, in the high Arctic. We need to understand better the impacts of climate change there, and the acceleration of climate change, and I’m working with my colleagues across government.”
Gibbs of Evidence For Democracy has noted that the new federal Arctic lab, announced by the Harper government, is 1,200 kilometres south of PEARL and won’t be able to do the same level of monitoring and research.
All in all, many scientists, contacted by National Observer for this article said the government was missing a key issue: creating a stable environment for long-term research. Public and private sector scientists in Canada and researchers abroad say what’s needed now is long-term monitoring of the protective ozone layer in the upper atmosphere, as well as the smog-inducing ozone near the surface.
“You need to look at the ozone layer for 10, 20 years,” said Wolfgang Steinbrecht, a scientist at Germany's national meteorological service who did his doctorate in Toronto and worked at PEARL.
“Canada is playing a part, but it could play a bigger part," he added. "That will take a long-term commitment.”
The climate forum, Pedersen said, has also recognized that “outreach efforts nationally must be strengthened,” but he said “realizing them will require support, and that remains an unfilled need.”
Thomas Duck. Photo from Thomas Duck
Thomas Duck, an associate professor in Dalhousie's physics and atmospheric science department, said “it boggles the mind that the federal government would consider ending funding” for PEARL. National Observer file photo
Ending funds for Arctic lab 'boggles the mind'
Ottawa has not yet announced that funding for the Climate Change and Atmospheric Research (CCAR) program, which supports PEARL and six other projects, will be renewed after it runs out at the end of the year.
Personnel at the lab are already looking elsewhere for work, and money has been set aside to help with the logistics of closing up shop, said University of Toronto's Strong.
“CCAR is really what’s funding most of the science,” she said. “It’s not clear where people can go to keep the funding going for these projects... we’re certainly not getting any indications that there’s a delayed announcement, or there will be an announcement.”
Officials point to other funds set up by the government, and say researchers are free to apply to those, but it’s unclear how quickly that money can start flowing.
“Right now we’re taking measurements as normal, but sometime next year, we’ve got a little bit of money put aside to shut things down, and if there’s nothing to keep us going” the lab will find it hard to stay open, she said.
The situation is leading a string of prominent scientists to raise concerns. Christos Zerefos, president of the International Ozone Commission, said there are “uncomfortable feelings” in the scientific community studying ozone.
“We have strongly supported... that the Canadian government should continue funding the polar ozone research program,” he told National Observer.
Environment and Climate Change Canada scientist David Tarasick, who has spent over 30 years in the department, also called the move surprising. The CCAR programs, he said, “gave quite a boost to atmospheric science.”
"There doesn’t seem to be anything in the wings right now," he said in an interview. "That kind of surprises me, because usually, something else comes along. Otherwise, how do you fund all the people who are halfway through their careers?"
Thomas Duck, an associate professor in Dalhousie's physics and atmospheric science department, said “it boggles the mind that the federal government would consider ending funding” for PEARL.
“This represents a lot of lost scientific capacity, which impedes scientific progress,” he said, adding the end of CCAR will be “devastating.”
"PEARL is definitely not something that everybody has," added Steinbrecht. "If I was the minister, I would say, 'This is something where we’re strong, so let’s stay strong in that.'"
Science Minister Kirsty Duncan's office says the Trudeau government is “taking a comprehensive approach" to addressing climate change, "including significant investments" in research. Photo by Alex Tétreault
New centre 'not intended to replace' climate fund
Trudeau has appointed an award-winning scientist to his cabinet, after winning the 2015 election to address issues like these.
But the office of Trudeau’s point person on ensuring evidence-based decisions, Science Minister Kirsty Duncan, declined an interview with National Observer for this story.
An official from the ministers office, speaking on background, said the government understands that "the most up-to-date evidence is necessary to mitigate the harmful effects of climate change,” and is “taking a comprehensive approach to addressing this important issue, including significant investments in climate change research across government."
The official pointed to the most recent federal budget’s announcement of $73.5 million for a new Canadian Centre for Climate Services — part of a $260-million pot to implement government commitments on adaptation and climate resilience.
But that new climate services program was "not intended to replace" the program running out of money, confirmed Marissa Harfouche, a spokeswoman for Canada’s federal environment department, which will administer the new program.
"The details of the CCCS are not yet finalized. However, the planned focus of this centre is not research, but rather the sharing of climate-related information," she explained.
Harfouche said the centre will instead "work with provincial, territorial, Indigenous and other partners to make it easier for governments, communities, decision-makers, businesses and organizations to access data and information on climate science, and help support climate adaptation decision-making across the country."
The official in Duncan's office also noted the government's $40-million commitment to the National Research Council to "integrate climate resilience into building codes that will help prepare communities for the effects of climate change." Investments like that, the official said, "serve as proof of our government's commitment to addressing the threat posed by climate change in a concrete and comprehensive way."
Duncan’s press secretary, Ann Marie Paquet, also pointed out that Duncan has two upcoming science-related announcements in British Columbia this week: one connected with a hydrogen radio telescope, and another on the Natural Sciences and Engineering Research Council’s Discovery (NSERC) Discovery Grants Program, which Paquet called “the biggest science funding announcement of the year.”
“We are a government that believes in science and evidence, and we are certainly seeing clear signs that the planet is warming at a rate that is very concerning and that we all need to be working together,” Environment Minister Catherine McKenna told National Observer last week. She is seen here at a federal government announcement on Aug. 31, 2017. Photo by Alex Tétreault
NSERC says researchers can compete for fresh funding elsewhere
Lucy Lai, media and public affairs officer for NSERC, which has been running the expiring climate fund, said researchers supported by its dollars can compete for fresh funding through NSERC’s “existing suite of programs, many of which support climate science research.”
Two NSERC programs Lai pointed to are the Discovery grants, which Duncan will be announcing this week, and its Strategic Partnership grants. In addition, she said, the Networks of Centres of Excellence of Canada is hosting a funding competition that is open until Nov. 15.
The organization has four networks that support environmental research: ArcticNet at Université Laval; the Green Aviation Research and Development Network in Montreal; the Marine Environmental, Observation, Prediction and Response Network at Dalhousie University; and the Ocean Networks Canada Innovation Centre in Victoria.
ArcticNet’s current funding began in 2003 and appears to be wrapping up next year, according to NSERC’s website. Current funding for the centre in Victoria began in 2009 and also ends next year, the website indicates, while the green aviation network's funding has been running from 2009 and ends in two years. The Dalhousie centre's current batch of funding is set to run out in 2021.
Based on what its ministers are saying publicly, there’s no doubt that the Trudeau government understands the importance of research projects like these.
“We are a government that believes in science and evidence, and we are certainly seeing clear signs that the planet is warming at a rate that is very concerning and that we all need to be working together,” McKenna told National Observer last week.
“That’s scientists from across the globe, and Canadian scientists, and scientists from all the countries around the world, making sure that we have good science and that we’re making those decisions based on science, and that we’re all working together to really understand the impacts of climate change. We’re seeing extreme weather events, floods, hurricanes, droughts, all over the world. So we all need to be working together.”
National Observer also asked NSERC for a list of government programs outside their council that CCAR scientists can apply for.
In response, NSERC suggested a “sampling” of other government programs that Lai said, “may provide CCAR scientists with alternative funding opportunities” — as long as those scientists are eligible to apply and were competitive candidates.
These programs are the following: a climate change geoscience program at Natural Resources Canada; funded projects at Fisheries and Oceans Canada on oceans and freshwater; a greenhouse gases program and research initiatives at Agricultural and Agri-Food Canada; POLAR Knowledge Canada science and technology research projects; and funding programs at Environment and Climate Change Canada.
Environment Minister Catherine McKenna said an international ozone monitoring conference in Geneva, Switzerland this spring went off without any “negative feedback” for Canada. Photo by Alex Tétreault
Long-term data questioned at another initiative
National Observer reported last month on another example of long-term data that scientists say may be in jeopardy.
Tarasick, the Environment Canada scientist, gave advice to his superiors in 2015 recommending that an ozone monitoring station closed during the Harper era be re-opened. The Liberals say that's still being considered two years later.
That station and another remain closed, and other management changes remain in place, despite Trudeau personally attacking the Conservatives over those decisions when in opposition.
That means long-term data isn’t getting collected, said Tarasick. “It’s a real problem for the scientific community,” he said. Tarasick has recently published peer-reviewed research that made use of earlier data from the stations that were shut down.
“It’s really important to have stable funding, [so] that they can invest in themselves without always looking over their shoulder to where the next meal may be coming from,” he said.
It’s all too familiar for Steinbrecht, who has seen the PEARL lab stopped and started again due to the end of the climate and atmospheric sciences foundation.
“They usually have a program, they pour in a lot of money, they have a grad student do something for two or three years, and then when that is used up, that’s it,” he explained. “That happened when we were there, and it’s happened two or three times in the meantime.”
Meanwhile, Canada continues to tout the lab in international circles. In a presentation to an international ozone monitoring conference in Geneva, Switzerland this spring, Canada’s report labelled the funding-plagued polar lab as a “very well-used and equipped facility.”
McKenna's office has said that this meeting went off without any “negative feedback” for Canada.
However, the meeting did result in one recommendation suggesting that Canada could improve monitoring by submitting more data of UV radiation on a timely basis. This type of data is collected using a type of monitoring device invented by Canadians, called Brewer spectrophotometers.
Everybody has resource constraints, said Environment Canada’s Tarasick.
"My impression overall is that, since we essentially solved the ozone depletion issue with the Montreal Protocol, there isn’t the same level of public interest, and there isn’t the same level of funding and consequence.”
Drummond, the scientist from Dalhousie University, said Canada has a long way to go to catch up to the rest of the world.
“I am in South Africa at the moment in a major conference on atmospheric issues," he said, "and I have to say that Canada is not very present at this conference. I can only look on with envy at research programs in Europe, Asia, Africa, and South America — to say nothing of the United States, which put our programs to shame."
— with files from Mike De Souza
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Court ruling on HFCs deals another blow to Paris climate goals.
A U.S. court ruled the EPA lacked authority to regulate the powerful greenhouse gases, used for cooling and refrigeration. Industry had supported the regulations.
A U.S. court ruled the EPA lacked authority to regulate the powerful greenhouse gases, used for cooling and refrigeration. Industry had supported the regulations.
Marianne Lavelle
BY MARIANNE LAVELLE
FOLLOW @MLAVELLES
AUG 9, 2017
Hydrofluorocarbons, or HFCs, are potent greenhouse gases that have been used as coolants. Less damaging alternatives are available today. Credit: Alex Livesey/Getty Images
The federal appeals court's ruling this week striking down an Obama-era rule on air conditioning and refrigeration gases deals another significant blow to hopes of the U.S. reaching its target under the Paris climate accord.
The 2015 rule would have restricted the manufacturing of products containing hydrofluorocarbons, or HFCs. It was an important building block of the U.S. climate commitment, because HFCs are hundreds to thousands of times more potent than carbon dioxide at trapping heat in the atmosphere, though they have a shorter life span.
The rule had the potential to slash U.S. greenhouse gas emissions by as much as the equivalent of 72 million metric tons of carbon dioxide by 2025, according to an analysis by scientists at Lawrence Berkeley National Laboratory. That's equal to the pollution of 21 coal-fired power plants, or about 4 percent of the cuts that the United States needed to meet its goal under the Paris climate agreement.
And the U.S. had committed to go even further in reducing HFCs. At a meeting in Kigali, Rwanda, last October, the U.S. was one of nearly 200 countries that agreed to update the Montreal Protocol to phase out HFCs. The Berkeley lab scientists calculated even larger emissions reductions from the steps that were agreed to at Kigali—as much as 88 million metric tons by 2025 in the U.S.
Together with the rule struck down by the court, the U.S. commitment at Kigali would have fulfilled 9 percent of the U.S. pledge under the Paris accord.
It is not clear how the court ruling will affect U.S. efforts to implement the Kigali amendment, but it shows that at least some judges think the Environmental Protection Agency needs more specific authority from Congress to act on HFCs.
That could be a problem in the current Congress. The Trump administration has given no indication of whether it intends to bring the Kigali amendment before the Senate for ratification. (Sen. James Inhofe, R-Okla., has indicated he would oppose ratification. He says he sees it as an effort to shoehorn climate change policy into a treaty that was meant to address ozone depletion.)
U.S. Industry Leaders Supported the Rule
The rule to phase out HFCs was a climate change policy from former President Barack Obama's administration that many believed would survive the Trump era. Donald Trump's administration defended the rule in court, with the backing of two large U.S.-based chemical manufacturers that have invested heavily in alternatives that are less damaging to the atmosphere—DuPont spinoff Chemours and Honeywell International.
But in its ruling this week, a panel of the United States Court of Appeals for the District of Columbia Circuit found 2-1 in favor of two foreign HFC manufacturers—Mexichem Fluor of Mexico and France-based Arkema—holding that the EPA had no authority to regulate the gases under the Clean Air Act.
HFCs came into use as a replacement for an earlier generation of refrigeration gases, chlorofluorocarbons, or CFCs, that depleted the ozone layer of the atmosphere and were phased out under another international agreement, the 1987 Montreal Protocol. The EPA had sought to curb HFCs under a section of the law that implemented the protocol and phased out CFCs; the agency took HFCs off the list of safe alternatives due to their properties as greenhouse gases.
But because HFCs are not ozone-depleting gases, the court said the EPA cannot use that section of the law to phase them out.
"EPA's authority to regulate ozone-depleting substances ... does not give EPA authority to order the replacement of substances that are not ozone depleting but that contribute to climate change," wrote Judge Brett Kavanaugh, an appointee of President George W. Bush. "Congress has not yet enacted general climate change legislation."
"Although we understand and respect EPA's overarching effort to fill that legislative void and regulate HFCs... Here, EPA has tried to jam a square peg (regulating non-ozone depleting substances that may contribute to climate change) into a round hole (the existing statutory landscape)," he wrote. Kavanaugh was joined by Judge Janice Rogers Brown, a Bush appointee, in the majority. Judge Robert Wilkins, an Obama appointee, dissented, saying that the EPA was due deference for what he said was a reasonable interpretation of the statute.
'We Cannot Go Backward'
Policymakers around the world have focused on how to reduce HFCs, which have become the fastest-growing source of climate emissions as air conditioning and cooling have increased. They have the potential to cause up to half a degree Celsius of warming by 2100.
David Doniger, director of the climate and clean air program at the Natural Resources Defense Council, which intervened on the side of EPA, said the environmental group was exploring all options for appeals.
"The fact is, safer, climate-friendlier alternatives are readily available and should be used more to help cool our overheating world," he said in a statement. "It's also true that the U.S. has been a leader in advancing HFC alternative technologies. ... We cannot go backward, or the climate damage suffered by the American people will only magnify."
An EPA spokesperson said the agency is reviewing the ruling.
Separate Ruling Further Delays Clean Power Plan
The D.C. Circuit Court delivered a separate blow to the Obama climate legacy on Tuesday when it decided to extend its stay of litigation over the Clean Power Plan while the Trump administration works to repeal the rule. Environmental groups, health groups, and states have pressed the court not to wait, but to allow the case, which was argued before Trump took office, to proceed to a ruling on EPA's authority.
For now, the Circuit Court was unwilling to take that step, although two of the judges, Clinton-appointee David Tatel, and Obama-appointee Patricia Millett, in a concurrence, remarked that extending the 60-day stay in litigation, at the same time that the Supreme Court has stayed the rule itself, "has the effect of relieving EPA of its obligation to comply with that statutory duty for the indefinite future." But the judges said any challenge of the Supreme Court's stay would have to be decided by the Supreme Court. The high court is in recess until October.
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Scientists may have just found an unexpected new threat to the ozone layer.
New research suggests that frequent summertime storms in the Great Plains region could be depleting the protective ozone layer in the upper atmosphere, putting humans at increased risk of unhealthy exposure to ultraviolet radiation.
Lightning strikes in Denton, Tex., in May 2015. (Al Key/Denton Record-Chronicle via AP)
Severe storms over the central United States may be posing bigger problems beyond bad weather. New research suggests that frequent summertime storms in the Great Plains region could be depleting the protective ozone layer in the upper atmosphere, putting humans at increased risk of unhealthy exposure to ultraviolet radiation. And some scientists believe that climate change could make the situation worse.
The study, published this week in the Proceedings of the National Academy of Sciences, builds on a groundbreaking 2012 paper that was among the first of its kind to tackle ozone loss over the United States. According to lead author James Anderson, an atmospheric chemist at Harvard University, most previous studies have focused on the poles, where the icy temperatures are well suited for the chemical reactions that lead to ozone depletion. In fact, the famous “ozone hole” — a massive deterioration of ozone in the atmosphere spurred by industrial pollution and discovered in the 1980s — largely occurred over the Antarctic.
The Antarctic ozone hole finally appears to be recovering — mostly thanks to an international agreement called the Montreal Protocol, which prompted major global efforts to curb the emissions of chlorofluorocarbons, the chemicals that cause ozone to break down in the atmosphere. But ozone-destroying chemicals still linger in the atmosphere, and depletion still occurs on smaller scales. Recent studies have found a new “hole” in the Arctic being carved by leftover atmospheric pollutants.
And now, scientists say this process is not necessarily limited to the poles. The new study suggests that the right conditions — including chilly upper-air temperatures previously thought to exist only in the Arctic and Antarctic — occur in the United States as well.
In the past, this idea has drawn its share of scientific skepticism. But the latest version is apparently being taken seriously by none other than Mario Molina, one of the researchers who won a Nobel Prize in 1995 for his co-discovery of the threat to the ozone layer.
“These developments were not predicted previously and they represent an important change in the assessment of the risk of increasing UV radiation over the central U.S. in summer,” Molina said in a statement.
For ozone depletion to occur, a set of specific conditions is necessary. Certain chemicals must be present in the atmosphere — namely chlorine, one of the major components of chlorofluorocarbons, which can chemically react with ozone and break it up into other molecules. These chemical reactions also require the presence of water vapor, and they occur more quickly at lower temperatures.
Although these conditions are known to occur at the poles, scientists were skeptical until recently that enough water vapor was capable of rising into the stratosphere — the layer of the atmosphere where ozone is found — in the area over the United States, or that temperatures there could dip low enough. But the basis for the new study was finally laid several years ago, according to Anderson, when researchers discovered that some storm systems in the Great Plains were indeed capable of forcing water vapor all the way up into the stratosphere. Anderson and several colleagues published evidence of this phenomenon in their 2012 paper.
“That’s what triggered our first concern,” Anderson told The Washington Post. “And then the question became, well, how frequent are these storms? Do we have 100 a year? Do we have 50?”
In fact, the new study suggests that the region sees a whopping 4,000 of these storms on average each summer. An analysis of radar data from the central United States suggested that nearly 40,000 storms extended more than a mile into the stratosphere between 2004 and 2013. The researchers also examined summer temperature measurements from the stratosphere in this region and found that they were much colder than scientists had previously believed.
“In fact, those temperatures border on the same temperatures we see in the Arctic stratosphere,” Anderson said. This combination of conditions — low temperatures and water vapor being frequently injected into the stratosphere — “make the situation far more serious than we originally thought,” he added. They suggest that the region is prime territory for the destruction of ozone, meaning there’s possible concern for public health. The depletion of ozone allows for greater penetration of ultraviolet radiation through the atmosphere, putting humans at an elevated risk of developing cancer.
Following the publication of the original 2012 paper, some experts expressed the idea that chlorine levels in the atmosphere weren’t high enough for large amounts of ozone depletion to occur over the United States, according to Andrew Dessler, an atmospheric scientist at Texas A&M; University who was previously a PhD student under Anderson. But he noted that the new study incorporates observed atmospheric chlorine measurements in a model suggesting these depletion reactions can indeed take place under the conditions observed over the Great Plains.
That said, chlorine pollution in the atmosphere is also steadily decreasing, thanks to the Montreal Protocol. And some scientists say it’s likely that by the end of the century, chlorofluorocarbon levels will have returned to their pre-ozone-hole conditions. This means the threat of ozone depletion will probably continue to diminish in the coming decades.
This raises the question of how diminishing pollution levels and progressing climate change interact with each other in the future. In the new paper, Anderson and his colleagues suggest that climate change may significantly alter weather patterns over the central United States, potentially causing more of these storm systems to occur, and also that by cooling the stratosphere it could favor chemical reactions that deplete ozone.
“There’s a rapidly growing scientific literature connecting the increase in carbon dioxide and methane with the increasing number and severity of storm systems over the central United States,” Anderson said.
But Dessler cautioned that the reductions in atmospheric chlorine may lessen the impact of these potential future storms. “In 50 years, we might be having more water being injected, but the amount of chlorine is lower,” he said. “I don’t think it’s obvious that climate change combined with decreasing chlorine is going to make this process more important as time goes on.”
Still, pointing out the possibility that climate change could have an effect is part of what launched Anderson’s 2012 research into the spotlight in the first place. Previously, scientists had been adamant about keeping a clear separation between the pollution-related destruction of ozone and the long-term warming of the climate, which are physically caused by different mechanisms — the first by chlorofluorocarbons and the latter by carbon dioxide and other greenhouse gases.
According to Anderson, the next research step is to start tackling the uncertainties and verifying the chemical reactions that the authors say may be destroying ozone over the United States. And in the meantime, any immediate concerns about public health should be addressed with regular — perhaps weekly or even daily — UV forecasts for vulnerable regions, he suggested.
“It’s really surveillance and watching the system continuously and carefully with very high spatial resolution that provides what people will need,” he said.
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