After a decadeslong ban on harmful ozone-depleting chemicals, the ozone layer is finally healing. Could this be a model for tackling other environmental problems like climate change?
Image: picture-alliance/EFE/F. Trueba
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Finally, some good environment news: The Earth's protective ozone layer has been healing at a rate of around 2 percent since 2000, and could be completely healed by the middle of the century.
That's according to a United Nations report that praised the rate of success, which it attributed to the historic 1987 Montreal Protocol's ban on chlorofluorocarbons (CFCs) and other ozone-depleting substances.
If the current reductions in ozone-depleting emissions are sustained, the Northern Hemisphere could be healed by the 2030s and the Southern Hemisphere healed by the 2050s, the report detailed.
The hole above Antarctica, which was once as large as North America, could be completely recovered by the 2060s, the report found.
The 30th meeting of parties to the Montreal Protocol recently wrapped up in Ecuador with a unanimous decision to strengthen its enforcement.
Had it not been for the global agreement, much of the Earth's ozone layer would have been destroyed by 2065.
That would have had devastating consequences as the ozone layer protects life on the planet from the sun's damaging ultraviolet light, which causes skin cancer and cataracts in humans and other animals.
This bodes well in terms of the global community coming together to solve a planetary crisis, but some ozone problems still lurk on the horizon.
The ozone hole over the Antarctic demonstrated to the world the global effects of human activity on the atmosphereImage: NASA's Goddard Space Flight Center/Katy Mersmann
Mysterious spike in emissions
Although, the Montreal Protocol successfully reduced the release of ozone-depleting substances, researchers had been baffled by a slowdown in reductions of one particular gas, CFC-11.
The Environmental Investigation Agency (EIA) last July uncovered the source: China (also a party to the Montreal Protocol).
Posing as buyers, investigators with the London-based green group found that 18 factories in China were still manufacturing banned CFCs for sale as plastic foam in the booming construction sector because they were cheaper.
The EIA said several companies across China admitted to exporting CFCs by mislabeling them as hydrofluorocarbon (HFC) compounds. The Chinese government has since pledged to shut down those factories.
"If these CFC-11 emissions had continued at this level, the recovery of the Antarctic ozone hole would be delayed seven to 20 years," Paul Newman, co-chairman of the recent UN ozone layer report and chief Earth scientist at NASA's Goddard Space Flight Center, told DW.
Both HFCs and CFCs are key chemicals used in cooling devices. But now HFCs are coming under fire too. Though once marketed as an environmentally friendly alternative to CFCs since they don't deplete ozone, HFCs were later discovered to be a greenhouse gas thousands of times more powerful than carbon dioxide.
The recently agreed Kigali amendment to the Montreal Protocol targets HFCs and other ozone-depleting gases, yet is also expected to help curb climate change. The amendment will go into effect at the start of 2019.
Montreal Protocol as model
Despite gains on the ozone front, scientists remain concerned about the integrity of the Montreal Protocol.
"Any increase in ozone-depleting chemicals, as we have seen with CFC-11, risks damaging not just the work of the last 30 years — but also the reputation of the Montreal Protocol, and the potential it holds for the future," United Nations Environment Program spokesperson Keith Weller told DW.
The Montreal Protocol is the only UN treaty that has been ratified by all 197 member statesImage: picture-alliance/dpa
"The Montreal Protocol is one of the most successful multilateral agreements in history for a reason: The careful mix of authoritative science and collaboration resulted in the positive prognosis for the ozone that we see today," he added.
Not only did the protocol serve to curb emissions, but it shines as a positive example of what people can accomplish for global environmental good, he said.
Yet, healing the ozone can also have negative side effects.
Healed ozone, warmer Antarctic?
Warmer temperatures are expected in the Antarctic because an intact ozone layer traps slightly more heat.
Although scientists aren't sure exactly how much a healed ozone layer would increase temperatures over Antarctica, they do know that warming would impact the area that is already suffering from human-caused climate change.
Penguins are among diverse Antarctic wildlife threatened by climate changeImage: Imago/alimdi
Controlling greenhouse gas emissions would counteract a rise in global temperatures, benefiting the climate, Newman said.
"While climate change and ozone depletion are separate problems, there are some interesting overlaps," he pointed out.
If nations comply with the Kigali Amendment of the Montreal Protocol, "controlling HFCs will reduce climate warming of about 0.5 degree Celsius [0.9 degrees Fahrenheit] by 2100," Newman said.
Top 10 cities with the largest carbon footprint
Cities contribute a large part of global carbon emissions — a new model shows 100 urban centers make up 18 percent of emissions around the world. DW looks at the world's least climate-friendly cities.
Image: picture-alliance/AP/Joseph Nair
10. Riyadh, Saudi Arabia
The largest city in Saudi Arabia is also the most polluted, mainly due to its industrial activity. Looking at 13,000 cities, researchers found that highly populated centers contributed a major part of countries' total emissions. Large urban areas use up more than 70 percent of the world's total energy — meaning metropolises hold the power to change the global climate situation.
Image: picture-alliance/AP Photo/M. Schreiber
9. Greater Tokyo Area, Japan
Only about 2 percent of new cars sold in Japan's capital are environmentally friendly. The Tokyo-Yokohama urban area, with the world's largest urban population, emits a massive amount of CO2 every year — 62 million tons for Tokyo alone. But the recent adoption of the Tokyo Declaration gives some hope: 22 global megacities have committed to tackling air pollution and promote zero-emission vehicles.
Image: picture-alliance/dpa/M. Tödt
8. Chicago, United States
It's the third-most-populous city in the US, and it also has the third-largest carbon footprint. Pollution in the Chicago metropolitan area increased significantly between 2014 and 2016, according to a study by the American Lung Association. Chicago has also been ranked as the third-dirtiest US city. Any guess as to the other two?
Image: picture-alliance/AA/B. S. Sasmaz
7. Singapore
The many industries in this city-state are behind most of its CO2 emissions; the manufacturing sector will account for 60 percent of its emissions by 2020. But the government has realized it's time to act, and declared 2018 the year of climate action. It has also announced a carbon tax on highly polluting facilities. Singapore is also a main importer of sand — a scarce natural resource.
Image: picture-alliance/AP/Joseph Nair
6. Shanghai, China
It isn't surprising to find Shanghai in this ranking, as it's among the world's most populated cities. Congestion there has led to serious environmental problems, including air and water pollution. As in many other Chinese cities, power plants and nonstop traffic are the main causes for its carbon emissions. That's why it isn't uncommon to see people wearing masks as they move through the city.
Image: picture-alliance/Imaginechina/Z. Yang
5. Los Angeles, United States
Not everything in LA is like in the movies. The city's air quality has been ranked as the worst in the US. But California has set ambitious targets to reduce greenhouse gas emissions by 40 percent by 2030, using clean energy and supporting electric or hybrid cars. California Governor Jerry Brown has taken a leading role in the fight against climate change, opposing the Trump administration.
Image: picture-alliance/Bildagentur-online/Rossi
4. Hong Kong, China
The autonomous territory in southeastern China is densely populated; thousands of vehicles clog its roads, and coal-fired power plants and polluting industries spew smog into the air. In addition, its cargo shipping sector is responsible for up to 50 percent of the city's carbon emissions, according to its Environmental Protection Department.
Image: picture alliance/dpa/L. Xiaoyang
3. New York, United States
The most populous city in the US takes the bronze medal for carbon footprint. In January, the iconic metropolis sued the world's five largest oil companies — BP, Chevron, ConocoPhillips, ExxonMobil and Royal Dutch Shell — for their contribution to climate change and its effects on the city. The city has been intensively working to reduce its emissions, but still has a lot of work to do.
Image: picture-alliance/Sergi Reboredo
2. Guangzhou, China
In China's third-most populous city, factories and vehicles are continuously emitting harmful emissions. Smog is an everyday occurrence. But Guangzhou has committed to replacing its entire fleet of fossil-fuel powered buses and taxis with pure electric vehicles by 2020, after major campaigns by environmental groups such as Greenpeace.
Image: CC/Karl Fjellstorm, itdp-china
1. Seoul, South Korea
Seoul is the world's top city when it comes to carbon footprint. Air pollution is its biggest environmental and health concern: More than 30,000 tons of harmful pollutants are emitted from just 10 old coal-fired power plants, accounting for around 20 percent of South Korea's total pollution. In recent years, the city has suspended plant operations in an effort to tackle the problem.
