VOA慢速英语--联合国报告称地球臭氧层愈合中

United Nations Report Says Earth’s Ozone 1 Layer Is Healing

A new study says the protective layer of the Earth’s atmosphere is finally healing from damage by humans’ use of harmful chemicals.

Aerosol 2 sprays and coolants had been thinning the ozone layer since the 1970s. After scientists raised concerns about ozone-reducing chemicals, people and companies around the world stopped using them.

What is the ozone layer?

Ozone is a colorless combination of three oxygen atoms. The ozone layer starts at about 10 kilometers above Earth and stretches nearly 40 kilometers higher. The ozone layer is important because it protects Earth from the sun’s ultraviolet rays, which cause skin cancer, crop damage and other problems.

But man-made chemicals – called chlorofluorocarbons, or CFCs – can damage the ozone layer. In 1987, countries around the world agreed in the Montreal Protocol 3 to end the use of CFCs over time.

What the study shows

The United Nations released a study on the effects of the decreased use of CFCs at a conference in Quito, Ecuador in early November.

The study found that the upper ozone layer above the Northern Hemisphere should be completely repaired in the 2030s. The huge Antarctic ozone hole should disappear in the 2060s. The Southern Hemisphere should be healed by about the 2050s, the study showed.

Paul Newman is the chief Earth scientist at NASA’s Goddard Space Flight Center and co-leader of the study. He told the Associated Press the findings are good news.

“If ozone-depleting 4 substances had continued to increase, we would have seen huge effects,” said Newman. “We stopped that.”

Newman noted 5 that, at its worst in the late 1990s, about 10 percent of the upper ozone layer was depleted 6. Since 2000, the ozone layer has increased by about 1 to 3 percent every ten years, the report said.

This year, the ozone hole over the South Pole measured nearly 24.8 million square kilometers in area. That is about 16 percent smaller than the biggest hole recorded — 29.6 million square kilometers in 2006.

The hole reaches its largest size during September and October, when the Southern Hemisphere has its spring. The hole disappears by late December.

If nothing had been done to stop the thinning, the world would have destroyed two-thirds of its ozone layer by 2065, Newman said.

But the changes are not a complete success yet, said a University of Colorado atmospheric 7 science professor. Brian Toon, who was not part of the report, pointed 8 to some ozone measurements that have not increased yet.

“We are only at a point where recovery may have started,” said Toon.

The report noted another problem: New technology has found that a banned CFC is being used in East Asia.

How has the hole in the ozone layer affected 9 global warming?

On its own, the ozone hole has slightly helped protect Antarctica from the effects of global warming. Ross Salawitch is a University of Maryland atmospheric scientist who helped write the report. He said an undamaged ozone layer would actually trap greenhouse gases that cause global warming. Antarctica has heated up, but not as much as it likely would without the decrease of the ozone layer.

Salawitch said scientists do not know how much a healed ozone hole will continue to warm Antarctica. But they do know that decreasing the ozone layer would severely 10 damage the world and human health. Not permitting the ozone layer to heal “would be incredibly irresponsible,” he said.

NASA’s Paul Newman points to another step humans can take: The chemicals that have replaced CFCs need to be replaced with chemicals that do not worsen global warming. An amendment 11 to the Montreal Protocol that goes into effect next year would cut some of those gases.

“I don’t think we can do a victory lap until 2060,” Newman said. “That will be for our grandchildren to do.”

I’m Pete Musto.

Words in This Story

layer – n. an amount of something that is spread over an area

aerosol spray(s) – n. a substance that is kept in a container under pressure and that is released as a stream of very small drops when a button is pressed

coolant(s) – n. a liquid that is used to cool an engine or machine

ultraviolet ray(s) – n. rays of light that cannot be seen and that are slightly shorter than the rays of violet light

hemisphere – n. a half of the Earth

depleting – v. greatly reducing the amount of something

greenhouse gas(es) – n. any gas that adds to global warming by trapping infrared 12 radiation

replace(d) – v. to be used instead of something

amendment – n. a change in the words or meaning of a law or document

victory lap – idm. a celebratory act