Good News: Earth's Ozone Hole is Healing
There is big news about the environment: Scientists say a hole in Earth's protective ozone layer is starting to heal.
A new study confirms the hole is getting smaller. A report on the study was published late last month in the journal Science.
The scientists say the reason for the improvement is a reduction in the release of man-made chemicals into Earth's atmosphere. These chemicals are called chlorofluorocarbons or CFCs for short.
"It's a big surprise," said Susan Solomon, the lead writer of the report. "I didn't think it would be this early," she said.
Solomon is an atmospheric chemist and works at the Massachusetts Institute of Technology.
Ozone is a form of oxygen gas. It is found in the air we breathe and in the upper atmosphere. Near Earth, ozone in the air is a danger to life. It is a pollutant. But the ozone layer, 10 to 50 kilometers up in the atmosphere, protects life on Earth. It helps to block dangerous ultraviolet (UV) waves from the sun. It stops them from reaching the planet's surface.
Researchers first discovered the hole in the ozone layer over Antarctica more than 30 years ago.
The new report credits the shrinking ozone hole to a worldwide ban on chlorofluorocarbons.
CFCs once were commonly used in many products, including aerosols, cleaning substances, refrigerators and plastics. Scientists found that when released into the air, the chemicals damaged the ozone layer, creating the hole.
CFCs were banned when world leaders signed an agreement called the Montreal Protocol in 1987.
Susan Solomon compared the ozone hole to a patient that needs healing.
"It isn't just that the patient is in remission,'' Solomon said. "He's actually starting to get better. The patient got very sick in the ‘80s when we were pumping all that chlorine into the atmosphere."
Measurements taken in September showed the ozone hole has shrunk since the year 2000. The new numbers show that the hole is smaller by 4.5 million square kilometers. That is about half the area of the U.S. mainland.
One year was different, however. In 2015, the ozone hole got bigger, not smaller. After looking at scientific records, Solomon said that increase resulted from a natural event. She said it was caused by the eruption of the Calbuco volcano in Chile.
While the healing is coming earlier than many scientists expected, it is an ongoing, continuing process. The ozone hole will not be completely closed for at least another 30 years. Estimates are it will close by around 2050.
"We can now be confident that the things we've done have put the planet on a path to heal," Solomon said.
"There is a sense of ‘mission accomplished,''' said Mario Molina in an email to VOA. Molina works at the University of California, San Diego. He shared the 1995 Nobel Prize for Chemistry for his research on the ozone issue. He praised this latest study, but was not involved in it.
Not-so good news
However, there is other news about Antarctica that is not as good.
For the first time in four million years, Antarctica registered carbon dioxide (CO2) levels above the level of 400 parts per million. That information comes from U.S. scientists at the National Oceanic and Atmospheric Administration (NOAA).
"The far southern hemisphere was the last place on earth where CO2 had not yet reached this mark," of 400 parts per million (ppm), said Pieter Tans. He is the lead scientist of NOAA's Global Greenhouse Gas Reference Network.
"Global CO2 levels will not return to values below 400 ppm in our lifetimes, and almost certainly for much longer," he said.
Scientists say too much CO2 causes temperatures on Earth to rise.
CO2 levels usually go up in colder months. In the warmer months, plants in the northern hemisphere use some of it, and that lowers the levels. But NOAA notes that plants are not enough to stop the rise of CO2 levels. Those levels have risen every year since 1958, when measurements began.
Tans said that evidence shows that the CO2 increase is caused "entirely by human activities." These activities include burning oil and other fossil fuels for energy.
Because the burning of fossil fuel has been at a record high during the last several years, Tans said, the rate of CO2 increase has also been at a record high. He said some of the gas will stay in the atmosphere for thousands of years.
I'm Anne Ball. And I'm Bryan Lynn.
1.ozone layer 臭氧层
Media reports dubbed the annual thinning a hole in the ozone layer.
2.oxygen gas 氧气
Ozone is a highly reactive form of oxygen gas.
3.take in 吸收；领会
They both take in and expel matter.
4.carbon dioxide 二氧化碳
Carbon dioxide is converted into oxygen through the agency of plants.
1.CO2 levels usually go up in colder months.
go up 增长；上升
Shall we go up the stairs or take the lift?
This article is bound to go up in price.
2.He praised this latest study, but was not involved in it.
involved in 涉及；卷入
He is involved in gambling and prostitution rackets.
He never gets involved in unprincipled disputes.
最新研究已证实臭氧空洞正在缩小 。相关报告刊登在了上月底的《科学》杂志上 。
科学家称，臭氧空洞的改善得益于人类向地球大气层排放的人造化学物质的减少 。这种化学物质为氟氯化烃（CFC） 。
首席作者Susan Solomon写道：“这着实让人吃惊 。没想到情况好转得如此之快 。”
臭氧属于氧气的一种 。我们呼吸的空气及高层大气中都含有臭氧 。地球周边空气所含的臭氧对人类有害 。它是一种污染物 。而位于10-50千米高空的臭氧层却能够保护地球 。臭氧层可以阻挡太阳释放的有害紫外线，避免其照射地球表面 。
30多年前，研究人员首次在南极上空发现了臭氧层 。最新报道称，臭氧空洞缩小是因为全球禁止氟氯化碳排放 。
很多产品都含有CFCs，包括气溶胶、洗涤产品、冰箱以及塑料制品 。科学家发现，CFCs释放到空气里会破坏臭氧层造成臭氧空洞 。
Susan Solomon将臭氧空洞当做一名需要治愈的患者 。
Solomon说道，“患者症状不但出现缓解，而且逐渐好转 。当80年代的我们将氯化物排向大气层时，这名患者岌岌可危 。”
9月份采集的一份测量数据显示，2000年开始，臭氧空洞出现了缩减 。最新数据也显示，臭氧空洞缩减了450万平方千米 。约美国本土面积的一半 。
然而，有一年情况出现反转 。2015年臭氧空洞不缩反扩 。调查后发现，臭氧空洞扩大归咎于一次自然灾害 。这是由智利卡尔布科火山爆发引起的 。
臭氧空洞缩减比科学家预期的时间要早的多，这是一个不间断的持续过程 。臭氧空洞完全修复至少还需30年 。预计2050年臭氧层才能恢复正常 。
Mario Molina发给VOA的一封邮件中提到：“我们有一种‘完成使命’的感觉 。”Mario Molina在圣地亚哥加利福尼亚大学工作 。他凭借臭氧研究获得1995年诺贝尔化学奖 。他对最新的研究表示赞赏，虽然他本人并未参与 。
400万年来，南极洲二氧化碳的水平首次超过了千分之零点四 。这一数据由国家海洋与大气治理署（NOAA）的科学家提供 。
“全球只剩下南半球南部的二氧化碳尚未达到此水平 。”Pieter Tans说道 。他是NOAA全球温室气体参考网络的首席科学家 。
二氧化碳含量在寒冷月份时增长较快 。而在气候适宜的月份，北半球的植物会消耗一些二氧化碳从而降低了二氧化碳含量 。但NOAA指出，利用植物降低二氧化碳含量作用有限 。1985年起对二氧化碳含量测量至今，该含量一直呈上升趋势 。
Tans称，有证据表明二氧化碳含量增加完全是因人类活动造成的 。包括为了能源燃烧石油或化石燃料 。
Tans说道，过去几年间，化石燃料的使用已经达到史上最高水平 。二氧化碳的增长率也达到历史记录 。据说，有些气体会在大气层中停留数千年 。
我是安妮·波尔 。我是布莱恩·林恩 。