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更新日期:2011/04/13 05:00 洪美惠

週三, 2011-04-13 05:00 — 洪美惠 本文摘譯自2011年4月7日ENS日内瓦，瑞士報導；張桂芳編譯，蔡麗伶審校

        世界氣象組織（WMO）於本月5日公佈，由於地球大氣層中臭氧耗損物質持續存在，以及同溫層出現極度低溫，致使北極上空臭氧層流失的情形，於今年春季創下前所未有的記錄。

        世界氣象組織表示，儘管今年冬天北極的地面溫度高於平均溫度，然而北極上空的同溫層溫度卻比往年冬季更冷。所謂同溫層，也譯作平流層，只比最貼近的地表的對流層高一層，約在距離地表上空10公里至50公里的高度之間。

        該聯合國機構表示，不論是從北極地區的地表監測站、北極上空的熱氣球測站、或是從監測衛星得到的資訊均顯示，自今年入冬到3月下旬，北極地區的臭氧氣柱流失率約為40%。在此之前，整個冬天的最高破損率記錄為30%左右。

        世 界氣象組織秘書長雅羅（Michel Jarraud）表示：「北極同溫層對臭氧層耗損物質造成的破壞性仍相當脆弱，而這些耗損物質和人類活動脫不了關係。」他還指出：「任一冬季的臭氧層流失 程度取決於當年當季的氣象條件。2011年的臭氧層流失現象，提醒我們必須保持警覺，密切注意未來幾年內北極地區的情況。」

        就南極的狀況而言，由於同溫層持續呈現極低溫的狀況，以至於南極臭氧破洞成為每年冬春季的經常性現象。

然而就北極地區而言，此區每年的氣象狀況差異極大，其上空溫度總是比南極高，有時一整個冬天都沒有臭氧流失的狀況，但有時若極低溫持續超過一個「極夜」（polar night，或稱永夜，夜長等於一個太陽日），則可能導致臭氧大量流失。

        今年4月5日，俄羅斯西北部和部分斯堪地那維亞半島地區即曝露在臭氧破洞範圍之下，在此情況下，保護人們免受紫外線輻射傷害的臭氧總量，只剩下不到200陶柏森（Dobson Units，臭氧計量單位）。

        雅羅指出，儘管各國政府按《蒙特婁議定書》對造成臭氧層耗損物質加以限制，並成功降低此類化學物質相關生產和消費，但仍無法阻止空前的臭氧層流失現象。

        目 前像氯氟碳化物（CFCs）、海龍（halons）等過去曾用於冰箱、噴霧罐和滅火器等器具的化學物質，在議定書的規範下都已逐步禁用。世界氣象組織指 出：「若沒有《蒙特婁議定書》的規範，今年臭氧層層遭到的破壞極可能更嚴重。臭氧層恢復緩慢的主因，乃是由於造成臭氧層耗損的物質在大氣中停留時間為幾十 年。」

Arctic Ozone Hole Largest in History

GENEVA, Switzerland, April 7, 2011 (ENS)

        Ozone loss over the Arctic has reached a record level this spring due to the continuing presence of ozone-depleting substances in Earth's atmosphere and extremely cold temperatures in the stratosphere, the World Meteorological Organization announced on Tuesday.

        Even though this Arctic winter was warmer than average at ground level, it was colder in the stratosphere than for a normal Arctic winter, the WMO says. Just above the atmospheric layer closest to Earth, known as the troposphere, the stratosphere starts at an altitude of about 10 kilometers (six miles) and reaches up to an altitude of about 50 km (30 miles).

        Observations from the ground and from balloons over the Arctic region as well as from satellites show that the Arctic region has suffered an ozone column loss of about 40 percent from the beginning of the winter to late March, the UN weather and climate agency says.

        The highest loss previously recorded was about 30 percent over the entire winter.

        "The Arctic stratosphere continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities," said WMO Secretary-General Michel Jarraud.

        "The degree of ozone loss experienced in any particular winter depends on the meteorological conditions. The 2011 ozone loss shows that we have to remain vigilant and keep a close eye on the situation in the Arctic in the coming years," he said.

        In Antarctica the ozone hole is an annually recurring winter-spring phenomenon due to the existence of extremely low temperatures in the stratosphere.

        In the Arctic the meteorological conditions vary much more from one year to the next and the temperatures are always warmer than over Antarctica. Some Arctic winters experience almost no ozone loss, whereas cold stratospheric temperatures in the Arctic lasting beyond the polar night can lead to substantial ozone loss.

        This year, northwest Russia and parts of Scandinavia were under an ozone hole on April 5, protected from harmful ultraviolet radiation by less than 200 Dobson Units of ozone.

        Jarraud notes that the record ozone loss has occurred despite the success in cutting production and consumption of ozone-destroying chemicals chalked up by governments under the Montreal Protocol on Substances that Deplete the Ozone Layer.

        Substances such as chlorofluorocarbons (CFCs) and halons, once present in refrigerators, spray cans and fire extinguishers, have been phased out under the protocol. "Without the Montreal Protocol, this year`s ozone destruction would most likely have been worse," the WMO said in a statement. "The slow recovery of the ozone layer is due to the fact that ozone-depleting substances stay in the atmosphere for several decades."

全文及圖片詳見：ENS報導