巴拿馬，暴雨頻發(fā)，雨量不足

There is little doubt that climate change threatens Panama. Rising seas will submerge the low-lying Caribbean islands of San Blas, a tourist attraction and home to several thousand Guna, an indigenous group. Warmer temperatures will speed evaporation, and thus reduce water levels in Lake Gatun. But pinning blame for recent droughts on climate change is harder.

毫無(wú)疑問，氣候變化威脅著巴拿馬。海平面不斷上升，加勒比海上低海拔的圣布拉斯群島(San Blas)將被淹沒，這里既是旅游勝地，也是數(shù)千名土著古納人(Guna)的家園。氣溫升高將加速蒸發(fā)，進(jìn)而降低加通湖的水位。但越來(lái)越難將近年的干旱歸咎于氣候變化。

Panama’s worst droughts have happened during extreme occurrences of El Niño, a natural phenomenon in which warm water moves eastwards across the equatorial Pacific Ocean. Longer cycles like the Pacific Decadal Oscillation, which alternates every 20-30 years between warm phases that make El Niños stronger and more frequent and cooler ones, make the role of climate change harder to discern.

巴拿馬最嚴(yán)重的干旱都發(fā)生在極端厄爾尼諾現(xiàn)象期間，這是一種溫暖海水流向赤道東太平洋的自然現(xiàn)象。周期更長(zhǎng)的自然現(xiàn)象讓氣候變化的影響更難辨別。比如太平洋十年濤動(dòng)，其暖相位和冷相位的變換周期為20至30年，濤動(dòng)處于暖相位時(shí)厄爾尼諾現(xiàn)象會(huì)更強(qiáng)、更頻繁。

Residents of the capital do not doubt that changes are afoot. The rainy season once brought daily showers of three to four hours. Now the same amount of rain falls in an hour. Eight of the ten biggest storms in the city, measured by rainfall within 24 hours, have occurred since 2000. Despite those downpours, the canal area has had six straight years of below-average rainfall. The dry season is lengthening. This year it began a month earlier than usual and ended a month late. The current drought is the first severe one to occur in a mild El Niño year.

巴拿馬城的居民毫不懷疑即將發(fā)生的變化。過去，雨季每天有三到四個(gè)小時(shí)的降雨?，F(xiàn)在，一小時(shí)內(nèi)就有同等降雨量。巴拿馬城24小時(shí)內(nèi)降雨量最大的十次暴雨中有八次發(fā)生在2000年以后。盡管暴雨頻發(fā)，但運(yùn)河地區(qū)的降雨量已經(jīng)連續(xù)六年低于平均水平。旱季正在變長(zhǎng)。今年的旱季提前了一個(gè)月到來(lái)，又晚了一個(gè)月結(jié)束。當(dāng)前的干旱是首次在厄爾尼諾現(xiàn)象溫和的年份里發(fā)生的嚴(yán)重干旱。

This unprecedented concurrence suggests that climate change is directly responsible, the ACP believes. “To be completely sure you’d have to wait a hundred years,” notes Carlos Vargas, the ACP’s vice-president for water and environment. And even if climate change is not the culprit now, it may strengthen future El Niños, which would lengthen droughts and increase their intensity. Some scientists think that if, as expected, the equatorial eastern Pacific warms faster than other regions, extreme El Niños will double in frequency to once a decade by 2100.

ACP認(rèn)為，這種前所未有的并存現(xiàn)象表明氣候變化是直接原因。ACP水與環(huán)境事務(wù)副總裁卡洛斯·瓦爾加斯(Carlos Vargas)指出：“要百分百確定這一點(diǎn)還得等一百年。”而即使現(xiàn)在氣候變化還不是罪魁禍?zhǔn)?，它也可能在未?lái)加劇厄爾尼諾現(xiàn)象，讓干旱延長(zhǎng)并加重。一些科學(xué)家認(rèn)為，如果如預(yù)期的那樣，赤道東太平洋的升溫速度快于其他地區(qū)，那么到2100年，極端厄爾尼諾現(xiàn)象出現(xiàn)的頻率將翻倍，達(dá)到十年一次。

Water shortages imperil the canal’s expansion plans. In 2016 a new set of locks allowed the passage of NEOPANAMAX ships. The canal needs another upgrade to accommodate new “ultra-large” vessels. But work cannot start while water levels are so uncertain, ACP officials say.

水資源短缺危及運(yùn)河的擴(kuò)建計(jì)劃。2016年，一組新船閘建成，“新巴拿馬型”船只得以通行。為了能讓新的“超大型”船只通行，運(yùn)河還需要再次升級(jí)。但ACP的官員表示，水位如此不確定，無(wú)法開啟升級(jí)工作。

If droughts become frequent, shipping firms may favour more reliable routes between the Atlantic and Pacific oceans, such as rail lines across the United States. Someday, climate change could open up for navigation the ice-clogged Northwest Passage through the Arctic. That would cut by about 4,000km (2,500 miles) the length of a journey from Shanghai to New York, which is 19,500km via Panama.

如果干旱頻發(fā)，船運(yùn)公司可能會(huì)選擇大西洋和太平洋之間更可靠的路線，例如穿越美國(guó)的鐵路。未來(lái)，經(jīng)過北極冰封海域的西北航道可能會(huì)因氣候變化變得適于通航。屆時(shí)，從上海到紐約的航程將減少約4000公里，而經(jīng)巴拿馬運(yùn)河需航行1.95萬(wàn)公里。

To secure the canal’s future, the ACP has to plan now. “We cannot go back to what we had in the past,” says Mr Vargas. Already the ACP has stopped producing hydroelectricity from the Gatun dam. It is studying ways to raise water levels, including by digging a third artificial lake to supply Panama city and piping water from the Indio river to Lake Gatun. “They’re going to have to do all of them,” says Merei Heras, a former environment minister, sipping a drink in a café as rain pelts down. Deepening Lake Gatun is not an option because the mountains nearby would collapse.

為了確保運(yùn)河的未來(lái)，ACP必須立即制訂計(jì)劃。瓦爾加斯說：“我們沒法再回到從前。”ACP已經(jīng)停止了加通大壩的水力發(fā)電，現(xiàn)在正在研究提高水位的方法，包括挖掘第三個(gè)人工湖為巴拿馬城供水，以及從印第奧河(Indio)向加通湖送水。“這些項(xiàng)目都得上。”前環(huán)境部長(zhǎng)梅雷·赫拉斯(Merei Heras)在咖啡館里啜著一杯飲料說，外面大雨如注。加深加通湖是行不通的，因?yàn)楦浇纳襟w會(huì)崩塌。

Drought-proofing the canal will be disruptive, forcing people to move and hurting habitats down-river from water-diversion projects. Panama’s only answer to the global havoc caused by climate change, it seems, is to do local damage.

給運(yùn)河做防旱工程將產(chǎn)生破壞性后果，迫使人們搬遷，損害引水工程下游的自然環(huán)境?？磥?lái)，巴拿馬運(yùn)河應(yīng)對(duì)氣候變化造成的全球性破壞的唯一辦法就是在當(dāng)?shù)馗闫茐摹?/p>