Seas Are Rising at Fastest Rate in Last 28 Centuries
By JUSTIN GILLISFEB

The worsening of tidal flooding in American coastal communities is largely a consequence of greenhouse gases from human activity, and the problem will grow far worse in coming decades, scientists reported Monday.

Those emissions, primarily from the burning of fossil fuels, are causing the ocean to rise at the fastest rate since at least the founding of ancient Rome, the scientists said. They added that in the absence of human emissions, the ocean surface would be rising less rapidly and might even be falling.

The increasingly routine tidal flooding is making life miserable in places like Miami Beach; Charleston, S.C.; and Norfolk, Va., even on sunny days.

Though these types of floods often produce only a foot or two of standing saltwater, they are straining life in many towns by killing lawns and trees, blocking neighborhood streets and clogging storm drains, polluting supplies of freshwater and sometimes stranding entire island communities for hours by overtopping the roads that tie them to the mainland.

Such events are just an early harbinger of the coming damage, the new research suggests.

“I think we need a new way to think about most coastal flooding,” said Benjamin H. Strauss, the primary author of one of two related studies released on Monday. “It’s not the tide. It’s not the wind. It’s us. That’s true for most of the coastal floods we now experience.”

In the second study, scientists reconstructed the level of the sea over time and confirmed that it is most likely rising faster than at any point in 28 centuries, with the rate of increase growing sharply over the past century — largely, they found, because of the warming that scientists have said is almost certainly caused by human emissions.

They also confirmed previous forecasts that if emissions were to continue at a high rate over the next few decades, the ocean could rise as much as three or four feet by 2100.

Experts say the situation would then grow far worse in the 22nd century and beyond, likely requiring the abandonment of many coastal cities.

The findings are yet another indication that the stable climate in which human civilization has flourished for thousands of years, with a largely predictable ocean permitting the growth of great coastal cities, is coming to an end.

“I think we can definitely be confident that sea-level rise is going to continue to accelerate if there’s further warming, which inevitably there will be,” said Stefan Rahmstorf, a professor of ocean physics at the Potsdam Institute for Climate Impact Research, in Germany, and co-author of one of the papers, published online Monday by an American journal, Proceedings of the National Academy of Sciences.

In a report issued to accompany that scientific paper, a climate research and communications organization in Princeton, N.J., Climate Central, used the new findings to calculate that roughly three-quarters of the tidal flood days now occurring in towns along the East Coast would not be happening in the absence of the rise in the sea level caused by human emissions.

人為暖化 海平面倍數上升

最新研究指出，由於人為的全球暖化，地球海平面上升的速度是過去2800年的數倍。

一群國際科學家在全球20餘個地點，測量數百年和數千年來海平面的起落。他們發現，直到1880年代和全球工業化後，海平面在一世紀內上升約1至1.5吋（2.5至3.8公分）。在此期間，全球海平面的變化較諸之前2000年平均海平面上升或下降不到3吋。

但到20世紀，全球海平面上升5.5吋（14公分）。他們有九成五的把握確信，其中一半肇因於全球暖化。

自1993年起，海平面上升速度為每世紀上升一呎（30.48公分）。美國國家科學院學報22日刊登的兩項不同研究指出，到2100年，全球海洋的水位將上升到11至52吋（28到131公分），視地球上工業和汽車排放廢氣造成的溫室效應有多大而定。

羅格斯大學大氣地球科學教授卡普說：「毫無疑問，20世紀海平面上升最快速。因為在20世紀，石化燃料的使用使氣溫上升。」

卡普領導的研究探索了過去3000年海平面的變化。卡普和同僚為數世紀海平面起落繪製圖表時，發現海平面有下降趨勢，直到工業革命為止。20世紀海平面上升大半是人為所致。

卡普和他人進行的另一不同研究發現，自1950年代開始，美國27處海岸洪災約三分之二是人為氣候暖化造成。

德國波茨坦氣侯影響研究中心的研究作者之一拉斯托夫表示，海平面若如預期繼續上升18吋（45公分），將造成許多問題和財物損失，尤其是風暴造成的漲潮。

自19世紀以來，全球氣溫約升高攝氏一度，去年更創下自1880年有可靠紀錄以來最熱的一年。研究認為，過去10年的海平面上升，海水溫度升高及範疇擴大是原因之一。

即使人類馬上停止汙染大氣層，並遵守去年12月巴黎氣候會議決議，將全球升溫控制在與工業化前相比、不超過攝氏兩度以內，海平面在本世紀仍可能再上升9吋到24吋（23至61公分），恐導致部分地區出現大洪水，並波及其他地區。

原文參照：
http://www.nytimes.com/2016/02/23/science/sea-level-rise-global-warming-climate-change.html

紐約時報中文版翻譯：
http://cn.nytimes.com/science/20160224/c24climate/zh-hant/

2016-02-23．聯合晚報．A6．國際焦點．國際新聞組