A new U.S. space agency study warns the Earth this century could see rapid and catastrophic climate changes if man-made global warming levels are allowed to reach an internationally-recognized so-called “safe limit” of two degrees Celsius.
The NASA researchers examined prehistoric climate conditions during past interglacial periods - the time between ice ages - and compared them with the interglacial period the Earth is currently experiencing. The last interglacial period ended around 115,000 years ago when temperatures were less than one degree Celsius warmer than today, and sea levels were six meters higher.
The scientists say looking at how the prehistoric climate responded to natural changes gives them more insight into determining a dangerous level of man-made global warming for today’s world.
NASA study leader James Hansen says the findings show that Earth’s climate is more sensitive than even recent estimates suggest. He described the notion of limiting man-made global warming to an increase of two degrees Celsius above pre-industrial levels as “a prescription for disaster.”
Recent studies, including those by NASA, indicate the average global surface temperature since 1880 has gone up 0.8 degrees Celsius and is on course to continue rising by 0.1 degrees every decade.
NASA researchers say global warming of two degrees Celsius would more closely match conditions of an interglacial period that occurred some five million years ago when seas were about 25 meters higher than today.
For decades, a two-degree Celsius rise above pre-industrial age levels in average global surface temperatures was considered a safe margin. Many scientists now advocate a threshold of one degree or less and say more has to be done to decrease global warming caused by human activity, such as burning fossil fuels.
Developing and wealthy nations, however, remain deeply divided over how to reduce man-made emissions of climate-changing greenhouse gases, especially carbon dioxide.
An interglacial geologic period, such as the one Earth is now having, occurs when the North and South Poles are frozen, but glaciers do not dominate the rest of the planet.Scientists call the current interglacial period the Holocene epoch. The previous interglacial period is known as the Eemian epoch.
prehistoric (a) 史前的
catastrophic (a) 災難的;激變的
insight (n) 洞悉;深刻的理解<~into>
determine (v) 下決定；決意
estimate (n) 估價
notion (n) 概念；觀念
prescription (n) 藥方
on course (phr) 持續的發生；繼續朝向...的方向進行 <~ for sth/ to V>
一份美國航太機構(space agency)的研究報告指出，如果放任人類造成的地球暖化達到所謂國際公認的「兩度C的安全範圍」(so-called internationally-recognized)，地球將在本世紀看到快速而毀滅性的氣候變化。
科學家們研究史前氣候(prehistoric climate)與自然界變化的反應機制，對於確定人類引起的地球暖化(man-made global warming)所帶來的危害程度，可以更加了解(insight)。美太空總署(NASA)的研究發現(findings)指出，地球的氣候比起近幾十年來的預測(recent estimates)還要敏感的多(sensitive)，而所謂限制人類製造的地球暖化不超過前工業化時代(pre-industrial)攝氏兩度的想法(notion)，不啻是「引來災難的藥單」(a prescription for disaster)。最近的研究指出，自1880年之來，地球表面的平均溫度(average global surface temperature)上升了攝氏0.8度，現在是以每十年增加0.1度的速度持續上升(on course to continue rising)。
margin (n) 餘裕；餘地
advocate (v) 提倡；主張
threshold (n) 門檻
divided (a) 分裂的
dominate (v) 管理；治理
過去幾十年間(for decades)，地表增溫高於前工業時代的兩度內，常被視為一個安全的幅度(a safe margin)，但現有科學家主張(advocate)，應該要把這個安全的門檻(threshold)設定為一度，甚至是少於一度，為此人類必須更努力來減少引起地球暖化的人類活動(human activity)，像是燃燒石化燃料(burning fossil fuels)。但開發中國家和富裕國家對於如何減少溫室氣體(greenhouse gases)的排放量(emissions)，現仍有重大分歧(deeply divided)。
地球現正處於地質學上的間冰河時期(interglacial geologic period)，這指的是南北極都處冰封狀態(the North and South Poles are frozen)，但冰河還沒占滿(dominate)地表的期間。