澳科学家警告海平面上升问题

 CANBERRA, Oct. 14 (Xinhua) -- Australian scientists have made the alarming discovery that sea levels have risen more in the past century than at any other comparable period in the past 6,000 years.

Researchers from the Australian National University (ANU), based in Canberra, found that the 20-centimetre rise in sea levels since the start of the 20th century, caused largely by global warming and the melting of polar ice, was unprecedented¹.

The ANU study, a lengthy² analysis of historical sea level trends, showed levels have remained steady for thousands of years before rapid rises over the past 150 years, since global industrialization.

The study looked at the fluctuation³ of ocean levels over the past 35,000 years, based on ice volume changes around the world.

unprecedentedA two-decade-long collection of about 1,000 ancient sediment⁴ samples off Britain, north America, Greenland and the Seychelles formed the basis of the research, which was recently published in Proceedings⁵ of the National Academy of Sciences (PNAS).

Researchers could pick submerged sediments⁶ that may include tree roots, suggesting a previously⁷ lower sea level, or molluscs, which can be measured against the fossil record to determine the previous sea level.

The study has been described as the most comprehensive paper of its kind looking at the period.

Professor Kurt Lambeck, from the ANU, said sea levels have been oscillating by no more than 20 centimeters over several millennia⁸.

"In the last 6,000 years before the modern onset⁹ of sea level rise, the sea level has been quite stable," he said.

"We see no evidence for oscillations in sea level greater than say plus or minus 25 or 30 centimeters, on timescales of 100 years or longer, there's just no evidence for that."But he said there had been a rapid upward trend accompanying global industrialization. "For the last 150 years we've been seeing this increase, this rising sea level, at a rate of a few millimeters per year and in our older records we do not see similar behavior," he said.

Lambeck's team identified rising temperatures, which have caused polar ice to melt and thermal¹⁰ expansion of the sea, as a primary cause of the sea level increase.

"What we've seen is unusual, certainly unprecedented for these interglacial periods," he said.

"All the studies show that you can't just switch off this process. Sea levels will continue to rise for some centuries to come even if we keep carbon emissions¹¹ at present day levels.""What level that will get to, we are less sure about. But it's clear we can't just reverse the process overnight," he said.

1 unprecedented   

adj.无前例的，新奇的

参考例句：

• The air crash caused an unprecedented number of deaths.这次空难的死亡人数是空前的。
• A flood of this sort is really unprecedented.这样大的洪水真是十年九不遇。

2 lengthy   

adj.漫长的，冗长的

参考例句：

• We devoted a lengthy and full discussion to this topic.我们对这个题目进行了长时间的充分讨论。
• The professor wrote a lengthy book on Napoleon.教授写了一部有关拿破仑的巨著。

3 fluctuation   

n.(物价的)波动，涨落；周期性变动；脉动

参考例句：

• The erratic fluctuation of market prices are in consequence of unstable economy.经济波动致使市场物价忽起忽落。
• Early and adequate drainage is essential if fluctuation occurs.有波动感时，应及早地充分引流。

4 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

5 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

6 sediments   

沉淀物( sediment的名词复数 )； 沉积物

参考例句：

• When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后，体积的70-80％是水。
• Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵蚀所截削。

7 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

8 millennia   

n.一千年，千禧年

参考例句：

• For two millennia, exogamy was a major transgression for Jews. 两千年来，异族通婚一直是犹太人的一大禁忌。
• In the course of millennia, the dinosaurs died out. 在几千年的时间里，恐龙逐渐死绝了。

9 onset   

n.进攻，袭击，开始，突然开始

参考例句：

• The drug must be taken from the onset of the infection.这种药必须在感染的最初期就开始服用。
• Our troops withstood the onset of the enemy.我们的部队抵挡住了敌人的进攻。

10 thermal   

adj.热的，由热造成的；保暖的

参考例句：

• They will build another thermal power station.他们要另外建一座热能发电站。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

11 emissions   

排放物( emission的名词复数 )； 散发物（尤指气体）

参考例句：

• Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
• Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。