2006年VOA标准英语-Scientists Say Melting Permafrost Could Amplify

By Frank Ling
Washington
07 August 2006

New research shows that global warming might be worse than expected because of melting permafrost, permanently² frozen soil, which can release the "greenhouse" gas, carbon dioxide. Computer models predict higher future temperatures when these gases are taken into consideration.

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Frozen tundra³
  
Scientists say the Earth's rising atmospheric⁴ temperatures are largely caused by human-generated emissions⁵ of heat-trapping gases, mainly carbon dioxide. But recent findings suggest that the Earth is also a culprit. It, too, gives off carbon dioxide.

That is because vast amounts of carbon are trapped in permafrost. Over the ages, this frozen ground has accumulated layers of windblown dust, roots, and other organic, or carbon-containing, matter as glaciers⁶ advanced and retreated.

As long as the permafrost remains⁷ frozen, the carbon stays in the soil. But botanist⁸ Ted¹ Schurr of the University of Florida says higher temperatures will melt the soil, releasing greenhouse gases, which would boost temperatures even more. Schurr traveled to Siberia to collect samples of permafrost up to three meters below the surface. He reports in the journal Science that when the permafrost melted in the laboratory, microbes digested the carbon and converted it to carbon dioxide.

"It's like food in your freezer," explained Schurr. "If It's really cold, those bacteria and fungi⁹ can't do their thing. Now if you warm this soil organic matter up from below there, you unfreeze it, then they can metabolize it and convert it to carbon dioxide. This gas then goes into the atmosphere and contributes to the carbon there."

Scientists know how much carbon dioxide people put into the air each year, but until now it was not clear how much greenhouse gas the Earth could give off. Schurr found that the deposits deep in the Siberian permafrost were much greater than previously¹⁰ thought and could potentially double current carbon dioxide concentrations if released.

"We describe a really large pool of about 500 billion tons of carbon," said Schurr. "In comparison, the atmosphere right now has about 730 billion tons. So we are talking about almost as much carbon stored in permafrost in Siberia as there is in the atmosphere now. "

In another study in the journal Geophysical Research Letters, Margaret Torn at the University of California at Berkeley shows the climate impact of this additional greenhouse factor. "We found a significant amount of warming coming back from these feedbacks that we're not yet estimating," said Torn. "The Intergovernmental Panel on Climate Change, or IPCC, currently estimates that we could have warming by as much as 5.8 degrees Celsius¹¹ by the end of the 21st century. But if Earth responds as it has in the past, we would actually be committed to 7.7 degrees Celsius warming."

These latest studies are only steps toward a complete understanding of the atmosphere's complex nature. Scientists are still struggling to incorporate other greenhouse factors such as clouds, dust, and pollutants¹² into their analysis. Torn says as more is known about them, they will be used to refine current climate models.

1 ted   

vt.翻晒，撒，撒开

参考例句：

• The invaders gut ted the village.侵略者把村中财物洗劫一空。
• She often teds the corn when it's sunny.天好的时候她就翻晒玉米。

2 permanently   

adv.永恒地，永久地，固定不变地

参考例句：

• The accident left him permanently scarred.那次事故给他留下了永久的伤疤。
• The ship is now permanently moored on the Thames in London.该船现在永久地停泊在伦敦泰晤士河边。

3 tundra   

n.苔原，冻土地带

参考例句：

• The arctic tundra is at the top of the world around the North Pole.北极冻原是指北极点周边的地区，是世界最高的地方。
• There is a large amount of methane gas under the Siberian tundra.西伯利亚的冻土地带之下有大量的甲烷气体。

4 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

5 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。

6 glaciers   

冰河，冰川( glacier的名词复数 )

参考例句：

• Glaciers gouged out valleys from the hills. 冰川把丘陵地带冲出一条条山谷。
• It has ice and snow glaciers, rainforests and beautiful mountains. 既有冰川，又有雨林和秀丽的山峰。 来自英语晨读30分（高一）

7 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

8 botanist   

n.植物学家

参考例句：

• The botanist introduced a new species of plant to the region.那位植物学家向该地区引入了一种新植物。
• I had never talked with a botanist before,and I found him fascinating.我从没有接触过植物学那一类的学者，我觉得他说话极有吸引力。

9 fungi   

n.真菌，霉菌

参考例句：

• Students practice to apply the study of genetics to multicellular plants and fungi.学生们练习把基因学应用到多细胞植物和真菌中。
• The lawn was covered with fungi.草地上到处都是蘑菇。

10 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。

11 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

12 pollutants   

污染物质（尤指工业废物）( pollutant的名词复数 )

参考例句：

• Pollutants are constantly being released into the atmosphere. 污染物质正在不断地被排放到大气中去。
• The 1987 Amendments limit 301(g) discharges to a few well-studied nonconventional pollutants. 1987年的修正案把第301条（g）的普通排放限制施加在一些认真研究过的几种非常规污染物上。 来自英汉非文学 - 环境法 - 环境法