VOA标准英语2011--Experts: La Ni?a, Climate Change Impact

Experts: La Ni?a, Climate Change Impact East African Drought

Experts say the Pacific ocean phenomenon known as La Ni?a is partly to blame for the drought ravaging¹ the Horn of Africa.
But while the latest La Ni?a episode has ended, climate scientists are concerned about what the next few months will bring and the intensifying² effects of a changing global climate.
La Ni?a begins when eastern Pacific waters near the equator turn cooler than normal. A cascade³ of changes in ocean temperatures and wind currents follows, and the consequences are global.
Droughts and floods
The latest episode began in July of last year.
In the United States, altered winds pushed moisture away from the south, causing severe droughts that persist today, and toward the north, causing floods.
Half the world away, flooding in Australia this winter was also linked to La Ni?a, experts say.
And in Africa, "The easterly winds that are supposed to bring moisture into East Africa [were] reduced," says meteorologist Wassila Thiaw, head of the Africa desk at the U.S. National Weather Service's Climate Prediction Center. "There was less moisture coming into East Africa and therefore rainfall is reduced."
Rains that were supposed to fall over Somalia, southern Ethiopia and northern Kenya late last year failed.
Lost rainy season
The second rainy season in that part of the Horn of Africa, from March through May, failed, too, but for different reasons, he says.
"What played out here during the March-April-May season, we don't think that is really La Ni?a, but it probably mostly due to the atmospheric⁴ conditions that prevailed at that time."
He says La Ni?a's influence on the March-through-May rainy season typically is not as strong as on the October-through-December season. Natural variations in atmospheric conditions were enough to prolong the drought, he says.
Rainy season threatened
This La Ni?a episode ended in May. But Thiaw says there is a chance another one may begin by the end of this year.
"If that happens before the October-through-December rainfall season, then there's a high chance for us to be in another dryer-than- normal season," he says
That could be catastrophic for drought-stricken parts of East Africa, he says. But he cautions it is too soon to say whether it will happen, or how severe it would be.
Climate change?
La Ni?a and the related phenomenon called El Ni?o are natural cycles that happen every 3 to 5 years or so. Man-made contributions to global warming - auto⁵ and industrial greenhouse-gas emissions⁶, for example -- are a concern, too. But climate scientist Simon Mason at Columbia University's International Research Institute for Climate and Society says the human factor in the Horn's climate woes⁷ is less clear.
"East Africa is one of our big perplexing areas for the moment," Mason says.
Several groups around the world have developed computer models to predict how increasing greenhouse gases will change the climate.
"Most of the models are actually suggesting that East Africa will become wetter," Mason says. "However, if we look at what's been happening in East Africa at least for the last decade or so, it's actually been getting quite a lot drier."
Mason says that drying trend is at least partly due to global warming, which is contributing to rising temperatures in the Indian Ocean. That creates conditions that draw moisture away from East Africa.
'Need to do a bit of work'
However, current computer models do not capture this effect very well, Mason says. "So we need to do a bit of work there to work out what our models are possibly doing wrong."
Others question whether climate change is responsible for the trend. The National Weather Service's Wassila Thiaw says temperatures are rising in the region, but attributing this drought to climate change is difficult because there is so much natural variability in the weather patterns.
But experts say in terms of food production, it does not make that much difference whether it gets wetter or drier because it is sure to get hotter. They may not be sure about rainfall, but they are confident temperatures in East Africa will continue to go up.
Thirstier crops
Hotter weather means thirstier crops, according to agriculture economist⁸ Claudia Ringler at the International Food Policy Research Institute.
"So you actually need more water to get the same out of the crop at a higher temperature," she says.
Ringler notes that much of the land in drought-stricken East Africa is not very productive in the best of times. And, she adds, "it will not get any better. Even if we have a bit more rainfall, the general potential for food production in the region is not expected to improve dramatically in the region."
Furthermore, when the rain falls is in some ways as important as how much. Climate change tends to promote more heavy downpours with longer dry stretches in between. That is not good for raising crops, either, she says.
So Ringer adds that farmers and herders in East Africa need help becoming more resilient in the face of looming⁹ climate changes, whatever they turn out to be.

1 ravaging   

毁坏( ravage的现在分词 )； 蹂躏； 劫掠； 抢劫

参考例句：

• It is believed that in fatigue there is a repeated process of ravaging the material. 据认为，在疲劳中，有一个使材料毁坏的重复过程。
• I was able to capture the lion that was ravaging through town. 我能逮住正在城里肆虐的那头狮子。

2 intensifying   

v.（使）增强， （使）加剧( intensify的现在分词 )；增辉

参考例句：

• The allies are intensifying their air campaign. 联军部队正加大他们的空战强度。 来自辞典例句
• The rest of the European powers were in a state of intensifying congestion. 其余的欧洲强国则处于越来越拥挤的状态。 来自英汉非文学 - 历史

3 cascade   

n.小瀑布，喷流；层叠；vi.成瀑布落下

参考例句：

• She watched the magnificent waterfall cascade down the mountainside.她看着壮观的瀑布从山坡上倾泻而下。
• Her hair fell over her shoulders in a cascade of curls.她的卷发像瀑布一样垂在肩上。

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 auto   

n.(=automobile)(口语)汽车

参考例句：

• Don't park your auto here.别把你的汽车停在这儿。
• The auto industry has brought many people to Detroit.汽车工业把许多人吸引到了底特律。

6 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。

7 woes   

困境( woe的名词复数 )； 悲伤； 我好苦哇； 某人就要倒霉

参考例句：

• Thanks for listening to my woes. 谢谢您听我诉说不幸的遭遇。
• She has cried the blues about its financial woes. 对于经济的困难她叫苦不迭。

8 economist   

n.经济学家，经济专家，节俭的人

参考例句：

• He cast a professional economist's eyes on the problem.他以经济学行家的眼光审视这个问题。
• He's an economist who thinks he knows all the answers.他是个经济学家，自以为什么都懂。

9 looming   

n.上现蜃景（光通过低层大气发生异常折射形成的一种海市蜃楼）v.隐约出现，阴森地逼近( loom的现在分词 )；隐约出现，阴森地逼近

参考例句：

• The foothills were looming ahead through the haze. 丘陵地带透过薄雾朦胧地出现在眼前。 来自《简明英汉词典》
• Then they looked up. Looming above them was Mount Proteome. 接着他们往上看，在其上隐约看到的是蛋白质组山。 来自英汉非文学 - 生命科学 - 回顾与展望