托福阅读背景知识：全球变暖的影响

 　　Rice yields falling under global warming

　　全球气候变暖也与亚洲的一些主要大米出产国的耕地面积减少有关。

　　Global warming is cutting rice yields in many parts of Asia, according to research, with more declines to come.

　　Yields have fallen by 10-20% over the last 25 years in some locations.

　　The group of mainly US-based scientists studied records from 227 farms in six important rice-producing countries such as Thailand, Vietnam, India and China.

　　This is the latest in a line of studies to suggest that climate change will make it harder to feed the world's growing population by cutting yields.

　　In 2004, other researchers found that rice yields in the Philippines were dropping by 10% for every 1C increase in night-time temperature.

　　That finding, like others, came from experiments on a research station.

　　The latest data, by contrast, comes from working, fully-irrigated farms that grow "green revolution" crops, and span the rice-growing lands of Asia from the Indian state of Tamil Nadu to the outskirts¹ of Shanghai.

　　Describing the findings, which are published in Proceedings² of the National Academy of Sciences (PNAS), lead researcher Jarrod Welch said:

　　"We found that as the daily minimum temperature increases, or as nights get hotter, rice yields drop."The mechanism³ involved is not clear but may involve rice plants having to respire more during warm nights, so expending⁴ more energy, without being able to photosynthesise.

　　By contrast, higher temperatures during the day were related to higher yields; but the effect was less than the yield-reducing impact of warmer nights.

　　However, if temperatures continue to rise as computer models of climate project, Mr Welch says hotter days will eventually begin to bring yields down.

　　We see a benefit of [higher] daytime temperatures principally because we haven't seen a scenario⁵ where daytime temperatures cross over a threshold where they'd stop benefiting yields and start reducing them," he told BBC News.

　　"There have been some recent studies on US crops, in particular corn, that showed the drop-off after that threshold is substantial," said the University of California at San Diego researcher.

　　The 2007 assessment⁶ of climate impacts from the Intergovernmental Panel on Climate Change (IPCC) concluded that although a modest temperature rise could increase crop yields in some regions, for "temperature increases more than 3C, average impacts are stressful to all crops assessed and to all regions".

　　A study published at the begining of last year concluded that half of the world's population could face a climate-induced food crisis by 2100, with the most extreme summers of the last century becoming routine towards the end of this century.

 

1 outskirts   

n.郊外，郊区

参考例句：

• Our car broke down on the outskirts of the city.我们的汽车在市郊出了故障。
• They mostly live on the outskirts of a town.他们大多住在近郊。

2 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

3 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

4 expending   

v.花费( expend的现在分词 )；使用（钱等）做某事；用光；耗尽

参考例句：

• The heart pumps by expending and contracting of muscle. 心脏通过收缩肌肉抽取和放出（血液）。 来自互联网
• Criminal action is an action of expending cost and then producing profit. 刑事诉讼是一种需要支付成本、能够产生收益的活动。 来自互联网

5 scenario   

n.剧本，脚本；概要

参考例句：

• But the birth scenario is not completely accurate.然而分娩脚本并非完全准确的。
• This is a totally different scenario.这是完全不同的剧本。

6 assessment   

n.评价；评估；对财产的估价，被估定的金额

参考例句：

• This is a very perceptive assessment of the situation.这是一个对该情况的极富洞察力的评价。
• What is your assessment of the situation?你对时局的看法如何？