VOA慢速英语--专家称众多城市对热浪毫无准备

Many Cities Unprepared for Intense¹ Heat Waves, Experts Say

Many places in the northern half of the world are currently² facing record-breaking heat.

Several countries in the Middle East, including Iran, Kuwait, Oman and the United Arab Emirates, recorded days over 50 degrees Celsius³ in recent months. Moscow and Helsinki, Finland also reported their hottest June temperatures on record.

Several weeks ago, there was a record-breaking heat wave in the Pacific Northwest of the United States and western Canada. Oregon and Washington state reported almost 200 heat-related deaths.

Jennifer Vanos is an assistant professor at Arizona State University. She said: "(Heat) is different than other extremes because...it's invisible⁴." She added that when "it's something people have never experienced⁶ before, then it becomes a lot more dangerous."

A United Nations group on climate change says cities can be dangerous places during heat waves. City buildings and streets can make temperatures rise. And with more than 50 percent of the world's population living in cities, experts fear that heat-related health problems will become more common.

Urban heat islands

Cities can be several degrees hotter than rural⁷ environments. This effect is known as the urban heat island.

Hashem Akbari studies urban heat islands at Concordia University in Montreal. He said building materials in cities take in heat and hold it. Asphalt, for example, is a petroleum-based mixture used in streets and on the tops of buildings. Its dark surface reflects little light and absorbs heat.

At the same time, buildings are often close together, which means there are fewer trees and plants. Plants provide valuable cover from the sun. Plants also absorb water through their roots and use surrounding heat to evaporate⁸ the water from their leaves. With fewer plants, this natural cooling effect is gone, Akbari said.

Energy demands

To avoid the heat, people living in cities use electricity to power air cooling systems and fans. On a very hot day, those technologies use a lot of electricity.

Sayanti Mukherjee is an assistant engineering⁹ professor at the University at Buffalo¹⁰, New York. She said cities have "a higher population to serve, so the infrastructure¹¹ is working at a higher capacity¹² because of the demand."

But sometimes the electricity system is unable to supply enough power to meet the demand. If that happens, the system shuts down and the power shuts off.

Extreme weather events, however, are unusual. That makes it difficult for city planners and engineers to prepare for conditions that might not happen very often.

Materials in infrastructure

The materials used to make urban infrastructure also are affected¹³ by high heat.

Heat makes metal materials expand. Power lines, for example, are usually made with metal. Hot temperatures and high electricity demands cause the metal to expand and fall lower to the ground. The falling lines can touch trees or people and can cause fires or injuries.

Concrete and asphalt expand with heat too. Quick changes in temperature can create cracks in concrete and can cause buildings, streets or bridges to weaken¹⁴.

Finding¹⁵ solutions

Researchers are looking for ways to help urban populations live through extreme heat.

Vanos said cities should keep better records of heat-related deaths. She said these kinds of deaths are often underreported. Vanos added that city governments can help identify populations that are at risk and improve emergency services.

Akbari said more trees and grass are needed to cool cities. He added that structures should be built with new materials that are lighter¹⁶ in color and reflect more light. That would also lower temperatures and save energy.

To supply energy demands, Mukherjee said cities need to use more wind and solar power.

Experts say the heat-trapping carbon gasses have pushed the world's climate to an extreme.

"The more frequent and intense heat waves are showing that we need to prepare ourselves more to address this problem in the future," Mukherjee said.

Words in This Story

invisible — n. impossible to see : not visible⁵

reflect — v. to move in one direction, hit a surface, and then quickly move in a different and usually opposite direction

absorb — v. to draw in (heat, light, energy, etc.)

evaporate — v. to change from a liquid into a gas

resident¹⁷ — n. someone who lives in a particular place

infrastructure — n. the basic equipment and structures (such as roads and bridges) that are needed for a country, region¹⁸, or organization to function properly

capacity — n. the ability to hold or contain people or things

frequent –adj. happening often

1 intense   

adj.认真的，专注的；强烈的；紧张的；热情的

参考例句：

• Susan was an intense young lady.苏珊是一个热情的年轻姑娘。
• The quarrel caused her intense unhappiness.争吵令她极其不快。

2 currently   

adv.通常地，普遍地，当前

参考例句：

• Currently it is not possible to reconcile this conflicting evidence.当前还未有可能去解释这一矛盾的例证。
• Our contracts are currently under review.我们的合同正在复查。

3 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。

4 invisible   

adj.看不见的，无形的

参考例句：

• The air is full of millions of invisible germs.空气中充满了许多看不见的细菌。
• Many stars are invisible without a telescope.许多星辰不用望远镜便看不见。

5 visible   

adj.看得见的，明显的，显然的；n.可见物

参考例句：

• It is a visible star in the sky.这是一颗在天空中可见的星星。
• The warning lights were clearly visible.警示信号灯清晰可见。

6 experienced   

adj.有经验的；经验丰富的，熟练的

参考例句：

• Experienced seamen will advise you about sailing in this weather.有经验的海员会告诉你在这种天气下的航行情况。
• Perhaps you and I had better change over;you are more experienced.也许我们的工作还是对换一下好，你比我更有经验。

7 rural   

adj.乡下的，田园的，乡村风味的

参考例句：

• He lived a rural life.他过着田园生活。
• We left the city for a rural home.我们离开城市，去农村安家。

8 evaporate   

vi.蒸发，挥发，消失；vt.使蒸发，使挥发

参考例句：

• Clearly,the star wars problem was not going to evaporate.显然，星球大战问题并没有不了了之。
• It will evaporate like a spirit.它将来总要像幽灵一样化成云烟。

9 engineering   

n.工程，工程学，管理，操纵

参考例句：

• The science of engineering began as soon as man learned to use tools. 人类一学会使用工具,工程科学就开始了。
• It was the first great engineering works in the world. 这是世界上第一家大型的工程工厂。

10 buffalo   

n.(北美)野牛；(亚洲)水牛

参考例句：

• Asian buffalo isn't as wild as that of America's. 亚洲水牛比美洲水牛温顺些。
• The boots are made of buffalo hide. 这双靴子是由水牛皮制成的。

11 infrastructure   

n.下部构造，下部组织，基础结构，基础设施

参考例句：

• We should step up the development of infrastructure for research.加强科学基础设施建设。
• We should strengthen cultural infrastructure and boost various types of popular culture.加强文化基础设施建设，发展各类群众文化。

12 capacity   

n.能力，力量，接受力；容量，能量，容积

参考例句：

• She is employed by the president in an advisory capacity.她被总裁聘为顾问。
• This carriage has a seating capacity of 120 people.这节车厢定员120人。

13 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

14 weaken   

v.(使)变弱，(使)虚弱

参考例句：

• You can weaken the tea by adding water.你可以加水把茶弄得淡一些。
• We never weaken our efforts in face of difficulties.我们在困难面前从不软化我们的努力。

15 finding   

n.发现，发现物；调查的结果

参考例句：

• The finding makes some sense.该发现具有一定的意义。
• That's an encouraging finding.这是一个鼓舞人心的发现。

16 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。

17 resident   

a.居住的，居留的；住校的，住院的

参考例句：

• I've been resident in this place for five years. 我已经在这个地方住了五年。
• They engaged a resident tutor. 他们聘用了一名住家的家庭教师。

18 region   

n.地区，地带，区域；范围，幅度

参考例句：

• The students went to study the geology of that region.学生们去研究那个地区的地质情况。
• It is unusual to see snow in this region.这个地区难得见到雪。