2024年3月11日发(作者：手机swf转换mp4格式转换器)

Our Changing Atmosphere

我们所改变的大气

According to the National Academy of Sciences，the Earth's surface

temperature has risen by about 1 degree Fahrenheit in the past century，with

accelerated warming during the past two decades．There is new and stronger

evidence that most of the warming over the last 50 years is attributable to human

activities．Human activities have altered the chemical composition of the

atmosphere through the buildup of greenhouse gases ——primarily carbon

dioxide，methane，and nitrous oxide．

根据美国国家科学院的说法，在过去的一个世纪里，地球表面温度上升了大约1华氏

度，在过去的20年里加速变暖。有新的更有力的证据表明，过去50年的大部分变暖都

可归因于人类活动。人类活动通过温室气体的积累改变了大气的化学成分——主要是二氧

化碳、甲烷和一氧化二氮。

Energy from the sun drives the earth's weather and climate，and heats the

earth's surface； in turn，the earth radiates energy back into

space．Atmospheric greenhouse gases，( water vapor，carbon dioxide，and

other gases) trap some of the outgoing energy，retaining heat somewhat like

the glass panels of a greenhouse．Without this natural "greenhouse effect，"

temperatures would be much lower than they are now，and life as known today

would not be

possible．Thanks to greenhouse gases，the earth's average temperature is a

more hospitable 60°F．However，problems may arise when the atmospheric

concentration of greenhouse gases increases。

太阳释放的能量形成了地球的气候和气候，并温暖地球的表面；而地球也转而将能量

向太空辐射。大气中的温室气体（水蒸气、二氧化碳和其它气体）捕获住一些外溢的能量，

形成像温室玻璃板一样的效果保留住热能。如果没有这种自然的“温室效应”，气温将会

比现在低得多，今天已知的生命将不可能存在。幸亏有温室气体的存在，地球才会保持平

均华氏60多度的宜人温度。然而，当温室气体的大气浓度增加时，问题可能会出现。

Scientists generally believe that the combustion of fossil fuels and other

human activities are the primary reason for the increase concentration of carbon

dioxide．What has changed in the last few hundred years is the additional

release of carbon dioxide by human activities．Fossil fuels burned to run cars and

trucks，heat homes and businesses，and power factories are responsible for

about 98% of US carbon dioxide emissions，24% of methane emissions，and 18%

of nitrous oxide emissions．Increased agriculture，deforestation，landfills，

industrial production，and mining also contribute a significant share of

emissions．In 1997，the United States emitted about one-fifth of total global

greenhouse gases．

科学家们普遍认为，化石燃料和其他人类活动的燃烧是二氧化碳浓度增加的主要原因。

在过去的几百年里，人类活动增加了二氧化碳的排放。化石燃料燃烧来驱动汽车和卡车，

为家庭和企业供暖，给工厂提供动力，它们负责了美国大约98%的二氧化碳排放，24%

的甲烷排放，以及18%的一氧化二氮排放。农业、森林砍伐、垃圾填埋场、工业生产和