Unit 6：Effects on Climate and Ecological Environment 对气候和生态环境的影响
The role of carbon dioxide in the global heat balance is well recognized.二氧化碳在全球热量平衡的作用是公认。
Because CO2 can absorb thermal energy, it decreases the atmosphere’s emissivity, that is, its ability to radiate long-wave infrared and transparency to visible light is characterized as the “greenhouse effect”. 因为二氧化碳能够吸收热能，减少大气发射率，也就是说，它能够辐射红外长波和可见光，这种能力通常被称为“温室效应”。
This “greenhouse effect” is due primarily to water vapor ad carbon dioxide, which have strong infrared absorption bands. “温室效应”主要是由水汽和二氧化碳引起的，它们有着强烈的红外线吸收带。
Changes in atmospheric levels of either or both of these gases would ,of course ,affect the amount of heat or long-wave infrared trapped within the greenhouse and thus determine global climate .当然，大气层中一种或种这些气体的变化会影响被截留在温室内的热量和红外长波，从而决定了全球的气候。
Since 1890 atmospheric CO2 levels have increased from about 290 to 322 ppm. 直到1890年为止，大气层的二氧化碳水平由百万分之290增加到百万分之322.
Of this increase 25% has occurred in the past decade . 其中有25%是最近十年增加的。
Since 1958 the average annual increase has been approximately 0.7 ppm/yr .从1958年起，平均每年的增长量接近百万分之0.7。
If this trend continues ,atmospheric CO2 levels are expected to double by the year 2035AD.如果这个趋势继续下去的话,公元2035年，大气层中的二氧化碳水平将可能翻倍。
Based on some widely accepted climatic models ，，，，this doubling could result in the warming of surface temperatures in the mid-latitudes on the order of 2.4 degree, with greater potential warming in the polar regions.根据一些被广泛接受的气候模型，这种结果可能导致中纬度表面温度大约上升2.4度，同时伴随着极地地区巨大的潜在升温。
The augmentation of the atmosphere’s greenhouse effect from anthropogenically derived CO2 has the potential for significantly warming global climate .人类活动排放的二氧化碳使大气层的温室效应增加，在相当大程度上影响着全球气候变暖。
By increasing the length of the growing season, the consequences of this warming may in the short term be beneficial. 通过延长农作物的生长季节，短期变暖也许是有利的。
In the long term ,however , continued global warming may have deleterious effects on global agriculture.然而,从长远来看，持续的全球性变暖会对全球农业造成有害的影响。
According to a National Research Council report, climatic warming associated with increased atmospheric CO2 levels could be expected to cause significant changes in agricultural zones。。。。根据国家研究理事会的报告，气候变暖和大气层二氧化碳水平的增加可能会对农业地区带来巨大的变化。
These changes could include: (1) an expansion of arid and semiarid regions; (2) poleward advance of arid and arable zones; and (3) summer temperatures too high for full productivity of important middle latitude crops such as corn and soybeans .这些变化包括：（1）干旱和半干旱地区扩大；（2）干旱和耕作地区将向极地发展；（3)夏天温度太高对中纬度重要的高生产率作物来说不适宜,例如玉米和大豆。
The net effect of these changes would be to reduce areas suitable for agriculture and disrupt existing agricultural patterns in many regions in the northern hemisphere. 在北半球很多地区，这些变化的净效应将会减少适合耕作的地区，破坏现有的农业模式。
This could ,of course, result in severe economic disruption and untold misery for billions of people.当然，这也可能导致严重的经济破坏和亿万人不可言说的苦难。
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