Global Warming 全球暖化

Part 7 Global Warming 全球暖化

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. The heat-trapping property of these gases is undisputed although uncertainties exist about exactly how earth’s climate responds to them.

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, such as water vapor, carbon dioxide, 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. Instead, 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. Once, all climate changes occurred naturally. However, during the Industrial Revolution, we began altering our climate and environment through changing agricultural and industrial practices.

Before the Industrial Revolution, human activity released very few gases into the atmosphere, but now through population growth, fossil fuel burning, and deforestation, we are affecting the mixture of gases in the atmosphere.

Carbon dioxide is released to the atmosphere when solid waste, fossil fuel and wood products are burned. Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock. Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels.

Rising global temperatures are expected to raise sea level, and change precipitation and other local climate conditions. Changing regional climate could alter forests, crop yields, and water supplies. It could also affect human

health, animals, and many types of ecosystems and deserts may expand into existing rangelands. Unless we act now, our children will inherit a hotter world, dirtier air and water, more severe floods and droughts, and more wildfires.

But solutions are in sight. We know where most heat-trapping gases come from: power plants and vehicles. And we know how to curb their emissions: modern technologies and stronger laws. By shifting the perception of global warming from abstract threat to pressing reality, and promoting online activism. By pressing businesses to use less energy and build more efficient products. And by fighting for laws that will speed these advances.

温室效应”是指地球大气层上的一种物理特性。假若没有大气层，地球表面的平均温度不会是现在合宜的15℃，而是十分低的-18℃。这种温度上的差别是由温室气体导致的，这些气体吸收红外线辐射而影响到地球整体的能量平衡。受到温室气体的影响，大气层吸收红外线辐射的份量比它释放到太空外的垛，这使地球表面温度上升，这个过程就是“天然的温室效应”。但由于人类活动释放出大量的温室气体，结果让更多红外线辐射被折射到地面上，加强了“温室效应”的作用。

全球变暖是目前全球环境研究的一个主要议题。根据对100多份全球温度变化资料的系统分析，发现全球平均温度已升高0.3～0.6摄氏度。其中11个最暖的年份发生在80年代中期以后，因而全球变暖是一个毋庸置疑的事实。全球变暖将带来非常严重的后果，如冰川消退、海平面上升、荒漠化等等，还给生态系统、农业生产带来严重影响。全球变暖现象最终可能会导致全球变冷，形成另一次冰河时代。就像我们在美国电影《后天》里面看到的可怕情景。

因此，探求全球变暖的起因成为重要的研究课题。分析表明，虽然地球演化史上曾经多次发生变暖--变冷的气候波动，但人类活动引起的大气温室效应增长可能是主要因素。

各国政府、企业和科学家们逐步达成共识，大家必须迅速行动起来，与气候变化作斗争。目前人们已经采取措施限制二氧化碳的排放量。许多公司正积极应对二氧化碳限排时代的到来。

Part 8 El Nino and La Nina 厄尔尼诺和拉妮娜

El Nino and La Nina are opposite phases of the El Nino-Southern Oscillation (ENSO) cycle, with La Nina sometimes referred to as the cold phase of ENSO and El Nino as the warm phase of ENSO.

El Nino is a disruption of the ocean-atmosphere system in the tropical Pacific having important consequences for weather around the globe. Among these consequences are increased rainfall across the southern tier of the US and in Peru, which has caused destructive flooding, and drought in the West