When scientists scan the global horizon, over-fishing, loss of species habitat, water shortage, climate change, and invasive species look to be the biggest threats to the earth.

    研究者们环视全球，发现过度捕捞、物种栖息地缺失、水资源缺乏、气候变化和外来物种入侵是对地球最大的威胁。

    What will our world be like in 2050?

    到2050年的时候，我们的世界会是什么样子？
 
    Population Decrease and Increase 人口增减

    There are two features in the growth of world population. First, the annual increase in population in 15 European countries, in the past few years, has been only 300,000. The United Nations estimates that by 2050, the population of European countries will decrease from the current 0.72 billion to 0.63 billion. Second, the population in developing countries is growing rapidly. Over the past 50 years, the rate of increase in population has been fastest in the least developed countries. By 2050, the population of Africa is expected to reach 1.8 billion, 0.9 billion more than its current population.

    世界人口增长有两个特点。首先，在过去的几年中，欧洲15个国家每年仅增加人口30万。联合国预测，到2050年，欧洲人口将由目前的7.2亿下降到 6.3亿。其次，发展中国家人口正快速增长。在过去50年里，最不发达国家的人口增长率最高。到2050年，非洲总人口将达到18亿，比目前多9亿。
 
    Global Warming 全球变暖

    A recent research report published by the United Nations indicates that it is quite possible that the Earth's temperature is rising well above the previous estimate.

    最近由联合国公布的研究报告指出，地球温度的上升很可能远高于以前的估计。

    Such an outcome would have severe consequences, such as the collapse of the Greenland ice sheet and disruption of the Gulf Stream ocean current.

    这样的结果会造成严重后果，例如格陵兰冰层崩塌以及墨西哥湾流受阻。

    The Antarctic ice sheet, which contains 90% of the world's ice, has lost significant mass in the past few years. The discovery comes as a surprise to scientists, who thought that the continent would gain ice this century because of increased snowfall in a warming climate.

    占有全世界冰川总量90%的南极洲冰层主体在过去几年里显著萎缩。对于科学家们来说，这个发现出乎意料，因为他们曾经认为温暖的气候会带来更多降雪，从而在本世纪增加南极洲的总冰量。

    A research team from the University of Colorado used satellite data to estimate that the ice sheet will lose up to 48 cubic miles by 2050. In comparison, a city the size of Los Angeles uses one cubic mile of fresh water every year. Ice shelves in the Antarctic will have decreased by more than 7,200 square miles in the next four decades.

    科罗拉多州大学的研究小组利用卫星资料进行预测，到2050年（南极洲）冰层将会丧失多达48立方英里的冰量。与之相对的是，洛杉矶这样规模的大城市一年消耗的淡水总量也不过1立方英里。在未来40年里，南极洲冰架将缩减7200多平方英里。

    At twice the size of Australia, Antarctica is the Earth's fifth largest continent and contains 70% of its total fresh water resources.

    南极洲是地球第五大洲，面积是澳大利亚的两倍，拥有全球淡水资源的70%。
 
    Water Shortage 水资源短缺

    Africa's rivers face dramatic change that will leave a quarter of the continent severely short of water by the middle of the century, according to a global warming study published today.

    在今天出版的全球变暖问题研究报告称，非洲河流正面临巨变，这将导致在本世纪中叶，非洲四分之一的地区处于严重缺水状态。

    Even modest decreases in rain in western Africa will see rivers lose as much as 80% of their water, triggering a surge of what the scientists call "water refugees".

    即便是在西非出现降雨的适度减少，也会造成河流损失多达80%的水量，引发专家们称之为“水难民”的难民潮。

    "In those areas where there is already a water shortage, it's going to have a devastating affect," the study says. "If you're already walking 5 km to the nearest stream to get water, by 2050, it's going to mean walking 30 km or moving your whole household closer to the water source."

    该报告指出：“在那些水资源本来就很缺乏的地区，事情的发展将会带来灾难性的影响。如果现在需要徒步到5公里以外最近的水源地取水，到2050年就意味着要到30公里之外，或者只能搬到离水源更近的地方。”
 
    Four Wheels Good, Four Wheels Dad 成也汽车，败也汽车

    The car has transformed the lives of people, but the planet is paying too high a price. It is almost incredible to think that when our grandparents were born cars were a rarity. Today there are 620 million private cars worldwide, to say nothing of buses, vans and lorries. With current growth trends, that number is expected to reach a staggering three billion cars worldwide by 2050.

    小汽车改变了我们的生活，然而这个世界现在正为此付出高昂的代价。几乎让人难以想象的是，在我们祖辈出生的年代，汽车还为罕见之物。如今，全球光私人小汽车就有6亿2千万辆，更不用说公共汽车、货车和卡车了。按照眼下的增长态势来看，到了2050年，这个数字将达到惊人的30亿辆。

    If we continue to burn fossil fuels at current rates, levels of carbon dioxide in the atmosphere will reach 550 ppm (parts per million)--double pre-industrial levels--by around 2050. This will increase global temperatures between 1.4 and 4.8℃ by 2050, and sea levels will rise between 0.09 and 0.78 meters.

    如果我们继续按照目前的标准使用矿物燃料，到2050年全球大气中的二氧化碳含量将达到550ppm（百万分率）。这个数字是人类进入工业化社会前的两倍。受此影响，到2050年为止，全球温度将增长1.4到4.8摄氏度，海平面将升高0.09到0.78米。