如何给地球降温

    气候学家已发出警告：未来100年，全球气温将升高1．5℃～6℃，海平面将升高154．5厘米，沙漠将更干燥，气候将更加恶劣，厄尔尼诺现象将更为严重，全球变暖将直接或间接影响人们的生活。如何给地球降温？科学家提出了许多奇思妙想。

    美国氢弹之父、物理学家爱德华•特勒去逝以前曾有过设想：向空中抛洒铝和硫的粉末，给地球降温。按照他的计算，向空中抛洒100万吨铝硫粉末，可以使日照减少1 ％，从而起到降温作用。特勒提出的办法是要模仿大规模的火山爆发。1991年，波及范围达数百万千米的皮纳图博火山灰使地球气温下降了0．4l℃，而且持续时间达好几个星期。特勒设想：可以用飞行于13千米高空的飞机和部署于赤道上的美国海军大炮，向空中抛“火山灰”。但生物化学家们却给这种主张泼冷水，他们认为，散布于空中的这些硫和铝的微粒，很可能会严重干扰同温层。特勒还与人合作研究过其他使地球降温的方法：在轨道上放置5万面反射镜，发射一颗巨大的卫星，悬于地球与太阳之间，以挡住部分太阳辐射。

    除了特勒以外，还有许多科学家也在苦苦思索，希望能找到奇妙的办法给地球降温。美国物理学家洛厄尔•伍德有一个同特勒的设想一样离奇的计划：在地球和太阳之间的万有引力互相抵消处（即拉格朗日点），安装一面直径为2000公里的半透明镜子。他认为，这面巨大的滤光镜不但能减少温室效应，而且能充当地球的空调器：改变滤光镜的倾斜度，以增加或减少透过它的太阳辐射量。但谁来支付超过1000亿美元的巨额费用呢？此外，这面滤光镜不但会破坏同温层，而且还有可能妨碍紫外线的通过（紫外线具有清理太空的功效）。

    有科学家从加强地球对太阳辐射的反射率的角度，探索给地球降温：将数以十亿计的白色聚苯乙烯高尔夫球投向海洋；将地球上的所有房屋的房顶都涂成白色。美国的一位科学家提出了一项更具有诗意的方案：将数千平方公里的阴云“染白”。通过向阴云喷一些微粒，使微小的雨滴数至少增加10％。这样，由于光学作用，层积云就会被照亮变白，就会反射更多的太阳光。

    还有人提出用深埋二氧化碳的办法给地球降温。美国和欧盟已拨巨款来研究在海洋和地层中埋藏二氧化碳的办法。从理论上讲，海洋和地层可以贮藏人类在几千年间生产的二氧化碳。研究人员要验证的是，二氧化碳溶解在海水中，是否会干扰海底生物的生存，因为二氧化碳溶解于海水后，会使海水酸化。

    Love to sink into your chairs and relax when you get to school. Then you will not be happy to hear that schools all over the world are seriously considering exchanging traditional desks for ones with no seats at all — Yes, that means you will be encouraged to stand through those already too long math and science lessons! Why would anyone even think of putting kids to such cruelty. Experts say it improves their health and helps fight obesity. While that may seem a little far-fetched (牵强的), the officials at the few schools around the world seem to agree.

    Among them are educators from the College Station Independent School District in Texas, who recently completed a week-long experiment involving 480 students across three elementary schools. The 374 kids that agreed to participate in the study were provided a device that helped record step count and calorie consumption over the entire period.

    All 25 teachers involved in the study reported that students appeared to be more alert and concentrate better, when allowed to stand. The one thing that did surprise the researchers was that younger kids were more willing to stay standing than kids in higher grades. They believe this may have something to do with the fact that after years of being asked to “sit still”, older kids have a harder time adjusting to this unexpected freedom.

    American schools are not the only ones reporting success with stand-up desks. Four schools in Perth, Australia, which have been testing them since October 2013, have seen similar results. In May 2014, Grove House Primary School in West Yorkshire, became Europe's first test one, with a seven-week trial that involved the use of desks made by Ergotron in their fifth-grade classrooms. While official results are not out yet, early reactions from both teachers and students, have been extremely encouraging.

    The findings of these studies and others done previously, all seem to mean that allowing kids to move around in classrooms is a win-win for students and teachers — it helps kids get healthier and provides educators with a more attentive audience.