新浪首页 > 新浪教育 > 国际在线 > 科学家称地球能源失衡导致全球变暖

http://www.sina.com.cn 2005/05/08 22:19  国际在线

  Using satellites, data from buoys and computer models to study the Earth's oceans, scientists have concluded that more energy is being absorbed from the Sun than is emitted back to space, throwing the Earth's energy "out of balance" and warming the planet.

  Scientists from the National Aeronautics and Space Administration (NASA) (Washington, D.C.), The Earth Institute at Columbia University (New York), and Lawrence Berkeley National Laboratory (California) have confirmed the energy imbalance by precisely measuring ocean heat content occurring over the past decade.

  The study, which appears in this week's Science Express, a feature of Science magazine, reveals that Earth's current energy imbalance is large by standards of Earth's history. The current imbalance is 0.85 watts per meter squared (W/m2) and will cause an additional warming of 0.6 degrees Celsius (1 degree Fahrenheit) by the end of this century. This is equal to a 1-watt light bulb shining over an area of one square meter or 10.76 square feet. Although seemingly small, this amount of heat affecting the entire world would make a significant impact. To put this number in perspective, an imbalance of 1 W/m2 maintained for the last 10,000 years is enough to melt ice equivalent to 1 kilometer (6/10ths of a mile) of sea level.

  The Earth's energy imbalance is an expected consequence of increasing atmospheric pollution, especially carbon dioxide (CO2), methane (CH4), ozone (O3), and black carbon particles (soot). These pollutants block the Earth's radiant heat from escaping into space, increasing absorption of sunlight and trapping heat within the atmosphere.

  "This energy imbalance is the 'smoking gun' that we have been looking for," says James Hansen, director of NASA's Goddard Institute for Space Studies, part of The Earth Institute at Columbia University, and the lead author of the study. "It shows that our estimates of the human-made and natural climate forcing agents are about right, and they are driving the Earth toward a warmer climate."

  Scientists know that increased radiation takes longer to manifest in the world's oceans longer than it does on land; the ocean, instead of showing an immediate temperature increase, holds the heat in storage within its depths, thus delaying a response to human-induced, or anthropogenic, climate change. The ocean's delayed response is similar to what happens during the summer months, when the ocean takes longer to warm up than do land surfaces. The building heat within the ocean's depths is what is known as "thermal inertia."

  The lag in the ocean's response has practical consequences. For one thing, it means that there is an additional global warming of about 1 degree Fahrenheit that is already "in the pipeline," and has not yet manifested in overall ambient temperatures. Even if there were no further increase of human-induced gases in the air, climate would continue to warm about that much over the next century.

  The lag in the climate response is both a boon and a problem for policy-makers. The delayed response of thermal inertia provides an opportunity to reduce the magnitude of human-made climate change before it is fully realized, provided that actions to reduce climate forcing agents are undertaken. On the other hand, if the world decides to wait for more overwhelming evidence of climate change, thermal inertia implies that still greater climate change will be in store, which may be difficult or impossible to avoid.

  Warmer water temperatures around the world may also lead to other significant climate-related consequences. "Warmer waters increase the likelihood of accelerated ice sheet disintegration and sea level rise during this century," Hansen said. Since 1993, data from satellite altimeters, used to measure sea level, have shown that the world's oceans have risen by 3.2 centimeters (cm), or 1.26 inches, per decade (plus or minus 0.4 cm).

  Although 3.2 cm may appear to be only a slight increase, it is twice as large as sea level rise in the last century.






  美国宇航局戈达德太空研究所主管、这项研究的负责人詹姆斯·汉森表示:“这种能量失衡就是我们一直在寻找的‘烟枪 ’,它显示出,我们对人为和自然气候的促成因素的估计是正确的,它们使地球趋向一种更为温暖的气候环境。”




  世界范围内,变得更暖的海水温度同样会引起其它一些显著的和气候有关的结果。对此,汉森表示:“在本世纪内,更暖的水温加速了冰盖崩溃的可能性,同时海平面也会随之升高。”自从1993年以来,人造卫星测高计(常常被用来测量海平面高度)提供的数据就显示,每10年内,世界上各海洋都升高了大约3.2厘米或是1.26英寸(含正负0.4厘米);虽然区区3.2厘米看起来只是轻微的升高,但这几乎是上个世纪海平面升高的两倍。 (文/王高山)

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