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http://huzhangao.blog.163.com/blog/static/4527095820096208125120/
由于在全球变暖中起到了促进作用，二氧化碳被搞得声名狼藉，而且这也是罪有应得。然而，科学家们称，5,500万年前地球温度有过一次神秘的升高，但是这次升高不能完全责怪二氧化碳。新的研究显示，当时还有其他情况造成了地球的升温，只是没人知道这到底是什么样的情况。
Over the past couple of decades, researchers have been gathering data about a mysterious event known as the Paleocene-Eocene Thermal Maximum (PETM). The data, derived from drill cores brought up from the deep seabed in the Atlantic and Pacific Oceans, show that the surface temperature of the planet rose by as much as 9°C within 10,000 years during the PETM, which itself started out warmer than our current world. Temperatures stayed at this elevated level for nearly 100,000 years.
在过去的几十年中，研究人员一直在搜集一桩神秘事件的数据资料，该事件被称为“古新世-始新世极热 (PETM)”事件。这些数据资料来自大西洋和太平洋深海海床的岩心。资料显示：在古新世-始新世极热时期，地球的表面温度在一万年之内升高了多达9摄氏度，而那个时期一开始就比当今地球的温度还要高，上升之后的高温水平一直保持了近10万年。
On the surface, the culprit appeared to be CO2. For reasons unknown, atmospheric concentrations of the gas rose by about 700 parts per million, from 1000 ppm to 1700 ppm--more than four times higher than today's level of 385 ppm--during the PETM. That much of an infusion of the well-established greenhouse gas should have been plenty to spike temperatures.
从表面上来看，罪魁祸首好象是二氧化碳。不知是什么原因，古新世-始新世极热时期大气中的二氧化碳浓度从1000 ppm（百万分之一千）到1700 ppm，上升了大约700 ppm，比当今的二氧化碳水平（385 ppm）高出4倍。既然已经确定有这么多温室气体进入大气，那么本应该足以使气温升高到峰值了。
But a new analysis doesn't fully support this scenario. Oceanographer Richard Zeebe of the University of Hawaii, Manoa, and colleagues ran carbon-cycle simulations of the oceans and atmosphere based on the data yielded by the sediment cores. They even simulated what would happen to global temperatures when they increased the atmosphere's sensitivity to doubling CO2 levels--to 2000 ppm--during the PETM. The most they could achieve was a warming of 3.5°C, they report online this week in Nature Geoscience. That means some other phenomenon must have pushed up temperatures by as much as 5.5°C, the team says. So at present, the unexplained warming represents a gap in understanding about what causes significant and rapid climate change.
但是，新一轮分析并不完全支持这个设想。夏威夷马诺大学的海洋学家理查德·齐伯及同事以沉积物岩心提供的数据资料为基础，进行了海洋和大气的碳循环模拟。他们甚至还进行了以下模拟：把古新世-始新世极热时期的二氧化碳水平加倍（达到2000 ppm）的情况下，提高大气的敏感性，看看全球的气温会发生什么情况。不久前，研究人员在《自然-地球科学》（Nature Geoscience）杂志在线版上报道说，模拟所获得的最大温度升高值是3.5摄氏度。研究小组称，这意味着一定是某种其他的现象将温度提升了多达5.5摄氏度。因此，目前这种莫名其妙的温度升高给研究人员的理解造成了缺憾，无法使他们彻底明白是什么引起了重大而急剧的气候变化。
"It's possible that other greenhouse gases such as methane could have contributed to the [PETM] warming," Zeebe says. It's also possible that the models are underestimating the climate response to CO2 increases. If that's the case, it "would mean our understanding of the climate system is incomplete," he says.
“有可能其他的温室气体，如甲烷，对全球变暖起到了促进作用，”齐伯说。也有可能这些模拟低估了气候对二氧化碳升高的敏感性。“如果情况是这样，那就意味着我们对气候系统的理解并不到位，”他说。
Zeebe's team is now looking at smaller warming events that occurred within several million years after the PETM. "We're currently trying to find out whether or not [they] were caused by the same mechanism," he says. The idea is to determine whether the PETM warming was unique "or a universal feature."
现在齐伯的研究小组正在关注古新世-始新世极热时期之后几百万年之内所发生的较小的变暖事件。“我们目前正在进行努力，希望能够发现这些较小的变暖事件是否也由相同的机制引起，”他说。他们的想法是要确定古新世-始新世极热时期的变暖特点是唯一的还是普遍的。
Geochemist Gabriel Bowen of Purdue University in West Lafayette, Indiana, applauds the work. "We've long had a hunch that something was fishy about the climate response during the PETM," he says. "This study puts the nails in the coffin of the idea that climate during the PETM responded to CO2 alone." Says Bowen, "The urgent challenge now facing us is to find out what was amplifying [temperatures] during this event and understand what it means for Earth's future."
印第安纳州普渡大学西拉法叶分校的地球化学家加布里埃尔·鲍恩赞成这项研究。“长期以来，我们有一种直觉：古新世-始新世极热时期的气候反应有些可疑，”他说，“这项研究推翻了该观点：古新世-始新世极热时期的气候只对二氧化碳有所反应。”鲍恩还指出：“现在我们面临的紧急挑战是，找出那次事件中进一步提高气温幅度的因素，然后搞清楚这对于地球的未来意味着什么。”
译自：美国《科学》杂志网站（14 July 2009） |
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发表于 2009-7-28 23:58
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谢谢哈
斑斑今天闹心了
