2005 Ties for 2nd Warmest Year Ever
摘要:Predictions early in 2005 that the year would be the warmest on record turned out to be off the mark. A new study finds last year tied for the second-warmest year since reliable records have been kept starting in the late 1800s.2005年早些时候曾有人预计,去年将是有观测记录以来地球历史上最暖的一个年头。不过,现在看来这个预言显然没有实现,因为新的研究数据显示,2005年实际上是自1800年温度记录保存以来的地球第二最暖年。
Predictions early in 2005 that the year would be the warmest on record turned out to be off the mark. A new study finds last year tied for the second-warmest year since reliable records have been kept starting in the late 1800s.
The global average temperature in 2005 was 0.54 degrees Fahrenheit (0.3 Celsius) warmer than the long-term average, tying a mark set in 2002.
But a puzzling general pattern, seen the past three decades, persisted: The most significant warming occurred in the Arctic, where the ice cap is shrinking at an alarming pace.
Since November 1978, the Arctic atmosphere has warmed seven times faster than the average warming trend over the southern two-thirds of the globe, based on data from NOAA satellites.
"It just doesn't look like global warming is very global," said John Christy, director of the Earth System Science Center at the University of Alabama in Huntsville.
The warmest five years since the 1890s, when reliable record-keeping began:
1. 1998
2. 2005
2. 2002 (tie)
4. 2003
5. 2004
Scientists agree the planet is warming. Ground in the Northern Hemisphere that's been frozen since the last Ice Age is melting and collapsing.
But they are still debating exactly how much and to what extent humans are contributing by burning fossil fuels that create greenhouse gases.
In a report last May, researchers said they know very little about how Earth absorbs and reflects sunlight, crucial factors that control climate. Other studies have indicated that increased output from the Sun is responsible for more of global warming than was previously realized.
"Obviously some part of the warming we've observed in the atmosphere over the past 27 years is due to enhanced greenhouse gases. Simple physics tells you that," Christy said. "But even if you acknowledge the effects of greenhouse gases, when you look at this pattern of warming you have to say there must also be something else at work here."
Nobody's sure what that might be.
"The carbon dioxide from fossil fuels is distributed pretty evenly around the globe and not concentrated in the Arctic, so it doesn't look like we can blame greenhouse gases for the overwhelming bulk of the Northern Hemisphere warming over the past 27 years," Christy said.
"The most likely suspect for that is a natural climate change or cycle that we didn't expect or just don't understand."
2005年早些时候曾有人预计,去年将是有观测记录以来地球历史上最暖的一个年头。不过,现在看来这个预言显然没有实现,因为新的研究数据显示,2005年实际上是自1800年温度记录保存以来的地球第二最暖年。
据美国“生活科学”网站1月6日报道,2005年全球平均温度比2002年以来的平均温度高出了华氏0.54度(0.3摄氏度)。不过,在过去近30年来一直存在的一个令人迷惑的温度变化模型仍然在持续——多数显著的变暖现象发生在北极,北极冰山正以令人担忧的速度迅速减少。
据美国国家海洋和大气局的数据显示,自1978年11月以来,北极圈气候变暖的速度比地球南部大部分地区的气候变暖速度整整快了7倍。美国阿拉巴马大学地球系统科学中心主任约翰·克里斯蒂说:“全球变暖其实看起来并不是全球性的。”自有可靠数据以来,全球自19世纪90年代至今最暖的5年依次为:1998年、2005年、2002年、2003年和2004年。
科学家们普遍同意地球变暖的说法,也都知道北极圈中自上次冰河时代冰冻的土地正在快速地融化和消失。但问题是,对于人类活动产生的温室效应到底应对此负多少责任,科学家们却是各执一词。
在去年发表的一份报告中,科学家们承认几乎不了解地球是如何吸收和反射阳光的,而这却是控制气候的最至关重要的因素。其他研究也显示,太阳放射出的热量增加,似乎更应该对全球变暖的现象负责。
克里斯蒂说:“很显然,我们在过去27年中所观察到的变暖现象中的一些部分,是由于温室气体排放量增加引起的。最简单的物理学就可以告诉你这一点。但是,就算承认温室气体的作用,当看到这种奇怪的变暖模式时,你就不得不承认肯定还有别的什么在起作用。”
过去27年间,地球平均温度上升了华氏0.63度,北极地区的温度则上升了华氏2度。克里斯蒂说:“电脑模拟一直预计由温室气体引起的全球变暖现象将会在热带地区最为严重。”然而,热带地区温度在过去27年中仅仅升高了华氏0.3度。
“燃烧释放的二氧化碳非常均匀地散布在全球,并非只集中在北极。所以过去27年间出现的北半球加速变暖的情况,好像并不能仅仅责怪温室气体。最有可能的原因是,这是一种我们从没想到的或者说根本不能理解的自然气候变化或循环。” |