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simple2007银虫 (著名写手)
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【转贴】《自然》：全球变暖将会暂停十年
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《自然》：全球变暖将会暂停十年 洋流的改变可能暂时性地抵消了温室效应 作者：杨筱亦 来源：成都商报 发布时间：2008-5-3 气候变暖速度的两倍，这对北极地区的生态系统构成了严重威胁。 新华社/法新社 全球气候变暖将开始“中场休息”，时间大约是10年。 这是全球首个十年期气候预报。德国研究小组声称，全球平均气温与正常水平相比仍将会持续偏高，但21世纪头7年所呈现出的气温不再进一步升高的势头，很可能还将再持续10年。 洋流改变抵消温室效应 德国研究小组的努力是世界范围内首次正式发布的十年期气候预报。这项研究成果刊登在5月1日出版的《自然》（Nature）杂志上。 为什么会有这种结论？研究小组称，海洋洋流的自然改变有可能会暂时性地抵消不断上升的温室气体排放所产生的影响。 普林斯顿大学地球物理流体动力学实验室科学家汤姆警告说，这项预测“非常大胆”。 即使没有全球变暖，十年期的气候变化也会产生巨大的社会和经济影响。举例来说，这种变化被认为可能会导致飓风季里飓风密度的升高或降低，又或者是长期干旱的重复发生。研究者说，仅此就使得这一十年期的气候预报具有极高的价值。而由于与百年期的气候预测使用的都是同样的计算机模型，因此相对后者，十年期这种更短期的预测更加现实。 结论：太平洋地区温度不变 这一建立气候模型的最新努力来自于德国莱布尼兹海洋科学研究所和汉堡的马克思·普朗克气象研究所。但他们在其全球模型中所使用的是一种相对非传统的方法。 但是，一些研究者认为，对于十年期的气候预测，大气的变化显得过于迅速而没有多大用处。德国研究小组则希望利用变化速度更慢而规模更大的洋流模型以及它与大气的相互作用来取代。 研究小组发现，在引入海洋温度测量后，这一模型预测气候变化的能力有力显著的提升。结果是：在未来十年，欧洲和北美的大部分地区表面温度将会出现轻微的下降。同时，太平洋热带地区的海洋温度将不会出现较大的改变。总体上，这将导致一段时期全球平均气温的相对稳定。 气候变暖仍是大趋势 去年，英国哈德利中心气候预测和研究小组提出了他们自己的十年期气候初步预测。除了所谓未来自然条件“难以预测的变化”和人为的温室气体排放、阳光浮尘等，这个小组将海洋和大气条件综合作为了他们研究的基础。而他们最终的预测是：自然的变化在某种程度上将抵消全球变暖，虽然他们同时也预计气候将会持续变暖。至少在2009年之后的5年里，有可能打破目前最热年份的记录。 这两个小组都承认，这样的模型要真正投入使用还有大量的工作要做。举例，研究者希望能够获得5000米深处的海洋温度测量。然而对大多数人来说，现在谈论这些预测有多大用处还为时过早。 （《自然》（Nature），453, 84-88，N. S. Keenlyside，E. Roeckner） [ Last edited by star580 on 2009-7-5 at 17:08 ] |
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2楼2008-05-06 08:32:20
不太相信结果，仍然会看方法
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ljf2000(金币+3,VIP+0):感谢参与！
ljf2000(金币+3,VIP+0):感谢参与！
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Nature 453, 84-88 (1 May 2008) | doi:10.1038/nature06921; Advancing decadal-scale climate prediction in the North Atlantic sector N. S. Keenlyside et al. Abstract: The climate of the North Atlantic region exhibits fluctuations on decadal timescales that have large societal consequences. Prominent examples include hurricane activity in the Atlantic, and surface-temperature and rainfall variations over North America, Europe and northern Africa. Although these multidecadal variations are potentially predictable if the current state of the ocean is known, the lack of subsurface ocean observations that constrain this state has been a limiting factor for realizing the full skill potential of such predictions. Here we apply a simple approach—that uses only sea surface temperature (SST) observations—to partly overcome this difficulty and perform retrospective decadal predictions with a climate model. Skill is improved significantly relative to predictions made with incomplete knowledge of the ocean state10, particularly in the North Atlantic and tropical Pacific oceans. Thus these results point towards the possibility of routine decadal climate predictions. Using this method, and by considering both internal natural climate variations and projected future anthropogenic forcing, we make the following forecast: over the next decade, the current Atlantic meridional overturning circulation will weaken to its long-term mean; moreover, North Atlantic SST and European and North American surface temperatures will cool slightly, whereas tropical Pacific SST will remain almost unchanged. Our results suggest that global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming. Editor's Summary Decadal climate prediction The fluctuating climate of the North Atlantic has profound consequences, inducing changes in hurricane activity, surface temperatures and rainfall from North America to Europe and Africa. In principle, these changes could be predicted if the current state of the ocean were known, but the necessary subsurface observations are lacking. Keenlyside et al. now show that detailed knowledge of the ocean state is not strictly necessary for producing useful predictions on decadal timescales. Their approach, which has proved its worth in 'retro-spective' forecasts, uses existing sea surface temperature observations to improve the forecasting power of climate models. The new model predicts that over the next decade, natural climate variations in the North Atlantic and tropical Pacific oceans will temporarily offset the projected anthropogenic warming: surface temperatures in Europe and North America may even cool a little during this period. Methods Summary Simulations Results are based on three sets of simulations with the ECHAM5/MPI-OM coupled general circulation model24 (IPCC version). (1) Three integrations (twentieth century-RF/A1B), from 1860–2015, started from different points of a control simulation. Before 2000, radiative forcing follows observations (greenhouse gas and sulphate aerosol concentrations, solar cycle variations, and major volcanic eruptions), and after 2000, it follows the IPCC A1B scenario. Predictability due to radiative forcing is estimated from these simulations. (2) Three coupled integrations (SST-restored), from 1950–2005, initialized from the twentieth century-RF simulations and with identical radiative forcing, but with relaxation towards SST constructed from the coupled model climatology with observed SST anomalies superimposed. The relaxation constant is strong (0.25 d-1) between 30° S and 30° N, and decreases linearly to zero between 30° and 60° S and between 30° and 60° N; poleward of 60° S and 60° N the model is fully coupled. (3) Nine hindcasts and two forecasts (three-member, ten-years long), initialized from the SST-restored simulations during the period 1955–2005. Radiative forcing is as in the twentieth century-RF simulations, except for solar cycle variations, which are repeated from the previous 11 years, and major volcanic eruptions. The latter that occurred during a hindcast are not included, and the impact of any that occurred before the hindcast is damped away with an e-folding time of one year. |
3楼2008-05-06 08:56:49
calanus
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4楼2008-05-06 09:45:02
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5楼2008-12-13 10:57:50
