气象人看“气候门”
最近听丁先生上课老先生诙谐地提起&气候门&，只是课时有限，没有发表看法。此事，中科院丁仲礼副院长也曾含蓄表态：质疑是科学的第一要务，面对气候变化理性置疑也是一种科学态度。不过丁院士毕竟不是气候学家，只是从科学的精神角度来提醒大家不要人云亦云。关于气候变暖，就连以气候变化为研究方向的本人也曾怀疑过。今天浏览了下&气候门&的相关网页，发觉其实是被反气候变化论者恶意曲解了。问题起自09年的黑客袭击气候学家私人信件，称气候学家蓄意更改数据，隐瞒事实，且通信中使用trick(戏法)这样的词，说明是在愚弄大众。气候学家的回应是，&我们用&戏法&这个词，指的是一种解决问题的巧妙方法，不是&秘密&&魔术&。本人宁可信任气候学家的解释，因为对于气候变化的不确定性问题，确实是让至顶聪明的科学家也头疼的事，无奈之下，抑或兴奋之下，在私人通信中，调侃地使用trick这样的字眼，并不过分。实际上地球系统自身有着高度的不可预测性，因而气候变化也是一个高度复杂的体系。气候预测至少存在着诸如由未来社会经济发展所决定的温室气体排放情景的不确定性，以及气候敏感性，气候预测模式结构的不确定性等等，对于如此复杂的系统进行研究、预测，不确定性是不可避免的，有时也称为&气候变化的科学不确定性&，这是一个公认的业界难题。另外，导致气候门事件的升级还有一个原因，关于增温趋势的争议，反对者说，从上世纪70年代以来，到1998年，全球的平均温度是在上升的，也就是有增温的趋势，而从1998年至今的十年，增温趋势没有了（当然1998年仍然保持着最高纪录）！本人也无法理解这个事情，不过丁先生说这个是可以解释的，我想无非是从更长的时间尺度上去解释，不知道网上有没有丁先生的言论，没有时间去搜了。今天去旁听一个973立项的讨论会，谈到未来CO2情景时，有个外行提出能不能自己做一个情景，偶还举手示意：老师，这个CO2问题是全球性的，自己做也要对全球的未来经济发展做评估，这个人家IPCC已经做了，也最权威了，咱们何苦呢&&没想到老师的答复竟然是：现在大家不是对IPCC那套不信任吗，咱们能不能不用那个&&个人觉得，气候学家真是冤大头！世界上运算最快的计算机只有两个人在用，一个是军事学家，一个是便是气候学家，气象事业之艰辛可见一斑，同样的科技，一个人利用来制造战争，一个却在为了世界和平而努力（2007年IPCC获得诺贝尔和平奖）。&&&&& 不过这里值得反思的是，以往的气候变化科学研究与社会沟通之间脱节之严重，已经到了必须关注的时候。这一点IPCC在第四次的评估报告中已经使用了&可能&&很可能&等字眼，表明已经意识到这个问题。但是之后还需进一步与社会公众进行沟通，那些具有顶尖头脑的气候学家，在巨型机前转模式的时候，也应该考虑一下，我要怎么包装一下才能让公众更好地理解我的数据。这绝对是科学界一大尴尬的事，不过也许这也意味着，今后的科学研究都必须要考虑公众的理解力了，因为今天的世界人民文化水平都有了很大提高，也许可以说都有点科学精神了，也许这也是一种进步。当梳理完这些，本人也找到了些许思路，也许可以做一点点尝试。
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【转帖】科学家如何看“气候门”事件与气候变化
Bercovici, Pagani, Park and Wettlaufer: Perspectives on Climate Change
By John Wettlaufer, David Bercovici, Jeffrey Park and Mark Pagani
Guest Columnist, Guest Columnist, Guest Columnist, Guest Columnist
Published Thursday, December 10, 2009
This week begins the United Nations Climate Change conference in Copenhagen (the “COP15”), following the controversy of stolen emails from the University of East Anglia’s Climate Center. Both events have inspired a flood of news stories, editorials and blogs. Although climate change remains one of our most urgent contemporary issues, it is wise to step back and view the big picture of what entists do and do not understand about the Earth’s climate system and future climate change.
By its nature, scientific inquiry is highly competitive. “Scientific consensus” describes a state of shared knowledge in which each researcher is skeptical of the work of all other researchers. All ideas, interpretations, and data are aggressively cross-examined, debated and dissected to a degree rarely encountered in other professions. Scientists challenge prevailing ideas and concepts, and are often motivated to reveal the fallacy of commonly held perceptions. Climate science is no exception, and given the high-stakes nature of the topic, results are more highly scrutinized by scientists and policy makers than in many other scientific disciplines. There is a massive international community competing over and examining climate data and models — the principal results and interpretations are not generated by a few groups in isolation.
Our broad understanding of Earth’s climate system is based on observations, experiments and models by atmospheric chemists, meteorologists, glaciologists, solar and planetary physicists, oceanographers, geologists, geochemists, biologists, paleontologists, paleoclimatologists, paleoecologists and climate dynamicists. Finding agreement among these diverse groups is often as fractious as peace negotiations between warring nations. And yet, when it comes to the major issues of climate change, agreement exists.
We understand that Earth’s climate and temperature results from a complex interaction between solar heating, rocks, oceans, sea- and land-ice, water vapor, clouds, aerosols, biological processes, and greenhouse gases. Revealing the nature of these interactions and determining the direction of climate change as these variables are altered has required an unusually broad collaboration between scientists from a wide range of fields.
We know that the rise in carbon dioxide since the start of the Industrial Revolution has been the result of human activity, mainly from the combustion of fossil fuels. We know that carbon dioxide is a greenhouse gas, which traps heat and warms our planet. For an example of greenhouse warming, one need only look at our sister planet Venus, whose surface temperature makes rocks glow at night. Although Venus is closer to the Sun than is Earth, its extremely high surface temperature is mostly a result of its Carbon Dioxide-rich atmosphere.
An increase of Carbon Dioxide on Earth triggers other effects, called feedbacks, in response to increasing temperature. As surface temperature rises, more water evaporates from the ocean. Water vapor is another important greenhouse gas that causes more warming. Warmer oceans also do a poorer job of absorbing Carbon Dioxide from the atmosphere, while the melting of permafrost releases more Carbon Dioxide and methane, yet another potent greenhouse gas. All of these feedbacks lead to more surface warming. Warming also leads to a reduction of our “heat mirrors” — sea and land ice — which causes more sunlight to be absorbed by the surface of the Earth. This drives more warming and more ice melting, and so on. Positive feedbacks amplify the temperature effects of relatively small variations in Carbon Dioxide or other changes in the climate system, and it is for this reason that Earth experiences large swings in climate. It also warns us that the full effects of rising Carbon Dioxide levels do not occur overnight.
There are always complexities that are less well understood, like the role that clouds and aerosols (volcanic sulfates, bacteria, dust, soot) play in heating or cooling Earth’s temperature. These are important effects and are intensely studied.
We know that Earth’s surface temperature will continue to rise even if we immediately stop increasing Carbon Dioxide. The oceans are massive and take a long time to warm and catch up with surface temperatures, and as they do they absorb less and less carbon dioxide, while releasing more water vapor. However, there is no consensus as to how fast and how much warming will occur over the coming decades and century. This depends, to a large extent, on how much carbon is added to the atmosphere, as well as the “climate sensitivity to Carbon Dioxide”, which is the response of global temperature to the various feedbacks mentioned above. Determining the climate sensitivity is key to understanding how much warming we can expect. Magnitudes of climate sensitivity range from small to large and are different among the different computer models used to project future climate changes.
However, Earth’s history has something to say about climate sensitivity and the role of Carbon Dioxide as well. The reconstruction of Earth’s history reveals a story of slow and rapid climate change and clear evidence for immense variations in temperature. While most discussions in the popular press focus on the past 100 to a few 100,000 years and the precise relationship between Carbon Dioxide and temperature, it is informative to examine the full range of climate variations over millions of years.
Earth was, in fact, ice-free for most of its history. For example, Earth was much warmer and had no significant polar ice between 65 to about 34 million years ago. 55 million years ago, rapid, and massive releases of carbon acidified the oceans and warmed Earth’s surface about 5˚C above what was already a warm planet. At peak warming, about 50 million years ago, crocodiles roamed the Arctic amongst subtropical flora and fauna, even though the Sun’s intensity was lower than today. Much higher Carbon Dioxide during this time is revealed by various paleoclimate reconstructions, and subsequent global cooling is shown to have followed Carbon Dioxide decline.
Earth’s history tells us that the leading driver of climate change is the concentration of atmospheric carbon dioxide. Not the only driver, but the leading one. It also reveals that climate sensitivity to Carbon Dioxide is possibly much higher than discussed in policy-making circles. About 5 million years ago, Carbon Dioxide was as high or only slightly higher than 2009 AD values, and Earth reached temperatures 4˚C warmer than now, with sea levels tens of meters higher. The present-day location of Yale University was underwater.
Many lines of evidence and study tell us about the effects of carbon dioxide release. In the past, large increases in Carbon Dioxide corresponded to major warming events. It is unwise to think that today’s increase in Carbon Dioxide will, for some reason, produce a different outcome.
Mark Pagani is an associate professor of geology and geophysics, and a member of the Yale Climate & Energy Institute Executive Committee. John Wettlaufer is an A.M. Bateman Professor of Geophysics, Physics and Applied Mathematics. Jeffrey Park is a professor of geology and geophysics, and the director of the Yale Institute for Biospheric Studies. David Bercovici is a professor and chair of the Department of Geology & Geophysics, and the deputy director of the Yale Climate & Energy Institute.
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