这一点在关于海平面上升的讨论中表现得最为明显。研究者们知道海平面在本世纪上升得很快，一部分是因为山岳冰川的融化，一部分因为温水比冷水占的空间更大。新报告翻新了海平面上升的计算，将最乐观的估计数量定为1到2英尺，实际上稍微低于2001年的估计。尽管听起来没有多少，但实际上几个英尺可不是什么小数目——它们足以淹没许多低洼地带和沿海沼泽及湿地。这一数据多少还可以再行商榷。

然而，在过去的一年半中间，新的研究显示，由于格陵兰岛和南极的冰盾似乎已经开始更快地向海中漂移，海平面的上升速度可能会提高很多。这个新研究中的一些内容出现在艾尔·戈尔的电影《不愿面对的真相》里，詹姆斯·汉森在《纽约书评》中也提到了这个新信息；这就是最近海平面上升告急的原因。但IPCC的报告中对此只有一个简单的警告：“不能排除上升的数值可能更大，但由于对这些效应的理解的有限性，我们无法估计可能性的大小，或者给出海平面上升的上下限，”除此之外只字未提。

简而言之，新报告显然是一个很保守的文件。然而它的预测仍然令人恐惧，这恰恰说明我们所引起的变化有多大，这个变化远远超出了人们的理解。即使在这个保守的文件中，撰写小组也毫不含糊地指出：台风和飓风可能变得更频繁；北极夏季海冰将会退缩甚至可能消失；积雪也会缩小。今年年底，第二工作小组将列出这些变化对人类的影响，把海平面上升的高度转化成难民数量，说明温度和湿度上升对引起疟疾的蚊虫的影响以及热浪可能引起的农业损失。语言可能仍然苍白无力，但结论显然是活生生的。

IPCC历来避免采取任何政治立场，从未提出具体的政策，在新报告中它也保持了这一传统。然而，在关于气候变化的讨论中，报告却引入了一个明显具有困扰性的统计数据。由于碳排放与其对气温的影响存在一个时间差，因此，即使我们现在立刻停止使用煤炭、石油和天然气，每十年气温仍然会继续上升0.2摄氏度。但是，报告写道：“如果所有辐射效应介质（即温室气体）能够维持在2000年的水平，未来20年的气候变暖趋势将减少到每十年0.1摄氏度。”

上面这段话换成通俗易懂的语言，就是说：如果世界各国领导人当年重视了第一个IPCC的报告，在2000年之前就大力维持温室气体排放不再上升的话，气温的预期上升值就会减少到现在预期数值的一半。用realclimate.org专家的话来说，气候变化是一个带有高度“对拖延的惩罚”的问题：年复一年地拖延，惩罚也就变得越来越大大。

这也正是为什么关于气候最重要的新闻不是来自IPCC而是来自华盛顿。20年来美国毫无作为——两党配合默契，纹丝不动，而在本届新国会产生后的头几个星期，竟然掀起了一个行动的小高潮，从加利福尼亚州的参议院亨利·怀克斯曼到佛蒙特州的伯尼·桑德斯，再到亚利桑那州的约翰·麦凯恩等许多人提出一系列议案，呼吁多少都要确定碳减排目标。其中一些议案建议设立“上限与交易”制度，制定二氧化碳排放的整体限制，但同时允许企业自由买卖额定的排放权；这将为减碳措施创造出一个市场。

IPCC报告并没有提出具体的减排数字，但也明确地提出必须迅速深刻地进行减排，除此之外没有任何乐观的方法。报告还预测说，即使我们的措施都是正确的，气温仍然会剧烈上升，而且伴随着所有的物理变化（从一个或其他角度来说）。但是，我们也有理由期待：如果美国能够采取极端手段又快又狠地减排，气温可能会少升高2摄氏度，而走向失控的极地冰川融化也能得到制止。这意味着， 任何有用的立法必须立刻着手实行，并且有人能够将其长期、毫不妥协地坚持下去。同时得到相关委员会主席、加利佛尼亚州参议员芭芭拉·鲍克瑟支持的桑德斯法案就接近这个标准。它呼吁最终到2050年达到80%的减排；由他的总统候选人竞争对手巴拉克·奥巴马共同发起的麦凯恩法案在最终减排数量上就多少显得弱一些。但事情的商讨却迟迟难以开始，要知道，现在要尽快开始行动，这几乎和最终的数字一样重要。

没人期望布什总统会签署这样一个法案。实际上，就连他在今年的国情咨文中提到“气候变化”这个词，许多人都认为是一个小小的奇迹了。（至于他提出的让某些车辆更换燃料等蹩脚建议，大家都把它当作废话。）现在所发生的一切与下次总统大选的形势相互关联，立法最终可能在2009年得到通过和签署。IPCC报告的暗示很清楚：这次立法是我们最后一个重要的机会——除了全力以赴地在我们的经济中进行碳减排，在不断恶化的全球变暖面前，任何行动都毫无意义。当然，目前我们的经济只是问题的一部分，尽管我们的人均能源消费高于任何国家，但中国的总体碳排放量在2010年之前可能就会超过我们。即使我们自己开始行动，同时也必须想好如何以最快的速度领导一个大规模的国际行动。

唯一真正振奋人心的进展是去年开始的公众关注的颠覆性提高，这开始于卡特里娜飓风和艾尔·戈尔的电影。一月份，我们中的一些人发起了一个名为“stepitup07.org”的行动，号召美国人在4月14日在自己的社区中召开集会，呼吁国会采取行动。在网站开设短短几周之内，就有来自46个州的600多个团体表示要举行游行，很明白，这是美国有史以来针对全球变暖所进行的最大一次有组织活动。这些团体范围广泛，从环境组织到福音教会到大学学生联谊会都有，把他们联系起来的唯一纽带就是内心的感受（部分原因在于今年冬天的古怪天气）——大家感到地球已经遭受沉重打击，IPCC的评估报告用最保守的语言告诉我们这个打击有多么深重，也告诉我们：哪怕为了一个限制这个破坏的机会，我们也必须付出无穷的努力。

作者简介：比尔·麦奇本经常为《纽约书评》撰稿，米德尔伯里学院学者，著有《自然的终结》和《深度经济：社区的财富与长远的未来》

本文刊登于2007年3月15日发行的《纽约书评》。

同时感谢TomDispatch.com的汤姆·英吉尔哈德。

版权归比尔·麦奇本所有。
http://www.chinadialogue.net/article/show/single/ch/817-Warning-on-warming

Warning on warming
Bill McKibben

March 02, 2007
The UN climate-change panel’s new report is an opaque, conservative and nonpolitical document. Bill McKibben sums up its stark message: quick, deep cuts in fossil-fuel emissions are needed immediately.

When the Intergovernmental Panel on Climate Change (IPCC) issued its latest report in early February, it was greeted with shock: “World Wakes to Climate Catastrophe,” reported an Australian newspaper. But global warming is by now a scientific field with a fairly extensive history, and that history helps set the new findings in context -- a context that makes the report no less terrifying but much more telling for its unstated political implications.


Although atmospheric scientists had studied the problem for decades, global warming first emerged as a public issue in 1988 when James Hansen, a NASA scientist, told the United States Senate that his research, and the work of a handful of other scientists, indicated that human beings were dangerously heating the planet, particularly through the use of fossil fuels. This bold announcement set off a scientific and political furor: many physicists and chemists played down the possibility of serious harm, and many governments, though feeling pressure to react, did little to restrain the use of fossil fuel. “More research” was the mantra everyone adopted, and funding for it flowed freely from governments and foundations. Under the auspices of the United Nations, scientists and governments set up a curious hybrid, the IPCC, to track and report on the progress of that research.

From roughly 1988 to 1995, the hypothesis that burning coal and gas and oil in large quantities was releasing carbon dioxide and other gases that would trap the sun’s radiation on Earth and disastrously heat the planet remained just that: a hypothesis. Scientists used every means at their disposal to reconstruct the history of the earth’s climate and to track current changes. For example, they studied the concentration of greenhouse gases in ancient air trapped in glacial cores, sampled the atmosphere with weather balloons, examined the relative thickness of tree rings, and observed the frequency of volcanic eruptions. Most of all, they refined the supercomputer models of the earth’s atmosphere in an effort to predict the future of the world’s weather.

By 1995, the central Herculean tasks of both research and synthesis were largely complete. The report the IPCC issued that year was able to assert that “the balance of evidence suggests” that human activity was increasing the planet’s temperature and that it would be a serious problem. This was perhaps the most significant warning our species, as a whole, has yet been given. The report declared (in the pinched language of international science) that humans had grown so large in numbers and especially in appetite for energy that they were now damaging the most basic of the earth’s systems -- the balance between incoming and outgoing solar energy. Although huge amounts of impressive scientific research have continued over the twelve years since then, their findings have essentially been complementary to the 1995 report -- a constant strengthening of the simple basic truth that humans were burning too much fossil fuel.

The 1995 consensus was convincing enough for Europe and Japan: the report’s scientific findings were the basis for the Kyoto negotiations and the treaty they produced; those same findings also led most of the developed world to produce ambitious plans for reductions in carbon emissions. But the consensus didn’t extend to Washington, and hence everyone else’s efforts were deeply compromised by the American unwillingness to increase the price of energy. Our emissions continued to soar, and the plans of many of the Kyoto countries in western Europe to reduce emissions sputtered. (At the same time, most tragically of all, China and India had just begun their rapid industrial takeoffs using precisely the technologies we then knew were wreaking havoc; they did not seek or find much aid from the western countries that could have encouraged them to take a more benign path.)

In 2001, the IPCC issued its Third Assessment Report (TAR), but it coincided with the start of the Bush administration, which refused even to consider a serious policy for climate. The IPCC’s new Fourth Assessment of this February (known as AR4) arrives at a more congenial moment, as the new Democratic Congress takes up a wide variety of legislation designed, finally, to curb emissions.

The finding of the new report that attracted the most attention in the press was that scientists were now more confident than ever that the warming we’ve seen so far (about one degree Fahrenheit in the average global temperature) was caused by human beings. Instead of being merely “likely”, the conclusion was now “very likely”, which in the IPCC’s lexicon means better than a 90% chance. But it’s been years since any reputable scientist specialising in climate research doubted that conclusion. More important findings were ignored in accounts of the report and in some cases were obscured by the document’s very poor prose, which is much more opaque than its predecessors. Those findings include:

* The amount of carbon in the atmosphere is now increasing at a faster rate even than before.

* Temperature increases would be considerably higher than they have been so far were it not for the blanket of soot and other pollution that is temporarily helping to cool the planet.

* Alternative explanations for some of the warming (for example, sunspot activity and the “urban heat island effect”, the raising of temperatures in cities caused by high building densities and the use of heat-retaining materials such as concrete and asphalt) are now known to be relatively negligible.

* Almost everything frozen on earth is melting. Heavy rainfalls are becoming more common since the air is warmer and therefore holds more water than cold air, and “cold days, cold nights and frost have become less frequent, while hot days, hot nights, and heat waves have become more frequent.”

These facts serve as the prelude to the most important part of the new document, its predictions for what is to come. Here, too, the news essentially confirms the previous report, and indeed most of the predictions about climate change dating back to the start of research: if we don’t take the most aggressive possible measures to curb fossil-fuel emissions immediately, then we will see temperature increases of -- at the best estimate -- roughly five degrees Fahrenheit during this century. Technically speaking, that’s enormous, enough to produce what James Hansen has called a “totally different planet”, one much warmer than that known by any of our human ancestors.

The process by which the IPCC conducts its deliberations -- scientists and national government representatives quibbling at enormous length over wording and interpretation -- is Byzantine at best, and makes the group’s achievements all the more impressive. But it sacrifices up-to-the-minute assessment of data in favor of lowest-common-denominator conclusions that are essentially beyond argument. That’s a reasonable method, but one result is that the “shocking” conclusions of the new report in fact lag behind the most recent findings of climate science by several years.
That’s most obvious here in the discussion of the rise in sea level. Researchers know that sea levels will rise fairly quickly this century, in part because of the melting of mountain glaciers and in part because warm water takes up more space than cold. The new assessment refines the calculations of the rise in sea level and puts the best estimate at a foot or two, which is actually slightly less than the last assessment in 2001. Though it doesn’t sound like much, a couple of feet is actually a large amount -- enough to inundate many low-lying areas and drown much of Earth’s coastal marshes and wetlands. Still, it might be more or less manageable.

During the last eighteen months, however, new research has indicated that a far more rapid rise in sea level may be possible, because the great ice sheets of Greenland and the Antarctic appear to have begun moving more quickly toward the sea. Some of this research appeared in Al Gore’s movie An Inconvenient Truth, and James Hansen has written in The New York Review about this new information; it is responsible for much of the recent increase in the level of alarm. But it is not included in the IPCC report, except as a caveat: “larger values cannot be excluded, but understanding of these effects is too limited to assess their likelihood or provide a best estimate or an upper bound for sea level rise.”

In short, the new report is a remarkably conservative document. That it is still frightening in its predictions simply indicates the huge magnitude of the changes we’re now causing, changes far larger than most people fully understand. Even using its conservative projections, the panel states unequivocally that typhoons and hurricanes will likely become more intense; that sea ice will shrink and perhaps disappear in the summertime Arctic; that snow cover will contract. Later this year, a second working group will outline the effects of these changes on humans, translating inches of sea-level rise into numbers of refugees, showing the effects of increases in temperature and humidity on malaria-carrying mosquitoes as well as the impact of heat waves on crop losses. The language will still be bloodless, but the findings obviously won’t.

The IPCC has always avoided taking political positions -- it doesn’t recommend specific policies -- and it continues this tradition with its new report. In its discussions of the momentum of climate change, however, it does introduce one particularly disturbing statistic. Because of the time lag between carbon emissions and their effect on air temperature, even if we halted the increase in coal-, oil- and gas-burning right now, temperatures would continue to rise about two-tenths of a degree Celsius per decade. But, the report writes, “if all radiative forcing agents [i.e., greenhouse gases] are held constant at year 2000 levels, a further warming trend would occur in the next two decades at a rate of about 0.1ºC per decade.”

Translated, this means, to put it simply, that if world leaders had heeded the early warnings of the first IPCC report, and by 2000 had done the very hard work to keep greenhouse-gas emissions from growing any higher, the expected temperature increase would be half as much as is expected now. In the words of the experts at realclimate.org, where the most useful analyses of the new assessment can be found, climate change is a problem with a very high “procrastination penalty”: a penalty that just grows and grows with each passing year of inaction.

This is why the most important news about climate at the moment may come not from the IPCC but from Washington. After twenty years of inactivity -- a remarkably successful bipartisan effort to accomplish nothing -- the first few weeks of the new Congress have witnessed a flurry of activity. A series of bills have been introduced by people including California Representative Henry Waxman, Vermont Senator Bernie Sanders and Arizona’s John McCain which would call for more or less aggressive carbon-reduction targets. Some of the bills would set in place a “cap-and-trade” system that would set overall limits on emissions of carbon dioxide but would allow companies to freely buy and sell credits permitting them to emit certain amounts of it; this would produce a market for carbon-cutting measures.
The IPCC report doesn’t call for particular reduction figures. It does, however, make clear that reduction in emissions must be quick and deep. There is no more optimistic alternative. Even if we do everything right, we’re still going to see serious increases in temperature, and all of the physical changes (to one extent or another) predicted in the report. However, there’s reason to hope that if the US acts extremely aggressively and quickly we might be able to avoid an increase of two degrees Celsius, the rough threshold at which runaway polar melting might be stopped. This means that any useful legislation will have to feature both a very rapid start to reductions and a long and uncompromising mandate to continue them.

Sanders’s bill, also endorsed by California’s Barbara Boxer, who heads the relevant committee, comes closest to that standard. It calls for an eventual 80% cut in emissions by 2050. McCain’s bill, co-sponsored by one of his challengers for the presidency, Barack Obama of Illinois, is somewhat weaker in its eventual targets. But the bargaining has barely begun, and in any event quick initial implementation of any cuts will be almost as important as the final numbers.

No one expects president George W Bush to sign such a bill. In fact, it was widely considered a minor miracle that he uttered the words “climate change” in this year’s State of the Union address. (His limp proposal, centering on alternative fuels for some vehicles, was equally widely considered a dud.) What’s happening now has much to do with positioning for the next presidential election in 2008, and the legislation that will eventually be passed and signed in 2009. What the IPCC report makes clear by implication is that that legislation will be our last meaningful chance: anything less than an all-out assault on carbon in our economy will be rendered meaningless by the increasing momentum of global warming. And of course by now our economy is only part of the problem. Though we use more energy per capita than any other country, the Chinese may pass us in total carbon emissions by decade’s end. Even if we start to get our own house in order, we’ll need to figure out how, with desperate speed, to lead an equally sweeping international response.

The only really encouraging development is the groundswell of public concern that has built over the last year, beginning with the reaction to Hurricane Katrina and Al Gore’s movie. In January 2007, a few of us launched an initiative called stepitup07.org. It calls for Americans to organise rallies in their own communities on April 14 asking for congressional action. In the first few weeks the website was open, more than six-hundred groups in forty-six states registered to hold demonstrations -- this will clearly be the largest organised response to global warming yet in the United States. The groups range from environmental outfits to evangelical churches to college sororities, united only by the visceral sense (fueled in part by this winter’s bizarre weather) that the planet has been knocked out of whack. The IPCC assessment offers a modest account of just how far out of whack it is -- and just how hard we’re going to have to work to have even a chance at limiting the damage.

Bill McKibben is a frequent contributor to The New York Review and is scholar in residence at Middlebury College and the author of The End of Nature and Deep Economy: The Wealth of Communities and the Durable Future.

This article appears in the March 15, 2007 issue of The New York Review of Books

Thanks also to Tom Engelhardt of TomDispatch.com

Copyright 2007 Bill McKibben

减排肯定是对的。但变暖的原因能不能肯定是这个？昨天的环球时报上有一篇反面文章。