Will it cost the earth? How economists are pricing the ravages of climate change
The price of the US's "addiction to oil"goes far beyond the dependence on politically volatile states cited by President George W. Bush this week. According to the world's leading climate scientists, reliance on fossil fuels is creating a global warming disaster that could end up costing the earth.
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Faced with these threats, rational people and governments might be expected to reduce their greenhouse gas output.
But there is little appeal in taking costly action in the short term to stave off a long-term threat - especially one that, by its nature, is hard to calibrate.
Persuading individuals and businesses to take the action necessary to tackle climate change caused by economic activity itself requires an economic argument. But how to put a price on the world's climate and the catastrophes that may follow from global warming?
Attempts to fill a policy vacuum as the expiry of the Kyoto protocol in 2012 looms are suddenly turning environmental economics into one of the hottest areas of the discipline. The challenge is to find policies that will make the most efficient use of scarce resources and provide a rational basis on which to build an international consensus to address climate change among politicians and business people.
It has taken some time for the economics of climate change to enter the mainstream. While scientific knowledge in this area has leapt ahead, economic advances have been much slower. You do not have to look far for the reasons. Most economics theory is designed to cope with issues that are relatively short term or national. Even international economics is ill-equipped to deal with trans-boundary issues.
Economists find it hard enough to make an accurate forecast one year ahead, let alone 100. Yet environmental economics must grapple with a plethora of uncertainties - scientific and political - over a dauntingly long timescale. Small wonder then that Michael Grubb, chief economist of the UK's Carbon Trust, a government-funded organisation that advises business, declares: "Understanding the economics of climate change is like trying to understand the Big Bang without Newtonian mechanics."
Dieter Helm, a fellow of economics at New College, Oxford, adds: "The usual economists' toolbox looks puny against the scale of this challenge." Just as the experience of the unemployment of the 1930s required the reinvention of much of macroeconomics, so climate change needs new thinking too, he says.
The drawback of the traditional approach notoriously emerged in the mid-1990s when economists, commissioned by the Intergovernmental Panel on Climate Change, used a cost-benefit analysis to assess the damage to the environment. There was an outcry when it emerged that the analysis involved valuing the life of an American at 15 times that of someone in the industrially less-advanced world.
Another problem is that environmental goods - clean air and water, a stable climate - are rarely taken into account by standard economic analyses. For this reason, the United Nations has begun to promote the idea of "natural capital", as a way of valuing environmental goods so that they can be included in economists' equations.
As Klaus T?pfer, executive director of the UN Environment Programme, describes it: "The goods and services delivered by nature, including the atmosphere, forests, rivers, wetlands, mangroves and coral reefs, are worth trillions of dollars. When we damage natural capital, we not only undermine our life support systems but the economic basis for current and future generations. Targeted investments in this natural capital have a high rate of return in terms of development."
The UK can claim to be at the forefront of the debate, thanks in part to a decision by Gordon Brown, chancellor of the exchequer, to commission a review of the economics of climate change, headed by Sir Nicholas Stern, a former World Bank chief economist and senior Treasury official. Sir Nicholas's report will take a global view of the economic risks and possible benefits of climate change and assess the potential of economic instruments to address them. The findings will carry weight internationally since they will be part of the basis for UN discussions, due to begin this year, on the future of Kyoto.
Sir Nicholas spoke publicly about his review for the first time earlier this week, in a lecture to the Oxford Institute for Economic Policy. Outlining some of the complexities of establishing economic solutions to climate change he went on: "It is an international collective action problem . . . The simple standard theory of externality" - on the spillover effects of production or consumption for which no payment is made - "is useful but not a fundamental answer to the problem".
The first step, he said, was to convince all the governments involved of the need to take urgent action on climate change. The difficulty of achieving an international consensus is reflected in the history of the Kyoto protocol, which has been rejected by the US and Australian governments, and dogged with delays and disagreements (see right).
Countries such as the US have decided that the costs of compliance are too high. As Mr Helm points out, climate change is a global public "bad", creating incentives for individual countries to free-ride on others' emissions reductions: if one country reduces its emissions, the effect on global warming will be negligible but the effect on that country's competitiveness could besignificant.
Jonathan K?hler, of the Department of Applied Economics in Cambridge, thinks it is not necessary for everyone to sign up to an international agreement for progress to be made on emissions reductions. Market forces will do some of the work, he indicates.
"If you think climate change is a big problem and the world will have to do something, at some point there will be gigantic markets out there and big export opportunities for low carbon production technologies." He cites the example of Denmark, which captured a large slice of the market in wind turbines through its early investment in that sector.
Policies to combat climate change need to take into account the impact of technological change on reducing the cost of renewable energy sources. Mr K?hler, who is also a manager at the Norwich-based Tyndall Centre for Climate Change Research, says economic models that take this into account suggest that the cost of switching over to a low carbon energy environment is not high compared with the cost of investment in energy systems that would anyway be needed. What is not clear is how quickly this would happen and how much government intervention would be required.
The policy instruments available to governments traditionally include a carbon tax, limits on emissions and incentives to encourage the development of clean fuel technologies. Most economists favour market-based solutions as the most effective way to drive change in business practice (see below left) and encourage the development of new technology. In an open letter to Mr Bush in December, 25 US economists, including three Nobel laureates, urged the president to control greenhouse gas emissions through mechanisms such as setting limits on the amount of carbon dioxide countries could produce and allowing them to trade carbon allowances with one another.
Mr Helm believes that an alternative to subsidising a particular technology, such as nuclear fuel, in order to provide low carbon generation is to auction long-term carbon contracts. Under such a scheme, the government would auction carbon contracts for the supply of emission reductions over a long period - such as 20-30 years. The advantage for governments is that they are not obliged to evaluate industry claims about which technology is cheaper. Nor would they be obliged to sell a politically unpopular choice - such as nuclear technology - to a sceptical public. A similar scheme has been developed by the World Bank.
But bedevilling attempts to provide an authoritative analysis of the economic impact of climate change, and thus the economic instruments necessary to address it, is the high level of uncertainty that pervades the subject. Although the scientific evidence points clearly to the conclusion that human actions are having an effect on the climate, many important questions remain unanswered: for instance, the extent to which temperature will rise smoothly or in jumps and the probability of "high-impact" events such as the Gulf Stream changing direction.
Sir Nicholasbelieves his review, due in the autumn, will discover some of the answers. He said this week: "One of our key tasks is to find out whether you can be green and grow. There are a lot of arguments to suggest this is likely to be possible."
But, he hinted, the road to knowledge would not be easy: To understand the issues, "you need all the economics you ever learnt - and more".
气候变化经济学
美
国“石油瘾”（"addiction to oil"）所要付出的代价，远远超出该国总统乔治?布什(George W. Bush)上周（在国情咨文中）提到的对政局动荡的中东各国的依赖。全球顶级气候学家们认为，人们对矿物燃料的依赖正造成一场全球变暖的灾难，最终可能会以地球本身为代价。
面对这些威胁，可以预计：理性的人们和政府会减少温室气体的排放量。
然而，却没什么人呼吁在短期内采取成本高昂的举措，以避开某种长期的威胁――特别是当这是一种天生就难以准确评估的的威胁时。
要说服个人和企业采取必要行动，以解决经济活动造成的气候变化问题，这本身就需要经济学方面的论证。然而，应如何给全球气候及全球变暖可能造成的灾难来定价呢？
随着《京都议定书》(Kyoto protocol)即将于2012年到期，填补这一政策真空的种种尝试，突然使得环境经济学成为该学科最热门的领域。目前的挑战在于，要找出能够最有效地利用稀缺资源的政策，并提供一个有利于达成国际共识的理性基础，以便在政治家和商业人士中解决气候变化问题。
气候变化经济学用了一段时间才步入主流。尽管该领域的科学知识取得了飞速发展，但经济方面的进步却相对缓慢得多。你无须费力寻找其背后的原因。绝大多数经济学理论都是用来处理那些相对短期或本国的问题。即便是国际经济学，在应对跨国境问题时也是捉襟见肘。
经济学家们发现，要想准确预测一年以后的事，就已经非常困难，更不用说100年以后了。然而，环境经济学必须在一个长得令人生畏的时间跨度内，应对太多的不确定性因素――包括科学和政治两方面的因素。难怪英国政府资助的商业咨询组织碳信托(Carbon Trust)首席经济学家迈克尔?格布(Michael Grubb)宣称：“要领会有关气候变化的经济学，就像试图在没有牛顿力学理论支持的情况下，去理解宇宙大爆炸。”
牛津大学新学院(New College, Oxford)经济系的迪特尔?赫尔姆(Dieter Helm)补充说：“在如此规模的挑战面前，经济学家们的常用工具似乎微不足道。”他表示，正如上世纪30年代的失业经历要求重塑宏观经济学中的很多内容一样，气候变化也需要新思维。
上世纪90年代中期，（有关气候变化）传统思维方式的缺点令人不悦地开始显现。当时，经济学家们受政府间气候变化问题小组(Intergovernmental Panel on Climate Change)委托，使用成本效益分析法来评估其对环境的破坏。在上述分析中，对一个美国人生活的估价，是生活在欠发达地区人口的15倍，此消息一出，抗议之声顿起。
另一个问题是，标准的经济学分析极少将环境商品纳入考虑范围，譬如清洁的空气和水、稳定的气候。为此，联合国开始推广“自然资本”的概念，将其作为一种环境商品的估价方式，以便将此种商品纳入经济学家的考虑之中。
正如联合国环境规划署(UNEP)执行董事克劳斯?托普弗(Klaus T?pfer) 所描述的那样：“大自然提供的商品和服务，包括大气、森林、河流、湿地、红树林和珊瑚礁，其价值当以万亿美元计。当我们破坏自然资本的时候，我们不仅在破坏我们的生命支撑体系，同时也在破坏今人与后人的经济基础。从发展角度而言，针对这种自然资本的投资有很高的回报率。”
英国可以宣称自己处于辩论的最前沿――这在一定程度上要归因于财政大臣戈登?布朗(Gordon Brown)的一个决定，即对气候变化经济学进行委托研究。该项研究由世界银行(World Bank)前首席经济学家、财政部高级官员尼古拉斯?斯特恩(Nicholas Stern)爵士领衔进行。斯特恩爵士的报告，将从全球角度研究环境变化所带来的经济风险和潜在利益，并就解决这一问题之经济手段的潜力进行评估。从今年起，联合国将就《京都议定书》的未来进行讨论，而上述研究结果将成为讨论的部分依据，由此产生重大的国际影响力。
上周，尼古拉斯爵士在牛津经济政策学会(Oxford Institute for Economic Policy)的一次演讲中首次公开谈论他的研究情况。他概述了对气候变化设置经济学解决方案的一些复杂因素，并接着说道：“这个问题需要国际社会共同采取行动……简单的外部标准理论”――这种外部性在于生产和消费产生的无报酬溢出效应――“是有用的，但不是该问题的根本答案”。
他表示，第一步是要让所有相关政府相信，有必要针对气候变化采取紧急行动。《京都议定书》的历史反映了达成国际共识的难度。该议定书已遭美国和澳大利亚政府的否绝，而且拖延和争执此起彼伏。
美国等国家认为妥协的代价过于高昂。正像赫尔姆所指出的，气候变化是全球公“害”，单个国家由此滋生了从他国减排行为中“沾光”的动机：如果一国减少其排放量，对全球变暖的影响微乎其微，但对该国竞争力的影响却意义重大。
剑桥大学应用经济系(the Department of Applied Economics in Cambridge)的乔纳森?克勒(Jonathan K?hler)认为，没有必要为了在减排方面取得进展，而要求每个国家都在国际协议上签字。他指出，市场力量将会起到一些作用。
“如果你认为气候变化是一个大问题，而全世界将不得不为此采取一些举措，那么从某个角度而言，将会出现巨大的市场和低碳生产技术的巨大出口机遇。”他援引了丹麦的例子。该国通过其对风力发电的早期投资，夺取了该领域的一大块市场。
应对气候变化的政策，要考虑到能降低可再生能源成本的科技变革所带来的影响。克勒表示，考虑到这一因素的经济模型显示，与无法回避的能源系统投资成本相比，向低碳能源环境转型的成本并不算高。目前尚不明朗的是，这种情况会以多快的速度发生，以及需要多少政府干预。克勒兼任廷德尔气候变化研究中心(Tyndall Centre for Climate Change Research)主管，该中心总部设在英格兰的诺里奇。
可供政府运用的传统政策工具包括征收碳（排放）税，限制排放，并激励发展清洁燃料技术。多数经济学家喜欢将以市场为基础的解决方案作为驱动商业惯例变革及鼓励新技术发展的最有效方法。去年12月， 25位美国经济学家（包括3位诺贝尔奖得主）联名给布什总统写了一封公开信，敦促建立相关机制，设定各国可排放二氧化碳量的上限，允许各国间进行碳排放权交易等，以控制温室气体的排放。
赫尔姆认为，除了对特殊技术（如核燃料技术）进行补贴，另外一个减少碳排放的方法是拍卖长期碳合同。这种方案是，政府拍卖碳合同，以便在长期内（如20年至30年）减少排放量。这样做对政府的益处是，它们没有义务对业界有关哪种技术成本更低廉的说法进行评估。它们也没有义务将政治上不受欢迎的选择――如核技术――兜售给抱怀疑态度的公众。世界银行已开发了一个类似的计划。
然而，（环境经济学）这一学科充满高度的不确定性，使得人们在尝试对气候变化的经济影响提供权威分析，并进而提供解决这一问题的必要经济手段的时候备受困扰。尽管有科学证据明确显示人类行为正对气候产生影响，但许多重要问题仍没有答案，例如：气温会平稳上升或跳跃上升至何种程度？“高影响”事件，如墨西哥暖流(Gulf Stream)转向发生的可能性有多大？
尼古拉斯爵士认为，他的考察（计划于秋季结束）将找到一些问题的答案。他于上周表示：“我们的关键任务之一是找出你是否可以使环保与发展并存。有很多论据表明这是可能的。”
但他暗示，通往知识的道路并不好走：为了搞清楚问题，“你需要运用所学过的所有经济学知识――甚至更多”。
