When Donald Trump announced last week that the US was pulling out of the Paris accord on climate change, other governments were rightly determined that the move neither derail the drive for lower carbon emissions nor allow the US to gain a competitive advantage.
不久前当唐纳德?特朗普(Donald Trump)宣布美国将退出巴黎气候变化协定时，其他国家政府明智地认定，此举既破坏不了全球推动减少碳排放量的努力，也不会让美国因此获得竞争性优势。
Thoughts immediately turned to carbon border tax adjustments, a way of instituting a single international price of carbon by penalising the exports of countries with no domestic emissions pricing of their own. Like the best climate change policies, it is an elegant idea, tweaking a price and allowing the free market to respond rather than attempting a complex series of direct interventions.
各国政府的想法立即转向碳边境调节税——制定统一的国际碳税标准，对那些在本国没有征收碳税的国家的出口商品施加惩罚。正如最好的气候变化政策一样，这是个绝妙的想法——调整价格并允许自由市场做出应对，而不是试图进行一系列复杂的直接干预。
However, like many good ideas, the reality is far more complex. Fiendish calculations requiring detailed data, together with potential legal impediments, unfortunately suggest a more piecemeal approach might yield better returns.
然而，像很多好点子一样，现实远比想象复杂。由于计算极为困难，需要详细的数据，还可能遭遇法律障碍，因此遗憾的是，更零散的策略可能带来更好的回报。
There are various models of carbon border taxes, but the general principle is that producers in countries with carbon pricing should be protected from being undercut by those in countries without. Variations include putting an import tariff on goods from trading partners without carbon emissions measures, or those that also involve a rebate on exports, similar to the operation of value added tax.
碳边境税有很多不同的类型，但一般原则是征收碳税的国家的生产商应该受到保护，使之免受不征收碳税的国家的生产商的低价竞争。碳边境税的种类包括，对那些不采取减排措施、或同时实行出口退税的贸易伙伴的货物征收关税，与增值税的操作类似。
However, imposing VAT, which is a percentage of a price, is straightforward. Working out a single price for carbon and delving deep into the vastly complex supply chains of a modern economy is not.
然而，征收增值税（按价格的一定比例征收）是直截了当的方法。而制定统一碳税并深入研究现代经济异常复杂的供应链，则没那么简单。
For a start, creating a comparable carbon cost across the varied forms of emission pricing — simple carbon tax, cap-and-trade and so forth — would be challenging. Some governments, such as Barack Obama’s administration, have sought to reduce carbon in more roundabout ways by tightening product standards, such as emissions standards for vehicles, and setting rules for power plants. All of these should clearly be taken into account, but translating them into a simple national-level price will be a highly complex and contested issue.
首先，在各式各样的排放税中——简单的碳税、“限量及交易”(cap-and-trade)机制等等——建立统一的碳税将会是一项挑战。一些政府（比如巴拉克?奥巴马(Barack Obama)政府）试图以更迂回的方式，通过收紧产品标准（比如汽车排放标准）以及为发电厂制定标准来减少碳排放。这些显然应该被纳入考虑，但把这些都转化成国家层面的简单碳税，将是一个极为复杂而具有争议的问题。
More broadly, taxing all manufactured exports from, for example, the US is clearly unfair to those produced in relatively low-carbon industries, or indeed low-carbon producers within each industry. For example, for goods like cars, which source from different sectors such as glass, steel and rubber, taxing them fairly would involve disaggregating the product into the carbon emitted from each sector, and preferably each producer within each sector. Taking a broader brush approach would give a competitive advantage to the dirtier producers inside each economy by taxing them the same as cleaner companies.
更广泛地看，比如对美国所有制造业出口产品征收碳边境税，明显对那些相对低碳的产业、或每种产业中确实更加低碳的厂商生产的产品不公平。例如，对于汽车（组件来自玻璃、钢铁和橡胶等不同产业）等商品来说，公平征税意味着，把商品按每个行业的碳排放进行拆分，最好精确到每个行业内的每家厂商。采取一刀切的办法，对污染企业和环保企业征收相同的税率，会使那些污染厂商得到竞争性优势。
A similar problem arises in disadvantaging states and cities within the US with their own carbon pricing schemes, such as California. The state-level cap-and-trade scheme is controversial there, and has led to “resource shuffling” whereby Californian producers game the system by buying stakes in out-of-state power generators, undoing the effect of carbon pricing. A blanket tariff on US exports will only worsen this problem and discourage local carbon-control initiatives.
同样，加利福尼亚州等美国国内拥有自身碳税方案的州和城市也被置于不利地位，这会导致问题。加州的州级“限量及交易”机制在当地引起争议，导致企业进行“资源重组”——加州制造商通过购买州外发电厂的股份来抵消碳税的影响，与该机制对抗。对美国出口商品统一征收关税，只会使该问题进一步恶化，挫伤当地碳排放控制计划的积极性。
Finally, assuming some emerging market countries will be exempt from the system, the US will have a powerful incentive to route the sales of its goods via those countries, in effect using them as a low-carbon offshore export platform.
最后，假设某些新兴市场国家将被免于征收碳税，美国将有强大的动力通过这些国家完成商品销售，实际上把它们作为境外低碳出口平台。
A carbon border adjustment system, then, would replicate the “rules of origin” problem arising from complex supply chains with which trade practitioners are all too aware.
那么，碳边境调节税将再次面临“原产地原则”问题——该问题源于贸易参与者都非常了解的复杂供应链。
As for its legality, supporters argue that a carbon border tariff would have a good shot at passing muster at the World Trade Organization. Either it could be organised through an official plurilateral agreement (involving fewer countries than a multilateral agreement) or it could invoke a WTO law allowing import restrictions to protect exhaustible natural resources.
至于碳边境税的合法性，支持者认为碳边境税很可能在世界贸易组织(WTO)获得通过。要么它可以通过官方诸边协议（涉及的国家少于多边协议）实现，要么可以促使WTO立法允许为保护过度消耗的自然资源采取进口限制。

But given the suspicion in which Mr Trump’s administration holds the WTO, a favourable ruling from its judicial panel is only likely to increase his willingness to ignore or leave the organisation altogether.
但鉴于特朗普政府控制着WTO的这种猜测，WTO专家小组的有利裁决只可能增强他忽视或彻底退出WTO的意愿。
Carbon border adjustments are theoretically elegant. But the technical complexities involved unfortunately suggest other solutions might be more constructive, including trying to encourage more states and cities inside the US to band together and impose their own carbon regimes from the bottom up, or trying to institute international low-carbon product standards for goods such as vehicles.
理论上，碳边境调节税是绝妙的想法。但遗憾的是，其中涉及的技术层面的复杂性意味着其他解决方案可能更有建设性，其中包括尝试鼓励美国更多州和市团结在一起、自上而下地推行各地的碳机制，或尝试为汽车等商品制定国际低碳产品标准。
There is a heartening amount of political will from the major economies to press ahead with carbon emissions reduction in the face of Mr Trump’s destructive decision. But the technical challenges of designing an international carbon border tax may be even harder than summoning the political will to create it.
令人振奋的是，面对特朗普破坏性的决定，主要经济体推进碳减排措施的政治意愿非常强烈。但制定国际碳边境调节税在技术层面上的挑战，可能比聚集各国制定该机制的政治意愿更难。
The writer is an FT leader writer
本文作者为英国《金融时报》的社评撰稿人