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来源:http://www.economist.com/news/science-and-technology/21679431-limiting-global-warming-2-c-above-pre-industrial-levels-more-political
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作者:Econmist
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发布时间: 2015-12-02
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1423 次浏览
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Mr Nordhaus himself agreed this estimate was “deeply unsatisfactory”. It was based merely on the observation that it did not push the climate into unknown territory, whose safety could not be assessed. So little was known about the impacts of warming at that stage, he wrote later, that his target was “a substitute” for balancing costs and damages.
Since then things have moved on. Some findings suggest even 2°C is too much. Other people argue that the limit is meaningless because it will surely be breached, and that more effort should go into adapting to a hotter world. Either way, once promulgated, the idea of a 2°C limit has taken on a life of its own. It received attention from European scientists at various workshops during the late 1980s. It was accepted in a report published by the Stockholm Environment Institute in 1990, even though this also found, based on its authors’ understanding of “the vulnerability of ecosystems to historical temperature changes”, that warming above just 1°C could trigger “rapid” and “unpredictable” consequences. Despite that, the report’s authors admitted it was too late to keep within such a limit, settling on 2°C instead. Pragmatic, certainly. But not strictly scientific.
Six years later, a meeting of the European Union’s Council of Ministers, which included Angela Merkel (now Bismarck’s latest successor, but then Germany’s environment minister), endorsed the limit, giving it political credibility. Thence it spread. By 2009 the G8 countries had signed on, and it was mentioned in the Copenhagen Accord—an agreement salvaged from the wreckage of the UNFCCC’s meeting that year. At the following get-together, in Cancun, Mexico, in 2010, a maximum rise of 2°C was established as the goal of international climate policy.
Despite its questionable past, the 2°C limit does have merits. By boiling the vast complexities of the climate system down into a single, comprehensible number it gives politicians something simple to aim at, and against which they can measure the success of their endeavours.