Pledges made at December's UN summit in Copenhagen are unlikely to keep global warming below 2C, a study concludes.

一项研究显示，去年12月哥本哈根举行的全球气候变化峰会上达成的将全球变暖控制在2华氏度以下承诺不太可能实现。

Poorer nations are unlikely to make a low-carbon switch without a Western lead

Writing in the journal Nature, analysts¹ at the Potsdam Institute for Climate Impacts Research in Germany say a rise of at least 3C by 2100 is likely.

The team also says many countries, including EU members and China, have pledged slower carbon curbs²（抑制） than they have been achieving anyway.

They say a new global deal is needed if deeper cuts are to materialise（物质化） .

"There's a big mismatch between the ambitious goal, which is 2C... and the emissions⁴ reductions," said Potsdam's Malte Meinshausen.

"The pledged emissions reductions are in most cases very unambitious," he told BBC News.

In their Nature article, the team uses stronger language, describing the pledges as "paltry⁵（不足取的，琐碎的） ".

"The prospects⁶ for limiting global warming to 2C - or even to 1.5C, as more than 100 nations demand - are in dire⁷（可怕的，极端的） peril⁸（危险，冒险） ," they conclude.

Between now and 2020, global emissions are likely to rise by 10-20%, they calculate, and the chances of passing 3C by 2100 are greater than 50%.

According to the Intergovernmental Panel on Climate Change (IPCC), this implies a range of serious impacts for the world, including
significant falls in crop yields across most of the world
damage to most coral reefs（珊瑚礁）
likely disruption to water supplies for hundreds of millions of people.

More than 120 countries have now associated themselves with the Copenhagen Accord, the political document stitched（缝纫，装订） together on the summit's final day by a small group of countries led by the US and the BASIC bloc⁹ of Brazil, China, India and South Africa.

The accord "recognises" the 2C target as indicated by science. It was also backed at last year's G8 summit.

Many of those 120-odd have said what they are prepared to do to constrain¹⁰（强迫，束缚） their greenhouse gas emissions - either pledging cuts by 2020, in the case of industrialised countries, or promising¹¹ to improve their "carbon intensity¹²" in the case of developing nations.

Some of the pledges are little more than vague（不明确的，含糊的） statements of intent. But all developed countries, and the developing world's major emitters, have all given firm figures or ranges of figures.

The EU, for example, pledges to cut emissions by 20% from 1990 levels by 2020; China promises to improve carbon intensity by 40-45% by 2020 compared against 2005; and Australia vows¹³ an emission³ cut of 5-25% on 2000 levels by 2020.

The Potsdam team concludes that many of the detailed¹⁴ pledges are nowhere near as ambitious as their proponents¹⁵（支持者，建议者） would claim.

They calculate that the EU's 20% pledge implies an annual cut of 0.45% between 2010 and 2020, whereas it is already achieving annual reductions larger than that.