Implications of Copenhagen Pledges

There is an excellent new potential reading on the Copenhagen Accord for climate change law and policy classes in a recent issue of Nature, Rogelj & Meinshausen, Copenhagen Pledges are Paltry, 464 Nature 1126-28 (2010) (subscription required). The authors analyze the likely implications of the pledges made by UNFCCC parties under the Copenhagen Accord.

Among the key take-aways of the analysis:

  1. Present pledges are likely to lead to emissions of 47.9-53.6 gigatons of carbon dioxide equivalent by 2020, about 10-20% higher than today’s levels;
  2. The pledges of most countries are extremely tepid: The lower end of the EU pledge would lead to smaller annual reductions through 2020 than what occurred on average of the past 30 years. The U.S. pledge translates into a mere 3% reduction below 1990 levels. The least ambitious end of China’s pledge tracks the business as usual scenario. Japan and China are the only two developed countries to make pledges consistent with the 2C goal;
  3. Even if emissions are halved by mid-century, there will be only be, at best, a “flip of the coin” chance of meeting the Accord’s goal of not exceeding a 2C temperature increase;
  4. Under the most pessimistic assumptions (assuming maximum used of banked emissions and surpluses from land use, land-use change and forestry), potential 2020 emissions from developed countries could be 6.5% above 1990 levels, substantially above projections if no additional mitigation measures were taken. Under the more optimistic scenario, without according land-use credits and using surplus allowances, results in emission of developed countries falling by 15.6% by 2020, far exceeding an emissions pathway to the 2C target;
  5. Given the current few pledges made for 2050, the Copenhagen Accord will almost certainly miss the 2C target, and there’s a 50% chance of exceeding 3C by 2100.
  • If nations agree to halve global emissions by 2050 from 1990 levels, we will need to reduce emissions 3-3.5% annually from 2020-2050, which would require “unprecedented political will;”
  • The only way to avoid cuts of this nature post-2020 is to substantially increase pre-2020 commitments, namely a 30% reduction below 1990 levels for developed countries, and 20% below business as usual levels for developing countries.

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