It should be possible to draw up a fair, ambitious and legally binding treaty on climate change after this week's United Nations summit in Copenhagen (see http://go.nature.com/sRCuKV). But the next few years are going to be crucial if we are to stand a reasonable chance of keeping global warming to below an average of 2 °C.
Pessimistic media reports reflect the views of only a few world leaders, including Canada's, who lack ambition and imagination. Other leaders, including the US and Chinese presidents and the summit host, Prime Minister Lars Løkke Rasmussen of Denmark, are still pushing for a strong agreement.
The science is clear. To limit average global warming to the 2 °C agreed by world leaders at July's G20 meeting, total greenhouse-gas emissions will have to peak around 2015 and then decline sharply. If emissions are more than 25% above 2000 levels in 2020, the risk of exceeding 2 °C in this century would be more than 50%, even if emissions were reduced to low levels by 2050 (M. Meinshausen et al. Nature 458, 1158–1162; 2009).
Canada should be playing a strong multilateralist part, fulfilling its international commitments, offering constructive proposals on difficult and tense issues, and looking for compromise when positions are entrenched. But Canada has not been constructive and it has isolated itself. It is the only country to have signed up for a target under the Kyoto Protocol and then stated that it has no intention of meeting it. Canada has put forward positions that have heightened, rather than eased, tension. It has argued that developing countries should take on 'hard caps' (which emissions must not exceed, even if production increases) — something no other country advocates. And it is uncompromising on issues such as using 1990 as a base year, which has blocked agreement.
The Copenhagen summit is a big challenge because industrialized countries such as Canada have yet to accept fully that they have a greater responsibility than developing countries for the problem of climate change, and a greater capacity to solve it. Because rich countries have used up so much atmospheric space in the course of their own development, they need to deliver substantial support so that poorer countries can develop without following our dirty path. Wealthy countries need to provide clean technologies and financing — some US$160 billion per year — so that developing countries can curb their own emissions and adapt to climate changes that are already happening.
Unfortunately, Canada is among the rich countries that have impeded progress in negotiations, and not just because it has disavowed its commitments under the Kyoto Protocol. Its 2020 emissions-reduction target is the weakest of all Kyoto parties' and it has not supported any options to deliver financing to the developing world. The needs are great. But so are the responsibilities and the opportunities. Canada and other wealthy nations can and must do more.
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