China and India are leading the way. Yes, I'm optimistic

This week's summit on climate change offered cause for confidence. But all nations now need to redouble their efforts
Nicholas Stern
guardian.co.uk, Wednesday 23 September 2009 21.30 BST

This week's summit on climate change at the United Nations in New York has given a strong boost to the negotiations over a major international treaty, but there remain a number of major obstacles that must be overcome before the crucial meeting in Copenhagen in December.
China, India and Japan, along with the private sector, all made positive and significant contributions at the summit.
Hu Jintao, the Chinese president, made specific commitments on curbing the growth in greenhouse gas emissions as China continues its extraordinary economic growth. While the president promised a reduction by a "notable margin" rather than a specific figure, there is no doubt that the cut will be significant. And the environment ministers of both China and India made important and constructive proposals for how their countries will reverse deforestation.
This was the kind of leadership I had hoped to see at the summit – organised by Ban Ki-moon, the UN secretary general – with developing and emerging countries showing that they can tackle climate change while continuing their efforts to reduce poverty. But we still have a long way to go before we can be sure that a strong agreement is in place for Copenhagen.
In the next couple of years, annual emissions of greenhouse gases are likely to reach a level of 50 gigatonnes of carbon dioxide equivalent. If we are to have a reasonable chance of avoiding a rise in global average temperature by more than 2C, annual emissions have to be cut to no more than 20 gigatonnes by 2050.
That means that the 9 billion people who will be living on the planet in 2050 must be producing, on average, no more than about two tonnes of greenhouse gases per year each.
At the moment, the rich industrialised countries of the European Union average about 10-12 tonnes per head of population, while the figure for the United States is almost 24 tonnes. China, by contrast, emits about 6 tonnes per head at present. Thus rich industrialised countries in particular must substantially reduce their emissions.
The developed countries must now demonstrate that they have the political will to reach a strong agreement in Copenhagen. In New York, Japan's new prime minister, Yukio Hatoyama, outlined how his country will reduce its emissions by 25% by 2020, compared with 1990. This was a positive example that few others matched.
President Obama has already committed to a cut of 80% in greenhouse gas emissions by 2050, compared with 1990. But the American Clean Energy and Security Act passed by the House of Representatives sets an interim target for 2020 that is not considered ambitious enough by many other countries. And it is not clear when, or even if, the Senate will pass a comparable act to reduce emissions.
It is these interim targets that should now be addressed by all countries during the coming weeks. If we are to reach the goal of reducing emissions to 20 gigatonnes by 2050, we must be at about 35 gigatonnes by the halfway point of 2030.
That means global emissions have to peak within the next five years and be steadily falling by 2020. And while the commitments by the largest emitters already on the table for 2020 offer significant cuts relative to today's emissions, they collectively fall 4 or 5 gigatonnes short of what is necessary if we are to be on a realistic trajectory to reach the 2030 and 2050 targets.
Developing countries should also sharply reduce their emissions – but they must be supported, financially and through technology sharing with the rich industrialised countries. Without commitments to such support, the negotiations ahead will prove very difficult.
Although the political leaders must devise and implement the right policies to guide national and global emissions trajectories, it is the private sector that will be the main engine in the transition to a low-carbon global economy.
In that respect it was very encouraging that 181 investors, collectively responsible for the management of more than $13 trillion in assets globally, launched a statement in New York last week to support a global agreement on climate change. The Leadership Forum for business leaders, which ran alongside the summit, also highlighted a tremendous variety of innovative ideas from within the private sector for the low-carbon transition.
So there are some reasons to be more optimistic about the prospects for securing a strong agreement in Copenhagen, following the New York summit. But the obstacles that remain are very big and will require an even stronger effort to overcome, starting at the G20 summit in Pittsburgh and continuing during the coming round of treaty negotiations in Bangkok next week.
There must be real vision, leadership and creativity, as well as a mutual understanding of the difficulties of making and implementing domestic policies. But if we can muster the effort, we can, as a world, forge a path towards a more prosperous and sustainable future – for us, our children, and generations to follow.