The recently concluded United Nations conference on climate change, in Poznań, Poland (see page 846), marked the last phase of eight years of foot-dragging by US negotiators. For one last time, the designated US representatives at international climate talks came from the administration of President George W. Bush, who rejected the Kyoto Protocol almost immediately after taking office and whose team has stalled any meaningful progress since.

But by this time next year, when the world's negotiators convene in Copenhagen to try to hammer out a deal to succeed the Kyoto accord, the lame ducks will be gone. In their place will be representatives of a new US president, Barack Obama, who has promised to make control of greenhouse-gas emissions a central focus of his administration.

How much progress Obama can make in his first 11 months remains to be seen, and it is far from clear that the world will be able to fashion a workable consensus in Copenhagen. But a consensus now seems much more likely than it was.

As if to dramatize how difficult the task will be, European Union (EU) representatives crashed and burned last week as they attempted to lay out the next phase of Europe's otherwise groundbreaking emissions trading scheme (see page 847). Caving to political pressure from Italy and Poland, among others, French president and outgoing EU chief Nicolas Sarkozy crafted a compromise that satisfies many — in the fossil-fuel industry, that is. Rather than holding heavy industries accountable for their emissions, the new deal gives the heaviest polluters significant leeway. The very industries that account for some of the highest levels of emissions, such as steel and cement, can now apply for exemptions that could grant them free emissions permits even after 2020. Everyone else will have to start paying in 2013.

EU leaders praised the deal, but the concessions it contains are likely to harm the trading system irrevocably, allowing industry to further delay the radical changes needed to clean up its business.

Climate leadership may pass instead to the United States, which will need to set tough emissions limits — and stick to them — if it wants to do better than Europe. If Obama is as serious as he claims to be about establishing a cap-and-trade regime, his administration will need to carefully consider the lessons of the European experience. For starters, a US system should avoid giving away emission permits so freely, and consider setting a minimum price for them.

A promising development on this front is Obama's appointment of Steven Chu, a Nobel prizewinning physicist and energy-technology advocate, as secretary of energy (see page 849). The energy department spent US$1.4 billion on research and development for renewable, fossil and nuclear energies in 2008 — less than a quarter of what it was 30 years before, when adjusted for inflation. Chu, who made renewable energy the raison d'etre of California's Lawrence Berkeley National Laboratory, which he has led since 2004, should reverse that trend. Chu not only 'gets' climate change, he gets its urgency. Private investment is making incremental advances in the short-term cost-effectiveness of renewable energy. But technology-driven, order-of-magnitude leaps are essential in the medium term: time for the long term has run out.

It was in 1997 — the year the Kyoto Protocol was adopted — that Chu won his Nobel prize for cooling atoms to a near standstill with laser light. He did the work at the now-moribund Bell Labs in New Jersey — a place Chu fondly remembers for favouring boldness. “Some failure was expected,” Chu said at a recent seminar, “but there was an emphasis on recognizing failure quickly, and moving on to other opportunities.” That is a credo worth adopting — both in the creation of carbon-free energies, and in the creation of carbon-emission markets.