Copenhagen: the road to success.

With the Copenhagen Climate Conference now approaching, there are plenty of reasons to be discouraged about the prospect of humanity's surmounting its greatest challenge.

While scientists report accelerated Arctic melting and warn that we are already perilously close to overshooting the maximum safe level of greenhouse gases in the atmosphere, climate negotiations are proceeding at a glacial pace. U.S. discussions with China and India have not yet moved beyond bland generalities, and even across the Atlantic, most of the deep sores opened with Europe during the Bush era have not yet been closed. Meanwhile, the odds of the U.S. Congress approving climate change legislation this fall are growing long.

But this is not the time for despair--much less to give up on tackling the greatest threat of our generation. Around the globe, new policies are beginning to reverse the surge in greenhouse gas emissions that marked the early years of this century.

Data for the first few months of the year suggest that in the United States, carbon dioxide emissions in 2009 will be 8 percent lower than they were in 2005, marking the sharpest decline in decades (and making it quite possible that 2005 marked the all-time peak). Other industrial countries are seeing similar declines.

While this shift reflects the severe recession now under way, it is not the only factor. The era of higher energy prices that began in 2004 is discouraging profligate energy use, while new policies to promote renewable energy, mandate fuel economy, and retrofit buildings have begun to have an impact--one that will grow in the years ahead. Meanwhile, a new wave of super-efficient buildings and vehicles is coming into the global marketplace.

Construction of coal-fired power plants has recently slowed in the United States and even in China, with much of the difference being made up by natural gas, wind, solar, and bio-energy plants, which for the first time ever are being added at significant scale--dwarfing new coal capacity in Europe and North America.

China and India have recently announced ambitious new efforts to expand the use of solar power, and are well on the way to becoming world leaders in this burgeoning new industry. In Africa, Kenya has also announced a groundbreaking plan for the development of renewable energy.

These developments should give government officials the courage to enact tougher emission targets. The goals recently endorsed by the European Parliament and the U.S. House of Representatives do not look as robust as they would have just a year ago. In fact, they are not only too weak to protect the climate, they are barely ahead of the "business-as-usual" path the world economy is now on. Even in fast-growing developing countries, policies that advance energy efficiency could slow the growth in energy demand (and emissions) without economic sacrifice, according to a 2008 McKinsey study.

A strong new Copenhagen climate agreement will build on the positive momentum now under way--and accelerate the transition to low-carbon economies around the globe. Failure, on the other hand, would be a monumental setback.

Christopher Flavin is President of the Worldwatch Institute.