Supporters hope that the Kyoto protocol will help to reduce global warming.© Getty Images

More than seven years after its inception, the Kyoto Protocol is finally up and running. From Wednesday 16 February, countries throughout the world must make good their promise to cut greenhouse-gas emissions.

The agreement, adopted in December 1997, could not be enforced until it had been ratified by a set of industrialized countries that, in 1990, were responsible for at least 55% of global greenhouse-gas emissions. That threshold was reached by Russia's ratification in November last year, which set off a 90-day countdown until the protocol could become law.

Environmental ministers from around the world will today mark the culmination of this countdown with a ceremony centred on Kyoto in Japan, the treaty's birthplace (see ""Kyoto decks itself for celebration":/nature/journal/v433/n7026/full/433562afs.html&contentfiletype=pdf"). "This marks the beginning of a new era in international efforts to reduce the risk of climate change," says Joke Waller-Hunter, executive secretary of the United Nations Framework Convention on Climate Change, which oversees the protocol.

Thirty-five developed countries now face the task of reducing overall greenhouse-gas emissions by 5.2%, relative to 1990 levels, before 2012. Each state has been given an individual target: Britain, for example, must curb its emissions by 12.5%; Japan must cut its own by 6%.

Giving credit

Nations will attempt to meet their targets by improving the fuel-efficiency of power stations, manufacturing plants and transport. The protocol also allows industries to earn 'carbon credits' that can be used to offset any overshoot on the emissions targets set for them by national governments.

These credits can be earned by investing in the United Nations Clean Development Mechanism, a scheme that funds the adoption of green technologies in developing countries. Alternatively, industries struggling to hit their targets can take advantage of trading schemes that harness international commodity markets to allow the buying and selling of carbon credits.

The activation of the 141-nation treaty also cements the pariah status of the United States and Australia. The two countries, which together account for more than a quarter of world greenhouse-gas emissions, have declined to ratify the agreement, claiming that it will damage their economies.

It now seems unlikely that either country will ever ratify the agreement, says Vicki Arroyo, director of policy analysis at the Pew Center on Global Climate Change in Arlington, Virginia. Both countries' emissions have risen by more than 10% since 1990, meaning that Kyoto's tight demands would now require their economies "to turn on a dime", she says.

But she holds more hope for efforts on a sub-federal level in both countries. "One would hope that Kyoto's activation will make the United States and Australia focus on creating comparable domestic programmes," she told news@nature.com.

Better state

There are signs that such moves are afoot in the United States, Arroyo adds. Senators Joseph Lieberman (Democrat, Connecticut) and John McCain (Republican, Arizona) have tabled a bill that calls for an emission-credit trading scheme similar to that established this year by the European Union (see ""The carbon game":http://www.nature.com/news/2004/041115/full/432268a.html").

The governments of California and of the New England states are investigating the possibility of implementing such 'cap-and-trade' schemes on a regional level. "Just because the US administration is not moving on this, it doesn't mean there's monolithic inaction," Arroyo says.

In a speech on 15 February, former US vice-president Al Gore criticized the "moral cowardice" of the Bush administration in declining to ratify the Kyoto Protocol. But he hailed regional US efforts at tackling climate change in the absence of federal backing: "They have filled the leadership vacuum." 

Pew Center on Global Climate Change, Arlington, Virginia