MARCH 2007

Seattle mayor Greg Nickels is hopeful that the US will soon join the global effort to tackle climate change. Building on comments he made in the BBC News website's Have Your Say pages, Mr Nickels says more than 400 US mayors are committed to curbing emissions - something the White House has so far refused to do.

It has been two years since the community of nations took the first, important step to address the biggest threat facing our planet - global warming. I remember very well the day the Kyoto Protocol took effect in 141 countries around the world, but not mine. In Seattle that winter, the warnings about the distant threat of climate change became all too real. The mountain snowfall that we rely on for clean drinking water and hydroelectric power literally didn't fall. We faced an uncertain year of water supply. I was concerned for my city, and I was worried about the future. And I was mad that my nation's government was sitting on its hands.

In the United States, we view ourselves as a great nation; a principled people with a history of rising to the challenge of the most serious international threats. Yet there we were, responsible for 25% of the greenhouse gas emissions causing a global meltdown, but somehow incapable of doing anything about it.

I was determined to show the world that intelligent life had not been snuffed out in America. So I asked nine fellow mayors to join with me in pledging to cut greenhouse gas emissions in our cities and meet the goals of the Kyoto Protocol. We also agreed to challenge other mayors from around the country to do the same; we called it the US Mayors' Climate Protection Agreement. Our initial goal was to get a symbolic 141 cities to join. Today, I am proud to say that more than 400 mayors have signed our climate commitment.

They represent 58 million people in cities from every state in the nation. They are Republicans, Democrats and Independents. They are leaders of some of our biggest cities and some of our smallest towns. And they are united in the knowledge that cities are the frontlines of the war on climate change, where the risks are most keenly felt and where the opportunities springing from the clean energy revolution will be seized.

Population centres on rivers and in coastal areas, from New York City and New Orleans to St Louis and Seattle, will bear the brunt of increasingly severe weather, flooding and rising sea levels associated with climate disruption. America's hottest and driest cities - places like Phoenix, Las Vegas, Los Angeles and Houston - are becoming more vulnerable to drought, water shortages and wildfires. Some communities in Alaska have even had to move as rising winter temperatures cause erosion, landslides and rapid melting of the permafrost. Winter snowfall in Seattle's home state of Washington is half what is was 50 years ago, and will be cut in half again in 30 years if we do not act aggressively to curtail emissions now.

The good news is that cities have long been the great incubators of ideas. That remains true today. In Seattle, we are already seeing a growing green economy create jobs and economic opportunities in fields such as energy, construction and transportation. Across the country, cities are trying new approaches to reducing emissions. They have focused on cleaner electricity production, reducing energy consumption in buildings and encouraging clean-burning cars and transportation. If an idea works well, it can be quickly adopted by other cities. If it fails, others can avoid the mistake.

Seattle:We have had success in Seattle. Our publicly owned electric utility, City Light, is the first in the nation to achieve net-zero greenhouse gas emissions, through a combination of renewable energy sources and carbon offsets - essentially paying others to reduce their pollution. It is a source of great pride: we are powering our city without toasting the planet!

Most of our garbage trucks run on cleaner biodiesel; cruise ships based in Seattle now plug into shore power rather than run their massive engines when in port.

And we are investing heavily in mass transit systems. More and more people are choosing to live in the city and close to their jobs. We are also making it easier to cycle and walk in Seattle.

We are now building a broad, action-oriented public campaign to encourage energy conservation in transportation, heating and lighting. And the private sector is also joining the effort by working to reduce their emissions through the Seattle Climate Partnership.

If Seattle were doing this work alone, it would be a symbolic gesture. But the fact that 400 other cities are working together to reduce emissions means that we are making a real difference for the future of our planet.

100 Mayors Unite: Last month, more than 100 mayors joined me in Washington DC to make our voices heard on the need for federal action. We asked Congress to take meaningful steps to protect the climate, and they have responded with a series of strong proposals. It was clear to me that the climate has indeed changed in the nation's capital. As mayors, we have accomplished much over the past two years. And while we have a great deal of work ahead, my mood has improved. The frustration has turned into a sense of hope that we have helped build a movement that will result in this great nation joining, even leading, the global battle for a stable climate.

Greg Nickels is the mayor of Seattle, and the founder of the US Mayors' Climate Protection Agreement

The Green Room is a series of opinion pieces on environmental topics running weekly on the BBC News website