The greenest city on Earth

I've a confession to make as the Seoul Summit nears the end. I have become fiercely competitive on climate change. That's why - in an interview with a powerful American outlet - I made the bold prediction here that London will be the greenest city on earth by 2012.

That deadline is more important to me than other Mayors at this conference because that's when the world comes to London for the Olympics. It's clearly a tough target but I am - my friends - determined to do my best to meet it.

On stage today I encouraged every delegate to join us for the Games - and tried to tempt them with my dream of what they could see on arrival.

Stepping off the train at Paddington, I'd invite them to pedal onwards using one of the beautiful bikes available for hire every 150 metres in central London by next summer.

The roads should be easier as they ease onto a cycle super highway, breathing sweeter air as they pass cars generating no fumes and little noise. Thousands of trees, planted as we speak, will be filtering the air and casting cool shadows over the pavements.

The claustrophobic clutter will have gone, our urban realm subtly but strikingly more attractive. There'll be plants growing on roofs, railway sidings and canal boats. London's parks will have harvested the large investment now going into them.

London by then will be out of the global recession - helped by the new opportunities in the green economy, the City of London leading the world in green financial instruments.

Construction will have been helped by a massive programme of retrofitting homes. We don't want to be lagging behind on lagging. We'll be generating electricity from what is now considered waste. And our low carbon zones will pioneer the very best and latest in environmentally sound products and practices.

This sounds utopian, but it's well within grasp. But it won't come through warm words and communiques which is why my stubborn call - here in Seoul - is for real action to make this dream for many of us come true.

Seoul - at the Olympic Park

Seoul for the C40 Summit

It's a long way to travel for a climate conference. My flight - as always - was offset. I'm travelling with just two of my aides, booking economy flights and seeking the best value for the taxpayer at every stage.

Nevertheless I feel a need to justify this trip. I hope the other Mayors signed up to the C40 group share that.

We cannot cross the globe to exchange platitudes and sign bland documents. Sharing best practice is valuable, passing on tips and subjecting each other to peer pressure on the vital challenge we all face of combating climate change is obviously useful. As Deputy Chair of this Group, and with London hosting the C40 Secretariat (though another city picks up that bill) I'm more than happy to be here. But if this summit is worth holding, it has to prompt practical and noticeable change. Colleagues will have their own ideas. I will propose my own at dinner tomorrow.

What I read on a long flight, and what i witnessed of South Korea from the airport is impressive. The 13th largest economy in the world has slowed down like everyone else, but it's still growing convincingly and the roads, rails, bridges and building into town are proof of the enormous infrastructure improvements that have gone along with that. But they're also on a mission to improve the feel of the city - much as I aim to do in London. A haggard old highway in the city centre has been cleared, an old waterway rediscovered and set in a striking urban park.

There are large clusters of trees as well as sky scrapers defining the view from my hotel window, and my jog, just now, took me through some beautiful landscape. I hear good things too about the site of Seoul's Olympics two decades ago and look forward to visiting that tomorrow. There are always lessons to be learned, and this seems a good place to study.