Prince Charles has a cunning plan to protect rainforests like this one along the banks of the Congo river © Stok/Greenpeace

The almost complete lack of green issues on the G20 agenda has had heads shaking both in our office and across the environmental movement, yet there was one result this week worth celebrating. It didn't come from the G20 directly, but the presence of so many world leaders was an excellent opportunity for Prince Charles to gather many of them together to talk about rainforests.

For some time now, the Prince has (like us) been promoting the idea that stopping deforestation in places like the Amazon and Indonesia is an excellent way to put the brakes on climate change. His recent trip to the Amazon (documented by the Sun's new environment editor) was just the latest demonstration of the Prince's passion for the issue.

Stability, growth, jobs all good - but where's the climate leadership? CC Image from London Summit on Flickr

Well, there we go. After the media circus, the protests, and a conference so exclusive that even some NGO participants were banned at the last minute, the G20 have pronounced, and it turns out that their environmental leadership is... er... down at the bottom of the document somewhere.

It's nice to believe that for one beautiful moment there was the chance to extract ourselves from the economic mess we've stumbled into, and at the same time create the foundations for the difficult but necessary tasks of addressing climate change.

Like helping China and India find a model for development which doesn't go hand in hand with rapidly rising carbon emissions, for example, or restructuring the way we ‘do business as usual' in the UK and taking advantage of our relative wealth to harness wind, wave and solar power (along with a whole heap of other clean technologies).

But it turns out that our leaders have dropped the ball completely. Read more »

During his election campaign President Obama placed a high emphasis on dealing with one of the greatest threats we all face - reducing the vast numbers of nuclear missiles held by both Russia and the United States.

As he put it in his inauguration speech "With old friends and former foes, we will work tirelessly to lessen the nuclear threat" In response to an arms control survey he was more specific – "I will not authorize the development of new nuclear weapons. And I will make the goal of eliminating nuclear weapons worldwide a central element of U.S. nuclear policy."

It was a great plan - take over an uninspiring section of grim corporate London and transform it into a fully-fledged climate camp, complete with a kitchen, toilets, workshop spaces and even a ceilidh.

As I made my way back to London on the train yesterday afternoon, I was getting messages from friends telling me to "come down, it's lovely." Camped outside the European Climate Exchange, the campers were there to point out that many of the problems that have caused the credit crunch - lax regulation, too much power handed over to big corporations, trust placed in unproven financial instruments - are just as relevant to how we're messing up dealing with climate change.

As the assembled G20 world leaders take a break from negotiations at the ExCel centre today - maybe have a few drinks, regard the lovely vistas of the Thames, and wonder to themselves how they can be as cool as Barack Obama - perhaps the words "Yes You Can" fluttering by at 45 mph will remind them that sorting out the global financial system to make it more equitable and sustainable is not some impossible dream, it's the only thing that's going to actually work.

That's because it's not only the economy which is in trouble, the climate is facing its own ecological-credit crunch. There's not much point fixing the finance system if we're going to ignore the climate crunch that threatens much bigger problems for the world.

We've got a message for the leaders of the richest nations in the world who are gathering here in London for the G20 meeting to discuss the global economic crisis - put the climate and people first.

15 activists unfurled this 50m x 30m banner from the bridge at the Guanabara bay in Rio de Janeiro, Brazil.

The climate crunch will soon make the credit crunch look trivial, and the G20 summit must tackle it now, writes Greenpeace UK Executive Director John Sauven writes for Comment is free.

This evening, 20 world leaders will gather in Washington, where they will dine at the table of their host, George W Bush, before attempting to perform life-saving surgery on the global economy.

Even in the face of the extraordinary repudiation delivered last week by the American people, Bush is unlikely to use the summit to also reshape the world's response to climate change. But that's exactly what his 19 guests should do.