In 1971 an environmental and antiwar ethic was taking root in Canada, and I chose to participate. As I completed a Ph.D. in ecology, I combined my science background with the strong media skills of my colleagues. In keeping with our pacifist views, we started Greenpeace.

But I later learned that the environmental movement is not always guided by science. As we celebrate Earth Day today, this is a good lesson to keep in mind.

At first, many of the causes we championed, such as opposition to nuclear testing and protection of whales, stemmed from our scientific knowledge of nuclear physics and marine biology. But after six years as one of five directors of Greenpeace International, I observed that none of my fellow directors had any formal science education. They were either political activists or environmental entrepreneurs. Ultimately, a trend toward abandoning scientific objectivity in favor of political agendas forced me to leave Greenpeace in 1986.

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Sadly, Greenpeace has evolved into an organization of extremism and politically motivated agendas.

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We all have a responsibility to be environmental stewards. But that stewardship requires that science, not political agendas, drive our public policy.

AL GORE wants to make a sequel to his Oscar-winning documentary on global warming – and despite Earth’s “rising fever” he is still hopeful for a happy ending.

We are, he says, all players in deciding the outcome.

Despite the success of his film An Inconvenient Truth and last year’s Live Earth concerts in raising awareness, the former US Vice President believes little has changed where it counts and the situation is even more urgent.

And he warns that while individual efforts such as changing to low-energy lightbulbs are important, it is more significant for world leaders to change laws to stop pollution pouring into the atmosphere and affecting the climate.

The man who is now as much part of the Hollywood Establishment as he was a political player with the Democratic Party is very careful not to upset any of his celebrity friends.

He wouldn’t dream of suggesting that their lavish jet-setting and gas-guzzling lifestyles could be reined in for the good of the environment.

When we point out that David Beckham has recently been given the dubious title of having the worst carbon footprint in history – clocking up enough air miles to fly to the moon and owning 15 gas-guzzling cars, Mr Gore shifts uncomfortably in his seat.

He knows what is coming next.

When asked what he would say to the football icon – a hero to millions – about his impact on the environment, Mr Gore refuses to be drawn.

He gives a huge belly-laugh at the notion that Posh and Becks could invest in an environmentally-friendly hybrid car such as a Toyota Prius.

He careful considers his answer before saying: “I don’t think that’s my place. I don’t want to get into personally criticising anyone.”