Geoffrey Lean: The public are ahead of the game on climate change

Thursday, Ben Stewart feared, would be the day he started a prison term. But instead of being banged up, he found himself "in the green room of The Jeremy Vine Show, next to Cliff Richard".

Uncharitable comparisons with frying pans and fires are not for him, however. Greenpeace's communications director – newly cleared, with five colleagues, of causing criminal damage to Kingsnorth power station in Kent – was "quite excited", though at the implications of the verdict rather than at meeting the man who recorded both "Congratulations" and "Jailhouse Rock".

He hopes it will be a "gamechanger", and he might conceivably be right. For the jury that acquitted the six activists may have done more to frustrate the Government's plans to build coal-fired powered stations than the pressure group has achieved in years. And it revealed a public concern about climate change that the main political parties – all lambasted in a report published the same day for backsliding on green concerns – have yet to understand.

The protesters scaled a 656ft chimney at Kingsnorth last October, painting the name "Gordon" down it, before being told to stop. They had aimed to add "bin it", appealing to the Prime Minister to junk plans for a new power station, which would emit three times as much carbon dioxide as the whole of Rwanda.

It cost energy colossus E.ON – which owns the power station and wants to build the new one – £30,000 to clean off the giant graffiti, and the activists were duly charged: Stewart faced up to 10 years in jail because he had already been arrested for a protest at Didcot two years ago.

They mounted a so-called "lawful excuse defence", which allows damage to be done to protect other property, bringing in top experts – including Professor James Hansen, one of the world's leading climate scientists – to explain the dangers of global warming.

The ploy has worked for Greenpeace before, most famously clearing its then leader, Peter Melchett, and 27 others who trashed a field of GM maize in Norfolk.

That was a turning point. The Crown Prosecution Service stopped charging people who destroyed modified crops with criminal damage, and other activists were encouraged to take similar "direct action". Last week's decision could well have the same effect – leading to a rash of protests at power stations, airports and other major greenhouse gases emitters – though Greenpeace is anxious to play this down.

More important, perhaps, is what it says about public attitudes to climate change. Ann Widdecombe, the local MP, last week angrily called the verdict "ludicrous", but the jury was no doubt at least partly drawn from her own constituents.

The jury in effect sat through a six-and-a-half-day seminar on global warming, in a forum where lying was illegal, and every statement could be challenged by top barristers. And, at the end, they decided that the danger was so immediate and serious that it justified taking extreme – and normally illegal – action against it.

"That is something the Government and the utilities need to take extremely seriously," says Professor Tom Burke, an aide to three environment secretaries. "It shows how seriously the public takes climate change."

Yet a report last week by the Green Alliance and seven top pressure groups concluded that, over the past year, the Government's approach to the crisis had been "contradictory and incoherent", the Tories' had been "more presentation than substance", while the traditionally green Lib Dems had been "markedly quieter" on the issues.

It's time for them to raise, and change, their game. For, in the end, the public, while on the same side, is likely to be less forgiving than the turbulent jurors of Kent.