By Alex Kirby
BBC News Online environment correspondent
One of the UK's foremost environmental thinkers, Sir Crispin Tickell, has accused British politicians of failing to give a lead on nuclear energy.
Treat nuclear power as a renewable energy, Sir Crispin says
Sir Crispin said nuclear power ought to enjoy comparison with "other forms of renewable energy" in making policy.
By intensifying natural climate change, he said, humans were pushing the Earth beyond its normal limits of tolerance.
Unless we changed both our thinking and our behaviour, we, like almost all other species, would face extinction.
Sir Crispin, formerly UK ambassador to the United Nations and warden of Green College, Oxford, was speaking at a conference on global change.
It was organised by Professor James Lovelock, another well-known environment scientist, who last month urged the nuclear option.
While it was hard to distinguish natural from human-caused processes, Sir Crispin said, "there is now a commanding consensus that human activities are having a significant if not decisive effect" in altering the climate.
He said there was still momentum in the Kyoto Protocol, the international climate treaty, "despite wilful US obstructiveness and Russian prevarication".
With limited reserves of fossil fuels, "the recent steep rise in prices for whatever reasons should be broadly welcomed as a useful warning of things to come".
So a switch to alternative energy sources was vital, and existing technologies - like solar, wind, biomass and tidal power - deserved much more support than they had received so far.
Looking for a lead
Last year, Sir Crispin said, he had chaired a group at Chatham House (the Royal Institute of International Affairs) looking into the nuclear industry's prospects, and he spoke in the light of his experience then.
He said: "I reproach this government and its predecessor for not putting more effort and resources into coping with the problems of high-level waste.
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"Next I reproach them for fudging nuclear issues. I believe the word 'nuclear' is now banned from No 10 Downing Street.
"One of the conclusions of the Chatham House study was that public opinion was persuadable if anyone wanted to persuade it."
He said the UK should be investing in new fusion technology in the Iter project, the world's biggest nuclear fusion reactor, and should decide soon whether to build it in France or Japan.
Sir Crispin said: "The problems of true cost, safety, proliferation, security, risk and the rest should be examined in a complete overall assessment of nuclear against other forms of renewable energy to lay a proper foundation for debate and future policy."
Referring to people's objections to increases in the price of petrol and diesel, Sir Crispin said: "We do not want a repeat of the ridiculous fuel protests in 2000 to which the government failed to respond with effective arguments.
"If the government turns jelly-kneed this time, we can truly despair... All over the world people have to change their ways and remodel their thinking.
"Otherwise Nature will do what she has done to over 99% of species that have ever lived, and do the job for us."
Sir Crispin, a former adviser to several British governments on environment and sustainable development, told BBC News Online: "When it comes to protecting the environment, the hardest thing we have to do is to find new ways of thinking."