By Helen Briggs
BBC News science reporter
Fundamentalism is hampering global efforts to tackle climate change, according to Britain's top scientist.
In his final speech as president of the Royal Society, Lord May of Oxford will say scientists must speak out against the climate change "denial lobby".
He will warn core scientific values are "under serious threat from resurgent fundamentalism, West and East".
Lord May completes his five-year term as president of the UK's academy of science on Wednesday.
"Ahead of us lie dangerous times," he will say in his fifth and final anniversary address.
"There are serious problems that derive from the realities of the external world: climate change, loss of biological diversity, new and re-emerging diseases, and more.
"Many of these threats are not yet immediate, yet their non-linear character is such that we need to be acting today.
"And we have no evolutionary experience of acting on behalf of a distant future; we even lack basic understanding of important aspects of our own institutions and societies.
"Sadly, for many, the response is to retreat from complexity and difficulty by embracing the darkness of fundamentalist unreason."
Lord May will say that fundamentalism applies not only to organised religions but to lobby groups on both sides of the climate change debate.
The climate change "denial lobby" and non-governmental organisations (NGOs) opposed to nuclear power are not exempt from a denial or misrepresentation of scientific facts, he told reporters in London.
Speaking in a week that saw the opening of climate talks in Montreal, and the re-opening of the nuclear power debate in the UK, he said there had to be open questioning and inquiry of such issues.
The huge problems with nuclear power had to be weighed against the problem of putting more carbon into the atmosphere and the future potential of land and sea turbines, he said; "rather than ruled out of discussion on what you might call some fundamentalist belief system".
'No easy recipe'
Another danger to the enlightenment of science came from the growing network of fundamentalist and lobby groups in the US that campaigned for creationism to be taught in science classes, he added.
"By their own writings, this group has a much wider agenda which is to replace scientific materialism by something more based on faith," he said.
He called on scientists to take a more active role in speaking out against so-called "intelligent design" and other threats to modern scientific values.
"The only thing I can see scientists doing is being more energetic as citizens - getting out there and trying to convince people that that's not a very wise way to behave," he explained. "That's no easy recipe."