The woman leading a front-running party in Alberta's provincial election has cast doubt on the widely-accepted scientific theory that human activity is a leading cause of global warming.

Wildrose Leader Danielle Smith made the comment in an online leaders debate organized by two Alberta newspapers.

"We have always said the science isn't settled and we need to continue to monitor the debate," said Smith in response to a direct question from a reader.

"We recognize the world is in a long-term transition away from hydrocarbon fuels. We believe the best way to reduce emissions is through consumer rebates for energy audits, microgeneration and home renovations, as well as broad-based tax breaks for investment in R&D for new environmental technologies."

A Wildrose official confirmed Smith's statement reflects a longtime party policy.

Smith has always been coy about whether she believes carbon dioxide emissions from human activity are altering the Earth's climate.

She declined to respond to Liberal Leader Raj Sherman's question:

"Danielle, are you seriously denying climate change?"

But during the debate she said her party believes that not enough is known about climate change.

Progressive Conservative Leader Alison Redford was non-committal on the science.

"Climate change is a real issue on the international stage with respect to energy production, our reputation and ability to export."

But the Tory-led Alberta government has long officially accepted the science behind climate change, as has the federal government.

They are joined by the rest of Canada's provincial and territorial governments, the U.S., Mexico, the European Union and the United Nations.

Most scientific bodies, including the Royal Societies of Canada and the U.K., as well as the American Association for the Advancement of Science, also accept that human activity is changing the Earth's climate.

A recent study in the journal Proceedings of the National Academy of Sciences surveyed 1,372 papers on climate and found at least 97 per cent of the most active climate researchers supported the standard model.

Andrew Weaver, one of Canada's top climate modellers, said the science is firm.

"It's more than firm, it's as solid as a rock," Weaver said from Morocco, where he's helping draft the latest U.N. summary of climate research. "The scientific community has used the word unequivocal.

"There are thousands of scientists working on this problem and if there was an Achilles heel to it, one person would find it. This is lowest common-denominator rhetoric."

Alexander Wolfe, a paleoclimatologist at the University of Alberta, agrees.

He said his research has shown that past periods of glaciation or global warm-up is strongly linked to atmospheric carbon. As well, predictions made by climate models a decade ago that assumed humans were behind climate change have been largely confirmed by real-world data.

Those disputing the data, said Wolfe, tend to be less active in new research. They also tend to be from outside disciplines such as geology.

"The candidate is expressing naivete," said Wolfe. "It's a real problem and it should be acknowledged by any serious political candidate for the premiership."

Andrew Leach, professor of energy economics at the University of Alberta, said Smith's comments may be a way to get the province's environmental and economic issues on the campaign agenda, from where they have been largely absent.

"That's the discussion I'd like to see: 'Here's how my view of both the scientific realities and the global and national political realities feed in to why my policy works,' " he said.