Confused by all the mixed messages about climate change? There's a good reason for that, says a public relations expert, who argues in a new book that the so-called global warming debate is a tug-of-war between clever PR tactics and sound science.

In 2006, Al Gore's Oscar-winning film "An Inconvenient Truth" catapulted the issue of human-caused climate change out of scientific journals and into the living rooms of average folks.

At the same time, then-president George W. Bush and his staff were touting research that not only questioned whether climate change was a man-made event, but whether it was happening at all.

But James Hoggan, a veteran Vancouver public relations executive, says many of the naysayers are groups with legitimate-sounding names that are actually funded by industries that would suffer economically by climate change legislation or other efforts to curb global warming.

"What I would call them is Astroturf groups," Hoggan told Canada AM earlier this week. "Basically fake grassroots groups of unqualified scientists saying that climate science is questionable."

Hoggan has written a new book on the issue, entitled "Climate Cover-Up: The Crusade to Deny Global Warming."

According to Hoggan, companies that want to dispute environmental science findings -- such as an energy companies seeking to refute climate change data -- hire public relations firms to lobby governments, and the public, to ensure that legislation and public opinion remain favourable to industry.

One way of doing this is to establish a lobby group that appears to be backed by sound science when in fact it is funded by industry money.

An example of this, Hoggan says, is the Advancement of Sound Science Center, formerly the Advancement of Sound Science Coalition. It was founded in the early 1990s by a public relations firm and funded by tobacco company Philip Morris.

The TASSC's job was to discredit research that proved a link between exposure to tobacco smoke and health problems such as cancer and lung disease.

According to Hoggan, such groups hire scientists who aren't devoted to the issue at hand -- "white coats for hire," as he calls them -- and charge them with sowing the seeds of doubt about the legitimate scientists' findings.

"The thing that these groups have in common is that they don't have qualified climate scientists doing climate science and they have a tendency to hide their source of funding," Hoggan says. "So my view is, and what we try to argue in this book, is that we should strip these groups of their right to hide their funding, and so people would know who these groups actually represent."

Hoggan says it's obvious the industry groups have successfully spread their message because media reports legitimize their claims, and because climate change legislation is stalled in both the U.S. and Canada.

"This is serious. If you look at climate mitigation policy in Canada, we don't have one. Essentially Canadian policy would result in an increase in greenhouse gas emissions," Hoggan said.

"So these groups have been highly effective at creating public doubt and taking the pressure off politicians to actually really do something about climate change."