A sceptic is someone who needs to examine the evidence before accepting an argument or theory and may not be convinced by that evidence. According to Michael Shermer, publisher of Skeptic magazine:
Scepticism is integral to the scientific process, because most claims turn out to be false. Weeding out the few kernels of wheat from the large pile of chaff requires extensive observation, careful experimentation and cautious inference. Science is scepticism and good scientists are sceptical.
Pascal Diethelm and Martin McKee describe denialism:
There is an overwhelming consensus on the evidence among scientists yet there are also vocal commentators who reject this consensus, convincing many of the public, and often the media too, that the consensus is not based on ‘sound science’ or denying that there is a consensus by exhibiting individual dissenting voices as the ultimate authorities on the topic in question. Their goal is to convince that there are sufficient grounds to reject the case for taking action...
Diethelm and McKee identify five tactics common to denial movements:
The global warming denial movement, particularly think tanks and front groups, have played an active role in disseminating every tidbit of information, whether verified or not, that discredits the idea of global warming.
For example, in 2006 Australian columnist Piers Akerman wrote an article labelling global warming warnings as alarmist in the Daily Telegraph newspaper. In it he quoted former head of the International Panel on Climate Change (IPCC), John Houghton, as having said "Unless we announce disasters no one will listen". Although this quotation appears to have been fabricated, it was subsequently quoted in more than three books, over 100 blog posts and some 24,000 web pages, often attributed to a 1994 book by Houghton, in which it does not appear.
New Scientist correspondent, Jim Giles, describes this phenomenon as an "informational cascade" that is amplified by the "echo chamber" of the internet. He suggests that the more a person hears a piece of information that more they are likely to believe it, particularly if it accords with ones existing beliefs ("confirmation bias").