The high level of consensus amongst the world's climate scientists is not widely known because the corporations that would be affected by measures to reduce greenhouse gas emissions have waged a deceptive campaign to confuse the public and policy-makers on the issue. They have used corporate front groups, public relations firms and conservative think tanks to cast doubt on predictions of global warming and its impacts, to imply that we do not know enough to act and to argue that the cost of reducing greenhouse gases is prohibitively expensive.
The US National Coal Association spent $US700,000 on this in 1992/93 alone.
In 2003 Republican Party political consultant Frank Luntz advised:
Voters believe that there is no consensus about global warming within the scientific community. Should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly. Therefore, you need to continue to make the lack of scientific certainty a primary issue in the debate. . . . The scientific debate is closing [against us] but not yet closed. There is still a window of opportunity to challenge the science [emphasis in original].
As Ross Gelbspan stated in Harper's Magazine the "confusion is intentional, expensively gift wrapped by the energy industries." It is in this way that corporate influence goes far beyond the millions of dollars in campaign donations made by the fossil fuel industry to politicians and political parties.
By promoting global warming deniers, business takes advantage of the media's need for balance, and consequently the debate appears to be evenly divided even though the vast majority of climate scientists support the global warming consensus and there are only a handful of scientists disputing it. Similarly, in the US congressional hearings on climate change tend to feature the testimony of similar numbers of deniers as mainstream scientists representing the International Panel on Climate Change (IPCC).