When truth is inconvenient there will always be those that discourage it. Few people, for example, are foolish enough to refute the causative link between smoking and respiratory disease that has been demonstrated in medical science since the 1950s, and yet lobbyists still, to this day, fund pro-smoking policies to protect the tobacco industry.
The same is true of climate science. The threat of fossil fuel divestment and enforced cuts in greenhouse gas emissions gives a clear motive for various stakeholders to promote climate denial. A recent study examining US tax records has suggested that between 2003 and 2010 a total of 140 foundations made over $558 million of grants to promote human-caused climate change as a scientific mistake. Unfortunately, this likely represents just the tip of the iceberg with potential donors, keeping an eye on PR, reducing the amount of publicly traceable donations.