Many of the researchers caught up in the "climategate" saga have spent years in the firing line of sceptics. And they have felt the heat.

In late 2006, I interviewed a number of them for an article in New Scientist magazine, which focused on how the propaganda war was shaping up prior to the publication of the next Intergovernmental Panel on Climate Change (IPCC) assessment the following year.

Kevin Trenberth had suffered abuse for publicly linking global warming to the exceptional 2005 Atlantic hurricane season, which culminated in hurricane Katrina. He told me: "The attacks on me are clearly designed to get me fired or to resign."

Ben Santer of the Lawrence Livermore laboratory in California, and formerly of the Climatic Research Unit at the University of East Anglia, was attacked for his role in writing the 1995 IPCC report, which claimed to see the hand of man in climate change. He said: "There is a strategy to single out individuals, tarnish them and try to bring the whole of science into disrepute."

Prof Mike Mann of Pennsylvania State University, fresh from his battle over the hockey stick in 2001, said: "There is an orchestrated campaign against the IPCC."

Funding trails to some of the more prominent sceptics also emerged at that time. Steve McIntyre, who runs the influential sceptic blog Climate Audit was free of financial conflicts of interest, but it emerged that prominent sceptic Patrick Michaels received hundreds of thousands of dollars in "consultancy" fees from the Intermountain Rural Electric Association, a coal-burning electric company based in Colorado. A leaked letter from the company's general manager, Stanley Lewandowski, said: "We believe it is necessary to support the scientific community that is willing to stand up against the alarmists."

The funding of climate sceptics has a long and probably ongoing history. In 1998, I revealed in the Guardian leaked documents showing that the powerful American Petroleum Institute (API) was planning to recruit a team of "independent scientists" to do battle against climatologists on global warming. The aim was to bolster a campaign to prevent the US government ratifying the Kyoto protocol.

The API's eight-page Global Climate Science Communications Plan said it aimed to change the US political climate so that "those promoting the Kyoto treaty on the basis of extant science appear to be out of touch with reality".

The leaked document said: "If we can show that science does not support the Kyoto treaty … this puts the US in a stronger moral position and frees its negotiators from the need to make concessions as a defence against perceived selfish economic concerns."

Its first task was to "identify, recruit and train a team of five independent scientists to participate in media outreach". It is not clear if the plan went ahead, but the policy objective was achieved.