The film's key contentions were that the increase in atmospheric temperatures observed since the 1970s was not primarily caused by emissions of greenhouse gases from burning fossil fuels, and that the modern focus on climate change is based in politics rather than science.
It is seen in some "climate sceptic" circles as a counter to Al Gore's movie An Inconvenient Truth, and credited with influencing public perception of climate science. It has reportedly been sold to 21 countries and distributed on DVD.
"It's very disappointing that Ofcom hasn't come up with a stronger statement about being misled," said Sir John Houghton, a former head of the UK Met Office and chair of the Intergovernmental Panel on Climate Change (IPCC) scientific assessment.
"I know hundreds of people, literally hundreds, who were misled by it - they saw it, it was a well-produced programme and they imagined it had some truth behind it, so they were misled and it seems Ofcom didn't care about that," he told BBC News.
I think this is a vindication of the credibility and standing of the IPCC
Rajendra Pachauri, IPCC
Ofcom defines a misleading programme as one by which the audience is "materially misled so as to cause harm or offence", and that Swindle does not meet this "high test".
"The programme has been let off the hook on a highly questionable technicality," said Bob Ward, former head of media at the Royal Society, who played a prominent role in co-ordinating objections to the film.
"The ruling noted that Channel 4 had admitted errors in the graphs and data used in the programme, yet decided that this did not cause harm or offence to the audience."
Plaintiffs accused the programme of containing myriad factual inaccuracies, but Ofcom says it was "impractical and inappropriate for it to examine in detail all of the multifarious alleged examples... set out in the complaints."
The regulator also says it is only obliged to see that news programmes meet "due accuracy".
The broadcaster argued that the judgement vindicated its decision to showcase the documentary.
"Ofcom's ruling explicitly recognises Channel 4's right to show the programme and the paramount importance of broadcasters being able to challenge orthodoxies and explore controversial subject matter," said Hamish Mykura, the station's head of documentaries.
"This is particularly relevant to Channel 4 with its public remit and commitment to giving airtime to alternative perspectives."
On another issue - whether contributors to the programme had been treated fairly - Ofcom mainly found against Channel 4 and the film's producer WagTV.
Former UK chief scientific adviser Sir David King had been misquoted and had not been given a chance to put his case, the regulator said.
Ofcom also found in favour of Carl Wunsch, an oceanographer interviewed for the programme, who said he had been invited to take part in a programme that would "discuss in a balanced way the complicated elements of understanding of climate change", but which turned out to be "an out-and-out propaganda piece, in which there is not even a gesture toward balance".
The film alleged that the IPCC's scientific reports were driven by politics rather than science, and Ofcom ruled the organisation had not been given adequate time to respond.
"I think this is a vindication of the credibility and standing of the IPCC and the manner in which we function, and clearly brings out the distortion in whatever Channel 4 was trying to project," said Rajendra Pachauri, the organisation's chairman.
Ofcom's Broadcasting Code requires Channel 4 to show "due impartiality" on "matters of major political and industrial controversy and major matters relating to current public policy".
Human hands are driving climate change, Ofcom acknowledges
The last segment of the programme, dealing with the politics of climate change, broke this obligation, Ofcom judged, and did not reflect a range of views, as required under the code.
But the main portion of the film, on climate science, did not breach these rules.
Ofcom's logic is that "the link between human activity and global warming... became settled before March 2007".
This being so, it says, climate science was not "controversial" at the time of broadcast, so Channel 4 did not break regulations by broadcasting something that challenged the link.
"That's a very big inconsistency," said Sir John Houghton. "They said it's completely settled, so why worry - so they can just broadcast any old rubbish."
While some of the 265 complaints received by Ofcom were short and straightforward, one group assembled a 176-page document alleging 137 breaches of the code.
Channel 4 will have to broadcast a summary of the Ofcom ruling, but it brings no sanctions.
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