Premieres 19 July at Outfest Film Festival, California; screens on 26 July at Woods Hole Film Festival, Massachusetts. Showing at US universities thereafter.

After watching Al Gore's straight-faced presentation in the 2006 film An Inconvenient Truth, director Randy Olson turned to humour to tackle the issue of climate change. “I really liked it,” he says of Gore's documentary in the opening to Sizzle, Olson's new film that premieres in Hollywood on 19 July, “but I kept thinking 'where are all the scientists?'”

Part documentary, part mockumentary, Sizzle follows Olson as he interviews scientists and sceptics from around the United States with the help of a crew of thinly drawn comedic characters. Director of the well-received 2006 documentary on intelligent design, Flock of Dodos, Olson is no stranger to portraying society's complex response to science. Sadly, Sizzle's mix of styles confuses his message.

The interviewees, including researchers such as Gerald Meehl at the National Center for Atmospheric Research in Colorado and Richard Somerville at the Scripps Institution of Oceanography in California, look as if they think they are being interviewed for a straight documentary. Then Olson's cameraman, a climate-change sceptic played by comedian Alex Thomas in a solid and funny performance, butts in with his own contribution, a running gag that the film turns into a point about scientific communication: when you ask dumb questions in everyday language, scientists suddenly start talking like 'normal' people.

Olson argues that data alone fail to convince people to care about climate change. What succeeds is anecdote and emotion. Indeed, the film contains very little data. The interviews are edited down to mere stubs, with no explanation of what climate change is or why we should laugh at the sceptics. Perhaps Olson assumes his audience has previous knowledge.

Olson heads to New Orleans in search of compelling anecdotes. With the caveat that the relationship between climate change and hurricanes is still being worked out, he argues like many before him, including Gore, that Hurricane Katrina is a window into a climate-changed world — even the richest nation on Earth disintegrates into anarchy in the face of terrible natural disasters. But once he gets there, Olson wanders off-topic, preferring to criticize the federal response to the hurricane.

The film is good in places and provides insights into the social response to climate change. But some of the mockumentary's jokes, meant to keep us watching, are rather stale: an elderly white woman — Olson's mother — goes out on the town with the young black camera crew, and the gay film producers throw several colourful hissy fits.

Ultimately, one is left wondering what the film aims to do. Does it argue that climate change is real, or discuss how we might convince people that it is? At the end of the film, Olson heads off to the editing studio to make a coherent story out of his footage. If only we had got to see that version.