Imagine a teacher who wanders into a classroom full of five-year-olds, sits down, pulls out a packet of cigarettes and starts to smoke them, exhaling puffs of cancer-inducing haze that waft into the little kids' faces.

"Please stop that," pleads one of the children. "My mummy says smoking gives you cancer."

"Rubbish," replies the smoker. "People have been dying of cancer ever since humans have walked the Earth. How did the cavemen die of cancer before cigarettes were invented, eh?"

Clearly, our cancer-stick smoking friend is employing a flawed, dishonest and ridiculous argument. We know that smoking increases the risk of cancer and other nasty diseases among the general population. The fact that Captain Caveman couldn't have had a 20-a-day habit is irrelevant.

The fact that a postmortem can't identify exactly which cigarette killed you, is also of little comfort.

Suggesting that an outcome – in this case death from cancer – can't have several different causes is a logical fallacy. This would be like claiming guns can't kill people because people were also murdered before guns were invented.

But as ridiculous as these examples are, it is this same wafer-thin and intellectually dishonest debating trick that has been deployed by Australian prime minister, Tony Abbott, and his environment minister, Greg Hunt, in recent days to dismiss the link between human-caused climate change and bushfires.

Earlier this week, Abbott said in an interview with the Washington Post:

Australia has had fires and floods since the beginning of time. We've had much bigger floods and fires than the ones we've recently experienced. You can hardly say they were the result of anthropic [sic] global warming.



Abbott's argument was the same one he used last week, when he suggested that because bushfires happened before humans raised carbon dioxide levels in the atmosphere by 40%, we shouldn't think this could have anything to do with bushfires happening now. He told radio listeners:

We have had bad fires since almost the beginning of European settlement, I think the first massive fires in Victoria were back in the 1850s.



Between these statements, Hunt told the BBC he had consulted Wikipedia "just to see what the rest of the world thought".

He reported that the Wikipedia entry "opens up with the fact that bushfires in Australia are frequently occurring events during the hotter months of the year. Large areas of land are ravaged every year by bushfires. That's the Australian experience."

As I outlined last week, scientists have been studying the links between bushfires and climate change for more than a quarter of a century.

As the Guardian has reported, the Australian government's own environment departmental website says there's a "growing and robust body of evidence" showing the number of extreme weather events will likely increase under climate change, and that Australia is already experiencing a rise in the number of these events, including bushfires.

However, Abbott dismissed with absolute certainty any suggestion that the recent bushfires in New South Wales could have anything to do with climate change. In an interview with climate sceptic News Corporation columnist Andrew Bolt, Abbott went further, saying such links were "complete hogwash".

This argument from history used by Abbott and Hunt is a version of one of the most popular of all talking points used by climate change sceptics and denialists – that "the climate has always changed" and so why should we think humans can cause the rapid changes being observed in recent decades.

A study published in the journal American Behavioral Scientist looked at 203 opinion articles written by 80 different US conservative columnists between 2007 and 2010 and found the argument that "the climate has changed before" was one of the most popular talking points.

Study authors Shaun Elsasser and Riley Dunlap, of Oklahoma State University, wrote:

Unlike the scientific literature, where debunked claims and findings can no longer be employed, in the "denialosphere" arguments never disappear – they are continually recycled. The result is an enormous number of arguments.



The most popular argument put by sceptical columnists was "there is no scientific consensus" (there is) followed by "it's cooling" (it's not) and "ice isn't melting" (it is).

Popular debunking website Skeptical Science also looks in detail at climate sceptic myths and ranks "climate has changed before" as the most popular of all denier talking points.

This is not the first time that Abbott has tried to argue that because certain climatic events might have happened before the industrial revolution, we shouldn't think that burning fossil fuels could contribute to changes in the climate now.

In 2010, Abbott let this logical fallacy loose on a classroom of school kids in Adelaide, telling them:

OK, so the climate has changed over the eons and we know from history, at the time of Julius Caesar and Jesus of Nazareth the climate was considerably warmer than it is now. And then during what they called the dark ages it was colder. Then there was the medieval warm period. Climate change happens all the time and it is not man that drives those climate changes back in history. It is an open question how much the climate changes today and what role man plays.



At least he didn't blow cigarette smoke in their faces.