Such doubts can be highly effective, particularly if they allow people to support agendas that are politically or economically useful to them.
One person who has managed to successfully merge expert and popular opinions is English physicist Professor Brian Cox, whose books and television programmes explain complex scientific phenomena in highly accessible ways. He recently said that ignoring best evidence and turning against experts is "the road back to the cave".
Modern civilisation, he says, has grown not because of gut instinct and guesswork but because of scientific understanding and thinking. "Being an expert does not mean that you are someone with a vested interest; it means you spend your life studying something. You're not necessarily right - but you're more likely to be right than someone who's not spent their life studying it."
If 100 of the best-qualified engineers were asked to assess the structural integrity of a house and 97 of them said it was unsafe, who would listen to the other three engineers and buy the house? Yet that is the foolishness of climate change denial. Furthermore, the basis for these decisions is often arbitrary and variable.
We all believe in the expertise at Nasa when it launches a rocket into earth's orbit then flicks it into space and lands it on a rock, but so many people conveniently ignore the organisation's knowledge and expertise when it confirms humans created climate change.
All of this might be a strange curiosity if the ramifications weren't so serious. Whether it is the erosion of coastal properties, an influx of climate refugees from the Pacific, or the economic impacts on our primary industries from severe weather events, New Zealand must prepare for some significant realities.
The worst of these problems will impact more greatly on generations to come, but to ignore them now is as unconscionable as it is selfish. It ought be seen as a crime.
One way in which everyday crime can be discouraged is to ensure that "capable guardians" are around to deter criminal activity. When it comes to climate change, the capable guardians are educated members of the public who counteract the deniers.
There may be differing opinions on what policies to pursue, but those who deny that climate change exists ought be shouted down like the charlatans that they are. Or better yet, looked upon with pitiful contempt and completely ignored.
There is no room to sit on the fence and say, "I don't know if it's true". Ignorance of the law excuses no one - and so it is with the laws of science.