New Zealand's top climate change scientists have rallied together to slam a visiting sceptic who is touring the country to proclaim global warming as a myth that should be ignored.
Lord Christopher Monckton, a former advisor to Margaret Thatcher, says human-induced climate change is not happening.
Read the latest: Climate change sceptic rejects criticism as 'hate speech'
The British aristocrat, the 3rd Viscount Monckton of Brenchley, is on a 16-venue nationwide speaking tour telling New Zealanders they shouldn't be worried about rising temperatures or sea levels.
Carbon taxes and emissions-trading schemes should also be scrapped because they are too expensive, he believes.
But government scientists and academics have warned that Lord Monckton's views are not based on science, and go against all the research they have done and read.
Dr James Renwick, associate professor of physical geography at Victoria University, dismissed Lord Monckton's views as "rubbish".
"He's a great showman and speaker, and climate change is a vehicle to self-publicise.
"But he has no training and has studiously avoided learning anything about science, I would say."
Niwa principal scientist Brett Mullan said Lord Monckton's views were "very damaging" for public perception.
Professor Dave Frame, director of the Climate Change Research Institute at Victoria University, described him as a "vaudeville act" to be ignored.
"Someone who goes around saying things we know are not true can actually be quite harmful."
Lord Monckton has rejected the claims as ''hate speech".
He once argued for the quarantine of AIDS patients in internment camp-like facilities, and is a vocal leader of the climate change-denying movement.
In Copenhagen in 2009, the member of the right-wing anti-European UK Independence Party (UKIP) caused fury when he called young climate activists, 'Hitler Youth'.
In 2011, he was forced to apologise after comparing Australia's chief climate adviser Ross Garnaut to a Nazi.
Lord Monckton, 61, has no scientific training, having studied classics and journalism. He has toured the world trying to convince people that climate change is being exaggerated.
Ahead of his Kiwi tour, which started on Monday in Matakana, Northland, he said he would provide "hard scientific and economic evidence" to support his claims.
He says global warming paused around 20 years ago, and previous Intergovernmental Panel on Climate Change (IPCC) predictions have all been "wrong".
Even if the world does heat up by three per cent this century, as predicted by the world's leading scientists, Lord Monckton says it's pointless - and too expensive - to try to stop it.
"It is 50 times less cost-effective to try to prevent global warming today than to let it happen and leave enough money to our grandchildren to allow them to cope, not only with any warming that may occur but with any other crisis that they may face," he says.
However Dr Mullan said there was "a huge amount of very solid science" to show an increase in greenhouse gases.
He accused Lord Monckton of picking data and statistics to suit his argument.
"The whole strategy of these sceptics and deniers is to take these things out of context to present a different picture," Dr Mullan said.
"That's not the way it's done in science. You look at the evidence for and against, analyse it objectively, and have it reviewed by other experts. It's not decided by who can come up with the fastest set of witty one-liners."
Lord Monckton promotes himself as an 'expert reviewer' for the IPCC's forthcoming Fifth Assessment Report, and says he'll take a "strictly scientific, economic, rational and logical approach" to global warming questions.
But Dr Mullan said anybody can offer themselves forward as an expert reviewer.
Those claims were an attempt to legitimise his arguments, Dr Mullan said.