Climate change sceptics are fighting back in the run up to the UN climate change summit in Copenhagen with a series of talks and conferences.
Professor Ian Plimer, a geologist from the University of Adelaide, has already been in the UK to address an audience of more than one hundred. He will return to speak alongside Lord Monckton of Brencheley at a 'climate change lunch' in London in early December.
Today a conference in Brussels will ask Have Humans Changed the Climate? Professor Ross McKitrick from the University of Guelph in Ontario and Professor Tom Segalstad from the University of Oslo, who both question the conventional science, will address the issue of global warming.
The lead speaker is an American atmospheric physicist Professor Fred Singer from the University of Virginia.
Speaking before the conference, he said there was no evidence that the increases in carbon dioxide produced by humans causes global warming. He said the temperature of the planet has always varied and even if temperatures do go up, that will be good for humankind.
"We are certainly putting more carbon dioxide in the atmosphere. However there is no evidence that this high CO2 is making a detectable difference. It should in principle, however the atmosphere is very complicated and one cannot simply argue that just because CO2 is a greenhouse gas is causes warming," he said.
But Ben Stewart of Greenpeace said the link between carbon dioxide and global warming is now as well proven as the link between smoking and cancer.
"Conferences like this are designed to create confusion and play into the very understandable psychology of denial that most humans have. Climate change is a massive threat to us and people want to hear it is not. This is what these people are relying on. Some are funded by fossil fuel companies so it is a very simple motivation, others have more complex reasons, but it does not change the fact they are wrong."