Mr Cook said organisers were not surprised that a few dozen climate change deniers had enrolled and were trying to discredit the course from the inside.

"It is ironic and somewhat precursive, because we're explaining the techniques of denial, and then when our course is being attacked or I'm being questioned, all those same techniques are on display," he said.

"It's happening in the forums of the course right now, we're seeing a small minority of the students who reject the science posting their arguments against it."

Mr Cook said the bulk of students were enjoying the first week of course material.

"We have a really powerful video of climate scientists talking about the persistent harassment they receive, the emails, the complaints to their universities, freedom of information requests for their personal details," he said.