"I can't see humans existing within 10 years. We can do nothing to stop the planet becoming too hot to grow food and support life. It is already happening and we have less than a decade left."
Starvation, dehydration, disease, and exposure will lead the way, he said.
Mr McPherson is out of step with mainstream climate science. Although it is widely accepted that unchecked climate change could threaten the human species at some point in time, most scientists say switching from reliance on fossil fuels to renewable energy will save the worst impacts and enable humanity to survive.
Professor James Renwick, a climate scientist at Victoria University, agrees that climate change is possibly the "biggest issue humanity has ever faced", but adds "though certainly humans won't all die off in 10 years or even 1000 years."
Mr McPherson cites scientific data including tipping points, positive feedback systems and exponential growth to back up his claims.
"Other scientists are specialists. They focus on a narrow topic. They do not consider the entire Earth system in their work," Mr McPherson said.
"Climate change and its impacts are here. Expect superstorms, extreme heat, high humidity, and increased spread of deadly diseases. Plants and non-human animals will die in ever-larger numbers. Civilisation will fail, leading to greatly exacerbated impacts."
Mr McPherson said he was not concerned that his message might alarm or distress people. "I'm a teacher. I relay evidence. I cite science. I'm not relying on a belief system."
He says he has been labelled an extremist and worse, and regularly receives hate mail.
"I've been accused of many things, extremist included. I'm merely connecting a few dots based on the work of other scientists. In a culture characterised by willful ignorance and the inability to think critically, these accusations are to be expected."
He said many people were liberated by his message. "Knowing they've been subjected to lies, they appreciate the truth and they act as if time is short."
