The new report, co-written by a former executive in the fossil fuel industry, is a harrowing follow-up to the Breakthrough National Centre for Climate Restoration's 2018 paper, which found that climate models often underestimate the most extreme scenarios.

Endorsed by former Australian defence chief Admiral Chris Barrie, the message is simple: if we do not take climate action in the next 30 years, it is entirely plausible that our planet warms by 3°C and that human civilisation as we know it collapses.

Under this scenario, the authors explain, the world will be locked into a "hothouse Earth" scenario, where 35 percent of the global land area, and 55 percent of the global population, will be subject to more than 20 days a year of "lethal heat conditions, beyond the threshold of human survivability."

Assuming we stay on our current trajectory, emissions will lock in a 3 degree Celsius (5.4 degrees Fahrenheit) global warming, setting off a disastrous chain off events which the report’s authors claim will lead to "a high likelihood of human civilization coming to an end."

According to the report’s central "2050 scenario," one billion people will be forced to relocate from unlivable conditions while food production will become inadequate to feed the global population, as first reported by VICE.

North America will suffer from devastating weather extremes including wildfires, heatwaves and drought — while other places in the world such as the Middle East and West Africa will become unlivable.

Meanwhile, 55% of the global population would be subjected to more than 20 days a year of lethal heat conditions, "beyond the threshold of human survivability."

"This scenario provides a glimpse into a world of ‘outright chaos’ on a path to the end of human civilization and modern society as we have known it, in which the challenges to global security are simply overwhelming and political panic becomes the norm," the authors claim.

The report, meant to serve as a briefing for policymakers, comes with a forward from retired Admiral Chris Barrie — chief of the Australian Defence Force from 1998 to 2002 — who commends the paper for laying "bare the unvarnished truth about the desperate situation humans, and our planet, are in."

Ecosystems will collapse, including coral reefs, the Amazon rainforest and the Arctic. North America will suffer from devastating wildfires, heatwaves, and drought. The great rivers of Asia will be severely reduced as will water availability right across the world, affecting roughly 2 billion people.

Rainfall in Mexico and central America will fall by half and agriculture will be nonviable in the dry subtropics. Semi-permanent El Nino conditions will prevail, and deadly heat waves will persist in some areas for more than 100 days a year. More than a billion people will be displaced.