A new report has warned there's an existential risk to humanity from the climate crisis within the coming decades, and a "high likelihood of human civilization coming to an end" over the next three decades unless urgent action is taken.

The report, published by Australian thinktank the Breakthrough National Centre for Climate Restoration, outlines an apocalyptic scenario that could see conditions "beyond the threshold of human survivability" across much of our planet by 2050. Their analysis calculates the existential climate-related security risk to Earth through a scenario set 30 years into the future.

The report refuses to downplay its bleak assessment of what could happen, warning of "an existential risk to civilization [..] posing permanent large negative consequences to humanity that may never be undone, either annihilating intelligent life or permanently and drastically curtailing its potential."

The authors argue we are now in a unique situation with no precise historical equivalent, with temperatures unlike anything humanity has ever experienced, and a population of nearly 8 billion people. This requires us to work towards avoiding catastrophic possibilities rather than looking at probabilities, as learning from mistakes is not an option when it comes to existential risks.

With that in mind, they propose a plausible and terrifying "2050 scenario" whereby humanity could face irreversible collapse in just three decades. So, here goes:

2020-2030

Governments fail to act on the evidence that the Paris Agreement isn't enough to keep Earth's temperature from rising, and will "lock in at least 3°C of warming". As projected by previous studies, carbon dioxide levels have reached 437 parts per million, which hasn't been seen in the last 20 million years. The planet warms by 1.6°C (2.8°F).

2030-2050

Emissions peak in 2030 and are reduced. However, carbon cycle feedbacks and the continued use of fossil fuels see temperatures rise by 3°C (5.4°F) by 2050.

2050

By 2050 there's a scientific consensus that we reached the tipping point for ice sheets in Greenland and the West Antarctic well before 2°C (3.6°F) of warming, and for widespread permafrost at 2.5°C (4.5°F). A "Hothouse Earth" scenario plays out that sees Earth's temperatures doomed to rise by a further 1°C (1.8°F) even if we stopped emissions immediately.

At this point the human impact is off the scale. Fifty-five percent of the global population are subject to more than 20 days a year of lethal heat conditions beyond that which humans can survive. North America suffers extreme weather events including wildfires, drought, and heatwaves. Monsoons in China fail, the great rivers of Asia virtually dry up, and rainfall in central America falls by half.

Deadly heat conditions across West Africa persist for over 100 days a year, and poorer countries are unable to provide enough artificially-cooled environments for their populations to be viable. Food production is severely affected, and inadequate to feed the global population. More than a billion people are displaced.

The knock-on consequences affect national security, as the scale of the challenges involved, such as pandemic disease outbreaks, are overwhelming. Armed conflicts over resources may become a reality, and have the potential to escalate into nuclear war.

In the worst case scenario, a scale of destruction the authors say is beyond their capacity to model, there is a "high likelihood of human civilization coming to an end".

With these horrific possibilities in mind for our near future, the authors recommend nations "urgently examine the role that the national security sector can play in providing leadership and capacity for a near-term, society-wide, emergency mobilization of labor and resources, of a scale unprecedented in peacetime, to build a zero-emissions industrial system and draw down carbon to protect human civilization."

It is doable. The most recent IPCC report lays out a future if we limit global heating to 1.5°C instead of the Paris Agreement's 2°C. There are ways we can prevent this future, we just need to act now.