In the global south, extreme climate change will push vast numbers of people from their homes, with large regions becoming uninhabitable; in the developed world, economies will struggle to survive demographic changes with massive workforce shortages and an impoverished elderly population.

This is the unprecedented upheaval that will reshape the planet that is described in a new book.

‘Nomad World: How to survive the climate upheaval’, by British-Australian environmental writer Gaia Vince, posits that over the next fifty years, hotter temperatures combined with more intense humidity are set to make large areas of the globe uninhabitable, potentially displacing 3.5 billion  people.

The book says people will be forced to flee the tropics, coastal areas and once arable lands to seek new homes.

It says this migration has already begun. Climate-driven movements are adding to a massive migration already under way to the world’s cities and the number of migrants has doubled globally over the past decade.

Ms Vince argues that the issue of what to do about rapidly increasing populations of displaced people will only become greater and more urgent as the planet heats.

“Have no doubt, we are facing a species emergency – but we can manage it. We can survive, but to do so will require a planned and deliberate migration of a kind humanity has never before undertaken,” she says.

Ms Vince argues climate change demands a dynamic human response, and the solutions are within our hands.

“We need to help people to move from danger and poverty to safety and comfort – to build a more resilient global society for everyone’s benefit. Human movement on a scale never before seen will dominate this century and remake our world. It could be a catastrophe or, managed well, it could be our salvation,” she says.

Ms Vince predicts large populations will need to migrate to survive, in many cases across continents.

And people living in regions with more comfortable conditions, especially nations in northern latitudes, will need to accommodate millions of migrants into increasingly crowded cities while themselves adapting to the demands of climate change.

“We will need to create entirely new cities near the planet’s cooler poles, in land that is rapidly becoming ice-free. Parts of Siberia, for example, are already experiencing temperatures of 30°C for months at a time,” she says.

The book says that In India alone, almost a billion people will be at risk. Another half billion will need to move within China, and millions more across Latin America and Africa.

“Southern Europe’s treasured Mediterranean cli- mate has already shifted north, leaving regular desert-like conditions from Spain to Turkey. Meanwhile, parts of the Middle East have already been made intolerable by increasing heat, lack of water and poor soils,” the book says.

It paints a picture of planetary upheaval occurring at a time of unprecedented climate change and also of human demographic change.

“Global population will continue to rise in the coming decades, peaking at perhaps 10 billion in the 2060s. Most of this increase will be in the tropical regions that are worst hit by climate catastrophe, causing people there to flee northwards,” the book says.

It looks ahead to a century of unprecedented, planetary human movement.

“We need to plan pragmatically now, adopting a species-wide approach to ensure our human systems and communities have the resilience to weather the shocks to come,” MS Vince says.

“We need to look now at where these billions of people could be sustainably housed. Doing so will require international diplomacy, negotiations over borders, and adaptation of existing cities,” she says.

Ms Vince says the Arctic will become a habitable destination for millions of people, while major cities will have to be abandoned.

She says human movement will be driven by climate change’s devastation of harvests, with soaring food prices; and by conflict driven by economic difficulties.

Also, it will be driven by extreme weather events and rising oceans.

The book cites United Nations International Organization for Migration estimates that there could be as many as 1.5 billion environmental migrants in the next thirty years alone.

After 2050, that figure is expected to soar as the world heats further and the global population rises to its predicted peak in the mid-2060s.

The book concludes that only human cooperation will provide solutions to the approaching climate cataclysm.

“We are a planetary species, dependent on a single shared biosphere. We must look afresh at our world and consider where best to put its human population and meet all of our needs for a sustainable future,” Ms Vince says.

“…we will, as refugees of nations, need collectively to transition to a sense of ourselves as citizens of Earth. We will need to shed some of our tribal identities to embrace a pan-species identity. We will need to assimilate into globally diverse societies, living in new, polar cities. We will need to be ready to move again when needed,” she says.

“With every degree of temperature increase, roughly a billion people will be pushed outside the zone in which humans have lived for thousands of years. We are running out of time to manage the coming upheaval before it becomes overwhelming and deadly. Migration is not the problem; it is the solution,” Ms Vince says.

Nomad Century by Gaia Vince, published by Allen Lane, $39.00