The chapter of Tim Marshall’s book Prisoners of Geography (see also these earlier excerpts: Africa is (still) big. And Africa’s rivers don’t help, Tim Marshall on the illiberal and undemocratic Middle East) that I found the most informative was the one on The Arctic, because this is the part of the world that he writes about concerning which I know the least.  How catastrophic - if catastrophic at all - global warming will eventually become, and whose fault it will be if it ever does become catastrophic and what to do about it , are all matters of fierce dispute.  But the fact of global warming is not in doubt, as Marshall explains (pp. 267-271):

That the ice is receding is not in question - satellite imaging over the past decade clearly shows that the ice has shrunk - only the cause is in doubt. Most scientists are convinced that man is responsible, not merely natural climate cycles, and that the coming exploitation of what is unveiled will quicken the pace.

Already villages along the Bering and Chukchi coasts have been relocated as coastlines are eroded and hunting grounds lost. A biological reshuffle is under way. Polar bears and Arctic foxes are on the move, walruses find themselves competing for space, and fish, unaware of territorial boundaries, are moving northward, depleting stocks for some countries but populating others. Mackerel and Atlantic cod are now being found in Arctic trawler nets.

The effects of the melting ice won’t just be felt in the Arctic: countries as far away as the Maldives, Bangladesh and the Netherlands are at risk of increased flooding as the ice melts and sea levels rise. These knock-on effects are why the Arctic is a global, not just a regional, issue.

As the ice melts and the tundra is exposed, two things are likely to happen to accelerate the process of the greying of the ice cap. Residue from the industrial work destined to take place will land on the snow and ice, further reducing the amount of heat-reflecting territory. The darker-coloured land and open water will then absorb more heat than the ice and snow they replace, thus increasing the size of the darker territory. This is known as the Albedo effect, and although there are negative aspects to it there are also positive ones: the warming tundra will allow significantly more natural plant growth and agricultural crops to flourish, helping local populations as they seek new food sources.

There is, though, no getting away from the prospect that one of the world’s last great unspoiled regions is about to change. Some climate-prediction models say the Arctic will be ice-free in summer by the end of the century; there are a few which predict it could happen much sooner. What is certain is that, however quickly it happens and dramatic the reduction will be, it has begun.

The melting of the ice cap already allows cargo ships to make the journey through the Northwest Passage in the Canadian archipelago for several summer weeks a year, thus cutting at least a week from the transit time from Europe to China. The first cargo ship not to be escorted by an icebreaker went through in 2014. The Nunavik carried 23,000 tons of nickel ore from Canada to China. The polar route was 40 per cent shorter and used deeper waters than if it had gone through the Panama Canal. This allowed the ship to carry more cargo, saved tens of thousands of dollars in fuel costs and reduced the ship’s greenhouse emissions by 1,300 metric tons. By 2040 the route is expected to be open for up to two months each year, transforming trade links across the ‘High North’ and causing knock -on effects as far away as Egypt and Panama in terms of the revenues they enjoy from the Suez and Panama canals.

The north-east route, or Northern Sea Route as the Russians call it, which hugs the Siberian coastline, is also now open for several months a year and is becoming an increasingly popular sea highway.

The melting ice reveals other potential riches. It is thought that vast quantities of undiscovered natural gas and oil reserves may lie in the Arctic region in areas which can now be accessed. In 2008 the United States Geological Survey estimated that 1,670 trillion cubic feet of natural gas, 44 billion barrels of natural gas liquids and 90 billion barrels of oil are in the Arctic, with the vast majority of it offshore. As more territory becomes accessible, extra reserves of the gold, zinc, nickel and iron already found in part of the Arctic may be discovered.

ExxonMobil, Shell and Rosneft are among the energy giants that are applying for licences and beginning exploratory drilling. Countries and companies prepared to make the effort to get at the riches will have to brave a climate where for much of the year the days are endless night, where for the majority of the year the sea freezes to a depth of more than six feet and where, in open water, the waves can reach forty feet high.

It is going to be dirty, hard and dangerous work, especially for anyone hoping to run an all-year-round operation. It will also require massive investment. Running gas pipelines will not be possible in many places, and building a complex liquefaction infrastructure at sea, especially in tough conditions, is very expensive. However, the financial and strategic gains to be made mean that the big players will try to stake a claim to the territories and begin drilling, and that the potential environmental consequences are unlikely to stop them.