Read more: 鈥�100,000 AD: Living in the deep future鈥�
FISHING boats in the North Sea bring up some strange things in their nets, from the bones of mammoths to ancient stone tools and weapons. Here and in many other places around the world, we are discovering the remains of human settlements on what is now the seabed. As the world changed after the last ice age, many of our ancestors were forced to abandon their homes. And over the next 1000 years, let alone 100,000, the world is going to change dramatically again, forcing billions of people to find a new place to live.
Some places would battle to survive even if sea level remained constant. The ancient Egyptian city of Herakleion disappeared beneath the Mediterranean Sea 2000 years ago as the soft sands of the delta it was built on subsided, and the same is happening to modern cities such as New Orleans and Shanghai. In Miami and elsewhere, seas and rivers are eroding the land that cities are built on.
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With a stable climate, it might be possible to save cities like these. But as the world continues to warm, rising sea levels are going to drown many of our coastal cities, along with much farmland. The changing climate will also affect people living well above sea level, making some areas uninhabitable but creating new opportunities elsewhere.
We don鈥檛 know exactly how much hotter the world will become. But let鈥檚 suppose events follow the Intergovernmental Panel on Climate Change鈥檚 鈥渂usiness as usual鈥� scenario, with greenhouse emissions continuing to grow until 2100 and then declining rapidly. Suppose, too, that we do not attempt any kind of geoengineering.
The most likely result is that the average global temperature will rise nearly 4 掳C above the pre-industrial level around the year 2100, peaking at 5 掳C sometime in the 23rd century (though it might well get a lot hotter than this). It will stay hot, too, as it will take 3000 years or so for the planet to cool just 1 掳C.
That might mean that the Greenland ice sheet will be almost gone in 1000 years, with the West Antarctic ice sheet following it into the sea, raising its level by well over 10 metres. That鈥檚 bad news given that coastal regions are home to much of the world鈥檚 population, including many rapidly growing megacities. As the sea level rises, billions of people will be displaced.
At least this will likely be a gradual process, though there may be occasional catastrophes when storm surges overcome flood defences. Large areas of Florida, the East and Gulf coasts of the US, the Netherlands and the UK will eventually be inundated. Some island nations will simply cease to exist and many of the world鈥檚 greatest cities, including London, New York and Tokyo, will be partly or entirely lost beneath the waves.
And as the great ice sheet of East Antarctica slowly melts, the sea will rise even higher. For each 1 掳C increase in temperature, sea level could eventually rise by 5 to 20 metres. So in 5000 years鈥� time, the sea could be well over 40 metres higher than today.
Even those living well above sea level may be forced to move. Some regions, including parts of the southern US, may become too dry to support farming or large cities. In other areas, flooding may drive people out.
Any further warming will cause catastrophic problems. A 7 掳C global rise will make some tropical regions so hot and humid that humans will not be able to survive without air conditioning. If the world warms by 11 掳C, much of the eastern US, China, Australia and South America, and the entire Indian subcontinent, will become uninhabitable (see map).
Yet the future will open up alternative places to live. In the far north, what is now barren tundra and taiga could become fertile farmland. New land will also appear as the ice sheets melt.
A rush to exploit the resources in newly exposed bedrock in Antarctica, for instance, could encourage settlement in its coastal regions (see map). If it stays hot enough for long enough, Antarctica will once again be a lush green continent covered in forests. Elsewhere, pockets of fresh land will rise out of the ocean in the space of hundreds of thousands of years, perhaps ripe for human settlement (see 鈥淟and ahoy!鈥�).
At some point our descendants could take control of the global climate. But it will take thousands of years to restore the ice sheets and get sea levels back down. By the time we are in a position to do so, some people may like life just as it is. The proud citizens of the Republic of Antarctica will fight any measure that would lead to their farms and cities being crushed by ice.
Land Ahoy!
New lands will rise from the sea. It鈥檚 time to start composing their national anthems
Throughout history, explorers have planted their flags on virgin lands. Today, there鈥檚 almost nowhere left on Earth where we haven鈥檛 set foot 鈥� but that won鈥檛 always be the case.
Plate tectonics and volcanism are continually creating new land. For example, future settlers are likely to find Hawaii has an extra island. For more than 80 million years, a 鈥渉ot spot鈥� of rising magma from deep within the Earth has punched through the floor of the Pacific Ocean to build a series of islands on the crust moving over it. This means Hawaii鈥檚 Big Island will soon get a baby brother off its south coast, formed by a submerged volcano called Lo鈥檌hi. It is growing fast and should emerge within 100,000 years, depending on sea-level rise. Geologists expect that its peak will eventually tower above all others in the Hawaiian chain.
In the much longer term, Europe and Africa could also get swathes of new territory. That鈥檚 because Africa is moving north-east by about 2.5 centimetres a year, gaining about a centimetre a year on Europe, which is moving in the same direction. In principle, this crunching could shut the Strait of Gibraltar within the next few million years. Without the inflow of Atlantic water, the Mediterranean Sea would eventually evaporate. Countries in southern Europe and on the north African coast would effectively expand across the newly exposed seabed until they join up.
If our descendants are still around millions of years from now, they may have to figure out how to divvy up whole new parts of the world.