Next ice ages

The next ice ages see the advance of Arctic ice sheets as far south as western Europe ("Return of the Ice").

“

Earth is at the peak of an Ice age. Ice sheets cover much of the northern hemisphere, leading to the destruction of many land and ocean habitats. Those species able to survive the cold must adapt to extreme changes in their environment. — The Future Is Wild: A Natural History of the Future.

”

The next ice ages are periods of global cooling and glaciation which occur from the end of the Human era to 5 million AD, the peaks of the seven-million-year Quaternary glaciation↗. More severe than the last ice age↗, the glacial periods see the extension of vast ice sheets across the Arctic Ocean, the northern continents, the Southern Ocean, and southern South America, as well as intense cooling, aridification, and desertification in ice-free regions.

The ice sheets rapidly recede at the end of 5 million AD, ending the ice age and ushering in a period of global warming, culminating in the hothouse world of 100 million AD. Both the beginning and end of the ice age cause significant extinction events.

Overview

“

Ice sheets over a kilometer thick cover most of North America and the whole of Scandinavia, reaching down into Northern Europe. — The Future Is Wild: A Natural History of the Future.

”

The extent of the glaciation as depicted on a map of 5 million AD (A Natural History of the Future).

Ice ages are periods of global cooling and extensive glaciation, which contain lengthy glacial periods and briefer, warmer interglacial periods, occurring at regular intervals. The entirety of the Human era and human civilisation occurred during one such warm interglacial of the Quaternary ice age, which began some 5 million years beforehand.

A new glacial period, representing the peak of the Quaternary ice age, began at the end of the Human era, a few thousand years after the present. Several "boom and bust" cycles of interglacials and glacials have occurred since, with the final glacial phase occurring in 5 million AD.

Compared to the Human era, the average global temperature at the peak of the ice age has fallen by just 5–6°C, but this is enough to bring about significant changes. In 5 million AD, the polar ice caps are at their most extensive, with the Arctic sheets extending to cover most of northern North America, Europe, and Asia. The ice here reaches up to 2 miles (3 km) thick in places. In the southern hemisphere, the Antarctic ice cap has extended far out into the Southern Ocean, covering Patagonia on the South American continent, and possibly reaching as far north as Buenos Aires in northern Argentina, significantly further north than during the last ice age. Temperatures on both ice sheets rarely rise above -60°C (-76°F).

Effects

“

The atmospheric temperature is so low that the air has little capacity for holding moisture. What was once one of the most productive agricultural lands on the planet for Humans is now little more than a vast, barren dustbowl. — The Future Is Wild: A Natural History of the Future.

”

The ice ages are ecologically disastrous, as the advancing ice sheets destroyed terrestrial and marine habitats. The onset of the ice age at the end of the Human era caused a severe extinction event which wiped out thousands of species. These extinctions were originally prompted by human activities such as energy consumption, but with the sudden onset of glacial conditions, falling sea levels and advancing ice sheets exacerbated the situation. Among the species which disappeared from the Earth at this time were humans. Although the status of humans, and the cause of their probable extinction, in The Future Is Wild is the subject of discrepancies, The Future Is Wild: A Natural History of the Future (2002) states that the ice age "led to the extinction of humans."

The evaporation and subsequent freezing of both freshwater and seawater greatly reduces the amount of liquid water in the ocean, lowering sea levels by 400–500 ft (120–150 m) compared to the Human era. Continental shelves and land bridges are exposed by the falling sea levels, increasing the overall size of the land, turning islands into peninsulas, and "fusing" landmasses. Excessive silting of the sea contributes to the total extinction of corals after some 540 million years of existence.

A dry ice age atmosphere has caused the near-dessication of the Amazon River.

The lower temperatures also cause widespread aridification and desertification. Cooler air holds less moisture than warmer air, so the colder atmosphere of the ice age leads to drier air and lower precipitation. The North American interior is hit the hardest, with the fertile rolling prairies of the midwest displaced by cold, arid deserts which support little life. In South America's Amazon Basin, decreased rainfall caused by the slightly cooler air is enough to dessicate the Amazon River, slowing its main branch to a trickle. With the fall in humidity, the Amazon loses much of its Human era diversity of plants and animals, which are replaced by grassland organisms adapted to live with droughts and fires.

End of the ice age

“

The icecaps contract, revealing the carved, scoured landscape beneath and leaving deep scars and heaps of displaced rubble over much of the Northern Hemisphere. The extremes of Earth's climate gradually soften, the blizzards cease, and the polar icecaps melt back until there is little ice left. It will be a longtime before Earth sees another ice age as severe as this one. — The Future Is Wild: A Natural History of the Future.

”

At the end of the ice age, the ice caps melt away almost entirely (A Natural History of the Future)

An increase in volcanic activity in 5 million AD brings the ice age to an end. The carbon dioxide released into the atmosphere efficiently absorbs and emits heat, causing a gradual warming of the planet, which begins to melt the ice sheets. In turn, the surface of the Earth becomes less reflective, allowing the planet to absorb rather than reflect more solar energy, contributing further to the rising temperatures. This cycle of chain reactions results in the complete disappearance of the Earth's ice caps.

Many ice age animals, which evolved under cold and arid conditions, are unable to adapt to the increasingly warmer and more humid world, resulting in another mass extinction.

The final retreat of the ice sheets occurs relatively rapidly, over just 2,000 years, and leaves the Earth almost ice-free for the first time in tens of millions of years. This marks the end of the Late Cenozoic icehouse, which began 39 million years beforehand. The melting of the ice sheets also creates extensive, devastating floods. The repeated glaciations created geological effects which persist long after the ice permanently recedes. Glacial till↗, rocky debris carried by the glaciers, was dumped at the edge of the ice, creating moraines↗, accumulations of rock, all over the Northern Hemisphere. Till carried underneath the advancing and retreating ice also carved permanent striations or gouges into the bedrock, some of which filled with meltwater and became scour lakes↗.

In the animated series

Human civilisation around the beginning of the ice age, as depicted in the children's series.

The early years of the next glacial period, around the end of the Human era, are depicted in the The Future Is Wild children's animated series. The ice age begins approximately 10,000 years in the future, in C.G.'s home time, and the changing environment seriously threatens humanity with extinction. To avoid this, scientists including C.G.'s father plan to relocate civilisation to a less hostile future period. C.G. is sent with the Time Flyer and a robot crew to scout future worlds in search of a suitable home.

Notes

• The Future Is Wild: A Natural History of the Future mentions that there have been several cycles of glacials and interglacials since the Human era. Glacial cycles are relatively regular, lasting for approximately 100,000 years, with long glacials and short interglacials. There would have been around fifty cycles between the Human era and the end of the ice age in 5 million AD.