We are heading for a New Cretaceous, not for a new normal (geological periods)

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https://aeon.co/ideas/we-are-heading-for...new-normal

EXCERPT: . . . As it happens, the Cretaceous is one of my favourite geological periods. It gave us the great chalk hills and cliffs that straddle Europe. It gave us figs, plane trees and magnolias. It nurtured little mammals, who suddenly blossomed when the then-lords of creation – Triceratops, Tyrannosaurus and their cousins – went extinct at the end of the period. It was also very warm, with global temperatures 3-10°C hotter than preindustrial levels.

­Should it come to pass, any new era with a Cretaceous-like climate wouldn’t precisely mirror the original. For a start, the continents were then in very different positions [...] But in a Cretaceous rerun, there would very likely be no ice at the poles once again, and sea levels would be about 216 feet (66 metres) above current levels. We would also see the creation of vast warm shallow seas with mineral deposits [...]

The only way I can possibly conceive of humans living in a New Cretaceous age is as a rump of scientists and technologists working in artificial, protected shelters, rather like the denizens of the novelist Italo Calvino’s invisible city of Baucis, in which people live up on stilts above the clouds ‘contemplating with fascination their own absence’.

We have recently become aware of a red line that humans are going to hit long before we approach Cretaceous conditions. In 2010, researchers showed that our species cannot survive for more than six hours at what’s called a ‘wet bulb’ temperature of 35°C (95°F). Wet bulb here means 100 per cent humidity, so it’s not 35°C as we know it. But in the great Indian agricultural belts of the Indus and Ganges, high-40s temperatures combined with 50 per cent humidity (which equates to that wet-bulb temperature of 35°C ) are going to prevail within decades.

While this is happening in hot agricultural regions, the urban world will face a perhaps even greater catastrophe. The UN’s most-likely temperature-rise prediction of 3°C would see forests growing in the Arctic, and entail the loss of most coastal cities through irreversible sea-level rise by the end of the century.

It is now widely accepted, by scientists at least, that human beings have become geological agents, hence the assignment of a new geological epoch: the Anthropocene. Human inputs into the environment, including artificial nitrogen fertilisers as well as CO2, now outstrip the natural cycles. The popular idea that geology and human concerns are totally incommensurate is belied by the fact that at times the Earth has moved very fast. Two great warming events – with a long cooling period in between – ended the last Ice Age 12,600 years ago, around 9,600 BCE. Both produced 10-degree spikes in Greenland ice cores. The first happened over only three years; the second, which ushered in the relatively stable conditions of the Holocene, happened over a period of around 60 years.

A lesson for today is that such a sudden and lasting change to the climate has consequences lasting thousands of years. That first warming caused an enormous lake to spread across North America as the Laurentide ice sheet melted, then eventually burst, leading to large-scale sea-level rise, and forming the Great Lakes and Niagara Falls some 2,500 years later. Britain was finally sundered from Europe 3,500 years after the start of the Holocene; and as the northern ice sheets melted, the land beneath them rose. This continues today in Sweden at a rate of almost 1cm a year.

This epoch, our epoch, is technically an interglacial one, and it was always going to end. The Earth has generally been violently unstable, or stably hostile, for long periods, either too hot or too cold for human civilisation. Had we not forced global temperatures upward through CO2 emissions, we would most likely now be facing a new Ice Age; as it is, the Holocene is ending as fast as it began with a new temperature spike occurring during normal human lifetimes.

So while we prattle about ‘the new normal’, we need to recognise that there was nothing ‘normal’ about the Holocene....

MORE: https://aeon.co/ideas/we-are-heading-for...new-normal
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