What Age Would You Be if You Didnt Know Your Age
Ice ages don't simply happen overnight, although some movies might have u.s. believe they do. These mythical events have shaped human being history, but what causes them and could a new ice age spell the end of the world every bit we know it?
What is an ice age?
Fundamental points:
- The terminal ice historic period was 12,000 years ago
- At that fourth dimension the sea level was 120m lower than today
- The onset of an water ice age is related to changes in the World's tilt and orbit
- The Earth is due for another ice age now merely climate change makes it very unlikely
An ice age is a time where a significant amount of the Earth's h2o is locked up on land in continental glaciers.
During the last ice age, which finished virtually 12,000 years ago, enormous ice masses covered huge swathes of land now inhabited by millions of people.
Canada and the northern USA were completely covered in ice, every bit was the whole of northern Europe and northern Asia.
At the moment the Earth is in an interglacial period - a short warmer period between glacial (or ice age) periods.
The Earth has been alternating between long ice ages and shorter interglacial periods for around 2.six million years.
For the last million years or and then these accept been happening roughly every 100,000 years - around ninety,000 years of ice age followed by a roughly x,000 year interglacial warm menstruation.
What causes an ice age?
Ice ages don't simply come out of nowhere - it takes thousands of years for an ice historic period to brainstorm.
An ice historic period is triggered when summertime temperatures in the northern hemisphere fail to rise in a higher place freezing for years. This means that winter snow doesn't melt, but instead builds up, compresses and over time starts to meaty, or glaciate, into water ice sheets.
Over thousands of years these ice sheets showtime to build upward - it seems to be in northern Canada when that first happens - and then they spread out across the northern hemisphere.
"Information technology's a long term trend over thousands of years to colder summers," Dr Steven Phipps, an ice sheet modeller, said.
Dr Phipps is as well a climate system modeller and palaeoclimatologist with the University of Tasmania.
The onset of an ice age is related to the Milankovitch cycles - where regular changes in the World's tilt and orbit combine to affect which areas on Earth get more than or less solar radiation.
When all these factors align so the northern hemisphere gets less solar radiation in summer, an ice age tin can be started.
Are we due for another ice historic period?
Based on previous cycles the Globe is probably due to get into an ice age virtually now. In fact, atmospheric condition were starting to line upwardly for a new ice age at to the lowest degree 6,000 years ago.
"If you look at what was happening prior to the industrial revolution, summers were really getting colder in the northern hemisphere. They've been getting colder for at least the terminal six,000 years, and so nosotros were definitely on that tendency," Dr Phipps said.
Merely that trend has now been comprehensively reversed considering of greenhouse gas emissions, according to Dr Phipps.
"There's no risk of us going into an water ice age at present because the greenhouse gases we've put into the temper during the industrial era have warmed the earth."
Although scientists cannot say nosotros take definitely prevented the next water ice age, it'due south certainly accepted that humans have had a significant part to play.
"There is really a hypothesis that information technology's not just industrial guild merely ever since humans began practicing large scale farming at least five,000 years ago, such every bit methane emissions from rice paddies," Dr Phipps said.
"So it's peradventure non but greenhouse gas emissions over the concluding 200 years that's stopped us going into an water ice historic period, but it'south actually greenhouse gas emissions for the last v,000 years that accept collectively helped to steer the states abroad from the next water ice age."
What would happen if there was an ice historic period today?
We may have delayed the onset of the adjacent ice age for now, but if another i came it would have pretty big consequences for human civilisation.
Besides the fact it would be an awful lot colder, huge regions where hundreds of millions of people live would become completely uninhabitable. They'd be covered in thick ice sheets and discipline to an inhospitable climate.
"Assuming it was like to the last one, so north America would be covered in water ice, the whole of northern Europe, the whole of northern Asia would be covered in ice," Dr Phipps said.
There would be a lot less agricultural land bachelor, so it would be very difficult to support the human population, Dr Phipps warned.
And the concrete shape of the continents would expect completely different across the whole planet.
A huge drop in body of water level of up to 120 metres would close downwardly marine channels - the Mediterranean Ocean, Torres Strait, Bass Strait and Bering Strait - and create new areas of land that could exist used for home or agriculture.
Body of water ports would no longer be on the sea, and anyone wanting water views would need to relocate big distances.
What we have the last water ice age to thank for...
Ice ages accept had an admittedly enormous impact on human evolution.
During the last ice age, which ran from nearly 110,000 years ago to 10,000 years ago, the lower bounding main levels immune humans to move out beyond the unabridged world.
"There was no Bering Straits, then north America and Asia were joined and that'due south really how humans first roamed into the Americas, they just walked over the land bridge," Dr Phipps said.
While there was even so some water betwixt Asia and Australia it took just a few short canoe trips to bring the first humans to Australasia.
"They would take come up over towards New Republic of guinea. There was no Torres Strait so humans could accept just walked from New Guinea to the Australian mainland. And there was no Bass Strait so humans could accept walked from the Australian mainland over to Tasmania," he said.
The whole dispersal of humans around the globe during the last 100,000 years was fabricated entirely possible by the fact we were in an ice historic period at the fourth dimension.
How practise nosotros know they happened in the past?
Information technology's a fair question - how can we know so much about these major events in the past? Scientists have a multifariousness of methods they utilize.
Evidence for the more recent ice ages comes from irresolute ocean levels in the past, which can be seen by looking at coral reefs or mod landscapes.
"That's how they first pieced together the evidence for glacial cycles. Looking at corals, and coral reefs and prove of by sea level changes in the tropics, they saw there was a bike of irresolute sea levels," Dr Phipps said.
Water ice cadre records also provide invaluable data on changes in temperature and greenhouse gases over the terminal 800,000 years.
Simply going back further into the by, evidence for ice ages in the last tens of millions of years is predominantly seen in ocean sediments.
"If you get out into the open ocean y'all can drill a cadre down through the sediments into the ocean bed and that can take you back tens of millions of years," Dr Phipps said.
And for the deep time water ice ages that occurred tens to hundreds of millions of years ago, scientists use the geological tape where the story of sea level and climate can be unravelled past analysing rocks of various ages.
Source: https://www.abc.net.au/news/science/2016-06-15/what-is-an-ice-age-explainer/7185002
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