We all know the Earth is heating up. We even used to call this phenomenon, now known as climate change, ‘global warming’.
Yet 720,000,000 years ago, the blue marble was a cosmic-sized snowball as it was engulfed in an ice age.
Glaciations – the formation of sprawling glaciers and ice sheets – can cause mass extinctions.
Now a study published in Science suggests humans may have halted the planet’s next major cold spell by burning fossil fuels.
But while that might sound like a positive, experts tell that it’s really not a good thing.
Humans ‘overpowered’ the Earth, expert says
An ice age is a drawn-out period when ice has crawled further south than normal.
During the last one, conditions became so cold that ice entombed land from the poles to the tropics, forcing life into the ocean. This preceded an era when mammoths and sabre-tooth tigers roamed the planet – meaning one of your favourite kids’ films isn’t wholly accurate.
What the study is talking about is ‘glaciation’, its author, Nicolás Young, tells .
‘Over the last 2,600,000 years, Earth has cycled in and out of glaciations,’ the geochemist at Columbia’s Lamont-Doherty Earth Observatory says.
‘The issue is that people, including scientists – and I’m also guilty of this – use “glaciation” and “ice age” interchangeably, even though we shouldn’t.’
Put simply, the Earth should be in an ‘interglacial period’, the balmy part that precedes a glacial period, and ultimately an ice age.
But how do we know this?
Young had a hunch that the Barnes Ice Cap, a bowling pin-shaped glacier in the Arctic wilds of Baffin Island, Canada, was growing larger recently.
If proved, it would suggest the planet was cooling.
Right now, the cap is 2,300 square miles, about four times the size of London.
That may sound huge, but around 20,000 years ago, it was a two-mile-thick ice sheet stretching the Arctic Circle as far south as Illinois.
A lot has changed in that time, so to test if it has re-grown, scientists picked frozen moss near the outskirts of the ice cap and estimated when it had been alive.
They also examined rocks to see how long they had been ice-free using atomic dating, checking for radiation crumbs called isotopes.
The ice, they discovered, reached its minimum size about 3,000 years ago before beginning to regrow 1,000 years later.
Humans have stood in the way of this regrowth, however. During the Industrial Revolution, we began burning fossil fuels to power factories, smelters and steam engines.
This belched greenhouse gases into the air, which kept the planet’s heat trapped before it escaped into space.
By 1960, the ice sheet began to shrink, as human-caused climate change drove up global summer temperatures.
Now the cap is melting by as much as one metre every year.
‘In the last few centuries, greenhouse gases and associated temperature rises have overpowered and reversed what should still be long-term cooling,’ says Young.
He adds that if climate change didn’t mess up the planet’s thermostat, it wouldn’t mean we’d be living in an ice age right now as glaciation happens at – pardon the pun – a glacial pace.
Global cooling would have slowly chilled the UK over a period of about 50,000 years before blanketing it in ice sheets.
‘These changes are so small initially that life would have been normal,’ says Young.
‘Possibly in a few hundred to a thousand years down the line, the UK might have started to experience some “noticeable” cooling.’
Is this… a good thing?
In short, no. ‘Climate change “saving us” should not be the take-home message here,’ says Young.
‘The cyclic expansion and contraction of ice sheets has been one of the most reliable patterns in the climate system over the last roughly 2.6million years – and we have suddenly stopped that.
‘This should give us pause.’
Professor Mary Gagen, a climate expert from Swansea University not involved in the study, says Young’s findings are ‘exciting’.
‘It’s neither a good or a bad thing in terms of the big picture understanding of how the climate system works,’ she says.
‘These changes cause small shifts in the amount of energy received on the surface of the Earth,’ Professor Gagen says, adding: ‘Essentially, the authors give a new view on that prediction, which is interesting; it’s a big, exciting conclusion, from evidence from one small ice cap.’
How much planet-warming gases are in the air is another factor, Dr John Hiemstra, a glaciologist also from Swansea University, says.
Carbon dioxide can certainly muddle Earth’s orbital forcing, meaning the planet ‘will not enter a glacial phase simply because heat is retained in the atmosphere due to high levels of greenhouse gases’.
This is what’s happening now, Dr Hiemstra says, so he’s keen to see further research.
‘This is how science advances,’ he adds. ‘A little step at a time.’
Get in touch with our news team by emailing us at webnews@metro.co.uk.
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