Burning fossil fuels may have prevented the planet's next major ice age, but experts say this is not a positive development. A study published in Science suggests that human activity has 'overpowered' the Earth's natural cooling cycle.
Study reveals halted glaciation
The study focuses on 'glaciation', the formation of sprawling glaciers and ice sheets, which can cause mass extinctions. The author, Nicolás Young, a geochemist at Columbia's Lamont-Doherty Earth Observatory, told Metro: 'Over the last 2,600,000 years, Earth has cycled in and out of glaciations.'
Young explained that the Earth should currently be in an 'interglacial period', the balmy part that precedes a glacial period and ultimately an ice age. To test this, scientists examined the Barnes Ice Cap, a bowling pin-shaped glacier in the Arctic wilds of Baffin Island, Canada.
Evidence from the Barnes Ice Cap
The ice cap is currently 2,300 square miles, about four times the size of London. Around 20,000 years ago, it was a two-mile-thick ice sheet stretching the Arctic Circle as far south as Illinois.
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 reached its minimum size about 3,000 years ago before beginning to regrow 1,000 years later.
Human impact on the climate
Humans have stood in the way of this regrowth. During the Industrial Revolution, burning fossil fuels belched greenhouse gases into the air, trapping heat 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,' said Young. He added 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 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.
Experts weigh in
Young said: 'Climate change "saving us" should not be the take-home message here. 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, called the findings 'exciting'. She said: 'It's neither a good or a bad thing in terms of the big picture understanding of how the climate system works.' She added that ice ages come and go because of orbital forcing, the way the Earth's distance from the sun changes over time, causing small shifts in the amount of energy received on the surface of the Earth.
Dr John Hiemstra, a glaciologist also from Swansea University, said carbon dioxide can 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'. He said he is keen to see further research, adding: 'This is how science advances. A little step at a time.'
