Global warming caused by fossil fuel emissions is blamed by scientists for intensifying storms, raising sea levels and prolonging droughts. Now there’s growing evidence of a positive effect: we may have delayed the next ice age by 100,000 years or more.
The conditions necessary for the onset of a new ice age were narrowly missed at the beginning of the Industrial Revolution in the 1800s, researchers at the Potsdam Institute for Climate Impact Research near Berlin wrote Wednesday in the journal Nature. Since then, rising emissions of heat-trapping CO2 from burning oil, coal and gas have made the spread of the world’s ice sheets even less likely, they said.
“This study further confirms what we’ve suspected for some time, that the carbon dioxide humans have added to the atmosphere will alter the climate of the planet for tens to hundreds of thousands of years, and has canceled the next ice age,” said Andrew Watson, a professor of Earth sciences at the University of Exeter in southwest England who wasn’t involved in the research. "Humans now effectively control the climate of the planet."
The study reveals new findings on the relationship between insolation, a measure of the Sun’s energy reaching the planet, levels of carbon dioxide in the atmosphere, and the spread of ice sheets that characterize an ice age. The researchers in Germany were able to use computer models to replicate the last eight glacial cycles and provide predictions on when the next might occur.
The scientists found that even without further output of heat-trapping gases, the next ice age probably wouldn’t set in for another 50,000 years. That would make the current so-called inter-glacial period “unusually long,” according to the lead author, Andrey Ganopolski.
“However, our study also shows that relatively moderate additional anthropogenic CO2-emissions from burning oil, coal and gas are already sufficient to postpone the next ice age for another 50,000 years,” which would mean the next one probably won’t start for 100,000 years, he said.
“The bottom line is that we are basically skipping a whole glacial cycle, which is unprecedented.”
Levels of CO2 have risen to about 400 parts per million now from 280 parts per million before the Industrial Revolution. The authors of the latest study signaled that if the concentration had been 240 parts per million at the time, the onset of a new ice age may have been triggered, and that farming practices before industrialization may have saved us from crossing that threshold.
“Whether this narrow escape from glacial inception was natural remains debatable,” the researchers wrote. “It has been proposed that pre-industrial land-use at least partly contributed” to the CO2 level registered in the 1800s.
While avoiding an ice age is a positive for humans, scientists have for three decades warned of the dangers of climate change, which may threaten the very existence of some nations as rising temperatures raise sea levels through both thermal expansion and by melting ice sheets. Envoys from 195 nations sealed a new agreement in Paris last month to contain the rise in temperatures since the 1800s to below 2 degrees Celsius (3.6 degrees Fahrenheit) and to work towards a 1.5-degree cap.
The last ice age lasted about 100,000 years, ending about 12,000 years ago. The northern ice sheets stretched as far south as the U.K. and Germany in Europe, as well as covering most of Canada and the northern U.S. An inter-glacial period would typically last between 20,000 and 30,000 years, according to Jonathan Bamber, director of the Bristol Glaciology Center at the University of Bristol.
“It is both remarkable and a little scary to think that, in a short space of time, humans have been able to modify the climate system in such a dramatic and profound way,” Bamber said in an e-mailed statement.