Global warming is likely to disrupt a natural cycle of ice ages and help delay the onset of the next big freeze until about 100,000 years from now, scientists say.
In the past million years, the world has had about 10 ice ages before swinging back to warmer conditions like the present. In the last freeze, which ended 12,000 years ago, ice sheets blanketed what is now Canada, northern Europe and Siberia.
In a new explanation for the long-lasting plunges in global temperatures, scientists point to a combination of long-term shifts in the Earth’s orbit around the sun, together with carbon dioxide levels in the atmosphere.
They said the planet seemed naturally on track to escape an ice age for the next 50,000 years, which is an unusually long period of warmth, according to a study led by the Potsdam Institute for Climate Impact Research.
But rising manmade greenhouse gas emissions since the Industrial Revolution began in the 18th century could mean the balmy period will last for 100,000 years, they say in the journal Nature.
The findings suggest human influences “will make the initiation of the next ice age impossible over a time period comparable to the duration of previous glacial cycles”.
“Humans have the power to change the climate on geological time scales,” lead author Andrey Ganopolski told Reuters.
He said the lingering impacts of greenhouse gases in a distant future did not in any way affect the urgency of cutting emissions that are blamed for causing downpours, heat waves and rising seas.
“The earlier we stop, the better,” he said.
Almost 200 governments agreed a deal in Paris last month to shift from fossil fuels to combat climate change.
Last week, another group of scientists said humanity had become a force in shaping the planet’s geology and suggested an “Anthropocene epoch” began in the mid-20th century, including factors such as nuclear tests and industrialisation.