Global warming could stave off next ice age for 100,000 years

Global warming is likely to disrupta natural cycle of ice ages and contribute to delaying the onsetof the next big freeze until about 100,000 years from now,scientists said on Wednesday.

In the past million years, the world has had about 10 iceages before swinging back to warmer conditions like the present.

In the last ice age that ended 12,000 years ago, ice sheetsblanketed what is now Canada, northern Europe and Siberia.

Humans have the power to change the climate on geologicaltimescales.-AndreyGanopolski, lead author of study

In a new explanation for the long-lasting plunges in globaltemperatures that cause ice ages, scientists pointed to acombination of long-term shifts in the Earth's orbit around thesun, together with levels of carbon dioxide in the atmosphere.

They said the planet seemed naturally on track to escape anice age for the next 50,000 years, an unusually long period ofwarmth, according to the study led by the Potsdam Institute forClimate Impact Research.

But rising man-made greenhouse gas emissions since theIndustrial Revolution began in the 18th century could mean thebalmy period will last for 100,000 years, they wrote in thejournal Nature.

The findings suggest human influences "will make theinitiation of the next ice age impossible over a time periodcomparable to the duration of previous glacial cycles," theywrote.

"Humans have the power to change the climate on geologicaltimescales," lead author Andrey Ganopolski told Reuters.

He said the lingering impacts of greenhouse gases in a fardistant future did not in any way affect the urgency of cuttingemissions now that are blamed for causing downpours, heat wavesand rising seas.

"The earlier we stop, the better," he said. Almost 200governments agreed a deal in Paris last month to shift fromfossil fuels to combat climate change.

Last week, another group of scientists said humanity hadbecome a force in shaping the planet's geology and suggested an"Anthropocene epoch" began in the mid-20th century with factorssuch as nuclear tests and industrialization.

'Deglacial' epoch?

"Like no other force on the planet, ice ages have shaped the global environment," said Hans Joachim Schellnhuber, director ofthe Potsdam Institute and an author of Wednesday's study. Hesuggested a new epoch might instead be called the "Deglacial".

Some past studies have suggested that global warming candelay ice ages, but Thursday's study laid down clear rules.

It said the start of past ice ages coincided with low levelsof solar energy reaching the Earth in northern summers, like incurrent times. But an ice age had not begun because ofrelatively high, apparently natural, levels of carbon dioxide inthe atmosphere since before the Industrial Revolution.

• A new geological epoch, the Anthropocene, has begun, scientists say
• Melting glaciers, rising sea level slow down Earth's rotation