At a Glance

If the tipping point is reached, not even the total elimination of greenhouse gases will prevent the earth from continuing to warm."Hothouse Earth: could be our new reality if global average temperatures rise to 2 degrees Celsius above pre-Industrial levels.

Earth is at risk of reaching aglobal warming tipping point that could transform the planet into a lasting and dangerous "hothouse," at which point nothing will prevent continued warming, a new study says.

According to research published Monday in the Proceedings of the National Academy of Sciences (PNAS), a to 2 degrees Celsius above pre-Industrial levels "may trigger other earth system processes, often called feedbacks, that can trigger further warming — even if we stop emitting greenhouse gases."

The researchersnote that even if the Paris Accord target of reducing emissions to keep temperatures below the 1.5-degree Celsius to 2-degree Celsius mark is met,that may not prevent "a cascade of feedbacks that could push the earth system irreversibly onto a 'hothouse earth' pathway."

"The current efforts by nations, which are not sufficient to meet the set in the Paris Agreement a few years ago, are unlikely to help us avoid this very risky situation," said lead researcher Will Steffen ofthe Australian National University in a press release.

If the climate hothouse threshold is breached, average globaltemperatures could climb to 5 degrees Celsius above pre-Industrial temps, while sea levels could rise to between 32 and 196 feet. At that point, many places on Earth would become uninhabitable, Steffen said.

The earth in the riverbed of the Rhine, which has dried up and torn open due to a lingering drought. This could be the norm on Earth if a tipping point of global warming is reached, scientists warn.

(Christophe Gateau/picture alliance via Getty Images)

The hothouse pathway “would almost certainly flood deltaic environments, increase the risk of damage from coastal storms, and eliminate coral reefs (and all of the benefits that they provide for societies) by the end of this century or earlier,” the study says.

Already Earth's global average temperature has risen 1 degree Celsius above pre-Industrial levels and is rising about0.17 degrees Celsius each decade, the study notes. That leaves just 1 degree Celsius of warming left before the tipping point is crossed.

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Steffen and his team identified 10 naturally occurring "feedbacks" or tipping elements that can lead to abrupt changeif a critical threshold is breached: permafrost thaw, the loss of methane hydrates from the ocean floor, the weakening of land and ocean carbon sinks and increasing bacterial respiration in the oceans.

Others include the dieback of the Amazon rainforest and boreal forest, a reduction of northern hemisphere snow cover, the loss of Arctic summer sea ice, and the reduction of Antarctic sea ice and polar ice sheets.

"The real concern is these tipping elements can act like a row of dominoes. Once one is pushed over, it pushes Earth towards another. It may be very difficult or impossible to stop the whole row of dominoes from tumbling over," Professor Steffen said.

This domino effectcould ultimately trigger the uncontrollable release into the atmosphere of stored carbon from the earth, leading to unstoppable warming.

The researchers urge a"collective human action" towardan accelerated "emission-free world economy"that just might "steer the earth system away from a potential threshold."