In a "Hothouse Earth" scenario, the planet will have a global average temperature 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) higher than the pre-industrial temperatures.  The sea level will also be 10 to 60 meters (32 to 197 feet) higher than it is today. 

"Our study suggests that human-induced global warming of 2 degrees Celsius may trigger other Earth system processes, often called 'feedbacks' that can drive further warming — even if we stop emitting greenhouse gases," lead author Will Steffen explains in a release from Stockholm Resilience Centre. 

A Domino Effect into a Scorching State

The study, published in the journal Proceedings of the National Academy of Sciences, noted 10 natural feedback processes, including permafrost thaw, loss of methane hydrates from the ocean floor, weakening land and ocean carbon sinks, increasing bacterial respiration in the oceans, Amazon rainforest dieback, boreal forest dieback, reduction of northern hemisphere snow cover, loss of Arctic summer sea ice, and reduction of Antarctic sea ice and polar ice sheets. 

A number of these are considered tipping elements with critical thresholds that, when crossed, could transform them "from friend to foe."  This means that feedbacks that currently store carbon could suddenly be uncontrollably releasing it and creating an even warmer world in the process. 

Even more alarming, co-author Johan Rockström describes the elements as potentially like a row of dominoes with the fall of a single one spurring on the fall of the next.  He adds that it may be difficult or even impossible to prevent the entire row of dominoes from tumbling. 

"Places on Earth will become uninhabitable if 'Hothouse Earth' becomes the reality," Rockström, the incoming co-director of the Potsdam Institute for Climate Impact Research, says. 

Can We Still Avoid A Hothouse Earth? 

Since there are several feedback processes that contribute toward the planet's descent into a state of "Hothouse Earth," just focusing on cutting greenhouse gas emissions isn't enough to keep the dangers at bay. 

According to the authors, creating new or enhancing existing biological carbon stores is essential as well.  A handful of ways to achieve this include improved management of forests, biodiversity conservation, and new technology. 

In the end, keeping a stabilized planet needs fundamental changes in the society, the study says.  As Steffen puts it, making sure that the world avoids a "Hothouse Earth" should include redirecting human actions from exploitation of the planet to stewardship of it.