Some parts of earth are at risk of becoming uninhabitable, with global average temperatures up to five degrees Celsius higher than pre-industrial levels, a new study warns.
The international research released on Tuesday says human-induced global warming of 2C could trigger environmental processes, or "feedbacks", leading to an irreversible "hothouse" climate.
A "hothouse" climate would also see ocean levels rise between 10 and 60 metres in the long-term.
Current global climate efforts were unlikely to help avoid the "very risky" situation and warming could still occur if greenhouse gases were no longer emitted, lead researcher Will Steffen from the Australian National University said in a statement.
"Many parts of the planet could become uninhabitable for humans," Professor Steffen said.
Nations needed to work together to greatly accelerate the transition towards an emission-free world economy, he added.
Scientists from Australia, the US and Europe studied the effect of 10 feedback processes, such as Amazon rainforest dieback, reduction of northern hemisphere snow cover and a reduction of Antarctic sea ice.
The elements could act like a row of dominoes, with one pushing into another, study co-author and executive director of the Stockholm Resilience Centre Johan Rockstrom says.
"It may be very difficult or impossible to stop the whole row of dominoes from tumbling over," he said.
The result would be an "uncontrollable release" of carbon, which was previously stored in the earth, into the atmosphere.
The scientists say global average temperatures are currently just over 1C above pre-industrial levels and rising at 0.17C per decade.
The research, published in the Proceedings of the National Academy of Sciences, warns that even if the carbon emission reductions called for in the Paris Agreement are met, there is a risk of the earth entering "hothouse climate" conditions.
The paper urges not only a reduction of carbon dioxide and other greenhouse gas emissions, but also new biological carbon stores through forest, agricultural and soil management.