At least five dangerous climate 'tipping points' – thresholds that can lead to large and irreversible changes – are approaching, scientists have warned.
Tipping points that may be triggered at today's temperatures include the collapse of the Greenland and West Antarctic ice sheets, widespread abrupt permafrost thaw, collapse of convection in the Labrador Sea, and massive die-off of tropical coral reefs.
Even at current levels of global warming, the world already risks passing five dangerous climate tipping points, and will pass more with each additional degree of warming.
The study's lead author David Armstrong McKay, of the University of Exeter, said: "We can see signs of destabilisation already in parts of the West Antarctic and Greenland ice sheets, in permafrost regions, the Amazon rainforest, and potentially the Atlantic overturning circulation as well.
"The world is already at risk of some tipping points. As global temperatures rise further, more tipping points become possible.
"The chance of crossing tipping points can be reduced by rapidly cutting greenhouse gas emissions, starting immediately."
Multiple climate tipping points could be triggered if global temperature rises beyond 1.5C above pre-industrial levels, according to the report in Science.
The research is based on a review of over 200 papers published since 2008, and comes alongside a conference – Tipping Points: From Climate Crisis to Positive Transformation – at the University of Exeter this week.
It shows that human emissions have already pushed Earth into the tipping points danger zone.
The new analysis indicates that Earth may have already left a 'safe' climate state when temperatures exceeded approximately 1C warming.
The researchers concluded that even the United Nations' Paris Agreement goal to limit warming to well-below 2C, and preferably 1.5C, is not enough to fully avoid dangerous climate change.
According to the assessment, tipping point likelihood increases markedly in the 'Paris range' of 1.5C to 2C warming, with even higher risks beyond °C.
To have a 50% chance of achieving 1.5C and thus limiting tipping point risks, global greenhouse gas emissions must be cut by half by 2030, reaching net-zero by 2050.
Co-author Johan Rockstrom, co-chair of the Earth Commission and director of the Potsdam Institute for Climate Impact Research, said: "The world is heading towards 2C to 3C of global warming.
"This sets Earth on course to cross multiple dangerous tipping points that will be disastrous for people across the world.
"To maintain liveable conditions on Earth, protect people from rising extremes, and enable stable societies, we must do everything possible to prevent crossing tipping points. Every tenth of a degree counts."
Watch: Earth barrelling towards 'uncharted territory', report warns