How would Earth cope if it had to deal with an extra 5 trillion tonnes of carbon emissions? Very, very badly, scientists say.
The study is by Canadian scientists and was published today in Nature Climate Change.
It models a 'worst case scenario' where:
Five trillion tonnes is five times what's currently in the atmosphere, and the results look pretty grim.
The world would be looking at an increase of around 8degC globally, and 17degC in the Arctic, by 2300.
The extreme temperature rise in the Arctic is due to "polar amplification", NIWA climate scientist Dr Sam Dean explains.
When the white snow and ice melts due to warmer temperatures, it reveals the darker ocean and land. That in turns heats more, which also increases the air temperature.
"The Antarctic would ultimately suffer the same fate, but this happens more slowly because of the significant time it will take to melt the large ice sheets covering the Antarctic continent," Dr Dean says.
The carbon increase would have an effect on rain too. It's thought rainfall in Australia and the Amazon could halve, while the tropical Pacific could be facing four times as much rainfall as usual.
Dr Dean warns the temperatures in the model aren't even the highest point the planet could reach.
"It should be noted that warming would continue to increase long after 2300, as the planet continued to adjust to such high levels of CO2."
Victoria University's Professor James Renwick says it's a "stark warning" for the future.
"The amount of warming and climate change shown by these results would throw global society into chaos and would likely result in billions of deaths, from hunger and conflict over resources."