An international report says rapid, far reaching and unprecedented changes are needed in all aspects of society to limit global warming.
The Intergovernmental Panel on Climate Change (IPCC) said limiting warming to 1.5 degrees compared to 2 degreesis necessary to ensure a more sustainable and equitable society.
The report provides key scientific evidence ahead of the December climate change conference in Poland, when governments review the Paris Agreement to tackle climate change.
It said every extra bit of warming matters, especially since warming of 1.5 degrees or higher increases the risks of long-lasting or irreversible changes, such as the loss of some ecosystems.
The lower limit would reduce sea level rise by 10 centimetres by the end of the century, the Arctic Ocean would be free of sea ice in summer just once a century instead of once a decade, and coral reefs would decline by around 70 percent rather than be completely lost.
It says "rapid and far-reaching" transitions are required and CO2 emissions will need to fall by 45 percent from 2010 levels by 2030.
"The report is clear that avoiding a warmer future above 1.5 degrees will bring significant benefits for millions of people who will face significantly reduced risks of flooding, food insecurity and climate stress, including Pacific communities," said Associate Professor Bronwyn Hayward from Canterbury University, one of the report's authors.
The world is already seeing the consequences of 1 degrees of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice, the report said.
The IPCC noted good news in that some of the kinds of actions needed to limit global warming to 1.5ºC were already underway, but they did need to accelerate, with current decisions vital to ensuring a safe and sustainable world.