If climate change continues unabated, average temperatures could rise by more than five degrees Celsius from pre-industrial levels.
The physical and human geography of the planet will be profoundly affected: 300 million people could become refugees as their homes succumb to drought or flood. Poorer countries will be among the worst affected.
The world's economic growth will be cut by 20 per cent or more. Each tonne of carbon dioxide that we emit now is causing damage valued at $85 or more.
The cost of action to reduce greenhouse gas emissions to avoid the worst impacts of climate change can be limited to around one per cent of global GDP each year.
A carbon pricing policy is needed so that, through taxation, emissions trading or regulation, people are faced with the full social costs of their actions. The aim should be to build a common global carbon price across countries and sectors.
Reducing emissions will make us better off. The long-term benefits of shifing the world onto a low-carbon path could be in the order of $2.5tr each year.
Barriers to energy efficiency must be removed. People must be educated about what they can do to respond to climate change.
Fostering a shared global understanding of the nature of climate change and its consequences is critical in shaping behaviour, as well as in underpinning both national and international action.