World leaders will gather in Paris next week for the UN climate change conference - also known as COP21 - in what is a crucial opportunity to combat global warming.
What's the summit for?
World leaders meeting in the French capital have the challenge of agreeing how to prevent climate change causing catastrophic damage. More than 160 countries have promised carbon emissions cuts sufficient to limit the average temperature rise to 2.7C. The hope is that further steps can be taken in Paris to limit the rise to 2C.
What kind of steps?
There are hopes for a "ratchet mechanism" requiring countries to revisit - and hopefully increase - their emissions pledges every five years. There are also hopes a longer-term emissions goal can be established that goes beyond 2030.
What are the sticking points?
Rich countries have pledged to give poor nations $100bn (£66bn) a year by 2020 to help them reduce emissions and adapt to climate change, but have come up with just half of it.
Developing countries also want "loss and damage" funds.
Which countries could scupper it?
Those which have the most to lose from shifting to green energy - oil and gas-producing nations such as Russia, Saudi Arabia and Venezuela - and the lowest-lying and poorest.