Almost 150 heads of state, including David Cameron, Barack Obama and Indian Prime Minister Narendra Modi, are heading to Paris for the start of the most important environmental meeting for decades.

Ahead of the summit, more than 175 countries have tabled pledges (known as intended nationally determined contributions, or INDCs) to cut their carbon emissions which, if enacted, would be enough to limit global warming to 2.7C. But the United Nations has pledged to limit climate change to 2C – and would much prefer it to be 1.5C. MORE