Representatives from nearly 200 countries are gathering in Poland for talks on climate change - aimed at breathing new life into the Paris Agreement.
The UN has warned the 2015 Paris accord's goal of limiting global warming to "well below 2C above pre-industrial levels" is in danger because major economies, including the US and the EU, are falling short of their pledges.
But scientists at the Intergovernmental Panel on Climate Change (IPCC) - the leading international body on global warming - last month argued the 2C Paris pledge didn't go far enough. The global average temperature rise actually needed to be kept below 1.5C, they said.
So how warm has the world got and what can we do about it?