COP21: Why do two degrees matter?

Global average temperatures in 2015 are likely to be the warmest on record, according to the World Meteorological Organisation (WMO).

A combination of a strong El Nino and human-induced global warming made the five-year period from 2011 to 2015 the warmest on record, researchers say.

The new findings are likely to feature prominently at the UN Climate Change Convention in Paris, when global political leaders and negotiators will aim to secure a new global deal that would limit emissions of carbon dioxide.

Climate negotiators agreed in Cancun in 2010 to commit their governments to "hold the increase in global average temperatures below 2C above pre-industrial levels".

BBC environment correspondent Matt McGrath assesses the significance of that figure, and why it is seen as the gateway to dangerous warming - all in less than the time it takes to make a coffee.

Produced by Marcus Thompson and Jean-Li Lee