In December 2015, the world agreed to the Paris Accord; to slash greenhouse gas emissions to hold global average temperature increase to 1.5 degrees C (over what it was before the Industrial Revolution), and, if we miss that target, to as far below 2 degrees as possible.
The International Energy Agency (IEA) is not an environmental agency. It advises governments about demand and supply of energy. Since 2012, IEA has warned that to avoid going over 2 degrees C, two-thirds of all known reserves of fossil fuels must stay in the ground until 2050.