It is one of the largest gathering of world leaders to ever come together in one place.
And many are saying this is the moment the world decided to save our planet.
ITV News International Affairs Editor Rageh Omaar reports:
Barack Obama's greatest struggle on climate change could be convincing the conspiracy theorists at home that it's not a hoax.
People across the globe have posed their questions for President Obama as he takes part in the UN Climate Conference in Paris.
The Prince of Wales said world companies 'pay no attention' to the damage their supply chains cause to forests.