UN Climate Chief said this reality is telling us that we need to do much more.

The threat posed to humanity by our warming planet has "never been worse", the United Nations' climate chief said Sunday at the opening of crucial talks in Poland.

"This year is likely to be one of the four hottest years on record. Climate change impacts have never been worse," Patricia Espinosa said as nations gathered to discuss their plan to avert environmental catastrophe.

"This reality is telling us that we need to do much more."