Questions have been raised about the slowdown in temperature rises in the past 15 years, with climate "sceptics" claiming it undermines the theory of climate change.
The Intergovernmental Panel on Climate Change's (IPCC) report acknowledges that there has been a reduction in the rate of warming between 1998 and 2012, and suggests it is the result of natural variation and the impacts of volcanoes and changes in the strength of the sun.
Over the long term, from 1951, climate models have matched what has happened to global temperatures, the report said.
Presenting the most vivid evidence to date, the UN's IPCC report has warned that humans are responsible for changes to the earth's climate.
The UN IPPC report into climate change, due out tomorrow, will say scientists agree the world is getting warmer, and humans are to blame.