One of the scientists leading the first section of the IPCC study said climate change "is the greatest challenge of our time."
Thomas Stocker said: "Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system.
"Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.
"Heatwaves are very likely to occur more frequently and last longer. As the Earth warms, we expect to see currently wet regions receiving more rainfall, and dry regions receiving less, although there will be exceptions."
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.