Climate change is poised to become the "biggest disaster in human history", claims leading environmental agency WWF UK, and could wipe out huge swathes of the planet's biodiversity, while bringing misery to millions of people.

As the Intergovernmental Panel on Climate Change prepares to release its latest report this Friday, WWF called for world governments to control CO2 emissions "before climate change devastates the planet".

WWF UK said the IPCC report is likely "to paint a frightening picture of a planet on the brink of humanitarian and environmental disaster".

Keith Allott, head of WWF UK's Climate Change Programme, said: "There is no time left for procrastination. Climate change is right here, right now and it is killing people and wiping out the very biodiversity that sustains us all.

"The science tells us that the effects of climate change are already being felt at both regional and global level and it's going to get a lot worse. This is a global emergency and we need an urgent global response."

The IPCC report is expected to confirm that the world's poorest and most vulnerable people, who have done so little to contribute to the causes of climate change, will be hit hardest by its effects.

Many of the world's poor live in the most vulnerable areas and will be hit by increasingly severe droughts, floods, hurricanes and disease, while having less capacity and resources to cope with the impacts, WWF UK said. Many communities also depend on ecosystems including forests and fisheries which will also be severely hit, it warned.

"Biodiversity is already under severe threat from many human activities but climate change will add greatly to existing stresses," said the environmental agency.

WWF has already noted the impact of climate change in many of its field projects, ranging from the arctic to the arid landscapes of Northern Africa, and said climate change was already affecting almost all species, including whales and polar.

In the oceans, coral reefs are under severe threat as temperatures rise, which WWF said will have a direct impact on the approximately half a billion people who rely primarily on fish from coral reefs and the one billion people who rely primarily on fish for food, especially in developing nations.

Sea level are rising, polar ice sheets are melting and fresh water sources are becoming increasing increasingly scarce in some areas as a result of climate change, fuelling conflict and the migration of environmental refugees.

Mr Allott added: "One reason that the climate crisis is not being tackled with the urgency it demands is that to most people's eyes it seems to be happening in slow motion.

"The IPCC report will make clear that huge impacts are already being felt and will leave no excuses for governments to duck their responsibilities to begin negotiations this year on emission reduction targets under the next phase of the Kyoto Protocol."