The report is the second chapter of the fifth assessment by the Intergovernmental Panel on Climate Change (IPCC), set up in 1988 to provide guidance for political action.
Activists believe that greenhouse gases - particularly carbon dioxide - that trap the heat from sunlight within the atmosphere are making the world warmer.
Deniers say temperature changes are natural and factors including solar activity are responsible and in any climate systems are too complex even for computer models to predict accurately.
Fire and Brimstone
Climate change could drive turbulence and conflict, prompted by migration from newly uninhabitable areas and jockeying for water and food, the latest IPCC report said.
Warming of around two degrees Celsius over pre-industrial times may cost 0.2-2.0 percent of global annual income, said the new report.This, in turn, will have consequences for agriculture. Yields of staples such as wheat, rice and corn will be squeezed, just as demand will soar because of population growth, it predicts.
The report says climate change will also have a ricochet effect on health, through the spread of mosquito- or water-borne diseases and heatwaves.
Vulnerable plant and animal species, especially in fragile coral reefs and Arctic habitats, could be wiped out.
Adding a further grim layer to the warning, the report said the most vulnerable ecosystems faced a potential "tipping point" that could pitch them into unstoppable decline.
No recent warming
The report comes amid an admission from the UK metrological office that the world has not warmed for more than 15 years.
Some deniers have gleefully turned on the data to say that global cooling has started, though there is no strong evidence to support such a claim.
The average temperature is a statistical construct based on multiple data sources.
Several of the earlier dire predictions of the IPCC have turned out to have been exaggerated including claims of disappearing Himalayan glaciers which it had to later retract.
The UK met office which critics have called a 'flag bearer of climate change' had to revise down its decadal forecasts, over the past two years with critics accusing the agency of errors turning out to have a 'warming bias'.
The 15 year 'pause' or 'hiatus' is now being partially explained as ocean absorption of heat.
Other explanations include Chinese coal power generation where some emissions are helping reflect heat back to space as well as changing solar activity.
Climate 'skeptics' claim that the IPCC is not a scientific body but an activist lobby group with a political intention of cutting greenhouse emissions, particularly carbon dioxide.
Some of the participating researchers have been accused of suppressed dissenting science.
Activists claim that climate change is 'settled science' which deniers say is more religious dogma than scientific inquiry.
The most ardent believers in man-made climate change treat 'non-believers' or 'deniers' as heretics, which critics have likened to the way the Christian church used to treat astronomers rather than the spirit of the 'scientific method'.
US Secretary of State John Kerry said the document sounded an alarm that could not be ignored.
"Unless we act dramatically and quickly, science tells us our climate and our way of life are literally in jeopardy," he was quoted as saying by AFP. "Denial of the science is malpractice.
"There are those who say we can't afford to act. But waiting is truly unaffordable. The costs of inaction are catastrophic."