In the first of four reports to be published this year, the Intergovernmental Panel on Climate Change (IPCC) said temperatures were probably going to increase by 1.8 - 4C (3.2 - 7.2F) by the end of the century, while it projected that sea levels were most likely to rise by 28 - 43cm.
Global warming is likely to influence the intensity of tropical storms.
"We can be very confident that the net effect of human activity since 1750 has been one of warming," co-lead author Dr Susan Soloman told delegates in Paris.
The report was intended to be the definitive summary of climatic shifts facing the world in the coming years. The agency said that it would use stronger language to assess humanity's influence on climatic change than it had previously done.
In 2001, it said that it was "likely" that human activities lay behind the trends observed at various parts of the planet; "likely" in IPCC terminology means between 66 per cent and 90 per cent probability.
Now, the panel concluded that it was at least 90 per cent certain that human emissions of greenhouse gases rather than natural variations are warming the planet's surface.
Climate change is becoming a crucial subject around the world, as reports warn that the Earth will become warmer as the years go by.
Paris, the City of Light, held a five-minute "lights-out" campaign Thursday to express concern over climate change. Even the Eiffel Tower, with its 20,000 sparkling bulbs usually lighting up the Paris skyline nightly, went dark between 7:55pm and 8pm local time.
Meanwhile, the Commonwealth Scientific and Industrial Research Organisation warned that if residents in Sydney do not cut water consumption by more than 50 per cent over the next 20 years, the city will become unsustainable.
