The IPCC report, due for release on Feb. 2 in Paris, draws on research by 2,500 scientists from more than 130 countries and has taken six years to compile.
"There are a lot of signs and evidence in this report which clearly establish not only the fact that climate change is taking place, but also that it really is human activity that is influencing that change," R.K. Pachauri, the IPCC chairman, told Reuters.
"I hope this report will shock people, governments into taking more serious action as you really can't get a more authentic and a more credible piece of scientific work. So I hope this will be taken for what it's worth."
The IPCC will say it is at least 90 percent sure than human activities, led by the burning of fossil fuels, are to blame for global warming over the past 50 years, sources say.
The new report is likely to foresee a rise in temperatures of 2 to 4.5 Celcius (3.6-8.1 Fahrenheit) this century, with about 3 Celcius (5.4F) most likely.
Pachauri told Reuters in an interview the findings of the report, which is the fourth of its kind, will be "far more serious and much more a matter of concern" than previous reports.
There is more evidence around the world that greenhouse emissions are causing temperature increases, sea level rises, the melting of glaciers, freak weather phenomena and the problems of water availability, said Pachauri.
"For example, the Arctic is clearly melting at faster rates than other regions of the world," he said. "The figures are in the report and it is much faster than what was anticipated."
"The impacts are clearly very serious for some vulnerable parts of the world. Small island states are clearly very vulnerable and parts of South Asia are vulnerable in respect of droughts and floods and also the melting of the glaciers."
Pachauri, also director of India's top environment centre, The Energy and Research Institute, said there was more awareness of climate change around the world today than ever before and applauded Europe and Japan for their efforts.
He said scepticism about the linkages between human activities and climate change was dwindling as more evidence came to light.
"I think the sceptics on climate change will continue, but the good news is that their numbers and their effectiveness is on the decline," Pachauri said.
"The gaps in knowledge will always be there in science but you use your judgement and that's what good policy is all about ... If you take action, the benefit is that you might actually be minimising the harmful impacts of global warming."