Their report, which must be unanimously approved, is to be released on February 2 and is considered an authoritative document that could influence government and industrial policy world-wide. Four participants told AP that the group approved the term "very likely" in February 2 sessions. That means they agree that there is a 90 percent chance that global warming is caused by humans.
"That is a big move. I hope it is a powerful statement," said Jan Pretel, head of the department of climate change at the Czech Hydrome-teorological Institute.
The last report, in 2001, said global warming was "likely" caused by human activity (66 percent chance). There had been speculation that the participants might try to change the wording this time to "virtually certain," which means a 99 percent chance.
But the Chinese delegation was resistant to strong wording on global warming, said Barbados delegate Leonard Fields and Zimbabwe delegate Washington Zhakata. China has increasingly turned to fossil fuels, which emit the greenhouse gases blamed for boosting the planet's temperature, to feed its huge and growing energy needs.
The US government delegation was not one of the more vocal groups in the debate over the "very likely" statement for manmade warming, said other countries' officials. Several delegates credited the head of the panel session, Susan Solomon, a top US government climate scientist, with pushing through the agreement in just 90 minutes.
US President George W Bush acknowledged for the first time last month that global warming is occurring, but he remains opposed to mandatory regulations to cap greenhouse gas emissions that many nations favour.
The report will also say that global warming has led to stronger hurricanes, including those on the Atlantic Ocean such as 2005's Katrina, said Fields and other delegates.
The delegates, staring at a countdown clock showing how little time they have left before the February 2 deadline, went into talks on February 1 well behind schedule and planned a late-night session.
A draft of the report predicts a temperature increase of between 1.5-5.8 C (2.5-10.4 F) by the year 2100, though that could be adjusted.
Another contentious issue is predictions of sea level rise. Scientists are trying to incorporate concerns that their early drafts underestimate how much the sea level will rise by 2100 because they cannot predict how much ice will melt from Greenland and Antarctica. In early drafts, scientists predicted a sea level rise of no more than 58 centimetres (23 inches) by 2100, but that does not include the ice sheet melts.
As the delegates held their evening session, the Eiffel Tower, other Paris monuments and concerned citizens in several European countries switched off their lights for five minutes to call attention to energy conservation, heeding a call by French environmental campaigners.
Some experts said that while well-intentioned, the lights-out could actually consume more energy than it would conserve by requiring a power spike when the lights turn back on - possibly causing brownouts or even blackouts.