The report, to be released on Friday after the conclusion of the meeting, is the first by the UN's Intergovernmental Panel on Climate Change (IPCC) since 2001 and the fourth since the body was launched in 1988.
The IPCC's reports are highly regarded for their neutrality and caution, and they wield a big influence over government policies, corporate strategies and even individual decision-making.
In 2001, the IPCC declared that carbon pollution from burning oil, gas and coal had helped drive atmospheric levels of CO2 to their highest in 420,000 years.
CO2 is the principal "greenhouse gas," a term that applies to half a dozen gases that linger invisibly in the atmosphere, trapping the Sun's heat instead of letting solar radiation bounce back into space.
Over the previous 50 years, temperatures climbed by around 0.1 C (0.2 F) per decade and most of the warming could be attributed to Man, the 2001 report said.
It predicted that by 2100, the global atmospheric temperature will have risen between 1.4 and 5.8 C (2.52-10.4 F) and sea levels by 0.09 to 0.88 metres (3.5-35 inches), depending on how much greenhouse gas is emitted.
Graphic showing how the earth is gradually becoming warmer. The world's top climate experts were geared for a four-day meeting in Paris where they are set to launch a long-awaited update about the scientific evidence for global warming.
Basing their judgement on a mountain of climate studies that have been published since then, the experts are expected to fine-tune these two range estimates.
The British daily The Independent reported Monday that a draft of the report that it saw forecast temperature increases of between 2.0 and 4.5 C (3.6 and 8.1 F) as highly likely this century, but that gains of 6.0 C (10.8 F) or more cannot be ruled out.
The scientists are also expected to point to fresh evidence that change is already happening and could accelerate.
Recent signs of damage to the climate system have been shrinking glaciers and snow cover in high mountains, a retreat of the North Pole's sea ice in summer and acidification of the seas caused by absorption of atmospheric CO2.
"Anthropogenic (man-made) warming of the climate system is widespread and can be detected in temperature observations taken at the surface, in the free atmosphere and in the oceans," said the draft of the report seen by The Independent.
The report is agreed by consensus among the some 500 scientists and government representatives in the IPCC's Working Group 1.
Two other volumes will be issued in April in what will be the fourth assessment report on climate change by the IPCC since it was established in 1988. The two others will focus on the impacts of climate change and on the social-economic costs of reducing greenhouse gases.Güncelleme Tarihi: 20 Eylül 2018, 18:16