Scientists: IPCC Report Should Serve as 'Wake-Up Call' The UN report states climate change "extremely likely" to be caused by humans.

Sept. 28, 2013 -- The new U.N. Intergovernmental Panel on Climate Change report should serve as a "wake-up call" to governments and society about the role of humans in global warming, scientists say.

"It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century," the IPCC's Fifth Assessment Report, which was published Friday, found.

"This report confirms with even more certainty than in the past -- that it is extremely likely that the changes in our climate system for the past half a century are due to human influence," Michel Jarraud, Secretary General of the World Meteorological Organization, which co-sponsored the IPCC, said in a statement.

"It should serve as yet another wake-up call that our activities today will have a profound impact on society not only for us but for many generations to come," he said.

Climate Panel Forecast: Higher Seas, Temperatures

More than 800 authors across more than 39 countries contributed to the working group's 2,500-page assessment, which draws on millions of observations and numerical data from climate model simulations.

The report, which contains the strongest wording yet on the existence of climate change and the role that humans play in contributing to it, states: "Warming in the climate system is unequivocal."

It also documents that the last three decades have successively been warmer at the Earth's surface than any preceding decades since 1850.

Scientists have predicted continued shrinking ice caps, rising sea levels, longer and more frequent heat waves, and wet regions receiving more rainfall and dry ones receiving less, as a result of these changes.

"Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system," said Thomas Stocker, Co-Chair of the IPCC Working Group I which released the report. "Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions."

Warming Plateau? Climatologists Face Inconvenient Truth

"As the ocean warms, and glaciers and ice sheets reduce, global mean sea level will continue to rise, but at a faster rate than we have experienced over the past 40 years," said Working Group I's other Co-Chair Qin Dahe.

The report's summary for policy makers also contained strong wording.

"It is virtually certain that globally the troposphere has warmed since the mid-20th century" and it is "extremely likely" that more than half of observed increase in global average surface temperatures from 1951 to 2010 was caused by human produced greenhouse gas activity, the report summary said.

The report had been met with some criticism, notably by skeptics and climate change deniers in the lead-up to its release.

The IPCC fourth report, released in 2007, also came under fire from critics when it was released for including incorrect statements on Himalayan glaciers and natural disasters.

Next year, two other working groups that release reports on climate change for the IPCC will reveal their findings on the impacts global warming has on adaptability and vulnerability, and a policy report on mitigation.