SCIENTISTS are more certain than they have ever been that humans are causing global warming, according to the most comprehensive report ever conducted into climate change, which predicts "with 95 per cent certainty" that people’s greenhouse gas emissions are heating the world.
The degree of certainty leaves little doubt that greenhouse gases such as carbon dioxide and methane are responsible for climate change and compares to a finding of 90 per cent certainty in the previous - fourth - assessment six years ago. This, in turn, was a significant increase on the 66 per cent certainty reached in 2001's third assessment and just over 50 per cent in 1995.
AR5 has 840 main authors recruited from 38 of the IPCC's 195 member countries, with British and American scientists making the biggest contribution.
At more than 3,000 pages, the report is so big that it will be released in three parts over the next 14 months. The first part, released today, covers the physical science of climate change. The second instalment will concentrate on the impacts of climate change and how to adapt to them, while the third will examine ways to curb the warming.
As with the other IPCC reports, AR5 is a synthesis of the findings of thousands of peer-reviewed research papers from the past few years. It comes at a crucial time in global climate change politics since it will be the last IPPC report published before the Paris summit in 2015, when the world's governments have pledged to reach hugely ambitious and legally binding targets to reduce their emissions in a bid to limit global warming to 2C compared to pre-industrial levels.
Today US Secretary of State John Kerry backed the report's findings, and pledged action on cutting emissions.
He said: “Boil down the IPCC report and here’s what you find: Climate change is real, it’s happening now, human beings are the cause of this transformation, and only action by human beings can save the world from its worst impacts.
"This isn’t a run of the mill report to be dumped in a filing cabinet. This isn’t a political document produced by politicians.
And UN Secretary General Ban Ki-Moon said: "This new report will be essential for governments as they work to finalise an ambitious legal agreement on climate change in 2015.
"To add momentum to this process, I will convene a climate summit in September 2014 at the highest level. The heat is on. Now we must act."
The report’s launch follows intense last-minute discussions in Stockholm last night to finalise the wording of the summary for policymakers.
Governments around the world are exercising extreme caution to ensure that the report doesn’t contain a significant error that could be seized upon by climate sceptics to discredit the research. The previous report in 2007 mistakenly claimed that the glaciers of the Himalayas were very likely to disappear by 2035, a point which the IPCC was forced to admit was wrong.
Last night’s discussions were largely concerned with how to present and explain the slowdown – or hiatus – in global warming over the past 15 years. This is a development which climate sceptics have used to further their case, but which the vast majority of scientists believe is only a blip in a clear long-term trend.
Scientists involved in the talks said governments have been particularly careful about the wording of this report to make it as difficult as possible for climate sceptics to capitalise on any errors.
The report has hardened the calls from climate campaigners for action on emissions reduction. In the UK, executive director of Friends of the Earth, Andy Atkins, said: “Scientists are now as convinced that humans are causing climate disruption as they are that smoking causes cancer - politicians can’t continue to stand idly by while the world goes spinning towards climate catastrophe.
“Tough action is urgently needed to end the planet’s dangerous fossil fuel fixation and to develop the huge job-creating potential of renewable power – with developed nations like Britain taking the lead."