The world's top scientists have issued the direst warnings yet about the threat from climate change.
After six years of research, they predict the average world temperature will rise by about three degrees by the end of the century - with potentially devastating consequences for melting ice caps and rising sea levels.
They also make the strongest causal link so far between human behaviour and global warming.
The evidence in a new report published in Paris has the finest pedigree - the work of the Intergovernmental Panel on Climate Change, which draws together 2,500 scientists from more than 130 countries.
The study highlights the strengthening international scientific conviction that human activity is largely responsible for the rise in the Earth's surface temperature.
The IPCC's previous assessment in 2001 rated the link between the warming planet and the actions of its inhabitants as "likely" - IPCC-speak for a probability rate of 66-90%.
The new report revises that to "very likely" - a greater than 90% chance that mankind is to blame.
That adds credence to those who insist that the recent unseasonal warm spells are more than simply atmospheric blips.
The London-based International Institute for Environment and Development said the IPCC report delivered "the most conclusive evidence yet that human activities are causing dangerous climate change."
Institute director Camilla Toulmin said: "It shows in stark terms that time is running out to cut greenhouse gas emissions and to help vulnerable communities prepare for the impacts ahead, some of which are already unavoidable."
