Evidence of human causes for global warming:"Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (human) greenhouse gas concentrations," the report says.
"Very likely" means at least a 90 per cent probability.
"The 2001 report said it was 'likely' that human activities were the dominant cause of warming in the last 50 years, or at least a 66 per cent probability.
"The level of confidence that humans are causing global warming has increased a lot," says the lead author of the report, Peter Stott.
"We have more models, better corroboration, a longer observation period and better methodologies... If you look at the way temperatures have evolved on individual continents you see very clearly that the models only predict this correctly if you include human greenhouse gases."
Temperature rises
The range of possible temperature increases this century has increased to 1.1° to 6.4° in this report from 1.8° to 5.4° in the IPCC's previous report in 2001.
The projected temperature increase to 2100 has risen largely because it is now considered that global warming will make nature less able to absorb carbon dioxide.
This alone could raise estimates by more than 1° this century - for the first time the IPCC gives "best estimates", giving greater certainty than predictions in earlier reports.
The best estimates range is for a 1.8° to 4.0° temperature rise by 2100 - only one of the six scenarios analysed generated a best estimate of less than 2.0° warming this century (1.8°). The EU target is for no more than 2.0 degrees average warming above pre-industrial levels. Temperatures have already risen 0.7° in the past century.
Previous temperature ranges amounted to "an expert judgment", says Scott. "Now they are based on a much more solid footing."
"For the first time we have a best estimate of what we can achieve if we keep emissions levels lower," says the report chairwoman, Susan Solomon. "I want politicians to do their job and I'll do my job."
The report does not include the possible warming impact of methane, a potent greenhouse gas, escaping from melting permafrost: "We don't have enough evidence to tell its importance on the global scale," said Ms Solomon.
It says it is "very likely" that extremes such as heatwaves and heavy rains will become more frequent. Warming is expected to be greatest over land and at high northern latitudes, and least over the Southern Ocean and North Atlantic.
Sea level rises
The report cites six models with core projections of sea level rises ranging from 18cm to 59cm this century. That is a narrower and lower band than the 9cm to 88 cm gain forecast in 2001.
If the Greenland ice sheet melts in the future proportionally to the temperature rises, then sea levels would rise by up to 79cm, not 59cm, this century.
Some models show an ice-free Arctic in summer by 2100 (meaning that sea ice floating in the water disappears, but not ice resting on Greenland). If the Greenland ice sheet melted completely that would lead to a 7m sea level rise.
"A 7m rise is not something imminent but would happen if you sustain a temperature increase over three degrees for millennia," says Jurgen Willebrand, the report's author with special expertise in ocean effects.
Changing ocean currents
The report predicts a gradual slow-down this century in ocean currents such as the one which carries warm water to north-west Europe.
"It's very unlikely there will be an abrupt breakdown in ocean currents in the 21st century," said Willebrand. "Most models predict a gradual slowdown this century but you shouldn't expect a fall in temperatures (in Europe), because global warming is happening."
Hurricanes
The report says it is "more likely than not" that a trend of increasing intense tropical cyclones and hurricanes has a human cause. It expects such tropical cyclones to become more intense in the future. "There may not be an increase in number, there may be a re-distribution to more intense events - which is what has been observed in the Atlantic since 1970," says Stott.
The full report may be read on the Irish Times website, ireland.com, and on the website of the intergovernmental panel, www.ipcc.ch/ and click on Download Summary for Policymakers