Scientists gathered from around the world will deliver the verdict on Friday morning in Paris on what the damage is -- how we've already permanently altered the planet.
The news will be heavy -- hard to take.
The exact wording of the report won't be final until the 9:30 a.m. press conference, but the basic science is in.
The world's scientists have produced these consensus reports every five years since 1991, but the biggest change since the last report in 2001 is clearly not in the science.
It's in the audience. This time around, far more people are ready to listen.
This sea change comes after two years of TV and cinema documentaries and specials, unseasonable weird weather extremes, heat spikes and downpours, backyard bugs, birds and flowers out of synch, disappearing mountain glaciers and ski seasons, as well as a rapidly growing chorus of alarmed politicians.
Already, the planet's news organizations are swarming around the scientists and government representatives huddling in Paris over the final wording.
Daily, the World Wide Web brings in hard news.
The latest includes the estimate by Indonesian scientists that 2,000 of the 18,000 gorgeous islands that comprise their country will, by the year 2030, be lost beneath the waves forever (or at least for a thousand years) because of rising sea level caused by global warming.
That's only 23 years from now. 2000 islands just gone.
Global warming's refugees have already begun to move from some Pacific islands. Some scientists predict such refugees will number in the unthinkable hundreds of millions well before the end of the century.
So, with reality setting in, many more eyes now turn with new appreciation to the hard-won consensus of the Intergovernmental Panel on Climate Change.
It involves the work of more than 2,000 scientists from more than 100 countries and is necessarily conservative due to the slow, inclusive and painstaking nature of the approval process.
"The IPCC is completely unprecedented in world history," preeminent climate scientist Richard Somerville told ABC News.
Somerville, now buried in the closed-door Paris meeting, is also currently moonlighting as historian to write a history of the IPCC.
"There's probably never been anything remotely like it among scientists -- for its global scale and long term assessment of a single problem," he says.
Somerville has worked for decades at California's Scripps Institution of Oceanography alongside other early harbingers of the global warming crisis, which virtually all scientists agree has been caused largely by emissions from the burning of fossil carbon in the form of coal, oil and gas.
The IPCC, whose gestation and founding in the 1980's Somerville witnessed from the inside, is now being recognized by more and more people around the world as the most authoritative single source of information about global warming.
With reality now setting in, more journalists are demanding explanations and predictions from scientists -- especially this week in Paris -- and a small but growing number of scientists are trying to become more articulate for them.
They are trying to avoid the "geek-talk," or scientific jargon, that makes most readers' eyes glaze over.
It's been a bone of contention.
Are the professional journalists to blame for confusion about the solidity of global warming science, or do scientists themselves share some of the blame?
"Scientists can be really infuriating, sometimes," says Susan Joy Hassol, a premier science analyst sought by many leading climate scientists, including IPCC officials.
For more than 20 years she has been helping scientists write professional studies as well as reports aimed at a broader public. Hasol has lately been giving talks about the problem for scientists in a number of cities.
"It's a constant struggle to help scientists get beyond the jargon, but it's never been more important for scientists to be clear for the public," says Hassol.
Just how important may become painfully clear as the public begins to absorb the news that will be released on Friday.
Whatever the exact final wording, some of the heaviest facts will be confirmations of news already featured in the IPCC's 2001 report.
The intervening five years have brought great improvements in the amount and quality of data and in the power of computers to discern its implications.
So another big change in climate news will be that, this time around, many more people feel the reality of the findings that were also in IPCC '01 -- such as this:
That's even if we immediately start drastic cuts in carbon and other greenhouse emissions, and permanently replace them with new sources of clean energy.
"The IPCC already reported that in 2001, though the evidence is even more powerful now," Hassol points out.
"This time," she says, "more people will probably be able to listen to it."
The challenge for the public, she and most climate scientists are saying, is to realize that the temperature rise won't even begin to level off in 50 years -- after that two-degree rise -- but accelerate, unless emissions are drastically cut now, well within the next 10 years.
The science delivered Friday morning in Paris is intended by the IPCC to be the bedrock for hopeful action.
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