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. Hassol 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:
No matter what we do, global temperatures, even if we begin to get their rise to level off 50 years from now, won't begin to actually decline before at least two centuries from now.
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.
Moreover, that no matter what we do, say the scientists, we are in for a rise of at least about two degrees Fahrenheit within the next 50 years -- over and above the 1.5-degree increase the world has experienced in the past 150 years.
And no matter what we do, they say, the new heat will mean sea level keeps rising for at least 1000 years -- though our actions should have an enormous influence on how much they rise.
"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.