The cherry blossoms came earlier than normal this year in Yokohama, Japan. By the time delegates from 70 countries, including UC Irvine’s Michael Prather, met to finalize another stark assessment for the Intergovernmental Panel on Climate Change, rain had whipped many of their delicate pink petals to the ground. Like much of the planet’s plant life, the iconic spring flowers bloom a week sooner, on average, than they did 1,000 years ago – thanks to human impacts.

Prather, an Earth system scientist who’s been a lead author on four of the IPCC’s five Nobel Prize-winning reports since 1995, glimpsed the falling blossoms outside the marathon meetings. Shortly after returning from Japan, he gave a sometimes wry, sometimes devastating primer on the findings and the grueling process of compiling them at a packed School of Physical Sciences event called “Climate Change – The Inside Story,” at which the new Ralph J. Cicerone & Carol M. Cicerone Endowed Chair & Fellowship Fund was unveiled.

“Unfortunately, things are looking bad,” Prather said in his habitual deadpan tone. “Since the IPCC began in 1990, we’ve tracked at the upper end of all of our projections for climate change. That’s still true.”

He and fellow scientists found that human-caused climate change is beginning to affect every continent and all the world’s oceans, from the tropics to the poles. Sea ice is collapsing; drinking water is dwindling; droughts and floods are increasing; coral reefs and marine life are dying out; and agriculture, fishing and other livelihoods are suffering. The evidence points to catastrophic losses by 2100 if drastic cuts are not made to the tons of carbon dioxide and other greenhouse gases being pumped skyward and if people can’t cope with the changes already in the pipeline.

“All of these effects will be five to 10 times stronger in the next 100 years if we don’t take action,” Prather said. “It’s nasty, nasty stuff – poverty, instability and disease. It’s brutal.”

Slivers of hope were offered. A figure he prepared showing different pathways to resiliency or loss was included in the report on the last day, at the insistence of government officials. More nations, communities and even industries are beginning to adapt, building bulwarks against rising seas or developing the new energy and water systems needed in a warming world. But Prather warned that, at best, such measures could help for the next 20 years. After that, if the atmosphere hasn’t been stabilized, all bets are off.

“It’s a funny gamble,” he said in response to an audience member’s question. “If you wait for too long, all your opportunities to change are gone and you wouldn’t survive.”

The report on impacts, adaptation and vulnerability and two others will form the scientific basis for the United Nations Framework Convention on Climate Change in 2015, at which nearly 200 nations must decide whether to sign on to a treaty addressing the challenges.

Noting that climate scientists have been hounded and dismissed as hacks in the editorial pages of The Wall Street Journal and elsewhere for at least two decades, Prather said the reports have swelled over time from a concise summary of the evidence and projected risks into a thick volume that thoroughly reviews the best current knowledge about climate change. For the latest IPCC assessments, hundreds of scientist-authors perused thousands of research publications, wrote their chapters, and then responded to tens of thousands of comments. “This is one of the most tightly reviewed documents I’ve ever seen,” Prather said.

At the Yokohama conference, per U.N. procedures, policymakers from a hundred or more governments convened to go through the 40-page summary line by line, with the express purpose of revising the text to be useful to the governments. “Our job is to make sure they don’t destroy it. But these are a lot of very worried, midlevel officials who must explain this document to their ministers,” said Prather, who wants a strong action plan ratified in 2015. “We want them to feel they own it and to get their buy-in. Usually, they’re better writers than scientists, so that’s helpful. The one case where we stop them dead is if they try to invalidate a scientific finding. They are not allowed to do that.”

Reminiscent of an old-school American presidential convention, the conference in Japan and another Prather attended in Stockholm six months ago featured floor huddles and heated verbal fights, sessions that lasted well beyond midnight and hours-long debates over single sentences.

“It’s a process of attrition,” said Prather. “You succeed only if you can compromise.”

After six days, the delegates ran out of time. Prather stopped by the Japanese meeting rooms on his way to the airport expecting to pick up a final copy of the report. He was astonished to find the plenary still at work, trying to finish up. But he and other delegates were proud of the headline work they’d done and hope it will make a real difference.

“I get depressed about the future. I don’t get depressed about the process. The important stuff shakes out. What came out in this summary for policymakers fairly represents the impending threats, the dangers based on the science,” he said. “But if you look at the biggest threat to society, it’s people’s behavior.”

At the end of his talk at UC Irvine, Prather displayed a marked-up copy of Bob Dylan’s “The Times They Are a-Changin” on the audiovisual screen. “Early climate change predictor,” he quipped about the songwriter.

He’d scrawled “Sea level rise” in red marker over half the lyrics: “Come gather ’round people, wherever you roam, and admit that the waters around you have grown, and accept it that soon you’ll be drenched to the bone. If your time to you is worth savin,’ then you better start swimmin’ or you’ll sink like a stone, for the times they are a-changin.’”

On the other half, Prather had scrawled “Government action”: “Come senators, congressmen, please heed the call. Don’t stand in the doorway, don’t block up the hall. For he that gets hurt will be he who has stalled. There’s a battle outside and it is ragin.’ It’ll soon shake your windows and rattle your walls, for the times they are a-changin.’”