What to look for in the UN’s mega climate report that’s out Friday

BY Jenny Marder  September 26, 2013 at 2:06 PM EDT

Get ready Friday for the first of a three-part, several thousand-page worldwide climate report. Photo of melting ice caps by KEENPRESS/Getty Images.

On Friday, the Intergovernmental Panel on Climate Change will release the first part of its fifth assessment report — a megadocument widely considered the authority on climate change science. The last time this report was released was six years ago, in 2007, and it resulted in the Nobel Peace Prize, awarded jointly to Al Gore and the report’s entire scientific panel. Meanwhile, here’s a cheat sheet on the report: what it is, who’s behind it and why we should or shouldn’t care about what it says.

What is the IPCC?

The IPCC, established by the U.N. in 1988, is short for the Intergovernmental Panel on Climate Change. But if the word “panel” to you implies a handful of scientists wielding power points while downing bottled water in a musty conference room, then no. We’re talking thousands of scientists who spend years tackling and assessing climate change’s most pressing questions. This first report alone featured 259 lead authors from 39 countries, and drew more than 50,000 comments.

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These are unpaid positions. Joel Smith, a coordinating lead author calls the work “a labor of love.” Michael Oppenheimer, professor of geosciences at Princeton University and also one of the authors, said he spent a combined total of three months out of the year for each of three years on his chapter. That’s no walk in the wetlands.

What specifically will the panel release on Friday?

On Friday, the panel will release Working Group 1, the first of the three-part report. This first section tackles the physical science — how the climate is changing. The other two, due in springtime, address the impacts of these changes — what they mean for us and for the environment — and what can be done about them. Finally, toward the end of 2014, the panel will release a synthesis report that ties it all up in a punchy, concise summary. Concise at least when compared to the report’s background material — expected to include several thousand pages of detailed scientific analysis from tens of thousands of peer-reviewed studies. In search of good bedtime reading? Panel’s got you covered.

How much has changed in the past six years?

Fundamentally, our understanding hasn’t changed much, Smith said. We know the climate is changing. We know this is causing the planet to warm. And confidence is higher than ever that humans are responsible for that warming, primarily through the release of greenhouse gases and the burning of fossil fuels.

But scientists over the last six years have gathered more data, and these data gathering systems have become more advanced. Computer models have become more refined, and as this BBC video points out, a worldwide network of floating observatories has improved how we collect ocean samples.

New satellite imaging data from space will be cited. So will historical evidence from ancient ice, rocks and tree rings.

“What people should look for is not any revolutionary change of our understanding, but a gradual improvement of our understanding,” Oppenheimer said.

What’s the deal with all the talk about a decline in warming?

There have been some questions about a slowdown or “hiatus” in the rate of warming over the past 15 years, and some governments are calling on the IPCC to address this in the report. Data indicates that from 1998 to 2012, the rate of warming slowed to about half the average rate since 1951. That contradicts projections in the earlier climate reports, and a paper published last month in the journal, Nature Climate Change concludes that “recent observed global warming is significantly less than that simulated by climate models.”

A keyword here is “recent.” And one possible explanation by scientists is that these are random climate fluctuations over a brief period of time, and when trends are viewed long term, the rate remains steady. Another hypothesis is that temperatures have been rising more slowly because more heat is being stored in the ocean.

“This is a very complex system,” Smith said. “We don’t understand the moving parts, but we do understand the fundamentals. We know the climate is changing — that’s a fact. And we’re highly confident that it’s because of human warming.”

Roger Pielke Jr., an environmental scientist at the University of Colorado at Boulder, says that the fact that the models don’t accurately predict the temperature increase represents “a big fat question mark.” And the IPCC, he said, should remove itself from the politics and “play it straight” by admitting it doesn’t know all the answers and simply laying out the various hypotheses.

“One of the problems with the climate debate is that sometimes scientists claim more certainty than they have about how the near-term might evolve,” he said. “And then if things don’t pan out, the scientific community could lose some influence.”

Has the report in its current format becoming outdated?

That depends on who you ask. Both Pielke and Oppenheimer say yes. Oppenheimer, for example, says that more focused reports might be of greater value. Reports on the impact of sea level rise, for example or tundra exposed to warming temperatures or methane hydrate in the seabed. He points to a recent IPCC report on extreme weather.

“I think it’s important that the IPCC continue, but it’s also important for them to refocus their efforts away from mega assessments and to focus instead on a few areas that are very important for policymakers,” he said.