I managed to get into the press briefing. RK Pachauri, the IPCC chair, led off, pointing out that the IPCC has 21 years of experience now and its process has stood the test of time. IPCC reports peer reviewed twice, and chapter authors are required to respond to all comments, and to justify their responses. (AR4 received over 90,000 comments, so that is quite a load.) After this peer review, the most widely circulated element of each IPCC report, the Summary for Policy Makers, must be approved word by word by all the world’s governments.
T. Stocker, co-chair of Working Group I (physical science basis), made a brief presentation of the evidence. Many different, largely independent data sets (he showed global temperature (+0.75°C since 1850), sea level rise (17 cm since 1900), and declining snow cover. He pointed to the AR4 statement that “warming is unequivocal,” but reminded the audience that natural variability will always be present, resulting in occasional colder and hotter than “normal” years.
Stocker emphasized that in the past century the climate system has exhibited changes that are unprecedented not only in amplitude, but also in rate, compared with what we know of the prior hundreds to many thousands of years. Widespread melting of ice margins has been observed in Greenland and the Antarctic. Emitted CO2 remains in the atmosphere for 1000s of years, causing irreversible changes in the climate and in ocean chemistry.
Chris Field, co-chair of WGII (human impacts), followed Stocker. Among other things, he mentioned that crop reductions are likely and increasing, producing substantial food insecurity, esp. in southern Africa and southern Asia. Infrastructure damage is likely and increasing, esp. in coastal areas (100s of billions of dollars). Biodiversity losses of a few percent up to as much as 30 or more percent in some key areas are likely. Field emphasized that vulnerability is not uniformly distributed: it will be concentrated on the world’s poor.
The level of impact scales with the level of emissions. At 2-3 degrees centigrade (a very real possibility by 2100), we are looking at a long term commitment to several metres of sea level rise, and impacts on the fresh water supplies for 2 billion or more people.
The briefing was only 30 minutes, so they took only about 5 questions. Inevitably, the last one regarded the stolen CRU emails: did Pachauri think the conference was being distracted by this issue? Pachauri’s reply: “I’ve been talking to all the negotiators; they don’t seem distracted. One or t countries [PNE: that would be the USA...] might like to seize on this and exaggerate the threat. This has had no impact on the findings of AR4.”
It’s a “recreational distraction,” he said. Cornered outside the briefing room, he was asked by a very insistent reporter (?) whether the IPCC would support an independent investigation into the CRU emails to see whether scientific fraud had been committed. Otherwise, the “reporter” said, your credibility is in question. “Our credibility is not in question,” Pachauri replied. I think he’s right.