If you're looking for a careful breakdown of the various allegations against the IPCC that have been swirling around over the past few weeks, then check out this RealClimate post. At this point, it seems like the only glaring error that's been uncovered in the IPCC's climate reports is that statement about Himalayan glaciers melting by 2035—a goof, yes, though hardly anything that's fatal to the broader body of climate research. (Plus there's a misstatement about flooding in the Netherlands, though that appears to be very minor.)
Meanwhile, over at Columbia Journalism Review, Curtis Brainard has been castigating American journalists for not paying enough attention to this story. It's true, most of the IPCC frenzy has been led by the British press. But the reason for that, it seems, is that the British press is much sloppier. Indeed, the guy fanning most of the allegations against the IPCC is Jonathan Leake of the London Times, who appears to print whatever misleading claims climate skeptics tell him to report and then actively ignores the scientists he talks to who try to set him straight. Here's RealClimate with the goods:
Leake, with “research” by skeptic Richard North, has also promoted “Amazongate” with a story regarding a WG2 statement on the future of Amazonian forests under a drying climate. The contested IPCC statement reads: “Up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state, not necessarily producing gradual changes between the current and the future situation (Rowell and Moore, 2000).” Leake’s problem is with the Rowell and Moore reference, a WWF report.
The roots of the story are in two blog pieces by North, in which he first claims that the IPCC assertions attributed to the WWF report are not actually in that report. Since this claim was immediately shown to be false, North then argued that the WWF report’s basis for their statement (a 1999 Nature article by Nepstad et al.) dealt only with the effects of logging and fire—not drought—on Amazonian forests. To these various claims Nepstad has now responded, noting that the IPCC statement is in fact correct. The only issue is that the IPCC cited the WWF report rather than the underlying peer-reviewed papers by Nepstad et al. These studies actually provide the basis for the IPCC’s estimate on Amazonian sensitivity to drought.
Investigations of the correspondence between Leake, scientists, and a BBC reporter (see here and here and here) show that Leake ignored or misrepresented explanatory information given to him by Nepstad and another expert, Simon Lewis, and published his incorrect story anyway. This “issue” is thus completely without merit.
I'm all for the U.S. press scrutinizing this issue, but Leake doesn't seem like the sort of journalist anyone should be emulating. Tim Lambert has more on Leake's "reporting." And more broadly, it's amazing how terrible many British newspapers have been on a variety of climate-science issues (though of course there are exceptions here and there). To take another example, Phil Jones, who used to head the Climate Research Unit at East Anglia before stepping down after the "Climategate" e-mails, recently had this exchange with the BBC:
BBC: Do you agree that from 1995 to the present there has been no statistically-significant global warming?
Jones: Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.
What he's saying is that the planet has been warming over the past 15 years, but a relatively short span of time like that often isn't long enough to say whether the trend is just due to statistical noise or not. That's a totally banal statement. You often need to look at a longer time frame to have high confidence that a trend is statistically significant and not just due to natural variance. Here's a post explaining the issue clearly. And, in fact, when you do look over a longer period—say, 20 or 30 years—the recent warming trend is quite pronounced and, yes, statistically significant. Yet British papers like The Daily Mail have headlines claiming that Jones said there's been "no global warming since 1995." That's not even remotely accurate.