Conservative media outlets are claiming that a leaked draft of the UN climate panel's upcoming report undermines previous predictions of rapid warming driven by rising CO2 emissions. But scientists say these claims are "nonsense" and that the draft report only adds to the existing body of evidence that manmade climate change is a serious problem.
A draft of the Intergovernmental Panel on Climate Change (IPCC) fifth assessment report, due to be published in fall 2013, was leaked by Alec Rawls, a blogger who volunteered to review the report despite having no scientific expertise. In a blog post on Watts Up With That, Rawls claimed that the draft report contains a "game-changing admission" that galactic cosmic rays have significantly contributed to global warming, undermining the scientific consensus that climate change is driven by human activity. But experts say Rawls "completely misrepresented the IPCC report," noting that he ignored a paragraph that explicitly states there is “high agreement” among scientists that cosmic rays do not have a meaningful impact on global temperatures. Dr. Steve Sherwood -- a lead author of the chapter in question -- told Australia's ABC News that Rawls' claim is “ridiculous,” adding: “we conclude exactly the opposite, that this cosmic ray effect that the paragraph is discussing appears to be negligible.”
Furthermore, as Skeptical Science pointed out, even if cosmic rays did influence global temperatures, “they would currently be having a cooling effect.” Dr. John Abraham of the Climate Science Rapid Response Team told Media Matters:
The IPCC report certainly was not saying the changes in the sun were causing the earth to warm. In fact, if the leaker was correct in his interpretation, the earth should be cooling right now!
But that didn't stop Investor's Business Daily from echoing his misinformation, claiming that the leaked draft “indicates the IPCC is actually admitting that a factor outside man's activities is playing a significant role in our climate.” IBD quoted Rawls' claim that the section on cosmic rays “completely undercuts” the IPCC's conclusion that manmade climate change poses a significant threat, without noting that Rawls is not a scientist and has been thoroughly discredited.
Meanwhile, climate contrarian blogger Anthony Watts claimed to have discovered the real "bombshell" in the draft report: a chart comparing observed changes in global average surface temperatures with projections from the four previous IPCC reports. The chart indicates that early UN projections may have slightly overestimated warming because they did not take into account natural factors like solar forcing or aerosols, which tend to have a cooling effect. But the draft notes that “observations through 2010 generally fall well within the projections made in all of the past assessments.”
Nevertheless, conservative media outlets seized on the chart to suggest that UN climate models are unreliable. The Washington Times cited the chart as evidence that “predictions of planetary warming have been overstated,” adding:
Despite the draft chart's implicit admission that climate models have exaggerated warming, IPCC has not backed down from the tale that carbon dioxide, a natural byproduct of industrial society, is heating the planet. At the same time, the organization realizes it can no longer hide from the widely known temperature data. Billions of dollars are at stake, and politicians expect IPCC to continue drumming up the fears of imminent cataclysm necessary for advancing their classic tax-and-spend liberal agenda.
Forbes columnist Patrick Michaels said the chart shows “how badly one of [IPCC's] most-cited series of predictions is faring,” and suggested that scientists may try to cover up the chart in the final report. But climatologist James Annan told Media Matters that Michaels misrepresented the chart by focusing on a narrow range of predictions and ignoring a the broader range of uncertainty depicted, including natural variability. Annan noted that “the observations are well within that range.”
Indeed, a recent analysis concluded that the first IPCC report, published in 1990, accurately predicted warming over the past two decades when adjusted to account for natural variability. The following chart from Skeptical Science illustrates that observed warming has been consistent with IPCC's original projections:
Another paper recently confirmed the accuracy of IPCC's 2001 and 2007 projections.
It is extremely likely that human activities have caused more than half of the observed increase in global average surface temperature since the 1950s. There is high confidence that this has caused large-scale changes in the ocean, in the cryosphere, and in sea level in the second half of the 20th century. Some extreme events have changed as a result of anthropogenic influence.