Fox News seized on a leaked draft of a U.N. climate report to suggest that climate change has been “overstated for the last 20 years.” But the draft itself clarifies that observed temperatures over the last 20 years have fallen within the range of past projections despite natural short-term variation.
Fox & Friends First claimed “scientists say” that “global warming been overstated for the last 20 years,” based on a draft of the fifth assessment report from the U.N. Intergovernmental Panel on Climate Change (IPCC). The report, which was leaked in December 2012 to a blog called "stopgreensuicide," contains a graph that conservative blogs claimed showed observed temperatures were lower than the projections of IPCC's first assessment report in 1990.
But scientists debunked this claim when the IPCC draft was first leaked in December. The draft itself notes that “Even though the 16 projections from the [previous temperature] models were never intended to be predictions over such a short time scale [1999-2010], the 17 observations through 2010 generally fall well within the projections made in all of the past assessments.” Indeed, as climatologist James Annan told Media Matters in December, “The grey bounds [...] indicate the range of uncertainty including natural variability, and the observations are well within that range” :
And as this graph from the climate science website Skeptical Science shows, the “best” projection from the IPCC's 1990 report is consistent with observed global temperature changes since 1990:
Furthermore, as the Union of Concerned Scientists' Aaron Huertas explained to FoxNews.com, some gaps between IPCC projections and observed temperatures are to be expected:
“It's important to keep in mind that there are natural short-term variations in global temperature that happen right alongside human-induced warming,” Aaron Huertas, of the Union of Concerned Scientists, told FoxNews.com.
“For instance, it would have been impossible for the IPCC to predict if a volcanic eruption might temporarily cool the Earth, as the Mount Pinatubo eruption did in 1991.”
University of Hawaii researchers have concluded that “large parts of the planet cooled as much as 0.7 degrees Fahrenheit” from 1992-1993 as a result of sulfur dioxide in the stratosphere from the eruption of Pinatubo. A study that adjusted for natural fluctuations such as this volcanic eruption found that the IPCC's report successfully predicted warming over the last 20 years.
Despite conservative media attempts to spin the leaked IPCC report, it actually solidified the case to act on climate change. As the New York Times reported, the “single most important conclusion” of the draft report was that “It is extremely likely that human activities have caused more than half of the observed increase in global average surface temperature since the 1950s.”