Global warming more modest than IPCC’s worst-case scenarios

earth sunA study published this week in the peer-reviewed journal ‘Scientific Reports’ revealed that global warming is not progressing at the rate suggested by the worst-case computer models released by the Intergovernmental Panel on Climate Change (IPCC). The study, which was led by Patrick T. Brown of Duke University, examined 1,000 years of temperature records that showed global warming was not progressing as fast as it would even under the most severe emissions scenarios as outlined by the IPCC.

The study showed that “natural variability in surface temperatures, caused by interactions between the ocean and atmosphere, and other natural factors, can account for observed changes in the recent rates of warming from decade to decade.”

Using the term climate “wiggles,” the researchers note they could slow or speed the rate of warming from decade to decade, and either heighten or cancel out the effects of greenhouse gas emissions, which are believed to cause global warming. If not properly explained and accounted for, these wiggles may alter the dependability of climate models and lead to an “over-interpretation of short-term temperature trends.

“By comparing our model against theirs, we found that climate models largely get the ‘big picture’ right but seem to underestimate the magnitude of natural decade-to-decade climate wiggles,” Brown said. “Our model shows these wiggles can be big enough that they could have accounted for a reasonable portion of the accelerated warming we experienced from 1975 to 2000, as well as the reduced rate in warming that occurred from 2002 to 2013.”

Brown, a doctoral student in climatology at Duke University’s Nicholas School of the Environment, said, “Statistically, it’s pretty unlikely that an 11-year hiatus in warming, like the one we saw at the start of this century, would occur if the underlying human-caused warming was progressing at a rate as fast as the most severe IPCC projections. Hiatus periods of 11 years or longer are more likely to occur under a middle-of-the-road scenario.”

Brown also noted that haitus periods of 11 years or longer, like the one we are currently experiencing, are more likely to happen under a “middle-of-the-road scenario” and not under the IPCC’s cataclysmic global warming narrative. Unlike climate models used by the IPCC, Brown’s research used observable data.

Eugene C. Cordero of San Jose State University and Steven A. Mauget of the USDA Agricultural Research Service in Lubbock, Texas, co-authored the new study with Brown and Li. Funding came from the National Science Foundation and the National Institutes of Health, both of which are branches of the U.S. government.