Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”
Today’s global media are ablaze with coverage of newly reported scientific findings purporting to show that anthropogenic global warming is leading to more extreme weather events such as heat waves, forest fires, and floods.
The findings are being made available in the early releases section of the Proceedings of the National Academy of Sciences (PNAS) and represent the work of a group of researchers from the Potsdam Institute for Climate Impact Research (PIK)—an institute which can be routinely counted on to produce rather alarming climate change studies. The new analysis, led by Vladimir Petoukhov, is no exception.
The researchers examined the trends in the daily patterns of air flow in the lower atmosphere and found that some patterns had become more persistent with time—a characteristic that leads to a slowdown in the forward motion of weather systems. Or as the researchers put it in their press release, “What we found is that during several recent extreme weather events these planetary waves almost freeze in their tracks for weeks.” To make sure you understand the implications, they added “Since many ecosystems and cities are not adapted to this, prolonged hot periods can result in a high death toll, forest fires, and dramatic harvest losses.”
While climate alarm plays well in the media, what doesn’t play so well is climate-as-normal.
Case and point: there are zero media stories about a similarly timed study purporting to show that any anthropogenic global warming influence on extreme weather events is too small to be reliably detected.
This study, available in the early-release section of the journal Geophysical Research Letters, was performed by the research team of James Screen and Ian Simmonds of the University of Melbourne. Screen and Simmons examined the trends in the daily patterns of air flow in the lower atmosphere and found little significant change. They note that “the changes in meridional amplitude over recent decades are relatively small compared to the year-to-year variability” and “that possible connections between [anthropogenic global warming] and planetary waves, and the implications of these, are sensitive to how waves are conceptualized.” They cautiously conclude that “[t]he contrasting meridional and zonal amplitude trends have different and complex possible implications for midlatitude weather, and we encourage further work to better understand these.”
[Layman’s translation: There are few significant changes in north-to-south extent of jet stream troughs or their forward speed. The data are so noisy that results are highly dependent upon what analytical method is chosen. The contrasting north-south and east-west changes in jet stream troughs have multiple influences that we haven’t sorted out yet, but it would be foolish to tie them to global warming at this time.]
So there are two different research teams studying the same issue; one screams that global warming is killing us, while the notes that the situation is complicated and requires additional study, and that it is difficult to relate any observed changes to global warming.
Such an example provides a perfect picture of how the media influences public opinion about science.
A large number of people will be exposed to the news that scientists are reporting that global warming is leading to more severe weather. This will be the majority opinion, as few folks are inclined to dig deeper than a sound byte or a single paragraph.
Virtually no one will be exposed to the scientific finding that the influence of global warming on severe weather is largely lost in the noise of the complex influences of a number of other factors.
And so the story of global warming science in the public eye grows asymmetrically, with alarming evidence receiving far more exposure than evidence for more modest changes and impacts, or, situation-as-normal findings.
We’re not blaming the media. While they have a clearly demonstrable bias, that’s just a convenient assist to their prime motivation: selling more ad space. The end-of-the-world-as-we-know-it always sells better than business-as-usual.
Where the science really needs to gets sorted out and fairly considered is in the summary “science assessment” reports that form the basis for policy (or lack thereof). Consider the document “Global Climate Change Impacts in the United States,” published by the U.S. Global Change Research Program (you can find it here).
As our work at the Cato Institute’s Center for the Study of Science plainly reveals, the representativeness of the science included in many government assessment reports is no better than it is in the popular media (you can find our companion report to the above-mentioned government report here).
Alarm not only sells papers, but also amps up the regulatory state.
Petoukhov, V., et al., 2013. Quasi-resonant amplification of planetary waves and recent Northern Hemisphere weather extremes. Proceedings of the National Academy of Sciences (Early Edition), doi:10.1073/pnas.1222000110
Screen, J.A., and I. Simmonds, 2013. Exploring the links between Arctic amplification and mid-latitude weather. Geophysical Research Letters, in press, doi: 10.1002/GRL.50174