When it comes to the mainstream media’s coverage of science, you can expect the occasional mistake. You might even tolerate their making the same error a few times. But when journalists perpetuate the same falsehoods year after year, these “mistakes” begin to smell like a deliberate campaign of lies designed to deceive a nonscientific public.
Such is the case with global warming in general—and with midlatitude storms in particular, our topic today.
The headline “Global Warming to Produce Pleasant, Mild Climate, and Weaker Storms” may not raise ratings or sell newspapers. But stating the exact opposite, in the face of overwhelming counterevidence, is just plain wrong.
As greenhouse gas levels increase, the poles are supposed to warm much more than the tropics. (A plot of surface temperature trends is evidence of that.)
The energy that fuels most of the midlatitude storms, fronts, and the jet stream is the difference between low-latitude and high-latitude temperatures—what weather nerds like to call “baroclinicity.” A drop in the temperature gradient lowers baroclinicity, weakening the jet stream and generating fewer, weaker storms. Which creates a media nightmare: Video of a weak storm does not make for captivating television.
In December, Mark Sinclair and Ian Watterson published a paper in the Journal of Climate on expected changes in midlatitude weather systems as greenhouse gas levels increase. They examined changes in baroclinicity and low- and high-pressure frequencies using a General Circulation Model (GCM) called CSIRO9, run with both “control” and doubled carbon dioxide (CO2) levels. Unlike in some other, related studies, instead of counting low-pressure systems, they looked at the general sense of spin of the air, what atmospheric scientists call “vorticity,” which the authors believe is a more accurate indicator of midlatitude storm activity than simply counting storms.
After comparing the increased CO2 run with the base run, they noted
“. . . diminished cyclone activity for the doubled CO2 simulation. For the [Northern Hemisphere], decreases of 10 percent to 15 percent largely followed the storm track. . . . Over the [Southern Hemisphere], decreases in cyclone activity are found over the entire hemisphere.
Furthermore, they concluded that
“Doubled CO2 leads to a marked decrease in the occurrence of intense storms as deduced from central vorticity. . . . Reductions in average cyclone central pressure that have been used in other studies to promote the possibility of enhanced storminess under greenhouse warming, are more likely the result of global-scale sea level pressure falls rather than any real increase in cyclone circulation strength. Such discrepancies underscore the need to ensure that measures of cyclone activity and intensity are realistic and do not introduce bias.
So even the climate models, which the media love to trump as the basis for all this furor in the first place, show weakening storms in the future. This inevitable result arises because of the differential warming between the poles and the equator.
But can climate models accurately reproduce the current midlatitude cyclone climatology? When Sinclair and Watterson compared the model’s control run with the observed baroclinicity, they found some significant differences. In general, the model underestimates the strength of the midlatitude winds in both hemispheres, and therefore produces fewer and weaker storms than are observed in reality.
In related research, the University of Virginia’s Bruce Hayden compared observed cyclone tracks over the continental United States to mean tracks produced by the Hadley Center GCM (HADCM2). The observed storm tracks are familiar to most Weather Channel afficionados: Alberta Clippers, which track along the United States-Canada border; Colorado Lows, which form east of the Rockies and travel through the Midwest and Great Lakes; and coastal storms that form near the Gulf of Mexico and skim the East Coast.
The storm tracks that the model produced bear little resemblance to reality. In the first comparison, for 2005 (a year that should resemble current conditions), Hayden notes:
. . . the Alberta storm track is not revealed at all in the GCM data. The Colorado storm track is delineated well, but the strong maximum . . . is not found in the observational record. . . . The storms tracking out of northern Mexico seen in the model output data are not a feature found in the observational record. The Atlantic Coast storm track is found in the model output but is displaced much further offshore than observed in the historical record.
Perhaps even more surprisingly, the modeled storm tracks for 2020 and 2085 are, for all practical purposes, the same. According to this GCM, storm tracks will remain the same despite a doubling of carbon dioxide. Hayden concluded that
The lack of detectable sensitivity on the part of the model is disturbing. If the models cannot make adequate projections about these fundamental . . . features of the general circulation of the atmosphere, how then are . . . output variables of the model, like precipitation and related hydrological processes, to be estimated with confidence?
True, these two studies are somewhat contradictory, but this should not be too surprising since they were based on different GCMs. They do share some consistent conclusions: (1) GCMs do not reproduce the existing storm patterns; and (2) For the next century, despite increasing CO2 levels, GCMs forecast neither stronger storms nor more storms.
So, the press is wrong on both counts. The media place their full faith in GCM forecasts of certain fields (such as temperatures, precipitation patterns, etc.), yet they blatantly ignore GCM forecasts when it’s convenient to do so (storminess, for example). The result is not science, it’s not news, and it’s certainly not science news. It is fiction reported as fact, which any properly raised first-grader would justly call a lie.
References
Hayden, B.P., 1999. Climate change and extratropical storminess in the United States: An assessment. J. American Water Resources Association, 35, 1387–1397.
Sinclair, M.R., and I.G. Watterson, 1999. Objective assessment of extratropical weather systems in simulated climates. J. Climate, 12, 3467–3485.
