Researchers say that as temperatures rise, the driest parts of the US could see a 30 per cent increase in kidney stone disease…warmer temperatures could extend America’s existing “kidney stone belt”, an area of the South East where men have been found to be twice as likely to develop kidney stones as in the North East.
Margaret Pearle, professor of urology at U of Texas Southwestern is the third author on the paper (but apparently wrote it) and is quoted,
“This study is one of the first examples of global warming causing a direct medical consequence for humans. When people relocate from areas of moderate temperature to areas with warmer climates, a rapid increase in stone risk has been observed. This has been shown in military deployments to the Middle East for instance.
Eric Berger quotes Dr. Paul Epstein of Harvard Medical School as saying the new study is “an elegant piece of work.” He isn’t kidding.
Image copyright PNAS.
There is little doubt about the relationship between kidney stones and weather/climate. That is not the point of this post, most of us are not urologists and have no interest in making light of a very painful experience. However, what is important to us is just how scientists, who do not do climate science as their day job, approach a problem such as this. What are their data sources, explanations for methodology choices, and justification for conclusions? Moreover, do their methods stand up to the same “rigorous” standards of climate scientists so often discussed here at Climate Audit?
The PNAS paper has a nice (and very short) section dedicated to materials and methods, which I will liberally quote/paraphrase for consumption — just make sure not to dehydrate yourself along the way.
GCM’s have shown an increase of about 1 degree C in Mean Annual Temperature (MAT) over the past 30 years. The UN IPCC AR4 model data is chosen (SRESa1b scenario, 850 ppm by 2100), and the annual MAT across the US was determined from the mean of the 19 IPCC SRESa1b scenario GCMs. The expected rises in midcontinent US MAT are on the order of 4-7°C by 2100.
Mean monthly surface air temperatures (TAS) were computed for each model and regridded to a 0.5°x0.5° mesh over North America. To minimize GCM bias, monthly model increments of TAS (model departure from the mean of 20th-century model, 20c3m, results) were determined, and the annual average increment was calculated for each model. These were downscaled to U.S. climate divisions (1–10 of these per state) by using intersection–area weighting, and future TAS values were computed by adding the increment to observed temperature normals (1895–2006) for each division.
When you have coarse atmospheric datasets like the UN IPCC AR4 data and want to combine them in some sort of bias-corrected weighted mean fashion, regridding to finer resolution would seem to add some unwanted artifacts. But, you may settle for knowing about these 1895-2006 climate normals?
The climate normals represent an instrumental record that is effectively population weighted within each division (weather stations are near people) and therefore most closely indicate the temperature experienced by the population. This can be important in areas with significant topographic relief.
I could not find a reference for the above reasoning. Fortunately, the authors provide an example to clear the fog:
Las Vegas, NV, has an observed divisional normal TAS (mean monthly surface air temperature) of 17.4°C. A direct average of SRESa1b TAS for that division at 2050 predicts an unreasonably low 15.4°C, which reflects an average of mountain and desert temperatures. The 2050 mean TAS increment of 2.8°C added to the normal gives a predicted MAT of 20.2°C, more consistent with expected temperatures in the populated desert valleys in that climate division.
That’s it folks. Somewhere in the middle of the paper, they go into uncertainties (couple token sentences) in the UN IPCC climate models but only to say that the other scenarios, A1B and SRESa2, the warming is even more severe (=kidney stones from the Sixth Circle).
But in the next paragraph, it turns out that the current kidney stone dataset is not so good for a variety of reasons. These include undiagnosed, asymptomatic stones, lack of correct documentation of recurring events, or those who just plain don’t go to the hospital. In fact, there could be up to a 35% error in the baseline prevalence of kidney stone disease! See, reconstructing climate records is nothing compared to ascertaining a census of those suffering of kidney stones.
There are of course countless medical conditions that are related to temperature and climate. If this is the first such study connecting possible medical conditions to potential warming, then it surely won’t be the last. The press coverage throughout the mainstream media and blogosphere is clearly adding well-deserved attention to the plight of stone sufferers, perhaps too much.
PS. The SE United States has actually undergone slight cooling over the past century.
It sounds like Hippocrates was expecting this exact situation to develop when he discussed the ethical practice of medicine. An interpretation of one of the points is highlighted in Wikipedia entry with plenty of irony attached:
I will not use the knife, not even on sufferers from stone, but will withdraw in favor of such men as are engaged in this work. … interpretation … To avoid attempting to do things that other specialists can do better. The “stones” referred to are kidney stones or bladder stones, removal of which was judged too menial for physicians, and therefore was left for barbers (the forerunners of modern surgeons). Surgery was not recognized as a specialty at that time. This sentence is now interpreted as acknowledging that it is impossible for any single physician to maintain expertise in all areas. It also highlights the different historical origins of the surgeon and the physician.
Couldn’t invent a better parallel.