I was curious about the fact that none of the climate-focused bloggers on my blog roll had written on the subject. Then it occurred to me – they’re climatologists, not biologists, so they decided not to write about something outside of their expertise.
Pat Michaels wasn’t bothered by this. In fact, he reckons that he’s demolished the paper:
I have to say that this was the easiest shoot-down in some time,
because, in my humble opinion, it was the worst paper that Nature
has published on global warming. Hot rumor: investigative
journalists are on the scent that Nature and Science are skewing
their reviews. Stay tuned.
Hmmm, OK, here’s the meat of his criticism:
Figure 1 is taken from the Pounds et al. manuscript. It shows the distribution of amphibian populations as a function of daily average maximum and minimum temperatures. It also shows the original range of the chytrid fungus.
Pounds et al. cite climate data from Columbia and Venezuela showing a decline in daily maximum temperature of 0.6ËC between the 1941-70 average and the 1981-90 average and a rise in daily minimum of 1.0ËC for the same period.
We have imposed these changes upon the Pounds et al. data in Figure 1. The number of new populations possibly effected by chytrid infestations as a result of the decrease in daily maximum temperature is two and it is four for the increase in daily minimum. There are 50 populations, meaning that 12% more of the populations are subject to chytrid infection.
Unfortunately, Michaels has made some serious errors.
- Michaels has “imposed” the changes in the temperature range on the graph by increasing the range of temperatures where the fungus thrives. This is obviously wrong.
- Pounds’ figure does not show the distribution of amphibian populations at all. Oddly enough, the researchers did not set up a weather station at each location where frogs had been observed. The graph shows how daily minimum and maximum changes with altitude. The dots are weather stations, not amphibian populations.
- Even if he was correct on points one and two Michaels’ conclusion about the percentages of populations affected does not follow. He assumes that the only way that a population could be affected is if the daily minimum or maximum falls into the pink band when it did not do so before. But this ignores the fact that each day the temperature varies between the minimum and the maximum. The correct question to ask, is what percentage of the time does the population spend in the pink band? This is related to the fraction of the interval from a filled circle (daily minimum) to the corresponding open circle (daily maximum). This fraction has increased for all populations below 3000 metres of elevation, so it is possible that a much higher percentage than the 12% that Michaels calculated could be affected
In previous posts about Michaels I showed how he
- authored a paper one that “disproved” global warming by deliberately removing almost one-third of the satellite data from his analysis
- co-operated with Ross McKitrick on another paper that managed to “prove” that global warming wasn’t happening by mixing up degrees with radians
- constructed a bogus measure of energy efficiency
- lied about Hansen’s predictions on global warming.