One million Species are being Endangered by Global Warming
Tyler Cowen at
Marginal Revolution points out a well reasoned rebuttal to the "scare quotes" being issued from
Chris Thomas at the University of Leeds, UK. published in Nature.
Tyler points to an article by Gregg Easterbrook
here
bq. NONSENSE IS IN NO DANGER OF EXTINCTION: Species loss is indisputably a problem--it's among the few environmental issues where trends are negative, and among the few that really worries me--but the Nature study on the subject, being widely promoted in today's press, is a monument to nonsense. "WARMING MAY THREATEN 37% OF SPECIES BY 2050," The Washington Post says on page one this morning. Well, a lot of things "may" happen. Let's break down the nonsense in this study point by point.
bq. First, though appearing in a prestigious science journal, this study, led by Chris Thomas of the University of Leeds, is nothing but computer modeling. No actual extinctions caused by global warming are established, nor is any confirmed relationship demonstrated between global warming and species loss. ... The study is entirely a computer simulation, and as anyone familiar with this art knows, computer models can be trained to produce any desired result.
bq. Computer models are also notorious for becoming more unreliable the farther out they project, as estimates get multiplied by estimates, and then the result is treated as specific. This is a 50-year projection, and everything beyond the first few years should be treated as meaningless statistically, given that tiny alterations in initial assumptions can lead to huge swings at the end of a 50-year simulation. Nature is a refereed journal, but it appears that all the peer-reviewers did was check to make sure the results presented corresponded to what happened when the computer models were run. There does not appear to have been any peer-review of whether the underlying assumptions make sense.
bq. This is especially true in light of the third problem with this study, namely, that past episodes of global warming have not produced the mass-extinction that the Thomas computer models project. Global average temperatures have risen one degree Fahrenheit in the past century--a reason I accept most global-warming theory--without any significant effect on species. Several frog species including the Costa Rican golden toad (there are hundreds of frog species) may have been rendered extinct by climate change in the past century, but that's not even in the general zone of the kind of impact this study projects.
bq. Estimates of global warming vary quite widely, as they too are driven by computer model, but the Intergovernmental Panel on Climate Change (IPCC), the most-cited source of global-warming projections, now expects somewhere around three to six degrees Fahrenheit of warming by 2100. (IPCC estimates are all over the map; set that aside for the moment.) Assuming that happens--many estimates are lower--we'd expect one or two degrees of warming by 2050.
European temperatures rose naturally by one or two degrees at the end of the "Little Ice Age" of the fourteenth through nineteenth centuries. This rise did not cause a mass extinction in the region; in fact, it appears to have caused few or no extinctions. Why would the same level of temperature increase suddenly trigger a mass extinction now?
Emphasis mine
Iain Murray at Tech Central Station weighs in
with the following:
bq. There are several reasons this claim should be laughed out of the court of public opinion. First, the research doesn't say what the researchers themselves claim. They have extrapolated to all species a model that looked at only 1,103 species in certain areas (243 of those species were South African proteaceae, a family of evergreen shrubs and trees). For one thing, we don't know how many species there are -- estimates vary from 2 million to 80 million -- and have only documented 1.6 million. However, assuming the 14 million figure widely used in the press reports is anywhere near accurate, the sample size is a mere 0.008 percent of the total species population of the planet, with certain species vastly over-represented (there are only 1,000 species of proteaceae on the planet). All the researchers have demonstrated is that, if their model is correct, certain species in certain habitats will run a risk of extinction. Extrapolating to the entire planet from this small, unrepresentative sample is simply invalid. So when the lead researcher told the Washington Post, "We're not talking about the occasional extinction -- we're talking about 1.25 million species. It's a massive number," he was guilty at the very least of over-enthusiasm, if not outright exaggeration.
bq. This problem would be devastating enough for the claims, if it wasn't the case that the model on which the calculations are made is itself suspect. It relies on the 'species-area relationship,' the idea that smaller areas support fewer species. A researcher at the evocatively-titled Golden Toad Laboratory for Conservation in Puentoarenas, Costa Rica, writing a commentary on the study for Nature, called this "one of ecology's few ironclad laws." The trouble is that there are many exceptions to this supposedly ironclad law. The wholesale deforestation of the Eastern United States, for example, seems only to have caused the extinction of one species of bird. While in Puerto Rico, the island's loss of 99 percent of its forest cover caused the loss of 7 out of 60 species, but after the deforestation the number of bird species on the island actually increased to 97. The species-area relationship (plotted as a linear function in 1859) seems to be a poor model on which to base extinction rates.
He continues with the following wonderful commentary:
bq. What about the link to global warming? The researchers assume that global warming will reduce habitat. Yet this isn't the case. The earth is not shrinking. The reduction of one area of habitat does not mean that it is replaced by void. Other habitats expand. And so far, all the evidence we have points not to desertification or other changes to less hospitable climates as a result of global warming. Instead, the increase of carbon dioxide in the atmosphere seems to have led to a six percent increase in the amount of vegetation on the earth. The Amazon rain forests accounted for 42 percent of the growth. To model only reductions in habitats and not expansions accounted for by global warming stacks the deck. The researchers created a model that dictated that global warming will cause extinctions. Surprise, surprise! When they ran the model that's exactly the result they got.
Sure, the earth is warming up - it's warming up from a couple hundred years of being cooler than normal. To say that humans caused this and can cure this is hubris of the worst order... Junk science.
Posted by DaveH at January 11, 2004 8:05 PM