TCS Daily


The Boston Orioles?

By Willie Soon - March 26, 2002 12:00 AM

Editor's note: TCS is proud to announce the birth of a new feature called the "Chartifact." Dr. Willie Soon will use helpful charts and illustrations to help educate and inform readers on the complicated subject of climate science. We hope you find this occasional feature useful, lively and instructive.

You may now have heard from reports in the media that "songbirds sound alarm on global warming's effect" (Atlanta Journal Constitution). So serious is the potential effect of warming on birds that the Washington Post fretted about "a Baltimore without orioles" and that even the black-capped Chickadee in my own state of Massachusetts "[c]ould vanish."

Further, the threat of global warming is not just a threat to birds. It's a threat to business. How so? "More than sixty-three million Americans are birdwatchers, injecting billions of dollars into local economies throughout the nation." In other words, if there are no songbirds, then there will be no money to be made off watching the birds. All of our springs may soon be silent without bird songs.

These gloomy news accounts came thanks to "The Birdwatcher's Guide to Global Warming" a report issued this month by the National Wildlife Federation and American Bird Conservancy. Unfortunately for the authors of the report, their speculation doesn't add up.

First of all, the study claims 63 million Americans - that's one out of four or five of us -- are birdwatchers. Can this be true? Are you a birdwatcher? Ask among your friends and families around your own backyard. Pool them to see if you can verify that claim.

This report then goes on to say that due to global warming, "as many as 33 states could see a significant reduction in American Goldfinches in the summer" and "one model projects that there may be no Baltimore Oriole in Baltimore (or anywhere else in Maryland)." Further, it states that "although the mere thought of trying to deal with a problem big enough to change the climate of the entire world can be paralyzing, the solution is promisingly simple -- reduce emissions of greenhouse gases."

These claims are easily made, but there is little factual support for them.

There are two major problems with the analysis contained in this report. First, scientists only loosely know how a bird's physiology, habitat and food supplies are related to climate variables like mean seasonal temperature and precipitation, extreme values of coldest and warmest months, timing of snowmelt, and early arrival of spring. And if our understanding of that is limited, then how can any meaningful projection be made under a global warming scenario?

Second, even if all the interaction rules between birds and climate are perfectly known, is the best available climate model good enough to predict future climate change over the U.S.?

Dual Fallacies

The first problem is what might be called the fallacy of senseless projection. I say senseless mainly because climate may not even be a dominant factor causing the decline or extinction in various bird species as implied by this new study. Most of the current problems birds face are more related to urban development and changing regional pattern of natural landscapes including changing wetland and forest areas.

The authors of this report, while insisting on projections that are linked to climate, failed to admit to many unknown variables that could influence outcomes. Often times, admitting there are unknown variables can lead to better understanding and also help improve public confidence.

Two risk assessment experts, Holger Hoffman-Riem and Brian Wynne, corresponding in a recent issue of the scientific journal Nature, point out that "the impossibility of taking unknown processes and variables into account may be a more fundamental obstacle to credible risk assessment than our inability to describe the known interactions accurately."

The second problem with the report is what could be termed the fallacy of unnecessary over-confidence. Now, in the defense of this report, the two authors admitted that "while model results cannot be used to look at the fine point of how a given species' distribution might change, they can provide an impression of the possible direction and potential magnitude of change in suitable climate for the species." But it is precisely that, given the very poor ability of climate models in calculating regional climate change, it is really not possible to even get a "sense" of how the regional climate can be affected by added carbon dioxide, never mind how the climate will eventually affect the bird migration pattern.

The authors also note that they have relied on the Canadian Climate Center's General Circulation Model to project the regional climate change over U.S. That model doubles carbon dioxide concentration from pre-industrial levels. In order to help determine whether one can or cannot be confident of the climate model, we must take a step back.

Charting the Problems

Instead of pretending to understand the virtual reality of doubling carbon dioxide (which may be expected about 50 to 100 years from now if everything else stays the same), let's look at the following charts. The first chart shows the difference between the seasonal temperatures calculated by the Canadian Climate model (denoted as CGCMI) and the observed temperatures over the 1921-1980 period. These comparison charts are taken from careful studies by Ruth Doherty and Linda Mearns performed in support of the U.S. National Assessment Report on the Potential Consequences of Climate Variability and Change (2000).



Focus in on any season: winter, spring, summer or fall. If the model can predict the temperature correctly, then you would see the whole map to be filled in green. Instead, one sees, for example, bright red over the northeast and dark blue over the southeast in the winter season. That is the real alarming sign of how unreliable the regional temperature pattern calculated by the Canadian Climate model is: the bright red meant that the modeled temperature is too warm by about 10 degrees Celsius or about 18 degrees Fahrenheit; in contrast the dark blue region meant that the temperature there is too cold by roughly the same amount.

To demonstrate that this flaw is not simply limited to the Canadian climate model, examine a similar comparison between the observed temperatures and a climate model's predicted temperatures produced by the United Kingdom Hadley Climate Centre's General Circulation Model (HADCM2).



There are not only large differences between the model's predictions and actual observed temperatures, there are also large differences among the temperatures calculated from different models.

And as for how well climate models perform in simulating regional precipitation that "affects the timing and availability of flowers, seeds, and other food sources for the birds," consider what the world's foremost authority on precipitation, Dr. David Legates, noted in his March 13 testimony in front of Senator James Jeffords's Committee on Environment and Public Works:

On three separate occasions -- in 1990, 1996, and again in 2000 -- I have reviewed the ability of state-of-the-art climate models to simulate regional-scale precipitation. ... In all three studies, the varied models I have examined agree that northeastern Colorado receives substantially more precipitation than northwestern Louisiana! That is in marked contrast with reality, where Louisiana is obviously wetter than Colorado.

Attempting to assess risk, even in the face of many unknowns, can be worthwhile. However, the clear misuse of an apparently science-based research conclusion to promote a political agenda is troublesome. The NWF/ABC report was clearly obsessed only with the risks of global warming in shifting patterns of bird habitat; little of the potential benefits of warming, say, with respect to vegetation are discussed. This is all happening while the scientific foundation for climate projections is sorely insecure. All of which adds up to make for a report that's full of speculation and conjecture, but not scientific fact. That's for the birds.
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