Can Climate Models Predict Future Weather?

The Province newspaper reported Cohen’s results on the front page under the headline, “Weather Warning: BC will get wetter, stormier.” If that isn’t enough to pique your interest, the front-page warning continues: “Summer droughts, winter rainstorms, rising sea levels, more flooding, landslides and forest fires. That’s what’s ahead over the next 20 to 40 years as the world’s climate changes, and BC’s temperate weather turns extreme, an Environment Canada scientist warns.”

How accurate are these computer-model based predictions? Are they really meaningful and therefore reliable? Finding global climatic signatures from human activity is a monumental task. This is because heat energy added to the earth’s atmosphere by carbon dioxide is very small compared to other, natural forms of energy, like the heat carried by the world’s oceans and atmosphere as well as water vapor and clouds. Generating a computer mock-up of the climate system is a particularly monumental task given that much is still unknown about how these and many other forms of energy interact to affect climate.

According to the computer models, Canada should already be experiencing an increase in extreme high summer temperatures. But researchers from the Meteorological Service of Canada have proved the forecast wrong. “There is no indication of any consistent changes to the magnitude of extreme high daily maximum temperature during summer … [the] projection of increases in days with extreme high summer temperature has, at present, not been observed in Canada.”

What about extreme precipitation? Here, the same group of Canadian researchers said that “For the country [Canada] as a whole, there appear to be no identifiable trends in extreme precipitation (either frequency or intensity) during the last century. The observed increase in precipitation totals in the twentieth century was mainly due to increases in the number of small to moderate events.”

Researchers from the Meteorological Service of Canada, using the latest Canadian precipitation records, also determined that in “the last 50 years, heavy snowfalls in northern Canada have been increasing with marked decadal variation” (Zhang et al.) In other words, the observed pattern of change disagrees with the alarming forecast from most models that more snow will be melting, especially in areas of land-locked ice at high northern latitude areas of Canada.

But the strongest evidence against the claim of a marked global warming brought about by industrial activity predicted by the models is the temperature record of the lower troposphere (roughly 2 to 5 kilometre altitude), observed precisely by satellites and independently validated by balloon-borne instruments over the last 22 years. That layer of air failed to show any significant warming relative to the surface of the earth. This observed fact contradicts the prediction of all global climate models that the lower troposphere would warm faster and more strongly than the air near the surface of the earth as the concentration of carbon dioxide in the atmosphere rose over the last two decades.

Carbon dioxide, when released into the air, has a tendency to get mix quickly and so is distributed evenly throughout the whole column of the atmosphere. The air near the surface is dense and moist, so the addition of more carbon dioxide will introduce only very little imbalance of heat energy there. In contrast, according to the greenhouse effect theory, adding more carbon dioxide to the thinner and drier air of the troposphere will cause a chain of noticeable effects. First, the presence of more carbon dioxide in this uppermost part of the atmosphere will cause more infrared radiation energy to escape into space because there are more carbon dioxide molecules to channel this infrared energy upward and outward unhindered. Part of that infrared radiation is also being emitted downward to the lower troposphere and the surface where it is reabsorbed by carbon dioxide and the thicker air there. The layer of air at the lower troposphere, being in more direct contact to this down-welling radiation, is expected to heat more than air near the surface. Thus, adding more carbon dioxide to the atmosphere should cause more warming of the air around the height of two to five kilometres. In other words, the clearest impact of the greenhouse effect should manifest itself in the lower troposphere rather than near the earth’s surface.

The best data show no clear signal of the forecast global warming caused by industrial activity. The computer forecasts are exaggerating current temperature trends, so likely are exaggerating future warming. Since the computer forecasts are not yet reliable, British Columbians should put away their flood gear. As for the politicians? They should think twice before using these models as the basis for policy decisions. This is clear when you consider that the greenhouse effects, discussed above, are supposed to be one of the best known elements in the climate models that form the basis of the warnings like those on the front page of the newspaper.

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Dr. Sallie Baliunas is an astrophysicist at The Harvard-Smithsonian Center for Astrophysics and Deputy Director at the Mount Wilson Observatory. Dr. Willie Soon is a physicist at The Harvard-Smithsonian Center for Astrophysics and a senior scientist at the George C. Marshall Institute. They are both contributing authors to the Fraser Institute’s Risk Controversy Series.