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Polar versus Equatorial Warming

One of the earliest and consistent predictions of global warming theory is that the polar regions would increase in temperature to a far greater degree than the equatorial regions. This prediction is plausible for several reasons. First of all, the polar regions are subject to the ice-albedo feedback; i.e., as sea ice and snow fields melt the ground and open water absorb more of the Sun's radiation. Second, the air of the polar regions is dry, so dry that they are deserts as much as the Sahara is. Being dry the polar air has very little of the overwhelmingly most important greenhouse gas, water vapor. In moister regions carbon dioxide is a relatively small proportion of the greenhouse gases, but in the dry regions it is relatively more important. Thus if the concentration of carbon dioxide doubles there is relatively smaller effect in moister regions than in the dryer regions so the temperature effect of the increased carbon dioxide is greater in the dryer regions. But, if the atmosphere in the polar regions warms there will be more evaporation and thus a postive feedback from greenhouse effect of increased water vapor.

Some of the predictions from computer models are that there would be a five to one ratio of the increase in the temperatures in the polar region relative to the increase in the equatorial regions. All of this is plausible but how does the prediction compare with the facts. Theories and models fail generally not from what is included in them but from what is left out. Climate models are made up of components that derive from verified science such as thermodynamics and mechanics. Scientists from outside climatology look at these models and think they are valid because they consist only of components drawn from the hard sciences. The models can fail not because of what is there, but from what is not there. The real world is a much more complex system than what the models encompass. This is illustrated by the prediction of temperature change by latitude.

Robert C. Balling, Jr. gives a graph relevant to comparing a model prediction with the actual record. It is given in his article, "Observational Surface Temperature Records versus Model Prediction," which is published in Shattered Consensus: The True State of Global Warming (page 53). A fascimile of Balling's graph is given below.

Here we have the real world in all its complexity. Over the period 1970 to 2001 the Arctic region did have a greater temperature increase than the tropical region. It was not a five to one ratio however. The north polar region increased in temperature about 83 percent more than the tropic region. However in the south polar region there was no larger increase than the tropics, If anything the south polar region increased less in temperature than the tropics with Antarctica actually decreasing in temperature. If the increase in temperature in the north polar region is taken as a verification of the theory and global warming model then the record in the south polar regions is a denial of the validity of the theory and model. That is the real world in all its complexity.

Balling presents the estimates of temperature change by latitude from a model. He does not give the details of the model or models used for the estimates but he may be using results from models used by the Intergovernmental Panel on Climate Change. The model(s) generally overestimates the change in temperature but more so in the polar regions, particulary the Arctic. The model(s) predict that the temperature increase in the Arctic should be about four times what it is for the tropics. In the very high latitudes of the north polar region the temperature change is declining with latitude rather than increasing. It is not implausible that the actual temperature increase with latitude in the Northern Hemisphere is reflecting the effect of the band of urban-industrial civilization between 25°N and 70°N.

Another element left out of the comparison of temperature change by latitude is that there is much less global area in the higher latitudes than in the lower latitudes. Consequently the variability of zonal temperature is higher in the higher latitudes than in the lower latitudes. For more on this factor see Statistical Significance of Temperature Trends.

In the Southern Hemisphere the models predict an increase at 50°S that is about two and half times the actual increase. In Antarctica the model(s) predict a temperature increase which is about 30 percent larger than the temperature increase predicted for the tropics but the actual temperature change was negative.

The climate models have some successes but they are not hard science and they are not "ready for prime time." Human civilization would be greatly served if the climate modelers had the intellectual integrity to stop making sensationalistic predictions for the 11 o'clock news and admit much work must be done before the model projections are relevant for policy decisions.

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