Jay Wile
[Originally published as Yet Another Mistake Made in Climate Models]
When you read or listen to the news, you are faced with dire predictions about global warming, aka “climate change.” For example, ABC news states:
Global warming will be twice as severe as previous estimates indicate, according to a new study published this month in the Journal of Climate, a publication of the American Meteorological Society. The research, conducted by the Massachusetts Institute of Technology (MIT), predicts a 90% probability that worldwide surface temperatures will rise more than 9 degrees (F) by 2100, compared to a previous 2003 MIT study that forecast a rise of just over 4 degrees.
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Of course, a 9 degree Fahrenheit increase in global temperature will produce catastrophic results. How did the researchers come to the startling conclusion that there is a 90% chance it will happen? They used a computer model that attempts to simulate global climate under different scenarios. The problem, of course, is that the prediction is only as good as the model.
The obvious question, then, is how good are the models? The unfortunate answer is, “Not good at all.” As Distinguished Professor of Atmospheric Science Dr. John Christy has stated:
On average the models warm the global atmosphere at a rate three times that of the real world. Using the scientific method we would conclude that the models do not accurately represent at least some of the important processes that impact the climate because they were unable to “predict” what has occurred. In other words, these models failed at the simple test of telling us “what” has already happened, and thus would not be in a position to give us a confident answer to “what” may happen in the future and “why.”
Why are the models so bad? Because we don’t really understand climate science well enough to model it. A recent paper by Professor of Atmospheric Science Da Yang and his graduate student, Seth Seidel, provides a crystal clear example of what I mean. The paper’s abstract begins this way:
Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked.
Because of its lower molecular weight, water vapor is less dense than air at the same temperature, so air with a lot of water vapor floats in dry air at the same temperature and pressure. As the paper says, this is well documented. However, no one thought to see how that might affect the earth’s climate. Well, these two scientists decided to do just that, and based on their calculations, it actually cools the atmosphere.
Here’s a simplified explanation for why: In the tropics, we find regions of wet air and regions of dry air. At the same elevation, the regions must have roughly the same density. Otherwise, the less dense region would rise. Thus, if I have a stable region of wet air next to a stable region of dry air, the dry air must be warmer, so it has the same density as the wet air. Thus, at any given elevation, the dry regions will be the warmer regions. Well, water vapor is a potent greenhouse gas, so wet air doesn’t allow as much energy to escape from the earth as dry air. Since the dry air is warmer, there is more energy in it. That means the energy is more concentrated in the air that will allow more of it to escape. This, of course, results in the earth getting rid of more energy, which causes it to cool.
Now here’s the interesting part: the author’s calculations show that this effect becomes magnified the higher the ocean temperature. In other words, if the tropical oceans warm up, this effect will end up producing even more cooling. This is an example of a negative feedback system, where a change produces an effect that resists the change. The earth’s climate is full of negative feedback systems (see here, here, here, and here, for example). This is exactly what you expect for a well-designed system, and the earth is a very well-designed system.
In their paper, the authors state that the climate models from which dire warnings are generated have the ability to simulate this effect, but they don’t. They suggest that climate models should be adjusted to take the effect into account. Of course, I agree. Whenever we learn more about climate dynamics, the models should be updated.
However, my point is much more basic:
This is a well documented, well understood aspect of the atmosphere, but until now, no one has thought to see its effect on the earth’s climate. After investigation, it is found to produce negative feedback, which makes earth’s climate more resistant to change. If this well documented, well understood aspect of the earth’s atmosphere has not been properly taken into account in the climate models that are forecasting doom and gloom, how in the world can we put any faith in them?
