A letter writer in today's Star Tribune claims that the global warming predictions are based on the same science that can be "incapable of accurately predicting local conditions just hours into the future." The Strib titled his letter "Global warming, Flawed science".
I think his understanding of science is what is flawed. First, what is accuracy in weather forecasting? Does he want the exact temperature to the nearest degree and the exact amount of precipitation to the tenth of an inch? Even if he wants the temperature within five degrees and definite precipitation if predicted, it might not happen. Weather does not behave with such precision; there are just too many unknown quantities. We are dealing with chaos.
Consider dust devils. Walking down the street, one may see a small whirlwind of snow or dust, no more than a foot in diameter and three feet high, that comes and goes in an instant. What happens if the sun shines through a hole in the clouds on a large parking lot? Isn't there going to be a big temperature difference between the parking lot and a park or lake nearby? Weather is filled with these little anomalies that can affect local weather.
However, if one looks at weather prediction as giving the general trend for a given area, then I think most forecasters do a darn good job. Rarely do we have a forecast of a clear, sunny day and get a rainstorm. On the other hand, we may get a forecast of precipitation and get none, the weather having been blown in a different direction by some of the chaos that can't be measured.
In other words, weather forecasters and climatologists can make reasonable predictions about trends, but they cannot give precision for a very specific locale or time. For example, in global warming, Europe may get colder. Why? If melting Greenland glaciers dump enough fresh water into the Atlantic, the Gulf Stream could be disrupted by either the decreased salinity or the cooler water. If the Gulf Stream is disrupted, Europe will get less warm air.
