Saturday, September 02, 2006

Predicting the Weather - Foggedaboutit

I grew up in St. Louis where the mantra was, "If you don't like the weather now, wait an hour. My friend Mike Williams and his lovely wife have just moved from the "boring" perfect weather in West Los Angeles to the exciting, not-so-perfect weather in St. Louis. Mike posts that the weatherman is never right in St. Louis, and gives a few examples. He ends by suggesting that the huge number of variables in the weather system there makes it a tough job to predict weather with any accuracy.

Los Angeles, on the other hand, has far fewer variables. It is not going to include snow, sleet, tornadoes, hurricanes, or even under 40˚. And we would have the general sense that local weather jockies, Johnny Mountain and Dallas Rains, get it right most of the time. How hard is it to read "Sunny and mild tomorrow" every single day. They would then be correct about 300 days a year.

Look a bit deeper, however, and things begin to break down a bit. Since we know the general weather almost every day, we primarily want to know what the temperature is going to be. The high will probably be between 70 and 100, even more likely between 70 and 95 almost every day in Spring, Summer, and Fall. So, with that more limited issue to deal with, how does the local weatherman come out? Not too well!

I plan to do a longer term look over the next month or so, but for now I took the last two weeks. Here are the results as extracted from the Los Angeles Times between Tuesday Aug 22 and Saturday September 2, 2006.

The 5 day forecast was off by an average of 9.2 degrees
The 4 day forecast was off by an average of 8.2 degrees
The 3 day forecast was off by an average of 8.4 degrees
The next day forecast was off by an average of 5.4
The same day forecast was off by an average of 5.1

While it was heartening to see that the closer the forecaster was to the date being forecast, the closer they got to the actual temperature, it seemed astounding to me that we put any merit at all in these guesstimates.

In fact, using my own guess that the temp will not be above 95 or below 70 this time of year, I might then use 82.5 every day as my forecast. If I had done so, I would have done better than the forecaster. Their average was 81.36, over 1 degree further off than my estimate. Only on the same day forecast would I have been bested. Here, their estimate was average of 84.

OK! So What? So, these are the guys that are telling us to spend trillions of dollars and potentially wreck entire industries because of their predictions regarding global warming.

In a new study just released by the
Intergovernmental Panel on Climate Change, the most respected international agency making pronouncements of great certainty with regard to future global temperature changes, they have dramatically changed their estimates since just five years ago. Instead of a potential maximum leap of 5.8˚ C , they are now saying a maximum 4.5˚ C in the next 100 years.

If we were to take a look at this 20% revision in just 5 years, and we were to compare it to the revisions by the LA Times between the 5 day and next day forecast, it would not be unreasonable to suppose that the 50 year forecast might easily end up being off by a factor of 100%. In other words, maybe we won't have any warming, and we might even have cooling. And just for a moment imagine the magnitude of additional variables that go into an estimate of global warming over 50 years vs the temperature in LA in 5 days from now.

Wouldn't it make sense to get a bit better at this before we recommend purposely destroying our economy in the next 10 years in order to save our economy from an uncertain catastrophe in 50 years.

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