Guest post by David Middleton
My State is currently in the grip of a very severe drought…
Professor Andrew Dessler, an atmospheric sciences professor at our nation’s greatest university, recently authored a column about our drought in the Bryan-College Station Eagle…
Published Tuesday, August 30, 2011 12:05 AM
Paying the price for climate change
By ANDREW DESSLER
Special to The Eagle
Texas Gov. Rick Perry stirred up controversy on the campaign trail recently when he dismissed the problem of climate change and accused scientists of basically making up the problem.
As a born-and-bred Texan, it’s especially disturbing to hear this now, when our state is getting absolutely hammered by heat and drought. I’ve got to wonder how any resident of Texas — and particularly the governor who not so long ago was asking us to pray for rain — can be so cavalier about climate change…
I know that climate change does not cause any specific weather event. But I also know that humans have warmed the climate over the past century, and that this warming has almost certainly made the heat wave and drought more extreme than it would otherwise have been.
Dr. Roy Spencer had an interesting take on Dr. Dessler’s column in his blog…
Dessler vs. Rick Perry: Is the 2011 Texas Drought Evidence of Human-Caused Climate Change?
September 5th, 2011 by Roy W. Spencer, Ph. D.
One of the most annoying things about the climate change debate is that any regional weather event is blamed on humans, if even only partly. Such unscientific claims cannot be supported by data — they are little more than ambiguous statements of faith.
Andy Dessler recently made what I’m sure he thought was a safe claim when faulting Texas Gov. Rick Perry for being “cavalier about climate change” (as if we could stop climate from changing by being concerned about it).
Dessler said, “..warming has almost certainly made the (Texas) heat wave and drought more extreme than it would otherwise have been.”
This clever tactic of claiming near-certainty of at least SOME effect of humans on weather events was originally invented by NASA’s James Hansen in his 1988 Senate testimony for Al Gore, an event that became the turning point for raising public awareness of “global warming” (oops, I’m sorry, I mean climate change).
The trouble is that climate change theory predicts changes, up and down, in just about anything you can imagine. So, anything unusual that happens anywhere, anytime, is deemed “consistent” with global warming.
According to Dr. Spencer the current national drought conditions are not exceptional; nor is there any statistically significant trend…
And, while Texas is experiencing a record-setting drought; the “record” is just over a century-long and there is no trend at all…
The lack of a trend in the precipitation data made me wonder… Just how often should we be setting precipitation records if the annual variation is random?
The record only goes back to 1895. Does anyone know how often record highs and record lows should be broken in such a short time series?
At a record length of 117 years, there was a 1% chance of setting a new record high in the 117th year…
The probability, pn(1), that the nth observation of a series xm= x1, x2, … xn has a higher value than the previous observations [pn(1) = Pr(xn > xi |i < n)] can be expressed as:
pn(1)= 1/n (1)
provided the values in series are iid random variables.
The cumulative probability says that 5 records should have been set between 1895 and 2011.
So, let’s have a look at the data. I downloaded the summer precipitation data for Texas from NCDC’s “U.S. Climate at a Glance” page…
In order to analyze the frequency of record excursions, I plotted the absolute value of the annual summer precipitation anomaly along with an “expected records” curve…
There have been 5 record excursions from the average annual summer precipitation – Exactly what there should have been in a random series of numbers. And the records have occurred with the expected frequency of a random series of numbers. The fifth record excursion should have occurred between 1945 and 2030 – It occurred in 2007.