13 November 2009

Mother Nature's Two For One Sale on Record Highs

Posted by Dan Satterfield

Not that it will change any minds. The overwhelming evidence of the last decade has convinced all those it will I think, but just in case there are those who are just beginning to ask questions…

A few months back, I was adding up the record highs and the record lows for some sample years in the 1990’s and 2000’s. A friend tipped me to the raw data. He told me that there was a definite trend, with a marked decrease in record lows and  an  increase in record highs.

With just a little bit of research, I quickly spotted the pattern.  Since the planet is warming due to increased greenhouse gases, it was no real surprise. I really should have written something about it back then, but it would be anecdotal and not science.

Something interesting to understand here.

If the temperatures are being affected by heat from urban areas due to the urban heat islands, or changing land use, like cutting down the forest and putting in a housing development, then both the daytime highs and the nighttime lows will increase at roughly the same rate. If it’s due to greenhouse gases which tend to block the long-wave radiation from getting out, then almost all of the climate models agree with what the Physics predicts. That Being:

You should see a marked decrease in record lows, and a slighter increase in record highs.

(Michael Tobis has an exc. explanation of this in response to a reader comment on his blog- see the link below.)

Gerald Meehl,  Senior Scientist at the University Centers for Atmospheric Research in Boulder and others worked together to take a long and detailed (non anecdotal) look at this. The peer reviewed paper is in press in the AGU journal Geophysical Research Letters.

What they found is yet another independent confirmation of the climate changing due to greenhouse warming.

Take a look at this graphic from Mike Shibao at UCAR.

Screen shot 2009-11-12 at 23.33.06Below is a you tube video of an interview with Dr. Meehl.

Two of the best beat me to the punch on this story. Andy Revkin at “Dot Earth” at the NY Times and Michael Tobis of “Only In It For The Gold” You should read both of their posts today on this for an even better take on it.
There are now roughly twice as many record highs as record lows. The expectation from UCAR is that by 2050 we will see a ration of 20 to 1. That’s assuming we keep increasing the rate of greenhouse gas emissions. It can be hard to explain the difference between weather and climate.
This does it about as well as anything I’ve seen.
The cite on the paper by Meehl et.al is:

Meehl, G. A., C. Tebaldi, G. Walton, D. Easterling, and L. McDaniel

Relative increase of record high maximum temperatures compared to record low minimum temperatures in the U.S.

Geophys. Res. Lett., doi:10.1029/2009GL040736, in press