Guest post by Dr. Richard Alan Keen
Oh my God, I’m going to fry!!!
Watts Up With That posted a prediction by Noah Diffenbaugh at Stanford that heat waves will increase across the U.S. over the next few decades, with the largest increases being in the higher elevations of the Rockies, especially Colorado.
Since I live at 9,000 feet above sea level in central Colorado, I’m terrified! I don’t think I can handle more days over 80F (it’s never reached 90 here).
Since CO2 has already increased by 110 ppm, any effects of increasing atmospheric carbon should be noticeable by now. Here’s a chart of the highest temperature recorded in the state of Colorado for each year since 1888.
The hottest recorded in the state is a pretty good indicator of the occurrence of heat waves, and a trend should indicate a change in heat wave frequency. I didn’t want to break the beauty of the graph by plotting the linear trend line, which is essentially horizontal with an upward trend of about 0.5F over the 120 year period. That would indicate little change in the occurrence of extreme heat in Colorado.
Is extreme heat getting more frequent in Colorado? During the first half of the record, from 1888 to 1947, Colorado had 17 years in which some place in the state reached 110F or higher. Since then, there’s been 15 year with 110-degree readings. It appears that Colorado heat waves haven’t gotten the word that they’re supposed to increase with the rising CO2 levels.
It also appears that I needn’t worry about a 90-degree day at my weather station for a while (that’s one reason I moved here).
Steve Goddard has a wonderful post on Watt’s Up With That detailing trends (or the lack thereof) in Colorado’s summer climate.
Here’s a broader look at Colorado’s climate – annual statewide mean temperatures for 160 years of record from four sources.
The data shown are:
NCDC combined divisional averages for the state;
USHCN and Hadley CRU gridded values for the Colorado “box” (USHCN and Hadley are so similar they are averaged into one time series);
NCAR-NCEP reanalysis surface temperatures for the Colorado “box”; and
Regional averages from stations in Colorado and neighboring states before 1895, when there were fewer stations in Colorado.
There’s a wealth of information here and many possible interpretations. The 30-year running mean emphasizes the PDO and AMO contributions. Colorado appears to follow neither oceanic oscillation very closely, but rather appears to respond to a mix of both oscillations.
More important is the lack of an overall trend in the temperatures. Colorado is predicted by many models to have the greatest warming of any state in the “lower 48”, but so far this warming is not evident. The warmest 30-year period remains 1933-1963 at 45.6F, 0.1F warmer than the most recent 30 years and 0.3F warmer than the first 30 years (1850-1879). The net warming from 1850-79 to 1980-2009 is all of 0.2F.
Although a warming signal is not evident over the entire record, there has been a warming since 1900 (which is what NCDC and others advertise as evidence of a warming Colorado). Even if one chooses to ignore the cooling after the warm 1860’s and concentrate on the 20th century, the bulk of the warming of that century occurred in a few years around 1930 – a bit early to be due to CO2.
Dr. Richard Keen
Co-op observer, climatologist, author, and teacher.