Arizona's Wildfires and Climate Change
And so it begins again. In 2012, while much of the U.S. was experiencing a drought, out came the series of climate alarmism articles in the mainstream media. Now that the wildfire season is underway in the western states, we see the same pattern emerging again.
The Associated Press's recent coverage of the Arizona wildfires, in a story provocatively entitled "How climate change affected the Arizona wildfire," included the following claim: "In Arizona, where a drought has persisted for nearly two decades."
Moving over to NOAA's National Climatic Data Center (NCDC), the Palmer Drought Severity Index (PDSI) for Arizona can be obtained between 1895 and 2012 on annual (January-December) and summertime (June-August) bases. The PDSI indicates drought conditions when index values are less than -1.99. Between 1992 and 2012, the average annual PDSI for Arizona was -1.03 -- or in the mid-range region between moist and drought conditions. Only 9 years over this period had drought conditions. Similarly, the summertime PDSI average in Arizona during this timeframe was -1.75 (still not meeting the criteria of a drought), and only 12 years were classified as having summertime drought conditions.
I am unsure as to how the AP defines a nearly two-decade-long persistent drought, but by my definition, it should involve a drought during each and every year (otherwise it's not "persistent," is it?). The climate conditions in Arizona do not meet this definition.
We can also ask whether there are any significant (p<0.05) time trends in Arizona's annual and summertime drought indices since records began in 1895. The answer is no.
The climate record also clearly indicates that Arizona experienced far more severe drought conditions during the first few years of the 1900s than this state has seen up to the present. Since 1995, there has been no significant change in either the annual or summertime PDSIs. In fact, the trends since 1995 are about as non-significant as can be had (p-values of 0.91 and 0.99, respectively). How do the climate alarmists explain this?
What about Arizona's temperature? The AP writes the following:
Over the past 35 years, Arizona has seen dramatic warming, with the state's 10-year average temperature jumping from 59.1 degrees Fahrenheit in 1977 to 61.4 degrees last year -- an increase of 2.3 degrees.
Referring once again to the NCDC database, we find no significant trends in Arizona's average annual or summertime temperature since 1995, and even strong evidence of a near-significant (p=0.06) declining annual temperature trend since 2000.
These findings certainly don't support the following hysterical statements from the AP article:
Climate scientist Jonathan Overpeck of the University of Arizona said unless greenhouse gas emissions are curbed, huge, fierce wildfires will become the norm ... scientists point to the Nobel Prize-winning Intergovernmental Panel on Climate Change, which in 2007 predicted that warmer summer temperatures were expected to increase fire risk.
How do we reconcile articles stating that "climate change affected the Arizona wildfire" with ever-increasing anthropogenic greenhouse gas emissions over the past two decades and the corresponding absence of any annual or summertime changes in Arizona's drought index or temperature over this period of time? Answer: we cannot.
Here is a recommendation for the AP (and the media outlets that run their stories). If you are going to write a story on climate change and the Arizona wildfires, present the complete data record. Cherry-picking is fine for cherries, but it's not appropriate for scientific data, and it certainly does nothing to improve scientific literacy among the general public.