CLEVELAND - You've heard it on TV a lot. "This is the warmest March ever!" "Its the warmest decade ever!" "Unprecedented warmth on the way!" I'll admit, these headlines do grab your attention.
And then you see Graphs like FIGURE 1 above. It shows record high temperatures in the decade of the 2000's outpacing record lows by more than 2 to 1. And, it points to recent warmth beating out all decades since the 1950s. Wow. Its worse than we thought, right?
Well, not so fast. Yes, we seen some warm temperatures recently. In particular, March 2012 saw some intense heat. Chicago headlines touted March of 2012 as the warmest March on record. Wow. That's impressive.
What they didn't tell you was where the measurements came from. The thermometer in Chicago is currently located at Chicago O'Hare Airport. Its been there since 1980. Before that, it was at Midway Airport and various other locations in Downtown Chicago . You may know that Downtown Chicago is subject to cooling breezes off of Lake Michigan, especially during unusually hot days in early spring. So, saying that Chicago's heat wave in March was unprecedented is a bit misleading since temperatures have only been measured at O'Hare for a mere 30 years. Its possible, and even likely, that Chicago, near O'Hare Airport had warmer March's in the past.
Now, back to the claim that the 2000s is the warmest decade ever. Notice that the graph starts with the 1950s. If we look back a little farther, we see a different picture. FIGURE 2 shows record high temperatures by decade for all US states combined since 1890. Notice the amount of heat records set in the 1930s! Few of us remember the Dust Bowl years back then. It was definitely an incredibly warm and dry decade for the United States. Look at the Palmer Drought Index for October 1934 (FIGURE 3 above). More than 50 percent of the US was suffering from a major drought! Ohio was incuded in the exceptional drought that year. Compare that to last year's "unprecedented" southern drought (FIGURE 4 above). Yes, Texas was incredibly dry. But the drought did not encompass as much of the US last year as it did in 1934.
The bottom line: Last year, and recent years for that matter, were not even close to matching the amount of drought and heat experienced in the US back in the 1930s.
Recent high temperature records do not outshine the incredible warmth of the 1930s. Recent heat waves are not unprecedented here in Ohio, nor in the United States. We all tend to have short memories. And we all love flashy headlines!
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