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Heatwaves Much Worse In 1930’s Say EPA

August 30, 2013
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By Paul Homewood

 

high-low-temp-figure1-2013

http://www.epa.gov/climatechange/science/indicators/weather-climate/high-low-temps.html

 

The EPA comment:-

Heat waves were frequent and widespread in the 1930s, and these remain the most severe heat waves in the U.S. historical record (see Figure 1). Poor land use practices and many years of intense drought (the "Dust Bowl") contributed to these heat waves by depleting soil moisture and reducing the moderating effects of evaporation.

 

This is how the index is built up:-

Figure 1 shows the U.S. Annual Heat Wave Index, which tracks the occurrence of heat wave conditions across the contiguous 48 states from 1895 to 2012. While there is no universal definition of a heat wave, this index defines a heat wave as a four-day period with an average temperature that would only be expected to occur once every 10 years, based on the historical record. The index value for a given year depends on how often heat waves occur and how widespread they are. For example, an index value of 0.2 could mean that 20 percent of the country experienced one heat wave, 10 percent of the country experienced two heat waves, or some other combination of frequency and area resulted in this value.

   

They also present the graph below, showing the ratio of record daily highs and lows. Qualifying stations only have to have been operating since 1950, so there will be a much higher ratio of daily highs than if only stations operational in the 1930’s had been included.

To be fair to the EPA, this graph was based on work by UCAR’s Gerald Meehl. But as it is so misleading, why did they publish it?

 

high-low-temp-figure4-2012

http://www.epa.gov/climatechange/science/indicators/weather-climate/high-low-temps.html

from → Climate Change
2 Comments
  1. QV permalink
    August 30, 2013 11:01 am

    “While there is no universal definition of a heat wave, this index defines a heat wave as a four-day period with an average temperature that would only be expected to occur once every 10 years, based on the historical record. ”

    This seems to define a “heatwave” in terms of temperatures compared to normal levels, rather than in absolute terms.

    Is it possible that if temperatures increase over time, the temperature which would be expected to occur every 10 years would increase, resulting in no increase in “heatwaves” as defined above?

    It seems that using the above definition it would be possible to have a “heatwave” in a climate with temperatures below zero, if the normal temperature was cold enough.

  2. Brian H permalink
    September 1, 2013 1:24 am

    Climate Science is a mound of decaying cherries.

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