Guest essay by Larry Hamlin

The “gold standard” for EPA heat wave established data in the U.S. over the last 125 years is the U.S. Annual Heat Wave Index for 1895-2020 shown below which is Figure 3 from the EPA’s recently modified climate change heat wave indictors website.

The EPA notes the following description of the clearly obvious record high heat wave multi-day extreme heat event occurrences of the 19030s depicted in Figure 3 above as follows:

“Longer term records show that heat waves in 1930s remain the most severe in recorded U.S. history (see Figure 3). The spike in Figure 3 reflects extreme, persistent heat waves in the Great Plains region during a period known as the “Dust Bowl.”  Poor land use practices and many years of intense drought contributed to these heat waves by depleting moisture and reducing the moderating effects of evaporation.”

“Figure 3 provides another perspective to gauge the size and frequency of prolonged heat wave events. It shows the U.S. Annual Heat Wave Index, which tracks the occurrence of heat wave conditions across the contiguous 48 states from 1895 to 2020. This index defines a heat wave as a period lasting at least four days 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 such severe heat waves occur and how widespread they are.”

“Temperature data are less certain for the early part of the 20th century because fewer stations were operating at that time. In addition, measuring devices and methods have changed over time, and some stations have moved. The data in Figure 3 have been adjusted to the extent possible to account for some of these influences and biases, however, and these uncertainties are not sufficient to change the fundamental nature of the trends.”

Figure 3 of the EPA heat wave index reflects heat wave outcomes for the U.S. over the last 120+ years that is consistent with and supported by data presented in the Climate Science Special Report, Fourth National Climate Assessment (NCA4), Volume I report which presents an authoritative assessment of the heat wave climate science, with focus on the United States. 

Chapter 6 of the report titled “Temperature Changes in the United States” notes time related changes in the U.S. for Coldest and Warmest Temperature averages for the period from 1900 to 2018 as follows:  

“Time series (bottom) depict the area-weighted average for the contiguous United States. Estimates are derived from long-term stations with minimal missing data in the Global Historical Climatology Network-Daily dataset.”

The Climate Science Special Report further notes:

Since the mid-1960s, there has been only a very slight increase in the warmest daily temperature (Warmest Temperature graph above) of the year (amidst large inter annual variability). Heat waves (6-day periods with maximum temperature above 90th percentile for 1961-1990increased in frequency until the mid-1930’s, became considerably less common through the mid-1960s, and increased in frequency again thereafter (Figure 6.4 below). As with warm daily temperatures, heat wave magnitude reached a maximum in the 1930s. The frequency of intense heat waves (4-day 1-in-5-year events) has generally increased since the 1960s in most regions except the Midwest and the Great Plains.” 

Figure 6.4

EPA changed its Climate Change Indicators page for Heat Waves after Biden and the climate alarmist Democrats took power in 2020 with the new manufactured alarmist graphics trying to portray increasing heat waves while concealing the “gold standard” Heat Wave Index as shown below.

The “gold standard” measured data representing the prior 125 year period of U.S. heat wave occurrences and intensity was hidden in a tiny thumbnail size Figure 3 in the lower right corner and replaced with a page providing politically driven increasing heat wave climate alarmist deceptive graphics that excluded the period prior to 1960 thus removing over 60+ years of measured heat wave data from view (Joseph Stalin era disappearing act) as summarized below.

“A typical example is the indicator for heat waves. This is illustrated in the left panel of the figure below, depicting the EPA’s representation of heat wave frequency in the U.S. from 1961 to 2019. The figure purports to show a steady increase in the occurrence of heat waves, which supposedly tripled from an average of two per year during the 1960s to six per year during the 2010s.

Unfortunately, the chart on the left is highly deceptive in several ways. First, the data is derived from minimum, not maximum, temperatures averaged across 50 American cities. The corresponding chart for maximum temperatures, shown in the right panel above, paints a rather different picture – one in which the heat wave frequency less than doubled from 2.5 per year in the 1960s to 4.5 per year in the 2010s, and actually declined from the 1980s to the 2000s.

This maximum-temperature graph revealing a much smaller increase in heat waves than the minimum-temperature graph displayed so boldly on the EPA website is dishonestly hidden away in its technical documentation.”

“A second deception is that the starting date of 1961 for both graphs is conveniently cherry-picked during a 30-year period of global cooling from 1940 to 1970. That in itself exaggerates the warming effect since then. Starting instead in 1980, after the current bout of global warming had begun, it can be seen that the heat wave frequency based on maximum temperatures (right panel) barely increased at all from 1981 to 2019. Similar exaggeration and sleight of hand can be seen in the EPA indicators for heat wave duration, season length and intensity.”

“A third deception is that the 1961 start date ignores the record U.S. heat of the 1930s, a decade characterized by persistent, searing heat waves across North America, especially in 1934 and 1936. The next figure shows the frequency and magnitude of U.S. heatwaves from 1900 to 2018.

The frequency (top panel) is the annual number of calendar days the maximum temperature exceeded the 90th percentile for 1961–1990 for at least six consecutive days. The EPA’s data is calculated for a period of at least four days, while the heat wave index (lower panel) measures the annual magnitude of all heat waves of at least three days in that year combined.

Despite the differences in definition, it’s abundantly clear that heat waves over the last few decades – the ones publicized by the EPA – pale in comparison to those of the 1930s, and even those of other decades such as the 1910s and 1950s. The peak heat wave index in 1936 is a full three times higher than it was in 2012 and up to nine times higher than in many other years.”

The EPA also prominently featured a misleading and erroneous deceptive temperature display highlighting the numbers of daily high and high daily low temperatures over the period 1910 to 2020 as shown below.

However, comparisons of this deceptive data trend of numbers of daily high and daily high low temperatures compared to the “gold standard” measured heat wave index occurrence and intensity relevant trend data shows the numbers display scheme trend is clearly inconsistent with the measured U.S. EPA Heat Wave Index data trend by trying to hide the clearly dominant 1930s peak and exaggerate the post 1980 period as shown below. 

This deceptive temperature numbers scheme trend is also clearly inconsistent with the “Warmest Temperature” data trend presented in the Fourth U.S. National Climate Assessment Report that shows little increase in Warmest Temperatures after the 1960s as shown in the graph below.

The National Climate Assessment Report “Warmest Temperature” trend data graph above shows that the average maximum temperature during any given heat wave has declined in the U.S. from 101°F in the 1930s to 99°F since the 1980s. 

The deceptive temperature numbers scheme trend is also clearly inconsistent with the “Warm Spells” (heat wave) data trend over the 1900 to 2018 period presented in the Fourth U.S. National Climate Assessment Report by trying to conceal the clear record high heat wave occurrences and intensity of the 1930s and exaggerate the post 1980s period as shown in the graph below.

The National Climate Assessment Report average duration of “Warm Spells” (heat waves) shown above has declined from around eleven days during the 1930s to 6.5 days during the 2000s. In other words, the average duration of heat waves have declined by nearly 41% since the 1930s.

The same complete lack of trend consistency is also present in another deceptive graphical portrayal using the record daily high and record daily low ratio data to falsely suggest increasing temperatures and heat wave trends compared to the “gold standard” heat wave occurrence and intensity data trend as shown below. 

This same clear inconsistency exists in comparisons of record high and low ratio data trend schemes compared to “Warmest Temperature” data trend and “Warm Spells” (heat wave) data trends respectively from the Fourth U.S. National Climate Assessment Report by these schemes trying to hide the peak temperature and heat wave period of the 1930s while exaggerating the post 1980 period as shown in the graphs below.

The use of politically contrived deceptive schemes using number of daily highs and high daily lows and ratios of number of daily high and lows are completely inadequate and inappropriate to substitute for measured warmest temperature and heat wave data trends in defining the climate behavior over time in the U.S. that  long established and superior scientific assessments by the EPA Heat Wave Index data trends and National Climate Assessments Report Warmest Temperature and Warm Spells data trends have provided.   

However, comparisons of the number of daily U.S. maximum temperatures above 100- and 105-degrees F over the period from 1895 to 2018 (with that data showing that very hot days in the U.S. over 100 degrees F were much higher in the 1930s than at any other time in the last 125 years) is clearly consistent with the U.S. “gold standard” heat wave occurrence and intensity data trend as shown below.

Additionally, the USCRN temperature network maximum temperature anomaly measurements for the contiguous U.S. also provides consistent agreement with the EPA heat wave index data trend associated time interval as shown below from a prior WUWT article      


“NOAA measurements of temperature anomaly data across the contiguous 48 U. S. States (Parameter: Maximum Temperature Anomaly; Time Scale: 1-Month; Months: All Months) using its most reliable USCRN temperature anomaly measurement data system establishes that the U.S. is not experiencing increasing “extreme heat” as presented and established below using NOAA temperature anomaly data which clearly shows that the nations maximum temperature anomaly measurement data has no increasing trend and in fact has declined since temperature anomaly peaks in years 2006 and 2012.”

Biden and the Democrat’s Administration scientifically unsupported “extreme heat” politics is promoting climate alarmist advocates to manufacture politically contrived  deceptive propaganda schemes using graphically devised presentations that are both misleading and erroneous in falsely portraying that the U.S. is experiencing increasing “heat waves” and “extreme heat” to push its massively costly, bureaucratically onerous, scientifically flawed and completely real world meaningless climate alarmist agenda.   

via Watts Up With That?

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October 25, 2021