Guest essay by Larry Hamlin
NOAA’s U.S. contiguous U.S. summer (June through August) measured minimum and maximum temperatures trends over the period 1895 through 2024 (shown below from NOAA’s Climate at a Glance Times series data website) show clear and distinct differing temperature trend increasing growth compared to the calculated average temperature trend outcome.
The minimum temperature trend outcomes after 1985 climb significantly faster than do the maximum measured temperature trend outcomes. U.S. population data shows an increase of about 100 million during the 1980 to 2023 period.
Since the average temperature is not a measured value but instead the calculated mathematical average of the minimum and maximum measured temperatures {(TMax + TMin)/2} the average temperature calculated trend outcome is controlled and dominated by the much larger increase occurring in the minimum measured temperature trend versus the maximum measured temperature trend.
This differing trend distinction can be more clearly seen in the graphs below where the NOAA Climate at a Glance website time period interval is broken into the time intervals from 1895 to 1950 and 1950 to 2024 (where the Tavg value is controlled by Tmin not Tmax) respectively as shown below.
This outcome is consistent with and reflects the results of Dr. Spencer’s recent study shown below and found here.
Dr. Spencer also provided another study which displayed in graphical form the UHI impacts of U.S. and Global wide temperatures during the period June 1850 through June 2023 as shown below and found here.
In addition to large population growth UHIs acting as a prime driver of rising calculated Tavg temperature outcomes, these temperature measurements are also being significantly impacted by NOAA’s improper siting of thousands of temperature measurement stations.
These thousands of improperly sited temperature measurement devices do not meet NOAA/NWS siting standards and are located far too close to artificial heat sinks that falsely increase both maximum and minimum temperature measurements as addressed in detail here with an example clearly illustrating this huge system wide measurement problem shown below.
As noted in this report (page 18) the year 2019 Oak Ridge National Laboratory measurement station data accuracy experiment showed that flawed station siting temperature measurement impact outcomes were much greater during the evening periods (heat sink contributions to minimum temperatures were a factor of 3 larger than maximum day temperature contributions) versus during the day.
NOAA bases its evaluation of U.S. and global average temperature anomaly value changes over time by using and comparing the calculated Tavg values over time.
As indicted by the temperature measurement graphs and studies noted above NOAA’s contiguous U.S. calculated Tavg increasing trend values since about 1985 are clearly driven upward by station measurement siting flaws and UHI Tmin outcomes versus Tmax measured outcomes.
This results in NOAA’s calculated Tavg assessments of increasing temperature anomalies over time being a flawed and exaggerated claim driven by NOAA’s measurement siting inadequacies and population growth driven UHI impacts – and not “climate change”.
This outcome is also applicable to NOAA’s global wide calculated Tavg temperature anomaly increasing trend assessments as well.
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