Dr. Roy Spencer writes:
[F]or the average “suburban” (100-1,000 persons per sq. km) [weather] station [in the lower 48 States], UHI is 52% of the calculated temperature trend, and 67% of the urban station trend (>1,000 persons per sq. km). This means warming has been exaggerated by at least a factor of 2 (100%).
This also means that media reports of record high temperatures in cities must be considered suspect, since essentially all those cities have grown substantially over the last 100+ years, and so has their urban heat island.
To put a point on it: The “average” temperature of the U.S. (a meaningless statistic in itself) is dominated by readings taken at urban and suburban weather stations. It follows that the “average” is greatly inflated by the UHI effect, which prevails in about 2 percent of the area of the lower 48 States. It also follows that the cause of real “warming” (if there is any) is unknown because climate models are scientifically invalid.
Dr. Spencer’s result comes as no surprise to me. I wrote this four years ago:
The average annual temperature in the city of Austin, Texas, rose by 3.7 degrees F between 1960 and 2019, that is, from 67.2 degrees to 70.9 degrees. The increase in Austin’s population from 187,000 in 1960 to 930,000 in 2019 accounts for all of the increase. (The population estimate for 2019 reflects a downward adjustment to compensate for an annexation in 1998 that significantly enlarged Austin’s territory and population.)
My estimate of the effect of Austin’s population increase on temperature is based on the equation for North American cities in T.R. Oke’s “City Size and the Urban Heat Island”. The equation (simplified for ease of reproduction) is
T’ = 2.96 log P – 6.41
Where,
T’ = change in temperature, degrees C
P = population, holding area constant
The author reports r-squared = 0.92 and SE = 0.7 degrees C (1.26 degrees F).
I plugged the values for Austin’s population in 1960 and 2019 into the equation, took the difference between the results, and converted that difference to degrees Fahrenheit, with this result: The effect of Austin’s population growth from 1960 to 2019 was to increase Austin’s temperature by 3.7 degrees F. What an amazing non-coincidence.
How about them apples?