By Paul Homewood

Roy Spencer has carried out a detailed analysis of how UHI may be affecting US temperature trends.

He concludes that at least half of the claimed increase of 0.26C/decade since 1973 is due to UHI:

In short, he has ignored the USHCN network of stations, which have been heavily adjusted for Time of Observation Bias (TOBS) and homogenised, but are also affected by UHI. Instead he concentrates on 311 stations with hourly data, which thus avoids the need for TOBS.

These two graphs tell the story:

Fig 2 plots the temperature trends for all USHCN stations against the 2020 population density. There is a marked correlation between the two, the higher the population density the high the temperature increase.

A similar pattern emerges with the 311 ISD stations, many of which have low population density as they are at out of town airports.

Extending the linear fit back to zero population suggests the real US temperature trend, excluding the spurious UHI element, is only 013C/decade.


February 13, 2021 at 07:15AM