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The extent to which two widely-used monthly temperature datasets are affected by urbanization bias was considered. These were the Global Historical Climatology Network (GHCN) and the United States Historical Climatology Network (USHCN). These datasets are currently the main data sources used to construct the various weather station-based global temperature trend estimates.
Although the global network nominally contains temperature records for a large number of rural stations, most of these records are quite short, or are missing large periods of data. Only eight of the records with data for at least 95 of the last 100 years are for completely rural stations.
In contrast, the U.S. network is a relatively rural dataset, and less than 10% of the stations are highly urbanized. However, urbanization bias is still a significant problem, which seems to have introduced an artificial warming trend into current estimates of U.S. temperature trends.
The homogenization adjustments developed by the National Climatic Data Center to reduce the extent of non-climatic biases in the networks were found to be inadequate, inappropriate and problematic for urbanization bias. As a result, the current estimates of the amount of “global warming” since the Industrial Revolution have probably been overestimated.
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Just a quick correction. Line 886: “in try” probably should be “to try”
An addition to figure 11: I’ve found that the 694 german stations processed by GHCN v4 have become significantly more urbanised between 1975 and 2020. Within a 20 km radius, built-up areas increased by 71.3…71.5% and population density by 7.6…7.7%. (data coming from Orwell2022 on X and extracted from klymot)
Between 1988 and 2025, 482 weather stations were discontinued. 87% of these have been discontinued since 2001, with the focus on rural stations (15% less built-up area than the average).
The crackdown was particularly severe in 2013: 224 particularly rural stations were discontinued (with an average population density 18% lower than the average).
Between 2003 and 2015 GHCN v4 on discontinued more than 50% of germany’s long term (100a+) records.
If you look at Germany’s complete DWD station network though you don’t see these discrepancies at all. Stations being opened and closed on average fall within the same rural classification as the legacy stations, although the general increase in BU should be similar to +71.5%, since german settlement area doubled 1950…2005 and increased even four-fold 1883…2007.
Maybe someone should investigate this on a global level. The deviation from the averages of the station network are too large to be just coincidential. Maybe this falls in line with the “Pause buster” efforts following a very cold 2010 and climate gate 2009.