That’s a good point, Honor. As far as the temperature index is concerned, the fact that urban stations are warmer than others is not the problem. The problem is that cities grow over time, which can make urban stations show a greater heating trend over time. That’s why all temperature indexes either have an express UHI correction (GISS) or use an algorithm that removes any warming bias due to the heat island effect. The authors did not do what one has to do to correct for any bias: analyze the trends over time. They also didn’t test to see if the temperature difference they observed was due to differences in elevation, differences in latitude, etc. There was nothing in the paper that justified the creation of their home brew station set.
UHI is one of the zombie issues that deniers bring up again and again, regardless of the evidence. Anthony Watts spearheaded the Surface Stations project to prove that poor station siting, especially urban areas, was the cause of the warming. He and his volunteer acolytes photographed weather stations, classifying them by quality. But when the data was gathered, it turned out that his high quality stations showed a greater heating trend than his low quality ones.
https://www.ncdc.noaa.gov/ushcn/station-sitingWhen climate skeptics, funded by Koch, formed a team to do their own global temperature index, one of the issues they scrutinized was, They tested their index for UHI and wrote a paper that showed their index (Berkeley Earth) had no UHI bias. And, to the sounds of weeping and wailing and gnashing of denier teeth, there was no significant difference between the skeptic’s temperature index and the other indexes prepared by mainstream climate scientists.
http://static.berkeleyearth.org/papers/ ... -1-104.pdfhttp://berkeleyearth.org/2018-temperatures/Incidentally, the Berkeley Earth team went into their project highly skeptical of the adjustments to raw data discussed in the OP. They described their findings Judith Curry’s blog.
https://www.google.com/amp/s/judithcurr ... -data/amp/They found no evidence of skullduggery. Their analysis also shows how Tony Heller’s complaints about the adjustments are one big cherry pick. The US represents around 5% of the land surface area. The smaller area one picks, the easier it is to find adjustments of larger magnitude. The paper shows that, if you look only at Africa, the adjustment algorithm results in a cooling trend. And Heller picked a smaller subset of the US weather stations precisely because it showed the trend he wanted, without ever explaining that the adjustments were higher because of changes made in that set of stations to standardize them. With Heller, it’s always cherries.
“The ideal subject of totalitarian rule is not the convinced Nazi or the dedicated communist, but people for whom the distinction between fact and fiction, true and false, no longer exists.”
― Hannah Arendt, The Origins of Totalitarianism, 1951
