Wood Romances

A new paper[1] by Spencer and Christy was published on urban heat islands (UHI), and I'd like to clarify what it says and what can actually be claimed as a result of it. The reason why has to do with a recent blog post from WUWT that claims the paper shows that 65% of global warming is due to UHI warming effects, rather than increasing greenhouse gas concentrations. Chris Rotter at WUWT says, A new study from the University of Alabama in Huntsville addresses the question of how much the Urban Heat Island (UHI) effect is responsible for the higher temperatures at weather stations across the world. Dr. Roy Spencer and Dr. John Christy have spent several years developing a novel method that quantifies, for the first time, the average UHI warming effects related to population density. Their finding: no less than 65% of “runaway global warming” is not caused by our emissions of carbon dioxide, but by the urbanization of the world. There's very little in this that resembles what the...

In another post , I covered some of the many reasons why scientists have concluded that urbanization biases are not responsible for any significant fraction of global warming. In order to avoid too much duplication with that post, I'll only briefly summarize the reasons: Homogenization Corrects Urbanization Bias. While cities are warmer than rural areas, they warm at about the same rate as rural areas. The bias is caused by urbanization. That is, as rural areas become more urban, they will warm at a faster rate than rural and urban areas. This bias is effectively removed by homogenization. Very Rural Stations Warm at Least as Rapidly as All Stations. Wickham et al 2013 compared the most rural land stations globally and compared them to all land stations. The study found that "very rural" stations were warming at least as rapidly as all stations. If urbanization biases were making a significant contribution to global warming, then the most rural stations would warm more sl...

Baltimore's Inner Harbor It is well-documented that cities are significantly warmer than rural areas. This effect is commonly described as an urban heat island (UHI). Some argue that some (or all) of the increase in global temperatures can be explained by the effect of the UHI effect on global temperatures. It makes some intuitive sense that this might be the case, but let's consider some important lines of evidence that suggest otherwise. Urbanization Bias Is Corrected with Homogenization. While urban areas are warmer than rural areas, urban areas are warming at about the same rate as rural areas, so temperature anomalies are not significantly affected by urban heat islands.[1] The bias actually comes from urbanization. As a rural area becomes more urban, it will warm at a faster rate than cities and rural areas. An area that is rural in 1950 but urban in 2020 will become progressively hotter due to urbanization, and not changing climatic conditions. However, numerous studies ...