Here's the original research: Observed increase in local cooling effect of deforestation at higher latitudes (treehugger.com)
Population density, for example, influences how many people are at risk in a given hot spot and alters a city's willingness to invest in local cooling. (scientificamerican.com)
(Global average temperature fell by about a degree during the Little Ice Age, although scientists have struggled to quantify local cooling.) (sciencemag.org)