Cities cause Global Warming

Well, local warming at least:

Some parts of the Twin Cities can spike temperatures up to 9°F higher than surrounding communities thanks to the “urban heat island” effect, according to a new study from the University of Minnesota.

The study, which was funded by the Institute on the Environment and published in the Journal of Applied Meteorology and Climatology, used a network of 180 sensors deployed throughout the Twin Cities metropolitan area in residential backyards and city parks to paint the most detailed picture anywhere in the world of how temperature varies with time and place across pavement-filled metropolitan areas and surrounding communities.

Recording surface air temperatures every 15 minutes from August 2011 through August 2014 across nearly 2,000 square miles and using U.S. Geological Survey data to fine-tune differences at the neighborhood level, the study uncovered several surprises. Among them:

Temperatures in the urban core of Minneapolis, St. Paul and Bloomington average 2 °F higher in summer than in surrounding areas

The differential spiked as much as 9 °F higher during a heat wave in July 2012

Urban heat island effect is stronger at night in summer and during the day in winter

In urban areas during the winter when snow cover is less pervasive, temperatures are higher than rural areas in the daytime by an average of 2 °F.

I've been posting on the subject of Urban Heat Island for years; this is a good overview.  There has been a dismissiveness from the scientific establishment about this subject, but this peer-reviewed paper seems to be getting it right.  And the conclusion is inescapable: UHI raises daily low temperature readings and the "homogenization" computer programs use this anomaly to adjust rural weather station temperatures upwards.

Do this for hundreds of cities world wide and you do indeed get Global Warming.

The data sets are a frightful mess.  That's about the only thing "settled" about Climate Science.

More old Borepatch posts on this topic here, here (this one is excellent), and here.