By Steven Goddard and Anthony Watts
Fort Collins, Colorado is most famous for Balloon Boy, and Boulder, Colorado is most famous for Jon Benet and Ward Churchill.
Both are hotbeds of Climate Science, with familiar names like Roger Pielke (Jr. and Sr.) Walt Meier, William Gray, Kevin Trenberth and Mark Sereeze. Both are of similar size (Boulder 91,000 and Fort Collins 130,000) and located in very similar geographical environments along the Front Range – about 50 miles apart. The big difference is that Fort Collins has tripled in size over the last 40 years, and Boulder has grown much more slowly. Fort Collins population is shown in blue and Boulder in red below.
Until the mid-1960s, NCDC temperatures in the two cities tracked each other quite closely, as you can see below. Again, Fort Collins in blue, and Boulder in red – with Fort Collins temperatures shifted upwards by two degrees to normalize the left side of the graph. Since 1965, temperatures in Fort Collins have risen much more quickly than Boulder, paralleling the relative increase in population.
The graph below shows the absolute difference between Fort Collins temperatures and Boulder temperatures since 1930. There is some sort of discontinuity around 1940, but the UHI imprint is clearly visible in the Fort Collins record. The Colorado State Climatologist, Nolan Doesken manages the Fort Collins Weather station. He has told me that it has never moved or changed instrumentation. and that he believes the increase in temperature is due to UHI effects.
Roger Pielke Sr. further commented:
“the Fort Collins site did have the introduction of the CSU Transit Center a few years ago, although this is well after the upturn in temperature differences between Boulder and Fort Collins started to increase.”
From the promotional photo on the CSU website, the Fort Collins USHCN weather station (below) seems reasonably sited.
However when you look at the Google Earth street view, you realize that it is surrounded by concrete, asphalt, nearby parking, and a building just 7.5 meters away (By the GE ruler tool). It would rate a CRN4 by the surfacestations rating. It also appears to have been modified since the promo photo was taken as there is a new fence with shrubbery and wood chips surrounding it.
Besides the pressure of CSU expansion, Fort Collins has seen an increase of about two degrees since 1970, corresponding to a population increase of 90,000. This is probably a little higher than Dr. Spencer’s estimates for UHI.
The Boulder weather station is similarly sited since the concrete path is just under 10 meters away.
It is at the campus of NOAA’s and NIST’s headquarters in Boulder. Anthony Watts visited the station in 2007 and took photos for the surfacestations project. Like Fort Collins, it gets similar expansion pressure due to nearby construction as seen in this aerial photo.
Here are the temperature records fro these two USHCN stations:
There is some UHI effect visible in the Boulder record below, but much less than Fort Collins.
We have two weather stations in similarly sited urban environments. Until 1965 they tracked each other very closely. Since then, Fort Collins has seen a relative increase in temperature which tracks the relative increase in population. UHI is clearly not dead.