Further holes have been blown in the regularly adjusted global and local surface databases that show increasingly implausible rates of warming. The latest work from Messrs Roy Spencer and John Christy reveals that since 1978 about half of the summer night-time warming across 10 mostly metro areas of Canada was due to increased urbanisation. This urban heat effect accounted for 20% of the day-time warming produced by ‘homogenised’ temperature datasets. The two atmospheric scientists recently published similar results showing 50% less warming over 50 years across the eastern United States.
As the scientists note, the issue around correct temperature measurement is important “since rational energy policy should be based upon reality, not perception”. To the extent that global warming estimates are exaggerated, “so will be energy policy decisions”, they note. Reductions in actual warming mean “climate models become increasingly irrelevant”.
Dr. Roy Spencer and Professor John Christy both work out of the University of Alabama in Huntsville, where they compile the accurate UAH satellite monthly temperature record. This consistently shows less global warming than surface datasets, but is rarely mentioned in the mainstream media. In January, Google AdSense demonitised Spencer’s blog showing the UAH monthly records on the grounds that it contained “unreliable and harmful claims”. Professor Christy is the Alabama state climatologist, and Dr Spencer is partly funded through his office.
Their grounding-breaking work attempts to remove distortions caused by increasing urban heat, and uses human-made structure density data over 50 years supplied by the Landsat satellites. They use a dataset of urbanisation changes called ‘Built-Up’ to determine the average effect that urbanisation has had on surface temperatures. Urbanisation differences are compared to temperature differences from nearby weather stations. More detail on the methodology behind their work can be found here.