A new U.S. Geological Survey (USGS) study bolsters evidence that weather stations relied upon by government scientists to measure global warming are being encroached upon by heat-trapping, artificial surfaces that can bias thermometer readings.
USGS found 32 percent of weather stations in the U.S. Historical Climatology Network (USHCN) used by the National Oceanic and Atmospheric Administration (NOAA) saw impervious surface (like concrete and asphalt) area increase more than 20 percent between 2001 and 2011.
“What this suggests, is that like Las Vegas, which has had huge infrastructure boosts in the last 50 years, that the minimum temperature is creeping upwards, and that biases the mean temperature used to look for the ‘global warming signal,’” veteran meteorologist Anthony Watts wrote on his blog Watts Up With That.
Watts has been arguing for years that thermometers read asphalt and other impervious surfaces too hot because “such things act as heat sinks, which increase the night-time temperature when they released the stored energy from the sun that was absorbed during the day as infrared, warming the air near the thermometer.”
These heat sinks bias “the minimum temperature upwards,” according to Watts, who co-authored a study last year that found well-sited stations only exhibited 2/3 the warming trend of poorly-sited stations.
Watts’ study suggests NOAA was “adjusting” temperature readings to match those of “compromised” stations where temperature readings were showing more warming than “unperturbed,” well-sited stations.
“NOAA would do well to remove stations that have been encroached upon like this, but they stubbornly hold onto this flawed data, insisting they can ‘adjust’ it to be accurate,” Watts wrote. “I say bollocks to that.”
These “unperturbed” stations don’t need to be adjusted by NOAA because they had not been moved, had any equipment changes, or change in the time temperatures were observed.
“Since the USA is so highly over-sampled with thousands of weather stations, it is far better to discard noisy and imperfect data, and use only those stations that have not been biased by infrastructure increases, but retain only the best stations with pristine data,” Watts wrote.
NOAA temperature adjustments have come under increased scrutiny in recent years. Critics, like Watts, have pointed to the fact that thermometers can be located many miles apart and be biased by their immediate surroundings.
For example, data from the most advanced climate monitoring system shows the U.S. has undergone a cooling trend over the last decade.
NOAA’s U.S. Climate Reference Network (USCRN) consists of 114 stations and was developed to provide “high-quality” climate data. USCRN stations were put in areas NOAA expects no development for the next 50 to 100 years.
NOAA essentially chose locations so they don’t need to be adjusted for “biases” in the temperature record. These stations show a slight cooling trend over the U.S. for the past decade.
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