So, what has this NOAA experiment found? The bottom image (Image #3) tells that story - when compared to measurements from the old, inaccurate, non-pristine network, temperature "warming" in the U.S. is being overstated anywhere from
+0.5°C on average, up to almost +4.0°C (+0.9°F to +7.2°F) in some locations during the summer months.
To clarify, this range of overstatement depends on the given new and old stations being compared. However, when the new network versus old network results are examined in total, for the recent summer heat wave in the U.S., the old stations were reporting bogus warming during July that amounted to some
+2.1°F higher than the actual temperatures.