Canberra’s “hottest ever” September record due to thermometer changes and a wind profiler

With only a million dollars a day it’s hard for the BoM to keep up with their own stations. Luckily Bill Johnston has arrived to help out for free. The BoM announced that it was Canberra’s hottest ever day last week, but forgot to check whether the heat was due to the site moving three times, changes in thermometers and a wind profiler they installed themselves in 2010.

Normally the BoM would detect and correct for these sorts of things by using Homogenisation Magic (HM). That’s where they spot these effects by comparing a station with surrounding stations. However in this case HM missed all three site moves and the wind profiler. It looks like those might add up to 2.2°C of artificial warming. Nothing to worry about, but the hottest ever record will have to be shredded, and naturally, the BoM will need to issue a correction with at least as much fuss and coverage as the mistaken headlines. It’s only fair…

After the effect of rainfall is removed there are at least three site moves, a screen change, equipment change, and alterations to the surrounding area that may influence the site. These step changes align with documented […]