"Scott W" wrote in message
...

From comments here and elsewhere the biggest criticism seems to be that the
probe at Heathrow may be too sensitive - the spike that people seem to be
worried about would not have been recorded with the old style
Mercury-in-glass thermo.

I don't think that's necessarily the correct conclusion. Without knowing the
response times of the relevant glass and electronic sensors it's difficult
to say, but my first instinct would be that the two are probably not very
different.

What I was flagging up elsewhere in the thread is that the peak was very
transient and being able to see this is a result made possible by the
one-minute resolution in the data record offered by a modern electronic AWS
as compared to the traditional one-shot Tx value in each 24-hour period.
It's entirely possible that many other records and near-records might show a
similar transient effect, but that will only become evident over time as the
records are studied and published in more detail.

But the other points were wondering to what extent this might be an internal
instrumental peak that's not fully representative of the surrounding air
mass and/or, as others have said, whether central Heathrow is a special
case. Just to repeat, this doesn't invalidate any record - it appears to be
a valid site-specific reading, but it might help to understand what was
happening.