Stuff nobody cares about

These days "I believe the science" really means "I believe the science that my team endorses".  I've mostly stopped posting much about climate science because people don't care about the actual, you know, science.  It's devolved into tribal posturing.

But here is a grab bag from the past few months of actual, you know, climate science.

The impact of urbanization on global temperature

While we all know that urban areas are warmer than rural areas, especially at night and during the summer, does an increase in urbanization lead to spurious warming at the GHCN stations that experienced growth (which is the majority of them)?

And, even if it did, does the homogenization procedure NOAA uses to correct for spurious temperature effects remove (even partially) urban heat island (UHI) effects on reported temperature trends?

John Christy and I have been examining these questions by comparing the GHCN temperature dataset (both unadjusted and adjusted [homogenized] versions) to these Landsat-based measurements of human settlement structures, which I will just call “urbanization”.

...

NOAA’s homogenization produces a change in most of the station temperature trends. If I compute the average homogenization-induced change in trends in various categories of station growth in urbanization, we should see a negative trend adjustment associated with positive urbanization growth, right?

But just the opposite happens.

[Borepatch comments]  So the science as performed today takes a known problem of urbanization induced (false) temperature rise and corrects it so that it rises even more.  But remember, kids - the arctic will be ice-free by 2013.  Just ask Al Gore.

Changing how you measure record temperatures to get more record temperatures

The Australian Bureau of Meteorology (BoM) regularly claims new record hot days, and Australian scientist report that heat records are now 12 times more likely than cold ones. But how reliable – how verifiable – are the new records?

I have been trying for five years to verify the claim that the 23 September 2017 at Mildura was the hottest September day ever recorded in Victoria. According to media reporting at that time, it was the hottest September day all the way-back to 1889 when records first began. Except that back then, back in September 1889, maximum temperatures were recorded at Mildura with a mercury thermometer. Now they are recorded with a temperature probe that is more sensitive to fluctuations in temperature and can thus potentially record warmer for the same weather.

In the absence of any other influences, an instrument with a faster response time [temperature probe] will tend to record higher maximum and lower minimum temperatures than an instrument with a slower response time [mercury thermometer]. This is most clearly manifested as an increase in the mean diurnal range. At most locations, particularly in arid regions, it will also result in a slight increase in mean temperatures, as short-term fluctuations oftemperature are generally larger during the day than overnight.” Research Report No. 032, by Blair Trewin, BoM, October 2018, page 21.

To standardise recordings from temperature probes with mercury thermometers, one-second readings from probes are normally averaged over one minute – or batches of ten second readings are averaged and then averaged again over one minute. That is the world-wide standard to ensure recordings from temperature probes are comparable with recordings from mercury thermometers. But the Australian Bureau of Meteorology do not do this, instead they take one-second instantaneous readings and then enter the highest of these one-second spot readings for any given 24-hour period as the official maximum temperature for that day.

[Borepatch comments] You will no doubt be shocked to learn that with all these new record high temperatures, Sydney has just experienced the longest consecutive number of days with a high temperature reading below 30 degrees Celsius in 130 years.  And remember, the highest temperature ever recorded in the USA was in 1913.  Also remember that 14 States set high temperature records (that stand to this day) in the summer of 1936.  That was 87 years ago.