Jennifer Marohasy
On 11 November 2011, the Australian Bureau of Meteorology replaced the probe in the automatic weather station that measures temperatures at Alice Springs Airport and the number of days with recorded temperatures above 40 degrees Celsius has increased significantly. This could have anything to do with anything related to changing gear and nothing to do with the weather. To know for sure, the office needs to make public parallel data for Alice Springs Airport, which is daily temperature data manually recorded from a mercury thermometer at the same weather station since May 21. 3, 1991 until at least April 1, 2019 (metadata here).
Alice Springs is close to central Australia and there are very few other weather stations in the area. Because the Bureau and other IPCC affiliated organizations use gridded methods to calculate climate variability and change, and because weather stations are far and few between central Australia, temperatures are recorded. at this station affects not only the calculation of the average Australian temperature, but also the global average temperature.
Although Alice Springs is a globally important weather station, I doubt it is reliably recording temperatures.
I have explained in previous posts in this series that the office uses a selection of different types of custom designed probes and that it does not numerically average with the highest instantaneous on-site readings or more. maximum for that day. We also know that while there is a mercury thermometer that also records temperature next to the probe in the Stevenson Monitor at Alice Springs weather station for at least 28 years, the office will not allow the generation of 28 years of data from this mercury thermometer. public. The Bureau has denied every Freedom of Information request I have participated in to date, and our most recent request is still being considered (in mediation) with the Administrative Appeals Court. Making this data public would be a quick way to confirm whether the probe in this automated weather station reliably records temperatures.
Just to be clear, since 1996, the Bureau has transitioned from manually recording daily temperatures from liquid in glass thermometers (mercury for maximum temperature and alcohol for minimum temperature) to a system automatically using probes, with probes more responsive to temperature fluctuations and thus capable of recording both hotter and colder for the same weather – except the Bureau has set limits on how cold temperatures can be recorded.
In Bureau Research Report No. 032 ‘Australian Climate Observation Reference Network – Surface Air Temperature (ACORN-SAT)’ Edition 2 (October 2018) Blair Trewin states:
In the absence of any other effects, devices with faster response times will tend to record higher maximum temperatures and lower minimum temperatures than devices with slow response times. than. This is most evident by the increase in the mean diurnal range. In most locations (especially in arid regions), it will also lead to a slight increase in mean temperatures, as short-term temperature fluctuations are generally larger during the day than at night.” (Page 21)
The limited parallel data I have from the Bureau’s Mildura weather station shows that for the same weather, a third probe was installed at Mildura on June 27, 2012. generally recorded warmer than 0.4 degrees C compared to mercury thermometers in the summer. I also explained that on the hottest days from June 2012 to January 2015 (parallel data available period), the observer did not enter a value from mercury in Form A8 . I suspect because the difference between the values from the probe and the mercury was so large that this data was rejected – never included in the official records.
It is clear from the calculations and graphs of my friend and colleague, Chris Gillham, that after the new probe was installed in Alice Springs in November 2011 and compared with 2009-2010, there was an additional 56 days at temperatures above 40 degrees Celsius (see chart included at the top of this blog post).
It is now important for the office to make public measurements from mercury thermometers that recorded temperatures in the same weather station in Alice Springs from March 21, 1991 until at least April 2019. This 28-year data will allow some comparisons with the temperatures from the new Alice Springs probe, which I hypothesize are exaggerating the maximum and, therefore, the global average temperature, which gives importance. Alice Springs’ importance to national and global temperature databases.
Mercury thermometers were used for official temperature measurements at Alice Springs until November 1, 1996.
According to the 2020 publication of the Bureau ‘An updated long-term homogeneous daily temperature data set for Australia’, the Bureau tested one-second variations within one minute at 6 a.m. and 3 p.m. on alternative temperature probes at 98 official weather stations. The Bureau reported an average increase in 1-minute temperature change of about 0.2 degrees compared with the previous poll at Alice Springs, while omitting this was negligible. The breakpoint is visible and compares only to the previous probe, giving no indication of any difference from the mercury thermometer or how this affects the record hot days. In order to properly assess the impact of alternative probes at all 98 official weather stations, the parallel data available from mercury thermometers recording temperatures at the same weather station needs to be made public as one. urgent problem.
In the absence of access to parallel data – and without any quality assurance and reliable research on issues arising from the Bureau’s transition to exploration – it is not possible to reliance on any statements made by the Bureau and/or other scientists using their data. data, about record hot days, fewer extreme cold days or a trend of faster warming that have been claimed, or anything like that.
Just to be clear, we can’t tell if the 1.5°C tipping point is imminent or if we have more time. That may be the case we have more time, if most probes at most of the 695 automated weather stations spread across the vast swath of Australia, as the probe is currently recording in Mildura, sometimes up to 0.4°C hotter for the same weather.
The extent of any artificial warming may vary depending on the type of custom designed transducer and local environmental conditions. As Blair Trewin wrote in the Bureau’s 2018 report (page 21): in arid regions, electronic probes are likely to produce higher maximums. This hypothesis could easily be tested if the Bureau provided access to, for example, 25 years of parallel data for Giles’ desert location.
Access to this data from Giles was requested by John Abbot under Freedom of Information on November 9, 2017 and denied by the Bureau on November 14, 2017.
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The graph featured at the top of this post, drawn by Chris Gillham as part of a series of reports we’re working on together, focuses not only on the change to probes in automated weather stations, but also including the conversion from degrees F to degrees C and related results. discontinuities in historical temperature records.
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