Doc. 102 RELEASED UNDER FREEDOM OF INFORMATION RELEASED UNDER FREEDOM OF INFORMATION RELEASED UNDER FREEDOM OF INFORMATION RELEASED UNDER FREEDOM OF INFORMATION RELEASED UNDER FREEDOM OF INFORMATION Doc. 103 There is mounting evidence that the coldest minima measured by the Bureau’s weather stations have not been entered into ADAM (Australian Data Archive for Meteorology). This is because of limits placed on the recording of temperatures below minus 10 degrees Celsius. The Bureau has not prevented the coldest minimum temperatures from being entered into the national data base. There are standard quality control measures applied to extreme temperatures to verify that they are real, and not the result of an error in the observing system (such as may be due to instrumental error or errors in the transmission of the data to the Bureau). This process is analogously applied to rainfall and other meteorological observations, since experience has shown that extreme values should be subject to verification. This is additional to the Bureau closing stations in cold locations, for example Charlotte Pass – while opening new stations in hot places. The Bureau’s method for analysing Australian temperature trends accounts for changes in the observing network over time. The network changes for a range of reasons. For example, during the early period of record, observations expanded with the settlement of the continent. More recently, changing infrastructure requirements has led to a shift in the siting of some instruments. The process of accounting for these changes has been independently reviewed by a panel of international experts and through the recent Technical Advisory Forum. The Bureau has an FAQ on this topic — FAQ #12 @ http://www.bom.gov.au/climate/change/acorn-sat/#tabs=FAQs Then there is the issue of how temperatures (above 10 degrees Celsius) are being recorded. Recent inquiries to the Bureau – consistent with observations of what is measured and then recorded by weather stations including at Thredbo, Goulburn and Borrona Downs – confirm that the reported minimum temperature is the coldest for the one-second reading. Because modern electronic probes react more quickly to second by second temperature changes this would make measurements from the automatic weather stations spread across the Australian continent since the 1990s, inconsistent with previous measurements. A faster response time in modern AWSs compared with a mercury or alcohol-in-glass thermometers has the potential to increase the range between maximum and minimum temperatures, known as the diurnal temperature range. This is one of the issues that is looked at when assessing the veracity of temperature trends both here, and overseas. In Australia, the ACORN-SAT analyses investigated RELEASEDwhether there is a wideningUNDER of the diurnal FREEDOM temperature range due toOF the introduction INFORMATION of AWSs, when compared with the earlier manual gauges, and found no evidence of any significant difference between the two. This result is published in the ACORN-SAT technical paper. http://cawcr.gov.au/technical-reports/CTR_049.pdf It should be noted that the AWSs where were not introduced to the network at a single point in time everywhere, which assists with this assessment. It should also be noted that the sensors within an AWS do not respond to second-by-second changes in temperatures in the surrounding environment. The sensors have a response time-function built in, which smooths their output, and the sensors are housed within a louvered Stevenson Screen (as were the manual thermometers) which provides an integration time for temperatures that is much longer than a second, and is similar to the response time for a mercury-in-glass thermometer. This is related to the exchange of air with the surrounding environment. The documented Bureau policy is for these readings to be averaged over a 10-minute period to provide compatibility with measurements from liquid-in-glass thermometers. This is not the case. The Bureau does not have such a policy in place. Further, the Bureau is remodelling minimum temperatures in the creation of its new homogenised ACORN-SAT dataset. For example, cooling in temperature minima at both Rutherglen and Deniliquin associated with the development of irrigation has been remodelled to show a warming trend. The Bureau does not deny this remodelling, simply justifying it on the basis that this land-use change constitutes a ‘non-climatic’ factor and therefore ‘a homogenisation process is justified’. I have written about this in the past, and corresponded extensively with the Bureau on the same. The Bureau’s methods for adjusting temperature records are entirely open, and have been subject to numerous independent reviews. Temperature trends over Australia are not dependent on temperature adjustments. The Bureau has provided a detailed breakdown of adjustments at Rutherglen and Deniliquin, and these can be found online: http://www.bom.gov.au/climate/change/acorn-sat/documents/station-adjustment-summary- Rutherglen.pdf http://www.bom.gov.au/climate/change/acorn-sat/documents/station-adjustment-summary- RELEASEDDeniliquin.pdf UNDER FREEDOM OF INFORMATION The Bureau’s FAQ # 13 details the impact of adjustments on temperature trends @ http://www.bom.gov.au/climate/change/acorn-sat/#tabs=FAQs It should also be noted that the Bureau does not explicitly adjust for temperature changes due to irrigation or land-use changes. In fact, the Bureau has detected, and noted, a likely cooling influence from irrigation at two sites, Mildura and Griffith, and has not adjusted for this influence. From the ACORN-SAT site catalogue: There was rapid development of irrigated agriculture in the Mildura region in the period between the two World Wars, and this appears to be associated with an anomalous cooling trend in maximum temperature at Mildura over this period (amounting to 0.3–0.4°C over 30 years). The non-ACORN-SAT site of Griffith, which has a similar history of irrigation development, shows a similar trend. http://www.bom.gov.au/climate/change/acorn-sat/documents/ACORN-SAT-Station-Catalogue-2012- WEB.pdf RELEASED UNDER FREEDOM OF INFORMATION ISSUES AND QUESTIONS To be clear, the actual measured value of minus 10.4 was ‘automatically adjusted’ so that it recorded as minus 10.0 in the key ADAM dataset. After three-days, and specifically following an outcry from weather enthusiasts across the nation, the value of -10.4 was reinstated. The temperature was not automatically adjusted, as described in the AWS review report. Q1. When exactly was the limit of -10.0 degree Celsius set for Goulburn? No -10.0 degrees C limit has been set for Goulburn. -10 degrees C is an automated trigger for flagging values that require further manual verification at sub-alpine sites (sites below 1000m). Q2. How was it determined that temperatures at Goulburn should not exceed a minimum of -10.0? See above. Q3. How many other weather stations have limits currently placed on the recording of minimum temperatures? There are no weather stations that have a limit on their minimum temperatures as per described the above. There was a hardware issue identified at some locations which prevented the transmission of temperatures below -10.4 degrees C, and this has been rectified at all locations where the occurrence of such temperatures is likelypossible. The hardware issue has affected a very small amount of data, and has not biased the veracity of the ACORN-SAT network of climate reference sites. Q4. Could the Bureau advise whether or not the actual measured temperatures have been stored for the weather stations where limits were set (e.g. Goulburn)? There have been no limits placed on the recording of actual temperatures below -10 degrees C. It should be noted that all minute data (temperature recordings for each minute of the day) are stored within the ADAM database. RELEASEDQ5. Could the Bureau UNDER make publicly available FREEDOM the stored values, which OF were notINFORMATION entered into the Australia Data Archive for Meteorology (ADAM) for all weather station for which limits have been in place? See above. The ADAM data base is extensive. While and the Bureau provides a great deal of data free to the general public via its Climate Data Online portal. HoweverFurthermore, all data in ADAM are available to the public, subject to cost recovery, and this data is accessed and used by researchers or commercially under appropriate terms. --- While the Bureau has been placing absurd limits on how cold a temperature can now be recorded at Goulburn and other locations, it has not undertaken basic quality assurance of temperature data as recorded at this, and other, weather stations. For example, there are a series of zero values recorded through December 1990 in the ADAM dataset as minimum temperatures for Goulburn airport. This question provides a basic premise for the existence of the ACORN-SAT analyses. That is, the Bureau undertakes a careful process of quality control and analysis at for data from over 100 climate reference stations to ensure that the characteriszation of temperature variability and change over time accurately reflects the real world. Goulburn is not an ACORN-SAT location. From the ACORN-SAT website: Among the hundreds of thousands of climate observations recorded in the Bureau’s database each day, it is unavoidable that some records contain errors. This can be due to automated equipment faults, human error in manual observations and a range of other glitches. The Bureau maintains a layered approach to correcting data errors. Each day, automated and semi- automated quality control systems identify observational errors using methods such as comparison with data from nearby sites. An extensive audit trail of data and metadata keeps track of corrections that may need to be applied. The data from each ACORN-SAT observing location is subject to ten different quality control checks.