Monday, 25 February 2019

Darwin's temperature data changed by BoM
interested readers can get some more nuts ’n bolts about ACORN 2.
TOP: Dilbert Cartoon used with permission.

Chris Gillham has compared the RAW data for Darwin with the manipulated data. A century apart the raw data show a cooling of 0.09ºC whereas the  adjusted data show 1.01ºC and 1.20ºC warming.

Chris on his waclimate site writes:

ACORN 2 influence on Australian temperature trends

The Bureau of Meteorology has again rewritten Australia's temperature history with the release of an update to its homogenised dataset that significantly increases the rate of climate warming since 1910.

The rewritten dataset increases Australia's per decade rate of warming by 23% and provides examples of algorithm miscalculations such as Carnarvon on the west coast having Australia's hottest ever daytime temperature at 51C.

In late 2018 the BoM provided access to the daily temperatures calculated by ACORN 2 (Australian Climate Observations Reference Network - Surface Air Temperatures), which is a revision of the bureau's ACORN 1 dataset of homogenised or adjusted raw temperatures at 112 Australian weather stations dating back to 1910.

It is assumed that ACORN 2 will replace the ACORN 1 dataset (introduced in 2012) as the historic reference used for comparison of modern temperatures. These are usually presented to the public as temperature anomalies compared to a 1961-90 baseline at each weather station.

The revision poses questions about the validity of the ACORN 1 temperature adjustments that for seven years (2012-2019) have inaccurately calculated Australia's warming trend since 1910. The revision's consequent widespread and significant historic temperature alterations pose questions about the validity of ACORN 2 itself.

It's worth noting examples of these alterations that have ACORN 1 listing Albany as having Australia's hottest ever day in 1933 (51.2C vs 44.8C originally), superseded by ACORN 2 which lists Carnarvon as having Australia's hottest ever day in 1953 (51.0C vs 47.7C originally).

Note: Researcher Ken Stewart has closely analysed ACORN 1 and ACORN 2 daily plots to determine trends, daily adjustments, records, diurnal temperature range, minima greater than maxima and the square wave phenomenon at all West Australian ACORN stations (link) and will be similarly analysing all Australian states and territories.

More at waclimate