Monday, 24 August 2015

How does the Australian Bureau of Meteorology ACORN-SAT data compare to its source?


In previous posts I’ve examined the Australian Bureau of Meteorology’s temperature records.

In this article, I examine the Bureau’s practice of ignoring data prior to 1910. I also look at the adjustments the Bureau has made to the original data. ACORN-SAT is the adjusted temperature record. CDO is, supposedly, the ‘raw’ data.

Here’s a few samples from the full article:

This graph shows all of the weather stations used by the BOM for ACORN-SAT but with the pre-1910 data included.

Two things stand out:

1. There was rapid warming from 1860 to 1900, much more than the little bit of warming seen since 1900.

2. 1900 was the hottest year since records started in 1860.

ACORN_CDO temperatures

The adjustments make the period 1910 – 1950 appear colder.

BOM ACORN Adjustments

There is nothing special about the years 2013 and 2014. I’ve shown four decimal places on the temperatures. In reality, we’d be lucky to measure to the nearest degree. So in 1900, the average maximum temperature was 27 degrees Celsius. In all the other years, the maximum average temperature was 26 degrees Celsius. No big deal.

BOM ACORN average maximum temperaturess

Unfortunately, I’m lead to the following conclusions:

1. The year 1900 is likely to have been the warmest on record.

2. The rate of warming from 1860 to 1910 it much larger that any warming experienced in the recent past.

3. There was a systematic downward adjustment of temperature records prior to 1950. This makes more recent temperatures appear warmer by comparison.

It’s may be coincidental that both the decisions to eliminate pre-1910 data and to systematically adjust pre-1950 temperatures downward, support the hypothesis of human-induced global warming.

If it is a coincidence, it’s a mighty big one.

Click here to download the PDF

Monday, 17 August 2015

Australian Bureau of Meteorology Station Data Review –continued.

In a previous post I address the question "Are the weather station descriptive data for the CDO and ACORN-SAT datasets consistent?"

In this post I address the question "How do the operational timespans of ACORN-SAT and CDO weather stations compare?"

You'll remember that ACORN-SAT is the "Australian Climate Observation Reference Network - Surface Air Temperature" dataset.  It is derived from the BOM’s Climate Data Online dataset.
Click here to visit the CDO site at the BOM

Here’s a quick summary of my findings:

1. The 112 ACORN-SAT weather stations are actually combinations of 202 CDO stations. It’s unclear why site identifications numbers were combined.

Here’s an example for Mackay, Queensland.

In CDO, Mackay had four different site identification numbers (033297, 033046, 033047 and 033119). In ACORN-SAT, these have all been combined under a single site number 033119. The identity of the other three sites is lost.

Mackay    033119    033297    MACKAY COMPARISON
Mackay    033119    033046    MACKAY POST OFFICE
Mackay    033119    033047    TE KOWAI EXP STN
Mackay    033119    033119    MACKAY M.O

2. There are 1703 CDO sites that could have been used for ACORN-SAT.  Just 202 were chosen for this purpose. It’s unclear exactly how these choices were made.

3. The BOM did not use any temperature data prior to 1910 for ACORN-SAT, despite data for one station being available back as far as 1855. The BOM explains that it didn’t include pre-1910 data as it was unreliable. Other claim the that1890s was a particularly hot period in Australia. In a future post I’ll look at the pre 1910 data in more detail.

Click here to download the full PDF document

The full PDF contains lots of detail about the stations, their starting dates of operation and the total time that various stations operated.