CLIMATIC MATTERS

Brian Gunter, Narooma, NSW, Australia http://members.westnet.com.au/brigun/aust_temp_trends.html

" The art of prophecy is very difficult, especially about the future." - Mark Twain

AUSTRALIAN LONG-TERM TEMPERATURE TRENDS

PRELUDE:

IF CLIMATE CHANGE IS REAL AND IS AS SERIOUS AS IS OFTEN CLAIMED WE SHOULD BE ABLE TO CONFIRM IT BY A SIMPLE EXAMINATION OF RECORDED CLIMATOLOGICAL DATA. TO PUT IT ANOTHER WAY, IF THE PAST TEMPERATURE RECORDS SHOW THAT OUR WORLD IS BECOMING INCREASINGLY HOTTER WE CAN REASONABLY CONCLUDE THAT WE HAVE A SERIOUS PROBLEM ON OUR HANDS.

KEEP IT SIMPLE! IF OUR TEMPERATURES HAVE BEEN RISING WE DON'T NEED COMPUTER MODELS, ICE CORES, TREE RINGS OR ECONOMISTS TO PROVE IT. WHY NOT USE THE DIRECT MEASUREMENTS OF AIR TEMPERATURE THAT HAVE BEEN DILIGENTLY COLLECTED THROUGHOUT AUSTRALIA OVER MORE THAN THE PAST CENTURY?

I HAVE CHECKED IT OUT USING TEMPERATURE DATA FROM 13 LOCATIONS THROUGHOUT AUSTRALIA. THESE ARE ALL LONG-TERM STATIONS, COMMENCING OVER 100 YEARS AGO, AND WITH LARGELY UNBROKEN RECORDS. I HAVE CHOSEN ONLY RURAL OR SMALL TOWN STATIONS SO AS TO AVOID THE UNCERTAIN URBANISATION EFFECTS ON TEMPERATURE IN CITIES.

ALL OF THE TEMPERATURE DATA USED IN MY ANALYSIS ARE RAW DATA (AS RECORDED BY THE OBSERVERS, WITHOUT ANY ADJUSTMENTS OF ANY KIND) AND WERE DOWNLOADED FROM THE BUREAU OF METEOROLOGY WEBSITE.

IF THE HISTORICAL TEMPERATURE RECORDS SHOW THAT OUR TEMPERATURES ARE ACCELERATING THEN WE CERTAINLY HAVE A PROBLEM AND NEED TO TAKE SOME ACTION. ON THE OTHER HAND, IF NO SUCH ACCELERATION IN TEMPERATURE IS EVIDENT THEN WE SHOULD RECOGNISE THAT EVEN DRASTIC ACTIONS (SUCH AS THE PROPOSED CARBON (DIOXIDE) TAX) WILL NOT HAVE ANY SIGNIFICANT EFFECT ON TEMPERATURE.

PLEASE READ ON AND MAKE YOUR OWN ASSESSMENT.

Many of my friends say that our summers are getting hotter and the winters are getting colder – but are they? Others say that floods are becoming larger and more frequent – but are they? And droughts are getting longer too – but are they? Our media are full of claims that recent ecological changes are caused by changing climate, whilst many studies and computer projections predict increasingly severe climate changes in the coming years. Many prominent politicians and economists tell us that things are going to only get worse. On the other hand there are many other people who passionately claim that the whole climate change question is vastly overstated. It is understandably all very confusing to most people!

So I decided to have an independent look at the question. Being a retired professional engineering hydrologist with many years spent analysing climate and river flow data, I feel that I have some qualification to make such an assessment. My initial approach was to return to basics and look at recorded long-term temperature trends in Australia. My thesis is that, if the predictions of accelerating temperatures in Australia are correct, this effect surely must be evident from the vast amount of temperature data that have been collected throughout Australia over the past 150 years. These data are available on the Bureau of Meteorology website.

My analyses involved 13 long-term stations located throughout rural Australia. The analyses were all performed over the same 101-year period, 1910-2010 (much of the temperature data prior to 1910 are of doubtful quality due to different instrumentation). Urban areas were excluded from the study in order to exclude the local effects of urban warming. For these 13 stations I extracted various annual temperature indices (such as mean annual, maximum monthly, minimum monthly and extreme temperatures for each year) and presented them graphically. Details of the 13 stations analysed are presented below.

My conclusions are:

- All of the 13 stations have very similar and consistent long-term temperature trends.

- Most of the temperature indices show that temperatures in Australia have been increasing at a more-or-less constant rate since 1910.

- An interesting exception is that most northern Australian stations have experienced (and undoubtedly enjoyed) a steady decrease in summer maximum temperatures since 1910.

- There is no evidence that the temperature trends in recent years (say, since 1980) are any different than for the rest of the period since 1910.

So what does all this mean?

- Temperature increases in Australia are not a recent phenomenon, but have been occurring at about the same rate (an average of about 0.7°C/century) over the past century. [ This is consistent with longer temperature records in Europe that show that temperatures there have been increasing steadily since the end of the Little Ice Age in the late 1600s. Similar trends in temperature were recorded from the late 1800s at Melbourne and Sydney ]

- There is no evidence (not even one index at one station!) that there has been any abnormal increase or decrease in the temperature trend in recent years. [ Some cyclic patterns are evident (wet, La Nina periods are cooler for example), but the recent years are within the historical variation from the long-term mean trend. ]

My advice:

- Be Alert? Yes, although temperatures have been generally increasing for the past century (and prior to that too), there is no evidence of any abnormal increase or decrease in temperatures in recent years, we should regularly reassess temperatures (say in five years time) in case there are any trend changes.

- Be Alarmed? No, not until there is some real evidence of a problem!

- Be Concerned? Yes, policies and decisions are often made on unproven presumptions. For example, the present “carbon tax” proposals in Australia presume that long-term temperature trends in Australia are accelerating – but it just ain’t true!

- Be -Ware! There is a lot of mis-information out there.

MY OVERALL CONCLUSIONS:

THERE IS NO EVIDENCE THAT TEMPERATURE TRENDS IN AUSTRALIA HAVE CHANGED OVER THE PAST CENTURY.

MOST TEMPERATURE INDICES HAVE INCREASED OVER THE PAST CENTURY AT MORE-OR-LESS CONSTANT RATES; ALTHOUGH SUMMER TEMPERATURES AT NORTHERN AUSTRALIAN INLAND LOCATIONS HAVE DECREASED, WHILE WINTER TEMPERATURES AT SOME SOUTHERN LOCATIONS HAVE ALSO DECREASED.

THE UNANIMOUS CONCLUSIONS AT THE 13 LOCATIONS ANALYSED WOULD BE EXPECTED TO APPLY THROUGHOUT AUSTRALIA.

THE CLAIM BY MANY ORGANISATIONS AND INDIVIDUALS OF ACCELERATING TEMPERATURE RISE IN AUSTRALIA IS CLEARLY INCORRECT AND THESE CLAIMS SHOULD BE URGENTLY REVIEWED.

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DETAILS OF THE ANALYSES

The 13 stations selected for the analyses are listed below. These stations are all located in rural areas or small towns. The stations had mainly unbroken records between 1910 and 2010 and were geographically representative (as far as was possible) of the Australian continent. Unfortunately no suitable stations could be located in the Northern Territory or Tasmania and there are other large expanses (especially in Western Australia and South Australia) with no suitable data.

All of the data were raw data (as measured by the local observers) and were downloaded from the Bureau of Meteorology website: http://www.bom.gov.au/climate/data/

LOCATION	STATE	BOM No.	COMPLETE YEARS *
Moruya Heads	NSW	069018	97
Wilsons Promontory	VIC	085096	96
Echuca	VIC	080015	100
Robe	SA	026026	100
Wilcannia	NSW	046043	79
Tibooburra	NSW	046037	87
Gayndah	QLD	039039	98
Boulia	QLD	038003	94
Richmond	QLD	030045	95
Burketown	QLD	029004	83
Marble Bar	WA	004020	94
Northam	WA	010111	94
Cape Leeuwin	WA	009518	101

NOTE: * Complete years based on both monthly maximum and minimum records.

Nine different annual indices of temperature were extracted for each of the 13 stations and these were plotted on an annual time base. The nine indices used were:

- Annual Mean Max Temp. This is the average of all 365 (or 366) daily maximum temperatures measured in each year.

- Annual Mean Min Temp. This is the average of all 365 (or 366) daily minimum temperatures measured in each year.

- Annual Mean Temp. This index is not measured, but is the average of the Annual Mean Max Temp and the Annual Mean Min Temp.

- Max Monthly Max Temp. This is the highest value of the average monthly maximum temperature measured in each year. This is usually the average January or February maximum temperature.

- Min Monthly Max Temp. This is the lowest value of the average monthly maximum temperature measured in each year. This is usually the average July or August maximum temperature.

- Max Monthly Min Temp. This is the highest value of the average monthly minimum temperature measured in each year. This is usually the average January or February minimum temperature.

- Min Monthly Min Temp. This is the lowest value of the average monthly minimum temperature measured in each year. This is usually the average July or August minimum temperature.

- Extreme Max Temp. This is the highest maximum temperature measured on any day during the year.

- Extreme Min Temp. This is the lowest minimum temperature measured on any day during the year.

A linear (straight) line was fitted through each of the plotted data sets and these “best fit” lines were added to the graphs. This is not intended to imply that all temperature trends are linear, but it is a more realistic reference base to assess trends than a constant mean that is normally used. The long-term linear trend rate (expressed as °C/century) for each index is tabulated at the end of each set of graphs. Cyclic variations around the long-term linear trendlines are often evident.

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MORUYA HEADS, NEW SOUTH WALES

ANNUAL TEMPERATURE TRENDS 1910-2010

http://members.westnet.com.au/brigun/aust_temp_trends.html

Linear Temperature Trends 1910-2010 (°C/century)

STATION

COMP YEARS

ANN MEAN MAX

ANN MEAN

ANN MEAN MIN

MAX MTHLY MAX

MIN MTHLY MAX

MAX MTHLY MIN

MIN MTHLY MIN

EXTR MAX

EXTR MIN

Moruya Heads

0.89

0.52

0.16

0.56

1.36

0.39

0.14

***

NOTES: *** No trend rate was computed as extreme data was available only since 1957.

Comments:

Annual and monthly temperature indices show average positive trends of between 0.14 and 1.36 °C/century over the past century.

There is some indication of a cyclical pattern with a minimum about 1960 and maximums about 1920 and 2000.

There is no evidence of any abnormal accelerating or decelerating temperature trends.

Extreme maximum and minimum temperatures show no abnormal trends since records commenced in 1957.

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WILSON’S PROMONTORY, VICTORIA

ANNUAL TEMPERATURE TRENDS 1910-2010

http://members.westnet.com.au/brigun/aust_temp_trends.html

Linear Temperature Trends 1910-2010 (°C/century)