Last night I presented a paper for the Sydney Institute entitled ‘Modelling Australian and global temperatures: what’s wrong? Bourke and Amberley as case studies’. The paper written with Ken Stewart, Dennis Jensen and John Abbot concludes with some thoughts on the New South Wales annual mean maximum temperature record. In particular we suggest that the record can be thought of as showing a cooling trend of -1.95 degree per century to 1960, and a warming trend of 2.48 degree per century since, Table 1.
Taking these values and thinking about them in terms of a rate of cooling for approximately 70 years (1890 to 1960) and then a rate of warming for 54 year (1960 to 2013), we can estimate how much New South Wales cooled and then warmed. The sum of these values gives us the net change, a value that if we then multiple by a total period of 124 years, gives an indication of the rate of cooling per century.
This trend of -0.021 degree C per century suggests that the earlier cooling was almost, but not completely, negated by the later warming. To be clear, the overall temperature trend for New South Wales, calculated from the unhomogenized maximum temperatures as recorded at locations with long series, is one of cooling.
Yes it does appear that warming never completely negated earlier cooling . . .and further. . .the longer time series, despite the possibility of human error, are telling a different story about the Aussie weather/climate.
My question remains unchanged. If 'IT' is not manifesting 'IT'self regionally or locally what is the SOMETHING we are all supposed to be doing about 'IT'?
And BoM does not OWN the weather/climate. but I would reasonably expect an entity like BoM to be at the forefront and proactive about these matters.
Luke and all,
A teaser for you. This link is a picture of a minimum thermometer.
http://www.eoearth.org/files/153801_153900/153842/min_slider.jpg
What temperature would you read the minimum here? Both my kids got it wrong. Hint: The bulb is on the left and the liquid column is orange coloured.
Its quite obvious, when you look at some of the data, that some of the past observers got it wrong as well. This is the kind of error the bureau should be mainly looking to correct. I would also like to see them annotate each change.
I looked at the images of Bourke and Amberley Post Offices and they aren't the best but at least for Bourke PO the main building has been there since 1879 but obviously not the TV tower. In the case of Bourke a new automatic weather station has been set up at the airport. During the 21 full months in 1995 and 1996 when the two sites ran in parallel the yearly results were around 0.3C/year warmer at the new site for maximums and 1.0C cooler for the minimums. Even adjusting for these amounts it still looks like Bourke was hotter in the early part of last century than it is now and if the records are to believed even hotter at the end of the 19th century.
I think I will go and talk with the pixies at the bottom of the garden. They seem to have more idea than some about scientific evaluations. And they are not a financial burden on the long-suffering taxpayers of Queensland and Australia.
Identifying trends and identifying causes are not necessarily the same thing.
The Aussie weather/climate is seemingly not really interested in conforming with most of it.
BoM is an entity made up of people who are just as vulnerable to human foibles as anywhere else.
That includes diligence.
Phill thanks for a discussion.
I agree with your points on site issues. If you haven't seen my comments above, Bourke has the issue of in my opinion of expanding trees and gardens. And a large comms tower installed when? . Which Google Street view and the NSW Digital Globe can illustrate. http://globe.six.nsw.gov.au/
Amberley enclosure is blackened (?!) in the ACORN station catalogue picture. And Google Earth and historical photos provide evidence of much earthworks and scraping in the area leading to what albedo and therefore what temperature changes I'm not sure.
But to Jen's point of UHI - Google Earth Streetview and the Queensland Globe http://www.dnrm.qld.gov.au/mapping-data/queensland-globe shows that the Gayndah post office station is in a nice garden but a Besser brick wall of the tyre shop is nearby which would soak heat. When was the tyre shop built? How does this all balance out?
So to select stations for case studies I am suggesting that station metadata in terms of instrument and observer changes and site environment changes over time need serious analysis as well as the trends in surrounding stations - are they consistent?
A site visit to talk to locals and the historical society photos may reveal even more. As for portraying that Bourke staff were super-diligent how would we know - seems to be mythologising not science. Maybe they were - maybe they weren't.
Mr Bear - who says it's a trend - when you've done some due diligence on site metadata and serious break point analysis report back. This is the style of same issue put to those who would claims a drying trend from a wet 1950s to a dry Millennium 2000s drought sequence.
Quite right Luke, the raw data isn't pure and has lots of problems. Nevertheless one can make an educated guess about the nature of these impurities.
My first guess would be that most of the things you mention are likely to bias the result in a particular direction for a given time of year/day. Of your listing above I would only classify, "growing and expanding trees and gardens and perhaps white quartz gravel", as having any possible cooling effect on day time temperatures. The others I would guess are generally creating heating biases. Even for gardens the claim can go the other way. ie That on cooler or windy sites the enclosed garden shelters and allows the sun to heats the surrounds.
My second guess is that many of these biases are increasing over time, particularly the urban expansion and runway upgrades. The problem here is that such changes are insidious and won't show up as discontinuities in the data stream.
My simple expectation would be that at very least the BOM adjustments should be net neutral over time and most probably should be actively countering known heating biases. The issue is they seem to be doing the opposite.