Posts Tagged ‘temperature change’

CRUTEM vs ACORN: Tasmania

February 8, 2014

Australia has done it again- we have beaten the Poms at their own game (and I don’t mean cricket).

The English climate scientists say the temperature trend for the island state of Tasmania is +0.48C per 100 years.

We’ve beaten that: we say it’s +0.81C per 100 years- better by 69%!

Today I looked at data now available as an interface with Google Earth.

I quote firstly directly from WattsUpWithThat:

Climate researchers at the University of East Anglia have made the world’s temperature records available via Google Earth.

The Climatic Research Unit Temperature Version 4 (CRUTEM4) land-surface air temperature dataset is one of the most widely used records of the climate system.

The new Google Earth format allows users to scroll around the world, zoom in on 6,000 weather stations, and view monthly, seasonal and annual temperature data more easily than ever before.

Users can drill down to see some 20,000 graphs – some of which show temperature records dating back to 1850.

This new initiative is described in a new research paper published on February 4 in the journal Earth System Science Data (Osborn T.J. and Jones P.D., 2014: The CRUTEM4 land-surface air temperature dataset: construction, previous versions and dissemination via Google Earth).

For instructions about accessing and using the CRUTEM Google Earth interface (and to find out more about the project) visit To view the new Google Earth interface download Google Earth, then click here CRUTEM4-2013-03_gridboxes.kml.

I immediately downloaded the new interface, and can report that it is indeed useful and fascinating.  Click anywhere and you can get mean temperature data and trend for that precise region, and individual weather stations as well.  It allows easy comparison between the temperature record as shown by the Bureau of Meteorology (BOM) and one of the world’s leading datasets produced by the renowned Climatic Research Unit in England.

Three things to note:

1.  CRUTEM4 uses data from back to the 1850s- BOM says it only uses data from 1910 as data previous to this may be unreliable.

2.  CRUTEM4 uses data from many more than the 104 ACORN sites used by BOM.  Some may be of doubtful quality.

3.  The results are vastly different.

I have downloaded data from CRUTEM4 and from BOM for Tasmania, as that appears to be the easiest region to compare records.  As you can see from the Google Earth image below, Tasmania fits fairly neatly into one 5 degree by 5 degree grid cell.

google earth tassie

First I show the annual data for both datasets:Tassie means

Note CRUTEM4 has annual data from 1883.  BOM has this as well but declares it to be unreliable.  Note also that the trends are vastly different- CRUTEM4 trend is +0.48C per 100 years, while BOM has it as +0.81C.  (+0.8C on their Time Series graph.)

(The difference is +0.33c- that’s an improvement of 69%! And they did it with only 5 sites, vs CRUTEM4’s 21.)

How was this done?  Apart from not including pre-1910 data, BOM also made some small adjustments to the raw data:bom-crutem

And that comparison is not with raw data, but with CRUTEM4.

So, what is the correct temperature trend for Tasmania?  The world acclaimed CRUTEM 4, or “world’s best practice” ACORN-SAT? Or neither?

It’s anyone’s guess.


Jones P.D., Lister D.H., Osborn T.J., Harpham C., Salmon M. and Morice C.P., 2012: Hemispheric and large-scale land surface air temperature variations: an extensive revision and an update to 2010. Journal of Geophysical Research 117, D05127. doi: 10.1029/2011JD017139.

Osborn T.J. and Jones P.D., 2013: The CRUTEM4 land-surface air temperature dataset: construction, previous versions and dissemination via Google Earth. Earth System Science Data Discussion 6, 597-619. doi: 10.5194/essdd-6-597-2013

No Excess Winter Warming for 103 Years!

January 9, 2014

Greenhouse Myth Buster No. 2

Another key indicator of greenhouse warming, a pattern of temperature change “uniquely associated with the enhanced greenhouse effect” according to Dr Braganza, is greater warming in winter compared with summer.

Not in Australia.

This is a graph of summer annual means minus winter annual means for the years 1910 – 2012, straight from BOM’s time series data.


No winter increase over summer in 103 years.  This summer- we find out in early March- will have to be less than +0.7 C above average to make  the trend ever so slightly negative (to 5 decimal places).

But then how will we get another “Angry Summer”?

The Hottest Year, but NOT due to Greenhouse Warming

January 7, 2014

ACORN-SAT- the gift that keeps on giving!

Unfortunately for doomsayers, the fact that 2013 was the hottest year on record in Australia is no evidence for the effects of greenhouse warming.  In fact, it is the very opposite.

Why?  Any sort of warming will eventually produce the hottest year on record.  But warming due to the enhanced greenhouse effect is quite special.  Warming due to greenhouse gases is evidenced by

greater warming of night time temperatures than daytime temperatures”

amongst other things, according to Dr Karl Braganza (

I discussed this in April  last year.  Now, with the updated data for 2013, it’s time for a reality check to see whether there is now evidence of greenhouse warming in Australia (a region as large as Antarctica, Greenland, the USA, or Europe, and supposed to be especially vulnerable to the effects of global warming.)

Once again I am using data straight from the Bureau’s website.

Fig. 1: Monthly maxima and minima with 12 month smoothing, December 1978 – December 2013, from

max v min linear

For the past 35 years, there is much LESS warming of night time temperatures than daytime temperatures.  And the divergence is increasing:

Fig 2: fitted with a 2nd order polynomialmax v min poly

Sorry, but this is not evidence of greenhouse warming over the period of the satellite era, when greenhouse gases have been increasing rapidly.  It is merely evidence of warming.

Weather predictions- final check

January 3, 2014

This is the final post in my series of checking a hunch that temperature change indicates a weather change 160 days later.

Back on November 3, I predicted:

2 to 10 unstable; 12-13-14; 16-17-18-19; 22-23-24; 26 to 31 unstable.”

I did not change this in December.

This is how  I went:

Dec2013 predictions check

I’ve marked with green bars the predicted dates of unsettled weather as above.  Red bars show the actual times.  They match.

And finally, here’s my graph showing predicted weather events for April to June.  Again, green bars indicate dates when weather events may be expected.Apr-June 2014

I will leave this topic for now, not because the method doesn’t work (it does!), but to concentrate on other interests.

2013 Minimum Temperatures Released

January 2, 2014

Ken Stewart, 2 January 2014

UPDATE 3 January: BOM has updated it’s time series graph, but not the raw data, which still finishes at 2012! See below.

I have calculated the annual 2013 minimum temperature anomaly for Australia, well before the Bureau of Meteorology.

Not including the 8 sites acknowledged as having anomalous warming due to the Urban Heat Island (UHI) effect, I calculate the straight mean (without area averaging) to be +0.82 C.  This puts 2013 as second warmest after 1998, and just ahead of 1973 and 1988.

I expect that the BOM will publish a figure of around +1.2C, and claim 2013 as the warmest on record for minima.

I calculated this by using daily Acorn data for 1910 to 2012 from  , plus daily minima for 2013 for these same sites from Climate Data Online.  I used Acorn data from 1961-1990 to recalculate monthly means for each site, and then calculated running centred 31 day means to estimate daily means for the same period.

Then I calculated daily anomalies for each site, and amalgamated these into a straight mean for Australia.

The result is as follows:

Fig. 1:  365 day running mean of daily data.acorn 365d 1910-13 no uhi

I will analyse Fig. 1 in some detail later.  But first, how does my calculation stack up against the BOM super computer?

Fig. 2: Annual (31 December each year) means of minima 1910 to 2012.Acorn ann v me 1910-12

My calculation is in green, BOM in red.  As you can see, the match is pretty close, and of course I have not used any area averaging.  But you would expect the results to be close, as I have used exactly the same data.  You will notice that the major differences occur in years of higher or lower than normal minima.  These appear to have become larger in the last 40 years.  The official annual figures show greater extremes, as shown above.

I have also calculated trends for the 1910 to 2013 period, and hope that this will persuade you of the futility of using linear trends for temperatures, and that if you cherry pick you can prove just about anything.  The next graph is a plot of the continuous running trend from 31 December 2013 all the way back to 1 January 1910.  That is, the linear trend through datapoints between any selected date and 31 December 2013.

Fig. 3: Continuous running trend, daily minima anomaliescont trend Oz no uhi

The vertical axis measures trend in degrees Celsius at particular points in time.  Note the rapid fluctuations at the right hand end.  I’m sure no one would be silly enough to calculate trends of only a few years’ data.

As the time period increases (moving from right to left) the fluctuations smooth out.  Note that Australia has had zero trend in daily minima since 21 July 1997.  Interesting, but no predictor of the future.

Moving further back in time, the plot shows the temperature trend increasing until the early 1940s.  Up until then the long term trend is fairly stable.  Since 1910 the trend is about 1.1C per 104 years.  The maximum trend can be calculated from 1922. Therefore, a cheerful cherrypicker can choose whatever time frame they like to produce a linear trend that suits.

Back to my graph of the 365 day running means of daily temperatures. Figure 1 again:acorn 365d 1910-13 no uhi

Note that the 365 day mean peaked in early November 2013 and has dropped since then.  The peak was at +0.94C, which is still below that of 1998 and 2006.

But also note that the rise of about +1.1C over 104 years is by no means steady.  There are several sharp rises and falls along the way.  Let’s have a closer look at these.

Fig. 4: Step changes in temperatureacorn 365d 1910-13 no uhi stepups

I have shown (starting in 2014) how the minimum temperature record of Australia features a series of sharp step ups, followed by slow declines.  I have indicated the start of these periods and the linear trend lines of each one.  There may have been one in 1926, and 2013 may (or may not) be the start of another such period.  They are more frequent and more pronounced in the past 40 years than in the first 60 years.  This appears to show a link to natural climate forces, such as the El Nino- Southern Oscillation.

I will analyse these results further in future posts, and may do the same for maxima as well.  (People are interested in maxima because “that’s how hot it is”.  I like minima because they tell you more about climate e.g. if they increase faster than maxima this may indicate greenhouse warming.)

Watch for the official 2013 minimum temperature anomaly:  probably +1.2C.

Update 3 January:

Here is the official BOM graph to 2013:

timesereis tmin to 2013

and it looks like a bit over +0.9C  +0.94 C, so less than I expected and closer to mine.

No Warming in North Australia for 31 Years

December 23, 2013

I’m nearly a year late with this, but I’ve only just noticed.

According to the Bureau of Meteorology’s official temperature records, for all of the Northern Australian region- the half of the continent north of 26 degrees South- the minimum temperatures are steadfastly refusing to rise.  From 1982 to 2012, the linear trendline for minima is on the decreasing side of dead flat.

Acorn tmin Nth Oz 82-12

This is longer than the 3o years regarded as the minimum period for analysing climate trends, and in spite of the massive increase in amount of CO2 emissions.  Note that 1982 and 2011-2012 were almost equally cooler than normal.

Remember  that one of the fingerprints of greenhouse warming is that minima should be increasing more than maxima.

Here is the 365 day running mean of daily minima anomalies of all Acorn sites in Northern Australia (more about this next year) up to early December this year:

tmin nth aust 1910-13a

Rather than a smoothly rising trend, the record is characterised by 10 to 15 year rapid rises and falls, responding to events in the Pacific and Indian Oceans.

This is a diagram of Australia’s climate regions:summer1213  regions

After New Year I will post about minima for other regions and Australia as a whole.

Merry Christmas to all.

It’s Official: a 27 Year Hiatus

December 13, 2013

Australia’s Bureau of Meteorology (BOM) has been publishing its brand new (less than 2 years old) temperature dataset, the Australian Climate Observations Reference Network- Surface Air Temperatures (ACORN-SAT, or Acorn), and using this to make scary pronouncements about our climate.

Back in March, I showed that there had been an 18 year pause in Australia’s mean temperatures.  In April I showed how Dr Braganza’s “Fingerprints of Global Warming” (from an article in The Conversation on 14/06/2011) are absent in Australia.  I included a passing reference to minima, which really needs a separate post, so here it is.

Why minima?  To quote Dr Braganza,

…Patterns of temperature change that are uniquely associated with the enhanced greenhouse effect, and which have been observed in the real world include:


  • greater warming of night time temperatures than daytime temperatures

Greenhouse theory suggests that greenhouse gases slow the normal rapid night time radiation into space, therefore minima should be increasing.  Australia as a region is roughly the same size as the USA, or Greenland, or Europe, or the Arctic or Antarctic, and is supposed to be at great risk from the effects of global warming, so the behaviour of minima in Australia should be of some interest.

So let’s see if this unique pattern of temperature change has been observed in the real world.

This is a graph of annual minimum temperature anomalies across Australia from 1986 (updated!) to 2012, sourced directly from Acorn data at the BOM website at tmin Australia

Which clearly shows that minimum temperatures have been cooling, not warming, for 27 years.

Strange, but true.  You won’t see that mentioned in any BOM publication.