Warming Has Paused, BOM Says!

Ken Stewart, 19 March 2012

Sorry, that title is a little misleading, isn’t it.  The Bureau of Meteorology didn’t actually say this, but the BOM’s own data does.  Loudly and clearly.

The Bureau’s brand-new, best quality dataset, ACORN-SAT (Australian Climate Observation Reference Network- Surface Air Temperatures) clearly shows the linear trend has been flat for 18 years.

So what of the Climate Commission’s report on “The Angry Summer” ,  and the Bureau’s apparent fixation with maximum temperatures in the past summer?

In the past, the BOM has been at pains to make clear that trends in climate can only be analysed over long periods of time. See for example, http://www.bom.gov.au/climate/glossary/climate.shtml   Three cold months have barely rated a mention in the past for this very good reason.  So why all the fuss over three hot months?  And if it is now OK for them to use a three month period in this way, surely it is OK for sceptics to point to a “pause” in warming over the past several years. A period of 18 years is 72 times longer than the “Angry Summer”!

In my last post I demonstrated how well Acorn annual mean anomalies from the 1981-2010 mean, match with UAH (the dataseries of atmospheric temperatures since late 1978 compiled by the University of Alabama- Huntsville):

I was astounded that some commenters at the various sites where this was published had doubts about the accuracy of the UAH data.  You can’t help some people.  That’s why I decided to play the warmists’ at their own game, by using only the Bureau’s own data, which shows, among other things, that there has been zero trend in the data since 1995.

Finally, as the Climate Commission is not likely to mention these, here are some other not so widely known facts straight from Acorn:

• 2012 had the coldest winter minima since 1983 
• 2012, at +0.11C, was the 36^th warmest year- equal with 1995, just ahead of 1957.
• The past three years- 2010, 2011, and 2012- were the coolest of the decade.
• 2012 was cooler than 9 of the previous 10 years- beaten by 2011.  2011 was exactly at the median anomaly for the past 103 years, at -0.13C, according to Acorn’s homogenised record.

Meanwhile the Climate Commission would have us believe that because a three month period has been a record, this is somehow proof of man-made global warming.

Why?  Because that’s all they’ve got left.

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How Angry Was Summer?

Ken Stewart, 17 March 2012

 We’ve all heard about the Climate Commission’s report, “The Angry Summer”.

Tom Quirk has been able to obtain UAH lower atmospheric data for Australia, and has put together a comparison of BOM and UAH data for Australia and his conclusions are correct- there has been no significant warming since 2002.

Fig. 1

I have used Tom’s work to compare the ACORN annual data with that of UAH.  I have to thank Tom- without his initiative I would not have been able to obtain UAH lower atmospheric data for Australia.

To compare Acorn with UAH I calculated approximate Acorn anomalies from a 1981-2010 climatology (the same as UAH), instead of BOM’s 1961-1990 climatology.

Fig. 2

The reasonably close match is remarkable, and confirms Tom’s finding.

This is in spite of all of our reservations about Acorn’s shortcomings, so it’s still good for something!

We may conclude that if BOM sticks to its 112 Acorn stations and maintains them, and if BOM manages to reduce the uncertainty in their data to +/-0.2C, then we can generally rely on their annual data into the future.   Note to believers in man-made global warming: do not read too much into this: it is “near enough for a sheep station”, but not near enough for predictions of doom.

That bears repeating: BOM’s Acorn annual data matches UAH satellite data reasonably well.

Let’s look at the Angry Summer- in fact all summers in the satellite era.

Once again I re-calculated approximate Acorn summer anomalies from the 1981-2010 mean, as UAH does.  Figure 3 shows the Acorn data for summers compared with UAH:

Fig. 3

According to BOM last summer was a record, yet the satellites say it was pretty ordinary- 14^th warmest out of the last 35.  The last time there was such a large discrepancy was 1983- the two series since then have been reasonably similar.

Again I ask: what’s going on?

A Tale of Two Records

The Bureau of Meteorology, in its recent media release, accepted and repeated by the media, made an astonishing claim:

Bureau of Meteorology confirms it’s been the hottest summer on record

Where did they get the data to make this claim?  Well, in their media release they said:

“Of the 112 locations used in long-term climate monitoring, 14 had their hottest day on record during the summer of 2012/13..”

112.  Not the 700+ of the AWAP (Australian Water Availability Project) used to make the claim about January 7 being the hottest day on record.  112 is the number of sites in the ACORN dataset.

So I’m sure all journalists reporting this claim would have referred to the BOM’s Time Series Graphs on their website, which use the ACORN data, to confirm just where this summer was the hottest on record.  Forgive the sarcasm- they plainly didn’t.  Let’s take a look.

First, here is the plot for the summer mean temperatures for all of Australia 1910-2012 (which includes January and February 2013):Yep, the 2012-13 summer mean was definitely the highest on (this) record.  There are 6 regions and 7 states/territories in Australia:Let’s see how each of these performed.

Northern Australia:Nope!

Southern Australia:Nope!

Eastern Australia:South Western Australia:South Eastern Australia:Murray-Darling Basin:What’s going on?

I am reminded that one way of calculating mean temperature is to average the minimum and the maximum.  Here’s the summer maximum for Australia:As expected.  Now the minimum:So we can blame the record mean on the record maximum temperatures.  Let’s look at the different regions.

Not Northern Australia.It’s Southern Australia:But not Eastern Australia.Not South Western Australia.Not South Australia (the State):Not Western Australia (the State):So the only part of Australia left that could be responsible for the summer maximum record, and consequently the mean, is this bottom part of WA not in the south west corner, or perhaps as well the southern portion of Queensland:It must have been a tad warmer than average there!

It doesn’t look to be hotter than South Australia or Victoria. By the way, this is Victoria:The problem:

The summer mean temperature for all of Australia, according to BOM, was the highest on record.  They confirm this with their graph of ACORN data.

The summer minimum was not a record by a long way.

Only Southern Australia’s maximum temperatures show this record.  No other regions were hotter this summer.  And this includes none of the smaller regions within Southern Australia.

Therefore we can conclude that BOM is flicking between two methods of calculating temperature and two datasets to find the “record” that fits their global warming mantra.

Please explain.

 

h/t Andrew Barnham