Archive for January, 2012

How Cold Was 2011? An Analysis of Australian Minimum Temperatures 1910-2011

January 28, 2012

Ken Stewart, 28 January 2012

Introduction

In March 2011 I analysed trends in Australian Maximum Temperatures from 1910-2010, and now I am following up with Minima.  Since that time I have looked at adjustments made by the Bureau of Meteorology (BOM) and in a paper co-written by Dr David Stockwell proposed an alternative network of climate sites we call the Minimally Adjusted Network (MAN).  This network comprises sites included in BOM’s High Quality (HQ) network but makes adjustments by comparison of overlapping raw data only.

I have further revised this network by removing all sites where there is less than two years of overlapping data, where there is less than 80 years of data, where the record shows spurious data, or where metadata supplied by BOM indicates serious problems.  I have deliberately included all urban sites including all capital cities except Darwin, usually at a nearby airport.  The MAN dataset for Minima now comprises 89 sites.

I shall explain with one example what “Minimally Adjusted” means.  Here is a graph showing the raw data available for sites near Cairns in North Queensland:

There is good overlap of 10 years from 1943 to 1952.  The graph shows Cairns Airport minima are warmer than the Post Office, and in fact the mean difference is 0.29 degrees.  Therefore the Post Office raw data may be adjusted up +0.29 degrees so that the two series are comparable, to give this graph of the spliced data:

No assumptions are made about the data, and no subjective decisions are made about whether to adjust and by how much, unlike the adjustments used in BOM’s HQ datasets.  No other adjustments are made.  If a site meets the criteria but the metadata indicates serious problems (e.g. Nhill) or the data appears to be spurious (e.g. Halls Creek), it is excluded.  As more metadata becomes available it may be that further sites will be excluded.

To compare temperature across Australia I convert all data to anomalies from the 1961 to 1990 mean for each site.  I then calculate the mean anomaly for each year for a selection of sites.  While I show data from 1910 to 2011, much 2011 data has still not been “quality assured”, so many annual means were not available.  For these sites I found the annual mean from the daily means, which is not the correct method, but is close.

 Caveat:  There is considerable uncertainty in all temperature data.  BOM says that Automatic Weather Station (AWS) data has an accuracy of +/- 0.3C.  Celsius thermometers (mercury in glass) have an accuracy of at best +/- 0.5C.  Fahrenheit thermometers, certainly no more accurate, were used before September 1972 and temperatures recorded before then were converted to Celsius for modern comparison.    The records show that in the Fahrenheit era, many observers used whole degrees even though BOM’s instructions to observers were to record temperature in tenths of a degree.  That’s hard enough on a Celsius max/min thermometer.  A number of quite recent observations appear to be recorded in whole degrees. The change to Celsius in 1972 may have led to an artificial warming relative to pre 1972.  Certainly the Australian temperature record must be treated with great caution.  Therefore my figures are subject to the same uncertainty.

Results

Here is the graph of Minima for all 89 MAN sites:

While Australian temperatures have been rising, it has been by no means a steady increase.  There was an enormous jump up in the 1970s.  The 4th order polynomial trend line shows the distinct fall and rise.  Are we following a natural cycle?  The next few years will be decisive.

What’s with WA?

Here’s Western Australia;

And here’s the rest of the continent:

Wildly different!  It’s worth putting both together to show the difference more clearly.

WA is clearly a different climate zone.

City vs Country

Not such a great difference.  Urban sites are warming slightly faster- UHI?- cooler up to 1950s, and in the 1990s, and are a little more variable, which is surprising.

Beach or Bush

Sites within 100km of the coast have much less variability than inland sites, due to the oceanic influence.  Inland sites have greater extremes, but the overall trends are very similar, except that coastal sites are getting warmer, whereas inland sites’ extreme peaks have been decreasing since 1973.  The extremes are at identical times, but the standout differences are 1973, 1976, and of course 2011.  Note the late 1970s step up is very clear.

North and South

The boundary line is the South Australia/ Northern Territory border.  First southern Australia:

Northern Australia:

Wildly different!  Note the warmest year by far was 1998, and 2011 was colder than any year since the 1970s.  Now let’s combine:

Note that northern minima- further from the South Pole- are warming faster than the southern.  The north has much greater extremes and appears to have peaked.

Maxima and Minima

I have plotted Maxima and Minima only to 2010.

While the linear trend for Minima is greater than for Maxima, and after initially decreasing, Minima anomalies have been rising since the 1940s, in the past decade (“the hottest on record”), minima have flattened.  The record means have been caused by much higher maxima.  This is especially visible in a plot of the annual Max-Min range, which shows the linear trend steadily decreasing as is expected with the Greenhouse Effect.  However, the range has increased steeply since the 1980s which is not what is expected.  This is not the signature of Anthropogenic Global Warming, at least in Australia.

Conclusion:

The Minimally Adjusted Network provides an alternative network of 89 long term sites with few adjustments to the raw data.  Uncertainties in the data accuracy of at least +/- 0.3C mean that the temperature record must be viewed cautiously.

There is little difference between Urban and Non-Urban minima.

Western Australia has a completely different climate to the rest of Australia.

Coastal and Inland trends are not greatly different, except for variability, until 2011.

Much can be learned from looking at Means, but an analysis of Minima yields further interesting information.  Remember: Anthropogenic Global Warming due largely to the greenhouse effect should be visible in Minima.  Temperature increase should be greater at night, in winter, and towards the poles.  It is plain, however, that in Australia this is not the case.

Since the 1940s, very cold years have been getting progressively milder, but since 1973 very mild years have been getting progressively cooler.  Further, the increase in minima is more pronounced in northern Australia than in the south- and while southern Australian minima have been steadily increasing, northern minima have a much greater variation and appear to be now decreasing.   The Range bewteen Maxima and Minima does not show the greenhouse Effect signal.   My guess is that El Nino/ La Nina conditions have a very large influence on northern Australian (largely Queensland) minima and consequently Australian minima.

The huge variations we see from the 1970s to about 2000 have decreased.  The huge step up of the 1970s (The Great Climate Shift) is clearly visible in the minima, but the next few years will show if it has run its course.  I expect it has.

And finally, 2011 was not particularly unusual- except in inland and northern Australia where it was the coldest since 1994.

Appendix:  Minimally Adjusted Network

Cairns Airport Broome
Cardwell Roebourne
Palmerville Marble Bar
Georgetown Geraldton
Richmond Kalgoorlie
Boulia Southern Cross
Camooweal Merredin
Ayr Wandering
Longreach Air Rottnest Island
Barcaldine Cape Naturaliste
Rockhampton Air Cape Leeuwin
Sandy Cape Lighthouse Jarrahwood
Gayndah Air Bridgetown
Cape Moreton Lighthouse Katanning
Amberley RAAF Albany
Charleville Esperence
Cunnamulla Perth
Miles Adelaide
Bollon Innisfail
Alice Springs Mackay
Yongala Maryborough Qld
Rayville Park Brisbane
Strathalbyn Park Dalby
Robe Hobart
Low Head Gunnedah
Launceston Ti tree Tamworth
Cape Bruny Inverell
Mildura Port Macquarie
Kerang Broken Hill
Cape Otway Lighthouse Newcastle
Laverton Bathurst
Rutherglen Orange
Omeo Dubbo
East Sale Sydney
Wilsons Promontory Lighthouse Bowral
Gabo Island Lighthouse Echuca
Tibooburra Benalla
Wilcannia Melbourne-Moorabin
Cobar Maryborough Vic
Tenterfield Ballarat
Glen Innes  
Yamba  
Jerrys Plains  
Mudgee  
Point Perpendicular  
Moruya Heads  
Wagga Wagga  
Deniliquin  
Hay  

Global Temperature Page- January

January 12, 2012

This page will be reposted around the middle of February, as soon as SOI and UAH data for the previous month are available.

The December UAH value is +0.13  making the running 12 month mean +0.15 +/- 0.1.  December SOI reached 23.

All through 2011 I watched my predictions get further and further away from the actual 12 month mean of UAH temperatures.  I decided to change two factors in my algorithm with startling results- the calculated 12 month mean temperatures are closer- much closer- at least for the last two years.   Here are my old figures and new calculations compared:

Month

Predicted 12 month running mean

Actual UAH 12 month mean

New Calculations

March 2011

+0.29 +/- 0.05

+0.27

+0.31

April 2011

+0.23 +/- 0.05

+0.25

+0.27

May 2011

+0.21 +/- 0.05

+0.22

+0.26

June 2011

+0.16 +/- 0.1

+0.21

+0.24

July 2011

+0.12 +/- 0.1

+0.21

+0.22

August 2011

+0.07 +/- 0.1

+0.20

+0.19

September 2011

+0.01 +/- 0.1

+0.19

+0.15

October 2011

+0.01 +/- 0.1

+0.17

+0.14

November 2011

0 +/- 0.1

+0.16

+0.13

December 2011

0.07 +/- 0.1

+0.15

+0.12

January 2012

0.08+/- 0.1

 

+0.12

February 2012

0.12+/- 0.1

 

+0.13

March 2012

0.15 +/- 0.1

 

+0.13

April 2012

0.17 +/- 0.1

 

+0.13

May 2012

0.18 +/- 0.1

 

+0.12

June 2012

   

+0.12

So we’ll see how we go this year!

Last month I tipped “the next major enhancement to weather with heavier rainfall should be in the last week of December to mid January”.   Two cyclones appeared and caused major flooding in the Northern Territory, plus a Christmas Day storm in Melbourne (probably not connected!) and heavy storms about the Queensland Central Coast, so a little earlier than I expected but not much.

Although there are extremes about right now (12 January) I expect the next major build up of heavy rain and possibly cyclones off the east coast around 22 January to mid February.  This is the usual time for the arrival of the Wet season in this part of Queensland- when school starts.

So here’s my plot of what global temperatures could be like over the next 11 years, excluding major volcanic eruptions or other unforseen factors.  These represent my long range predictions for 12 month running mean global tropospheric temperatures as recorded by UAH.  This is based on my analysis of the UAH record compared with the 120 month running mean of the Southern Oscillation Index with a lag of 11 years and the 12 month running mean of the SOI with a lag of 6 months.

The upper and lower limits are for the maximum and minimum historical values for the 12 month mean SOI (+23 and -23).   If the global 12 month means exceed either of the black lines for more than 2 years I would consider this prediction falsified.

I calculate as follows:

T(12)m,y = [(SOI(12) m-6, y) /9 + (SOI(120) m, y-11)] /12 + FF

where

T = 12 month running mean up to month m of year y of global atmospheric temperature anomalies in degrees Celsius

SOI = running mean of inverted SOI values for (12) or (120) months

FF = fine-tuning factor, which for long term purposes can be assumed to be +/- 0.1.

(FF is some factor I am unable to identify but may be related to PDO, aerosol concentrations, or maybe even CO2!)

Here is a plot of the calculated means vs actual UAH 12 month means since 1979.

Note there is great variability.  Far from falsifying my hypothesis, I consider that this clearly shows the effect of volcanic eruptions.  The correlation between my calculated and actual values for 12 month mean UAH from January 1998 (the year of the big El Nino) to December 2011 is 0.7348, and from 1979-2011 is 0.6898.

I also include graphs showing the contribution of various factors.

12 month running mean of SOI values is obviously related to UAH, but other factors are involved.

Running 120 month mean of SOI since 1876- note the big jump since 1976.  What if we advanced it by 11 years and combined it with the 12 month mean.

Here’s the calculated values 1979-2011.

I expect that I will need to rework my calculations in the light of future data.  In particular, I’m sure that the long term values have varying influence  which is why there is variation.  These are still early days.

2011 in review

January 2, 2012

The WordPress.com stats helper monkeys prepared a 2011 annual report for this blog.

Here’s an excerpt:

The concert hall at the Syndey Opera House holds 2,700 people. This blog was viewed about 12,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 4 sold-out performances for that many people to see it.

Click here to see the complete report.