Jennifer Marohasy

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How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 6)

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Dr David Jones, the head of climate analysis at the Bureau of Meteorology, recently attributed a decline in Melbourne’s rainfall to global warming.    Amongst various comments, he claimed in The Age that the autumn drying trend could be linked to either human-induced climate change through greenhouse gases or changes in the ozone layer over Antarctica.  

Ockham’s Razor, the principle proposed by William of Ockham in the fourteenth century: “Pluralitas non est ponenda sine neccesitate”, which translates as “entities should not be multiplied unnecessarily” would require that Dr Jones choose one or the other theory, greenhouse gases or depletion of the ozone layer, as an explanation for the decline in rainfall. 

But does either theory really represents much more than speculation? 

Indeed lead authors of the Intergovernmental Panel on Climate Change (IPCC) acknowledged just after the release of their last big report that  until major oscillations in the Earth System, including El Nino-Southern Oscillation, Pacific Decadal Oscillation, North Atlantic Oscillation and Atlantic Multidecadal Oscillation, are better understood regional climate, and in particular regional rainfall,  is a difficult problem.

Furthermore, there are perhaps other simpler explanations for the recent decline in rainfall. 

Indeed Dr Jones recently confirmed that his comments in The Age were based on data from just one weather station:  a site in Melbourne’s central business district.  

This brings us back to Part 1 of this series in which Bill Kininmonth, a meteorologist formerly with the Bureau, made comment that “the rain gauge in Melbourne’s central business district is now sheltered from the rain bearing winds of the southwest”.

How To Censor a Climate Sceptic

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Dr Roy Spencer is a well known climate sceptic who has published extensively in mainstream peer-reviewed scientific journals and earlier this year had a popular book published entitled ‘Climate Confusion’. 

Yesterday, November 3, 2008, two technical papers that Dr Spencer had recently submitted to the journal Geophysical Research Letters were outright rejected in back-to-back emails and on the same day all 78 reviews of his book on Amazon.com were removed from that website.

November 4, America Votes, Including on Energy

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The United States presidential election of 2008 is scheduled for today, November 4.  While the campaign was dominated initially by foreign policy and more recently by the financial crisis, there are other issues including energy.    The likely new President, Barack Obama, has promised $150 billion for renewable energy, while Republican hopeful, John McCain, has promised 45 new nuclear power stations and to expand domestic oil and natural gas exploration and production. 

The Obama “New Energy for America” plan also includes: short-term relief to American families facing pain at the pump; the creation of five million new jobs by strategically investing $150 billion over the next ten years to catalyze private efforts to build a clean energy future; within 10 years save more oil than is currently import from the Middle East and Venezuela combined; put 1 million Plug-In Hybrid cars — cars that can get up to 150 miles per gallon — on the road by 2015, cars that Obama will work to make sure are built in America; ensure 10 percent of electricity comes from renewable sources by 2012, and 25 percent by 2025; Implement an economy-wide cap-and-trade program to reduce greenhouse gas emissions 80 percent by 2050.

Cosmic Rays, Clouds and Climate (Part 2)

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THERE is a theory that the earth’s climate is influenced by cosmic rays that penetrate our atmosphere from outer space.  In particular it is thought cosmic rays influence the production of cloud condensation nuclei with periods of higher cosmic rays penetration associated with more cloudiness.   The power of what is known as the solar wind, the magnetic force associated with the sun, is thought to influence the extent to which these high-energy charged particles composed of protons, electrons, and ionized nuclei reach earth.   

The theory has been based to a large extent on correlations between climate and sunspot cycles.  There is now a research effort to establish a physically-plausible link between cosmic rays, clouds and climate including through laboratory experiments in clouding at the Cern Cloud Facility in, Geneva, Switzerland.    The theory and the experiments are explained in ‘Cosmic Rays and Climate’ by Jasper Kirkby, Surveys in Geophysics, Volume 28, pages 333-375. 

I know of no equivalent research effort looking at establishing a causal link between carbon dioxide and climate. 

This paper by Dr Kirby was first discussed here in a blog post by Paul Biggs on May 21 this year.  I’ve only just properly discovered it – and thought it so good you should read about it a second time.  I posted  ‘Cosmic Rays, Clouds and Climate (Part 1)’ on April 13, 2008.

How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 4)

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Dr David Jones, Head of Climate Analysis at the Australian Bureau of Meteorology, has claimed that over the past 11 years Melbourne’s rainfall has been about 20 percent below the long-term average.  

It is common to refer to “the long-term average” when discussing climate data, but if the climate along the East Coast of Australia tends to be dominated by either El Nino or La Nina conditions, how meaningful is an average? 

According to Associate Professor Stewart Franks, School of Engineering, University of Newcastle, when calculating a long-term average it is important to include an equal number of La Nina and also El Nino dominated periods.  

Professor Franks is a hydrologist with an interest in understanding the risk of flooding.    He has explained that if you take an annual maxima flood series for a northern New South Wales catchment, which is typical for the East Coast of Australia over the last 100 years, there have been two periods of El Nino conditions and a single La Nina. 

So when a long-term average is calculated from this data it probably underestimates the real risk of a big flood event.  In other words, if anything government policy and planning has underprepared us for big flood events. 

In the opinion piece by Dr Jones entitled ‘Our hot, dry future’ published by Melbourne’s The Age newspaper recently, he claimed the below average rainfall in Melbourne was due to global warming and that there was worse to come. 

But if the climate along the East Coast of Australia is a two state process dominated by El Nino or La Nina, then while Melbourne has experienced relatively dry conditions during the past 11 years, the expectation would be that at some point  we will move back into a La Nina dominated phase.    According to Professor Franks, it is probably a bit messier than that with periods that might not be dominated by either.

Nevertheless, it is reasonable to assume the longer the El Nino dominance continues, the likelier it is to end.  

So, rather than preparing for more drought as Dr Jones suggests, perhaps we should prepare for more floods?   Indeed climate always changes and floods and droughts are a natural hazard.

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For more information:

D. C Verdon & S. W. Franks, 2006.  Long-term behaviour of ENSO: Interactions with the PDO over the past 400 years inferred from paleoclimate records, Geophysical Research Letters, 33.

Part 1 of this series,
https://jennifermarohasy.com.dev.internet-thinking.com.au/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-david-jones-part-2/

Part 2 of this series,
https://jennifermarohasy.com.dev.internet-thinking.com.au/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-david-jones-part-1/

Part 3 of this series,
https://jennifermarohasy.com.dev.internet-thinking.com.au/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-david-jones-part-3/