Nelson's Column
Charlie Nelson's Blog
An inconvenient rain for the Murray Darling Basin Authority and Climate Scientists
October 2010 has been a pivotal month for rainfall in Melbourne. After 9 years of below average rainfall (1997 to 2005) Melbourne’s drought intensified over the period 2006 to 2009. In the first 9 years of drought, rainfall was 21% below the long-term average. In the last four years rainfall was 32% below average. The first six months of 2009 were the driest first six months on record – and records go back to 1856. But October 2010 confirmed signs emerging since September 2009 that the drought is ending.
There are important implications of the return to more average rainfall conditions in Melbourne and south-eastern Australia more generally. In particular, given that the recovery from drought was not predicted by climate scientists and is not consistent with the models currently used by climate scientists, there is a risk that complacency about water supply could increase to the extent that little action on water efficiency and allocation is taken before the next long drought.
October is, on average, Melbourne’s wettest month. But October 2006, 2007, 2008, and 2009 were all well down on average – by a cumulative 76%. The wettest October in this period, 2009, was 67% below average. By 16 October 2010, Melbourne had exceeded the October average and October 2010 rainfall to that data had exceeded the aggregate of the past four Octobers. By that date, it was already the wettest calendar year since 2005. By 23 October 2010, it was the wettest October since 2000. By that date, Melbourne’s rainfall had exceeded 500mm for the calendar year to date compared with a maximum annual total of 455mm over the period 2006 to 2009.
Total rainfall in Melbourne for the period November 2009 to 23 October 2010 was 659mm, above the annual average of 647mm.
I take some pride in having predicted that recovery from drought could happen. I have analysed the drivers of rainfall for Melbourne and these are important for the Murray Darling Basin as a whole – especially the southern part. In September 2009, I advised the Murray Darling Basin Authority, Melbourne Water, the Victorian Department of Sustainability and Environment, and Professor David Karoly of the University of Melbourne Earth Sciences Department that the recovery from drought was likely quite soon. I confirmed that prediction to each of these in March 2010. They all politely showed no interest or encouragement. My prediction was no doubt seen as being not credible and also inconvenient given the evolving Murray Darling Basin Authority plan and the large investment in the desalination plant and the north-south pipeline aimed at securing water for Melbourne.
But the start of the recovery from drought is not limited to Melbourne. Most of Victoria has shared in this recovery and some parts of the state have fared even better than Melbourne.
The four largest dams in Victoria are:
1. Dartmouth, 48% of capacity as at 25 October, compared with 30% a year earlier;
2. Eildon, 63% compared with 32%;
3. Hume, 99% compared with 39%;
4. Thomson, 32% compared with 20%.
This is a very substantial and welcome boost to storage levels.
There have been very good rains elsewhere in Australia too. On 1 October 2010, the Bureau of Meteorology issued a special climate statement reporting that September was Australia’s wettest September on record, although in many parts of Australia there remains a long-term rainfall deficit. Their statement is especially true for Victoria, but at least the deficit there has clearly stopped worsening.
New South Wales has been declared drought-free for the first time in nine years, as at 21 October 2010, by the New South Wales government.
By 11 October 2010, after torrential rain, water was flowing over the spillway at Wivenhoe dam in south-east Queensland – for the first time in almost 10 years. Just three years ago this dam, Brisbane’s largest, was below 10% of capacity.
There have been heavy rains in Alice Springs in central Australia (total to mid-September 567mm), after 2009 being the driest on record (77mm). Anecdotal reports from long-time residents of central Australia suggest that it is the greenest it has been in over 30 years, if not much longer.
Above average rainfall, especially in the northern part of the Murray Darling Basin has eased rainfall deficiencies present since 2001.
By October 2010, there was a natural flow through the mouth of the Murray River for the first time since 2002.
So October 2010 was not a good time for the Murray Darling Basin Authority (MDBA) to release a guide to the proposed basin plan, canvassing big cuts to irrigation allowances (ranging from 27% to 37%). It has been very poorly received by irrigators, as would be expected. But the timing did not help matters – it means that irate irrigators and other interested parties can claim that the rain is back and nothing needs to be done.
There is no doubt that too much water has been allocated to irrigators over the decades, that the environment has suffered and that a balance needs to be restored. But will enough people, and especially politicians, still have the will to bring about the needed changes now that there have been good rains?
These rains have not been predicted by the CSIRO or the Bureau of Meteorology (BOM), although they were predicted by me. Nor have the CSIRO or BOM convincingly explained the long drought and its intensification between 2006 and 2009, whereas I have at least identified the driving forces. These are natural forces and so the long drought and recovery from it do not require global warming as an explanatory factor.
As there is a degree of cyclicality to two of the driving forces, it is possible to identify the next period when extended drought is likely – it is 2017 to 2022. So the development and implementation of a plan for more balanced allocation of water resources is still urgent, despite good rains this year.
In May 2010, the South Eastern Australian Climate Initiative (SEACI) released a report from Phase 1 of their research into climate variability and change in south-eastern Australia. At a cost of $7.5 million, the sixty-odd scientists from CSIRO, BOM, and other organizations found that large-scale factors that influence the climate of south-eastern Australia cannot explain the decline in autumn rainfall. These factors include the El Nino – Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). The study found that:
- Changes in the Hadley Cell are leading to increasing surface pressure across the region, represented by the sub-tropical ridge (STR);
- The increase in the intensity of the STR is well correlated with decreasing rainfall in all seasons except summer;
- There is evidence that the changes in the Hadley Cell and STR are linked to global warming, rather than simply being a natural fluctuation in the global circulation.
The report states that: “Yet another possibility is that the current [rainfall] decline is a natural cycle in the climate of south-eastern Australia”. “..., it could be argued that a return to wetter conditions is likely in the near future, and that any association of the current dry period with global warming is simply fortuitous. This is considered to be unlikely by SEACI researchers”.
My analysis has convinced me that the extended drought can be explained by natural factors. The above statement in the SEACI report may have been directed at my dissent. In September 2009, I advised two of the contributors to the SEACI study that I had decoded the drought and that the factors driving it were natural – and so it was likely that there would be a return to more normal conditions. In March 2010, two months before the SEACI report was published, I advised both of them that the natural factors inhibiting rainfall had relented and so recent increased rainfall was likely to continue. Naturally, neither replied.
Rainfall since the start of September 2009 supports my argument for natural causes more than it supports the case for global warming being the cause. After all, global warming has not gone into reverse but rainfall has recovered!
The potential implications of this “inconvenient” rain include:
- A loss of confidence in climate science (their forecast are in error and the exclusion of natural factors by climate scientists means that they do not have a reliable basis for estimating the impact of anthropological factors on rainfall.); and more importantly,
- A decline in the will of the public and politicians to act on the policies needed to restore balance in the Murray Darling system. A return to complacency would be a disaster given the likelihood of another extended drought starting in about seven years.
In order to prevent complacency from setting in if good rains continue in 2011, as I expect, it is imperative that an understanding of the natural factors which drive rainfall be embedded in climate models and communicated effectively. Otherwise the next natural extended drought could be even more costly than the one just coming to an end.
My first paper on cycles in Melbourne’s rainfall can be read at www.charlienelson.com/moonrain.pdf. This paper was submitted to the House of Representatives Standing Committee on Industry, Science and Innovation enquiry into long-term meteorological forecasting and it was mentioned in their November 2009 report (page 49). My more recent paper, which fully explains the drought including the intensification in 2006 and the start of recovery since late 2009, is available at www.foreseechange.com.au.
Postscript
By 31 October 2010, the “Halloween” deluge in Melbourne further confirmed recovery from the long drought. Between 1 November 2009 and 31 October 2010, Melbourne received 718 mm, well above the annual average. October 2010 was the wettest October since 1975. Spring 2010 rainfall was above average with a month still to go.
Charlie Nelson
October 2010
Update: January 2011
The Bureau of Meteorology has now reported that 2010 was Australia's third wettest year on record (reliable records go back to 1900). The only wetter years were in 1974 (the wettest) and 2000. Melbourne had its wettest year since 1996 - 776.7mm compared with the average of 648mm.
The Murray Darling Basin had its wettest year on record (records also go back to 1900)! Water storages across the basin increased to 80% at the start of 2011, up from just 26% a year earlier. This is more consistent with my research which concludes that rainfall is cyclical than with the CSIRO research which concludes that rainfall has fallen due to global warming.
Already there are calls for delay in implementing the Murray Darling Basin Plan. As reported in The Australian on 6 January 2011 (page 1), National Farmers Federation president Jock Laurie said that six months of strong flows into the Murray Darling buys the government time to sit back and make sure they get this right. Opposition water spokesman Barnaby Joyce has backed calls for delay if it meant a better plan.