How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 1)
Posted by jennifer, October 14th, 2008 - under Opinion.
Tags: Climate & Climate Change
“THESE days, it can be hard to imagine how Melbourne ever earned a reputation as the gloomy, rain-filled capital of the south. But, growing up in the 1970s, my memories are full of muddy ovals, local creeks in flood and catching tadpoles in puddles that lasted for months on end. How things have changed.”
This is how David Jones, head of climate analysis at the Bureau of Meteorology, began an opinion piece entitled ‘Our hot, dry future’ published by Melbourne’s The Age newspaper on October 6, 2008.
The piece continued,
“Since 1996, each successive calendar year has brought the city below-average rainfall. With 299 millimetres recorded so far this year, and with just three months to go, it seems virtually certain that this year will become the 12th in a row that has failed to get to the average of 650 millimetres. September 2008 was the driest on record in Melbourne, and the outlook for the remainder of the year suggests that below-average rainfall will continue…
“We also know that over the past 11 years Melbourne’s rainfall has been about 20% below the long-term average, and that south-east Australia as a whole has now missed out on more than a year’s worth of its normal rainfall over the duration of the event. The run-off into Melbourne’s dams has been 40% below average over this drought period compared with the longer term, while regional areas have fared even worse. And the drought hasn’t ended.”
Dr Jones goes on to blame climate change for the drought and warns there is worse to come.
I recognise that Dr Jones is an expert on predicting future climates, but I am not sure he has adequately explained the recent past climate of Melbourne.
Climate always changes and in a country like Australia climate tends to naturally cycle between periods where there is a dominance of wet La Nina conditions and then dry El Nino. The 1950s and 1960s were very wet along the entire east coast of Australia, but since 1976 the median state of the Pacific Ocean has been towards El Nino that is dry conditions. Indeed Dr Jones was a young boy when it was relatively wet while his adult life has been dominated by El Nino conditions. Of course the built environment has also changed. Melbourne is a much more affluent city now than it was 30 years ago and along with affluence comes laser levelling of sporting venues and much improved drainage and flood mitigation so ovals dry out relatively quickly, creeks are slowed and puddles in public places now a thing of the past.
But there is more to this story.
Bill Kininmonth, a meteorologist formerly with the Bureau, has made the following comment about how the recording of Melbourne’s weather has changed over the years and how the rain gauge in Melbourne’s central business district is now sheltered from the rain bearing winds of the southwest:
“Although Melbourne’s observations commenced in 1851 the location and environment have changed over that time. The earliest observations commenced at Flagstaff Hill and then they changed to the Observatory site south of the Yarra. For more than 100 years the observations have been taken from the present site on the corner of Victoria Parade and Latrobe Street. However there has been urbanisation. The site has clearly lost exposure to the cooling southerly winds and the rain gauge is sheltered from the rain bearing winds of the southwest.
“Clearly it is difficult to draw a conclusion about Melbourne’s climate and the possibility that it might be changing. The urbanisation of the site should make the record indicate a hotter and dryer climate, whether or not that has occurred. Essendon airport was a previous non-urban locality in the vicinity but that closed in the early 1970s. Tullamarine is the current site but was not open during the dry periods of the first half of the 20th century. Laverton, likewise an early site with long data has also been closed.”
I shall post more tomorrow on Melbourne’s total catchment rainfall and water storage levels in Part 2 of ‘How Melbourne’s Climate Has Changed: A reply to Dr David Jones’
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Our hot, dry future, by David Jones, October 6, 200, The Age
http://www.theage.com.au/opinion/our-hot-dry-future-20081005-4udg.html
[...] ************************************* Read Part 1 here: http://jennifermarohasy.com/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-david-jones-part-2/ Read Part 2 here: http://jennifermarohasy.com/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-d... [...]
[...] Part 2 of this series, http://jennifermarohasy.com/blog/2008/10/how-melbourne%e2%80%99s-climate-has-changed-a-reply-to-dr-d... [...]
[...] brings us back to Part 1 of this series in which Bill Kininmonth, a meteorologist formerly with the Bureau, made comment [...]
[...] My main criticism of the article is that the BoM relies on Melbourne CBD rain data to back up their regional conclusions regarding “climate change” and drought, while the rainfall history is in fact affected by the growing urban heat island. Melbourne Regional Office 86071 (MRO), a weather station in Melbourne’s CBD is (a) excluded from their own High Quality (HQ) dataset and (b) shows a negative trend of 90mm (a stunning 13% of mean annual rain) over the last 153 years when compared to the nearest HQ station, Yan Yean 35 km NNW. So much of what they say in “Our hot, dry future”, is slanted by this amount, no wonder I am critical of much that the BoM publishes. Melbourne Regional Office weather station in Melbourne’s CBD which has rain data from 1855, is a site that has undergone enormous changes in its surroundings as the city has been built and expanded over the centuries, resulting in an ever-increasing urban heat island. The above illustration is from a 1997 BoM paper. High rise developments have increasingly affected wind and changing pollution levels over the decades could also cause variations in rain formation. Up to post WWII coal burning would have been common leading to much worse pollution than modern times, (note visibility data) and air quality data show improvements over say the last 40 years. These are just a quick sketch of some reasons why weather data from a large and expanding urban heat island is a most unsuitable source from which to draw conclusions about, climate change, regional changes and long term rain trends. Finally, the article contains another BoM failed prediction, saying in the second paragraph, “..the outlook for the remainder of the year suggests that below-average rainfall will continue.” Wrong BoM, the 2 month rainfall total for November-December for Melbourne Regional Office was 130.8mm compared to the long term mean of 118.7. Jennifer Marohasy featured 5 articles on her blog examining the subject during October 2008; the first titled How MelbourneÆs Climate Has Changed: A reply to Dr David Jones (Part 1) was posted on 14 October and parts 2 to 5 were later in the month… [...]
I’m horrified that my idea to make a great inland sea using a channel from SA to the dry salt lake Lake Eyre has already been proposed by smarter people then me years ago, this would have a milding effect on all of Australia especially erm Victoria and South Australia! To think these fires could of been a whole lot less if not avoided altogether makes me furious, over what uranium in the desert? The cost of building a channel?? What of cost the loss of life and communities?
Want to stimulate the economy give people jobs to build the channel not give junkies $5k to have babies, sometimes I wonder about this country I really do, even the Yanks know what effect the great lakes have on weather there.
I arrived in Australia in June 1967 and by the end of that year Melbourne had experienced its worst drought – in living memory. Monthly rainfall records from 1967 to the end of 2009 shows that droughts were followed by wet periods and then, by 2007, we were in another (cyclic) drought of sorts. When we think Melbourne we are really grouping a significant area in which there are equally significant efficiencies and deficiencies in rainfall. Werribee, Laverton to just mention two, have climatic conditions that would have long heard residents claiming climate change. however, their climate has nothing to do with climate change it’s within normal limits of acceptance.
Add a heaped ladle of confusing behaviours: all living things and particularly plants continue evolving, some, even before the “drought”, were in irreversible decline. The problem is that observers and commentators need to have lived, observed and computed what is really occurring locally before concluding that we are all in the grip of climate change. Observing incremental growth of trees can indicate what the effects the lack of optimum rainfall has on tree growth and to the best of my knowledge many trees have continued growing well despite all fears and claims.
What confuses many are the actions of municipalities such as the Melbourne City Council who in February of 2010 covered lawns in which trees grow with mulch, much of it infused with oil. The emotional response of most people will be “tree care in action” the truth is the mulch is wrongly positioned, but it’s neat, and it’s far too late to do any real good. It’s feel good mulch. The benefit would have been best received seven to ten years ago. To that that, drip irrigation was installed in early 2009, slicing through the roots of all trees. Some die as most of their hair roots had been severed. Adding to the damages, the MCC has a contractor who carries out its contractual obligations and in doing so drives their vehicles over the irrigated, often soggy lawns, compacting soils in which all of those supposedly valuable trees grow. Unless you have observed many trees being removed you the reader will not know. But if in the course of casual conversation you happened to correct a piece of information saying that most mature trees in the suburbs die from injury and neglect and not climate change, you are at worst considered a climate change denier or as in my case asked to explain.
Ivan Earl, Consultant Arborist. Melbourne. Australia