In Sydney, the Premier of New South Wales, Nathan Rees, yesterday blasted former state treasurer Michael Costa for being a global warming sceptic, and said a new era of climate change action would start immediately. Read more here.
Climate & Climate Change
Carbon tax is just tilting at windmills: Gary Johns
A carbon tax will not stop the need for climate adaption. Even under the Australian Greens’ scenario for a carbon-free economy, climate change will occur but the economy would be less able to afford to adjust. Read more here.
How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 5)
Dr David Jones, the head of climate analysis at the Australian Bureau of Meteorology, in an opinion piece, ‘Our hot, dry future’ has argued that over the past 11 years Melbourne’s rainfall has been about 20% below the long-term average experienced declining rainfall over the past 11 years .
In response, Dr Jennifer Marohasy posted ‘How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 3)’, which included a graph of high quality data of rainfall at Yan Yean, Victoria, because of its proximity to Melbourne.
The graph is from Mr Warwick Hughes based on Bureau of Meteorology data and shows that recent rainfall decline at Yan Yean is comparable to declines during previous droughts.
I have also graphed Bureau data for some of Melbourne’s catchment areas. While I couldn’t find a site with data extending back as far as the Yan Yean site, the Maroondah and O’Shanneyssy stations show a significant recent decline in rainfall that is greater than previous droughts in the 1896, 1925 and 1945.
Some of the Melbourne catchment areas rainfall data shows recent significant decline, but there are a number of problems with using bureau rainfall data for the Melbourne catchment. A main problem is that the Bureau does not have rainfall data for Melbourne’s largest reservoirs, Upper Yarra and Thomson back more than 30 years.
The best publicly available data on catchment area rainfall comes from Melbourne Water. However, Melbourne Water’s publicly available data is only from 1998 to 2008.
Without long-term high quality data of catchment area rainfall for all catchment areas, it is impossible to know whether the longer-term trend shows dramatic declines at many, or just some, places in the Melbourne catchment.
Nichole Hoskin
Blue Mountains, Australia
How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 4)
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.
******************************************
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/
How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 3)
IN an opinion piece entitled ‘Our hot, dry future’ published by Melbourne’s The Age newspaper on October 6, 2008, Dr David Jones, head of climate analysis at the Australian Bureau of Meteorology, suggested global warming was responsible for the current long drought in Melbourne and that there was worse to come.
I don’t think the article was very convincing. I am annoyed that it didn’t include any real data. While Dr Jones claimed that “We know that over the past 11 years Melbourne’s rainfall has been about 20% below the long-term average”, he didn’t explain what period this “long-term average” covers and what is the relevance of the last 11 years given it is accepted that over this period there has been a dominance of El Nino, and therefore dry conditions.
Key Australian Institutions have claimed for some time that we have a water crisis because of climate change.
Indeed in 2005 CSIRO published a “Melbourne Water Climate Change Study” claiming “…the greater Melbourne Region has had its lowest rainfall on record compared to all other periods of similar length.”
But as blogger, Warwick Hughes, showed some time ago, the period chosen was just 92 months, from October 1996 to May 2004.
In order to put their statement in some context Mr Hughes graphed high quality rainfall data for the weather station closest to Melbourne, Yan Yean, back to January 1863 – and he has just updated the chart to the end of September 2008.
A high quality version of this chart can be found at Mr Hughes’ website, click here.
The chart indicates that Melbourne experiences dry periods every so often and that the current drought is similar in magnitude to the droughts of 1896, 1925 and 1945. The chart showing 145 years of data, does not support the claim, made by Dr Jones in his article in Melbourne’s The Age, that there has been recent unusual climate change in Melbourne. Indeed periods of drought and flood are a natural hazard.
*************************************
Read Part 1 here:
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/
Read Part 2 here:
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/
GM Crops Implicated in Global Warming
It is absurd to suggest that genetically modified plants could influence the global climate, but the ABC, the public broadcaster in Australia, has suggested as much: read more here.
Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.
