Tuesday, March 12, 2013

Melbourne heatwave a sizzling autumn end to an angry summer

Melbourne is setting another temperature record: the longest number of days of any month where the maximum temperature exceeds 30 degrees Celsius.

Monday was the 8th consecutive day of above 30C heat with a forecast of at least two more days of temperatures in the mid 30s. That will make 10 continuous days before a cool change is expected late on Wednesday brings down temperatures to a milder high 20s.

The previous record for any month was 8 continuous days set in February 1961. For the month of March, seven consecutive days above 30C is the record set in 1995.

The average temperature in Melbourne during March is 23.9C. The hottest March on record was 1940 with an average of 28.9C which we may well be on track to exceed this year.

And if you were tossing and turning in bed due to the heat, here is the reason: Melbourne experienced it's warmest March night on record on Tuesday night (12/3) according to a news report. Temperatures fell to a minimum of 26.5 degrees. The previous record was a minimum of 26.3 degrees set back in 1927.

Yes - the long term trend just keeps getting hotter. But we have had autumn heat waves before, they just weren't as long.

Related: The Bureau of Meteorology have issued a special climate statement on the Autumn heatwave: A prolonged autumn heatwave for southeast Australia (PDF) The statement was issued 15th of March 2013

But Melbourne isn't the only place experiencing the heatwave. Seb Henbest highlighted a similar record has been broken at Mount Gambier in South Australia: so far nearly doubling the old record of 6 continuous days over 30C. And Wonthaggi in South Gippsland posted eight consecutive days of 30 degree or warmer weather, beating the previous record by two days according to Paddy Hannam in a Sydney Morning Herald report.


1940 March heatwave

There was a particularly savage one back in March 1940: "Yesterday was the sixth day of Melbourne's phenomenal autumn heat wave. The record length for a March heat wave is seven days, established in 1934, when the highest temperature was 103Fdeg. The maximum temperature record has been broken, and the record for duration will be equalled to-day." reported the Argus.

"Water consumption is reaching new records. In four days Melbourne has used 616,170,000 gallons, but the storage position is satisfactory." continued the report.

But we do have better refrigerated distribution and storage, including fridges in households now a days. Back in 1940 "Salad vegetables were almost unobtainable in Melbourne and the suburbs yesterday afternoon."

You can read more at: http://trove.nla.gov.au/ndp/del/article/12432610

Air-conditioners, refrigerated food storage have all been advances that help us to adapt. But these lengthy hot spells tend to catch the elderly unaware with greater chance of mortality due to increase in heart attacks, heat stress. These heatwaves will be at the lower end of normal by the end of the century, so our grandkids are going to do it much tougher, unfortunately.

Australia's Angry Summer

This autumn heatwave comes after an "angry summer" of heat, rainfall and flood level records being broken. In January I reported on Extreme Heatwave for Australia January 2013 - bushfires strike. Yes, records tumbled in heatwave as Julia Gillard linked bushfire to climate change.

The Climate Commission report details the many records broken. Professor Will Steffen who wrote the Angry Summer report said in an article on The Conversation website:

"All weather is influenced by climate change. The climate system is warmer and moister than it was 50 years ago, and this influences the nature, impact and intensity of extreme weather events. All of the extreme weather events of the angry summer occurred in a climate system that has vastly more heat compared to 50 years ago. That means that they were all influenced to some extent by a climate that is fundamentally shifting."

"The average temperature in Australia has risen by 0.9°C since 1910. The change in average temperature has greater impacts at the margins of the temperature scale. It is highly likely that extreme hot weather will become more frequent and severe in Australia over the coming decades. Australia's angry summer shows that climate change is already adversely affecting Australians."

See the Climate Commission's Key Facts of the Angry Summer (PDF), or download the full report: The Angry Summer (PDF).

  • The Summer of 2012/2013 was the hottest on record with temperature records being set in every state and territory.
  • For seven days running, from 2 to 8 January 2013, Australia experienced average daily maximum temperatures for Australia as a whole over 39 °C, easily breaking the previous record of four consecutive days over 39 °C set in 1972. T
  • There have only been 21 days in 102 years of records where the average maximum temperature across Australia has exceeded 39 °C; eight of these days happened this summer (2-8 January and 11 January 2013).
  • More than 70% of Australia experienced extreme temperatures at some stage during the heatwave of December - January 2012-13.
  • It was the Hottest January on record for Australia as a whole.
  • The Hottest day on record for Australia as a whole was set on 7 January, at 40.30 °C, surpassing the previous record set on 21 December 1972 (40.17 °C).
  • There were also many record temperatures set for individual locations.

But summer also saw record rainfall and flooding brought to the Queensland coast and Northern Rivers region of NSW from ex-tropical cyclone Oswald. Torrential rain, tornados on Queensland coast causing flash flooding and damage. The media were slow to connect the dots with this extreme rainfall event. I was one of the first to make the connection publicly with Queensland 2013 bigwet floods, tornados and climate change. Records broken for rainfall and flooding include:

  • On 28 January 2013, the most extreme daily rainfall of the event was recorded over the Gold Coast hinterland/New South Wales border ranges catchment, as well as the edge of the Brisbane River catchment. Sites in both of these catchments recorded rainfall for a 24-hour period in excess of 700 mm.
  • Rainfall from 22-29 January alone was heavy enough to break the January monthly rainfall records for the area between Rockhampton and Bundaberg.
  • The one-day rainfall averaged over the Burnett catchment in Queensland was nearly 70% higher than the previous record.
  • On 25 January 2013 many areas around Rockhampton recorded rainfall for a 24-hour period in excess of 400 mm.
  • Extreme rainfall from former tropical cyclone Oswald triggered severe flooding in many areas within 200 km of the Queensland and far northern New South Wales coastlines. Areas most affected were the Burnett catchment near Bundaberg in Queensland, and the Clarence catchment near Grafton in New South Wales. Both of these rivers reached record flood peaks.

For Victoria, the summer was described as one of the driest in decades. Major fires occurred across the state, including grassfires that threatened homes in Melbourne's northern suburbs. So an 'angry summer' morphed into an 'angry autumn' with people wondering when the heat will stop.

And these events all happened when the El Nino Southern Oscillation (ENSO) was in a neutral phase. El Nino events exacerbate high temperatures and drought for Australia. So things may get even worse during the next El Nino phase we experience. Indeed, Blair Trewin and Karl Braganza from the Bureau of Meteorology described some of the implications for us in an article on the Conversation:

"Australia has warmed by nearly a degree Celsius since 1910. This is consistent with warming observed in the global atmosphere and oceans. And it's going to keep getting hotter. Over the next century, the world will likely warm by a further 2 to 5 degrees, depending on the amount of greenhouse gases emitted into the atmosphere."

"Under mid-to-high emissions scenarios, summers like this one will likely become average in 40 years time. By the end of the 21st century, the record summer of 2013 will likely sit at the very cooler end of normal."

They also pointed out that the heat wasn't just restricted to Australia. "Many parts of southern Africa had their hottest January on record, while the month was also much hotter than normal in large parts of Argentina, Chile and Brazil. In parts of Patagonia, January temperatures were more than 4°C above normal." they said.

Indeed, the US has just experienced two extremely hot summers in 2011 and 2012, and the Russian summer of 2010 also setting heatwave records. "The latest global analyses have found that extreme high temperatures are increasing in frequency almost throughout the world, and the Australian results are consistent with that picture." said Blair and Braganza.

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