03.16.11
Recent Extreme Weather in Australia: Climate Change or La Niña?
Last week I went to an interesting seminar in the National Weather Center, given by Dr. David Karoly of the University of Melbourne, titled “The recent extreme weather in eastern Australia: A sign of climate change or the response to La Niña?”
Dr. Karoly is from Australia, but spent several years as a meteorology professor at the University of Oklahoma. His specialty is climate, more specifically climate change, and he is on the Intergovernmental Panel on Climate Change (thus he shared in the Nobel Peace Prize awarded to the IPCC and former Vice President Al Gore in 2007). On a side note, when Dr. Karoly and his wife moved back to Melbourne a few years ago, they gave me their cat, Ginger, the one I still have today.
Anyway, today I thought I’d summarize and share some of the main points from the seminar.
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Extreme Weather Events in 2010/2011
- Heavy rain events in Queensland, Victoria, Northern Territory
- Flooding in eastern Australia
- Category 5 Tropical Cyclone Yasi hit the northeast Queensland coast
- Heat waves / bushfires in southwest Western Australia
- Heat waves / bushfires in Sydney in January
Toowoomba and Lockyer Valley Flash Floods, 10 – 12 January
- 30 people killed in floods following heavy rains on 10 January
- 1 day rainfall of 298 mm (11.7 inches) on 10 January in Peachester, Queensland
- 3 day (10 to 12 January) rainfall of 617 mm (24.3 inches) in Peachester
- Not the heaviest rainfall, though; 25 to 27 January 1974 had a 3 day total of over 1000 mm (39 inches)
Brisbane Floods, 13 January
- No loss of life
- Followed very heavy rain in the Brisbane River catchment from 10 to 12 January
- River flood peak of 4.46 m (14.6 ft)
- January 1974 flood peak was 5.6 m (18.4 ft), following 1 day rainfall of 600 mm (23.6 inches), 3 day rainfall of 314 mm (12.4 inches)
- This year, “only” 166 mm (6.5 inches) in one day in Brisbane, so most of the flooding was from rain/flooding upstream
Victorian Floods, 12 – 14 January
- Rain and flooding
- Very moist, tropical air arrived with a trough
- Record high precipitable water, 64.8 mm (2.6 inches), observed with the 11Z sounding in Melbourne on 13 January…in 40 years of observations, this was 20% higher than the previous sounding record
Summer Rainfall, 2010 – 2011
- Record summer rainfall in Victoria, 30% higher than the previous record
- Highest summer rainfall in Queensland, but it was still much higher in the summer of 1973 – 1974
Record Rain in Darwin, Northern Territory 15 – 17 February
- Less unusual to have heavy rain in Darwin, but slow-moving Tropical Cyclone Carlos was unusual
- 1 day rainfall record of 368 mm (14.5 inches) on 16 February in Darwin
Category 5 Tropical Cyclone Yasi
- 1 death attributed to Yasi, as a result of fumes from a diesel generator
- Very well forecast tropical cyclone
- Landfall around midnight on 3 February, near Innisfail and Cardwell, Queensland
- Weather station at Clump Point observed a minimum pressure of 929 mb at landfall
Southwest Western Australia Lack of Rainfall
- Very dry, below average rainfall
- Fires
Are these events due to greenhouse climate change or natural variability?
La Niña and Summer Rainfall
- La Niña was very high during the Australian summer; one of the strongest on record
- La Niña brings stronger trade winds, warmer seas around northeastern Australia, and higher rains to the northeastern Australian coast and Indonesia
- Australian summer was also warm in many parts of the country, including the west coast
- The heavy rains and floods of the Australian 1973 – 1974 summer also occurred during La Niña
Sea-Surface Temperatures (SSTs)
- December 2010 saw SSTs 20% warmer than any other year (in about 100 years) around not just the northeast coast, but much of Australia
- There has been a warming trend in December SST anomalies since 1900
Climate Change Signals
- The area getting heavy rain has been increasing
- Significant increase in warm nights agrees with models that show this amount of warming attributable to anthropogenic climate change
- It is believed that climate change has led to record high SSTs around Australia and higher moisture content, likely contributing factors to the increased rainfall
- HOWEVER, it’s too early to link precipitation to climate change models, as this is much more difficult and not statistically significant right now
- While Queensland landfalling tropical cyclones occur twice as often in La Niña years, there has been a marked decrease in severe landfalling tropical cyclones since 1870…this is in contrast to the IPCC claim that there should be an increase in severity on average everywhere…not sure why there is this discrepancy
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If you have any questions or comments, let me know! For some figures showing rainfall totals and anomalies across Australia, I refer you to a previous post I made, The Big Wet.
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