News•March 1, 2013

Remarkable Summer in Australia Is its Hottest On Record

Australia: It's so hot right now.

Or rather, it was so hot this summer, that the country set a record for its hottest summer since recordkeeping began there in 1910, the country’s Bureau of Meteorology (BOM) announced Friday. For a country that has an arid climate and is prone to heat waves, that might not seem unusual.

Summer temperature departures from average in Australia from 1910 through 2013.
Click on the image to enlarge it. Credit: BOM.

But the summer was remarkable in almost every respect, as the Australian continent smashed records for heat intensity, geographic scope, and duration. Moreover, the heat continued a recent trend toward much warmer summers in Australia, and climate models show that, depending on global emissions of climate-warming greenhouse gases, Australia's summer of 2012-2013 could be the norm by the 2040s, the BOM said.

The record warm summer adding another data point to a spate of recent extreme heat events that some scientists say are becoming more common as a result of manmade emissions of greenhouse gases, such as carbon dioxide.

A 2012 study by NASA scientist James Hansen and others found that a new category of extremely hot summers, such as events that occurred in Russia in 2010 and Texas in 2011, has become far more common than would ever have happened without global warming.

Here are some of the sizzling data points:

The average summer temperature for Australia was 83.5°F (28.6°C), which was about 2°F (1.1°C) above average. That exceeded the previous record, set during the summer of 1997-98, by about 0.2°F.
A new national daytime maximum temperature record was set at 96.3°F (35.7°C).
The highest temperature recorded during the January heatwave was at Moomba, in South Australia, with a high of 121°F (49.6°C). All-time record high temperatures were also set in Sydney and Hobart. The temperature in Sydney climbed to a stifling 114.4°F on Jan. 18.
A record was set for the number of consecutive days when the average daily high temperature for Australia exceeded 102°F (about 39°C), with seven such days between January 2-8. The previous record was four days in 1973, according to BOM data.
January was Australia’s hottest month since recordkeeping began in 1910.
At one point during the January heat wave, meteorologists had to add a new color to the weather map as temperatures climbed off the standard charts.

The summer heat wasn't confined to the Australian continent, either. Southern Hemisphere land areas had their hottest months of December and January on record, as parts of Africa and South America also saw above-average temperatures.

According to a story published by the Australian website “The Conversation” by Blair Trewin and Karl Braganza, two BOM climate scientists, Australia has warmed by about 1.8°F (1°C), since 1910, although the rate of warming has been slightly lower during the summer months.

Temperature forecast for Australia during the worst of the January 2013 heat wave.
Click on the image to enlarge it. Credit: BOM.

Six of the 10 hottest summers in Australia have taken place since 2000, with just two occurring before 1990. That is about five times the expected rate without a warming climate, Trewin and Braganza wrote.

Scientists expect this warming trend to continue due to increasing amounts of greenhouse gases. The outlook for future summers in the Land Down Under is not pretty.

“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,” Trewin and Braganza said.

The scientists said the heat this summer was particularly striking, because it occurred without the warming influence of an El Niño event in the tropical Pacific Ocean. El Niño conditions, which are characterized by warmer-than-average sea surface temperatures in the equatorial tropical Pacific, can alter weather patterns worldwide and often favor warmer summers in Australia. Until this year, in fact, six of the eight warmest summers, including the top three hottest summers, took place during El Niño years, Trewin and Braganza said.

“This essentially means that the record was consistent with warming trends, and achieved without an extra push from natural variability associated with El Niño,” they wrote.

The Australian heat wave shows that in some cases, “a push” from natural sources of climate variability may no longer be required to yield extreme weather and climate events.

According to the 2012 Hansen study, which was published in the journal Proceedings of the National Academy of Sciences, during the period from 1951-1980, extremely hot summers covered just 1 percent of Earth’s land area. That number rose to 10 percent of the Earth’s land area by the period from 1981-2010, and even higher during the 2006-2010 period.

The study found that the odds of such extreme summers were about 1-in-300 during the 1951-1980 timeframe, but that had increased to nearly 1-in-10 by 1981-2010.

The study found that manmade global warming caused the Texas heat wave of 2011 and the deadly Russian heat wave of 2010 by dramatically altering the frequency of extremely hot summers.

“ . . . We can say with high confidence that such extreme anomalies would not have occurred in the absence of global warming,” the study said.

Other research has shown that the deadly European heat wave of 2003 and the Russian heat wave and wildfires of 2010 were also likely influenced by global warming.