Bob Henson ·

Above: A bushfire burns behind a property in Balmoral, abut 90 miles (150 kilometers) southwest of Sydney on Thursday, December 19, 2019. A state of emergency was declared in Australia's most populated region on Thursday as a record heat wave fanned unprecedented bushfires. Image credit: Peter Parks/AFP via Getty Images.

Australia is having a December heat wave for the ages, with some of the most widespread and intense heat ever observed on the island continent. The nationally averaged high temperature on Wednesday was an astounding 40.9°C (105.6°F), beating the previous daily record of 40.3°C from January 7, 2013. Even more impressive, Thursday topped the Wednesday reading by a full degree Celsius, coming in at 41.9°C (107.4°F).

Thursday’s reading is almost certainly the hottest nationally averaged high not only for Australia but for any continent on Earth at any time of year. All other continents see at least some of their summer heat modulated by the presence of either tropical rainforests or cooler midlatitude/high-latitude regions.

Australia's Nullarbor Plain is easily the hottest place in the world right now, with temperatures over 48ºC shortly after midday and still climbing. pic.twitter.com/q0TaTcmdnq — Ben Domensino (@Ben_Domensino) December 19, 2019

On Thursday, Nullarbor in South Australia topped out at 49.9°C (121.8°F). This is the highest temperature recorded anywhere on Earth in any December, and the fourth highest at any location on any date in Australian history. The current heat wave is not expected to topple the nation’s all-time single-location record of 50.7°C (123.3°F) set at Oodnadatta, South Australia, on Jan. 2, 1960. I wouldn’t rule out such a reading entirely, though.

Nullarbor is located just a few miles inland from the Southern Ocean. On January 23 of this year, Red Rocks Point station—located about three hours west of Nullarbor on the sparsely settled coast, and just 70 meters (230 feet) from the ocean—hit 49.1°C (120.4°C), which is apparently the hottest temperature recorded on Earth so close to open water.

Nullarbor has just 50 residents, but plenty of folks in Adelaide (pop. 1.3 million) suffered through that city’s hottest December day in 132 years of recordkeeping on Thursday, when the high at the West Terrace site hit 45.3°C (112.3°F).

Wildfires fueled by the heat and drought have been plaguing much of southern and eastern Australia in recent weeks. New South Wales was placed under a state of emergency Thursday, the state’s second such declaration in the 2019-20 bushfire season.

The most extreme heat will shift toward southeast Australia on Friday and Saturday. As winds increase, the fire risk is expected to ramp up, NSW Rural Fire Service (RFS) Commissioner Shane Fitzsimmons told Australia’s ABC news network. Record-setting heat may reemerge in southwest Australia next week as the pattern threatens to recharge.

At 5.30pm there are 106 fires burning, 53 are not yet contained, 2 are at Emergency Warning. It has been a very challenging day for the 2,500 firefighters currently in the field. Crews are continuing to work hard to protect homes on some firegrounds. #nswrfs #nswfires pic.twitter.com/MVqWr18qQV — NSW RFS (@NSWRFS) December 19, 2019

More than 11,560 square miles of land has burned across Australia over the past few months, as reported by the Associated Press and noted by weather.com. Six people have been killed and more than 800 homes destroyed. The iconic skyline of Sydney has been reddened by ash and smoke in recent weeks from a huge, long-burning fire just southwest of the metro area. The Sydney Morning News reported Thursday that air quality for the city has been rated “hazardous” on 28 days in the last two months.

All I can smell is smoke. All I can taste is smoke. My throat feels dry with ash. My head is pounding. And I’m at least 50kms but probably more like 100km away from any fire. It must be absolutely suffocating to be any closer. And it’s been smoky for weeks. #sydneysmoke (@melissakp) December 2, 2019

Figure 1. German tourists Julia Wasmiller (left) and Jessica Pryor take a selfie of downtown Sydney from the rock feature known as Mrs. Macquarie's Chair, wearing face masks due to heavy smoke, on Thursday, December 19, 2019. Image credit: Jenny Evans/Getty Images.

Sydney’s summer of smoke has increased the pressure on politicians to address climate change. Australian Prime Minister Scott Morrison drew protests Thursday as he vacationed in Hawaii while the record heat and deadly bushfires were raging. Morrison announced Friday local time that he will return to Sydney as soon as possible. Thus far, Morrison has refused to answer questions about the links between climate change and the bushfires.

Global heating and continental torching

Sunshine is at its peak in Australia right now, with the Southern Hemisphere’s summer solstice just days away. Fierce drought—including Australia’s driest spring on record, with a national average of just 27.4 mm (1.04”)—has left much of the nation parched. This has allowed the ample solar energy to go into warming the ground and atmosphere, rather than evaporating soil moisture. Up through November, this has been Australia’s second hottest year on record.

An especially strong positive mode of the Indian Ocean Dipole in the last few months has also fostered sinking air and dryness toward the eastern Indian Ocean, extending to Australia.

There’s more to the story, of course. Heat waves are one of the most straightforward consequences of the human-produced climate crisis now under way. As the average temperature rises, the extremes—the long tails of the bell curve—would be expected to move along with it, and the number of readings above a particular heat threshold would rise dramatically, especially for the hottest extremes, as shown in the embedded tweet below.

For those looking for a statistical explanation: https://t.co/rxmOnzni63 pic.twitter.com/UgoSz6kXot — Michael E. Mann (@MichaelEMann) December 19, 2019

There hasn’t been a lot of detailed research on how the temperature distribution might itself change with global warming. One such study, in 2018, projected that monthly temperature variability would generally increase with warming in the tropics but decrease elsewhere. Even if that’s so, hot extremes would still be expected to increase wherever the average temperature goes up substantially.

In a 2013 review paper on the topic, Lisa Alexander and Sarah Perkins noted, “While we may want to sort out the ‘variability issue’ for scientific reasons, it does not alter the fact that the future will be bleak with regard to heat extremes, especially in the most vulnerable communities, unless substantial mitigation policies and adaptation strategies are put in place.”

The future of Australian heat and drought

Australia is a natural laboratory for the ominous experiment of global heating from fossil fuel use. The continent is renowned as a land of “droughts and flooding rains”, meaning that it suffers frequent and intense swings from wet to dry and back. In a warming climate, droughts can easily become hot droughts, a trend already observed in places as far-flung as Victoria Falls and California. Temperatures can soar during such hot droughts. Moreover, as the jet stream retreats southward over the coming decades, heat domes will have an easier time building across the continent.

Figure 2. Annual mean (average) temperature over Australia from 1910 to 2018, along with the estimated range for 2019 as of November. Temperatures are expressed relative to the 1961-1990 average in degrees Celsius. This year will likely rank second hottest overall behind 2013, but it could prove to be the hottest on record. Image credit: Bureau of Meteorology.

Australia’s annual average temperature has climbed nearly 1.5°C (2.7°F) over the last century, a rate that’s about 50% faster than the global average. The last two decades have been especially brutal, with the so-called Millennial Drought encompassing the first decade of the century and a resurgent drought devastating southeast Australia over the last several years. Warm ocean temperatures off the northeast coast have wrought severe damage to the Great Barrier Reef, and in 2018 a World Heritage rainforest in Queensland burned for 10 days—a fire small in scope but powerful in psychological impact.

The executive summary of the definitive government report Climate Change in Australia is packed with ominous prognoses. To cite just three:

"There is very high confidence in continued increases of mean, daily minimum and daily maximum temperatures throughout this century for all regions in Australia.”

“Notably, the projected temperature increase for the hottest day of the year on average and the hottest day in 20 years on average is very similar to the projected increase in mean temperature.”

“The time in drought, as measured by the Standardised Precipitation Index, is projected to increase over southern Australia with high confidence….This is consistent with the projected decline in mean rainfall.”

“It’s clear to me that the extreme events we are experiencing right now in Australia and all over the world, are a sign of things to come,” wrote Australian climate scientist Joelle Gergis in a Guardian commentary in September. “Events that were considered extreme in today’s climate will become average in the future as records continue to be broken and the ‘new normal’ emerges.”

Gergis added: “The deeper we sink into denial, the more we commit ourselves to a reality where our children learn about environmental icons such as the Great Barrier Reef and our magnificent rainforests through history books, instead of being able to experience their wonder for themselves. Choosing to turn away from this moment to act will be the ultimate betrayal of future generations.”