The fourth day of a historic heat wave in Australia shattered monthly heat records for the state of Victoria and numerous localities, and caused destructive bush fires to expand their reach. In Victoria, the temperature of 118.2 degrees (47.9 Celsius) on Friday at Horsham and Hopetoun was the hottest December day on record for the state, crushing the old record of 116 degrees (46.6 Celsius) set in 1976.

The ongoing heat wave has set an extraordinary slew of records that are typically broken by fractions of a degree but, in this case, were broken by two degrees or more. Australia set records for the hottest day ever recorded nationwide on both Dec. 17 and 18, with the 19th likely to be ranked at least among the top five hottest days in the country’s history.

The Australian Bureau of Meteorology (BOM) reports preliminary data showing that for Dec. 18, the nationally averaged maximum temperature was 107.4 degrees Fahrenheit (41.9 Celsius). This beat the old record of 105.6 degrees (40.9 Celsius), which had been set the day before. Before this heat event, the country’s hottest day was Jan. 7, 2013, which had an average high temperature of 104.5 degrees (40.3 Celsius).

Human-caused global climate change is making heat waves such as this one more likely to occur, more severe and longer-lasting. An early analysis of the ongoing heat event shows that climate change may have made the Australian national heat record at least 20 percent more likely to occur now than in a climate that had not been influenced by human emissions of greenhouse gases. It’s possible that forthcoming research will show that this event could not have occurred without human-caused global warming, as previous analyses of other events have found.

Bush fires burning in several states spread smoke into some of Australia’s largest metropolitan areas again Friday, including Melbourne and Sydney. A southerly wind shift, which is forecast to bring cooler air with it, could wreak havoc on firefighting operations by pushing flames across containment lines in numerous deadly and destructive blazes from Victoria into New South Wales on Saturday, local time.

Dire predictions from bush fire front lines

The Bureau of Meteorology increased the fire risk level for the Greater Sydney region to “catastrophic” for Saturday, which is the highest fire danger level. In Penrith, which is about 30 miles west of downtown Sydney, the high temperature is forecast to reach 116.6 degrees (47 Celsius). Penrith is between the Wattle Creek Blaze and the massive Gospers Mountain Fire, which is 1,109,503 acres in size and burning out of control, according to the New South Wales Rural Fire Service. The Gospers Mountain blaze is being called a “mega fire” because of its size.

Rural Fire Service Deputy Commissioner Rob Rogers said the total of more than 800 buildings destroyed by fire so far this season in New South Wales is likely to grow this weekend.

“I think it’s a fairly sure thing that we’ll lose homes somewhere tomorrow; it will be a miracle if we didn’t,” Rogers said of the anticipated “catastrophic” fire risk.

Friday morning, the Rural Fire Service of New South Wales confirmed that two volunteer firefighters died while battling the Green Wattle Creek Fire near Buxton, in southwestern Sydney, when their vehicle hit a tree and rolled over.

“This is an absolutely devastating event in what has already been an incredibly difficult day and fire season,” the agency said in a statement.

This season, an area about 1.5 times the size of Connecticut has gone up in smoke, particularly from Victoria to New South Wales and Queensland. Satellite-derived data has shown that the country’s emissions of greenhouse gases have increased markedly for November and December because of combustion from these blazes.

The heat and fires prompted Australian Prime Minister Scott Morrison to return home early from a family vacation in Hawaii and issue a public apology for his ill-timed trip. “I deeply regret any offence caused to any of the many Australians affected by the terrible bush fires by my taking leave with family at this time,” Morrison said in a statement.

Supporters of Morrison’s Liberal-National coalition government have said bush fires are common, and there have been far worse droughts. But the intense heat and fires have contributed to the belief among many in the country, which is a big producer of coal, oil and natural gas, that climate change poses a fundamental threat to their way of life.

The climate context

According to a new BOM report on the 2019 bush fires, spring brought the highest fire weather danger on record in Australia, as measured by the Forest Fire Danger Index, with “record high values observed in areas of all States and Territories.”

Long-term climate trends in Australia show clear warming and an increase in extreme heat events. Last summer, for example, was the country’s hottest on record, and the BOM found that climate change exacerbated extreme heat events as well as droughts during the year.

Australia has warmed by just over 1.8 degrees (1 degree Celsius) since 1910, with most of the warming occurring since 1950. The BOM has found an uptick in the frequency of extreme heat events and severity of drought conditions during this period, as well.

Andrea Peace, a meteorologist with the BOM, stated in a video posted on Twitter that the heat wave has been “quite extraordinary.” For example, a Dec. 19 record set in Nullarbor, about 600 miles west of Adelaide. That location reached 121.8 degrees (49.9 Celsius), which stands as the hottest temperature ever recorded in Australia during December, and the fourth-hottest temperature ever recorded nationally at any time of the year.

Nine of Australia’s top 10 warmest years on record have occurred since 2005, and 2019 is likely to join that list. Globally, 2019 is a virtual lock to be the second-warmest year on record, according to NASA and the National Oceanic and Atmospheric Administration.

A. Odysseus Patrick contributed from Sydney.