“It is a wicked problem,” says Dr Karl Braganza at the Bureau of Meteorology, after running through Australia’s latest State of the Climate report.
The effects of rising heat on land and in the oceans, coupled with rising greenhouse gases in the atmosphere, are changing Australia’s climate rapidly and “flowing through to how our society, economy and other things operate”.
The report, released Thursday by the bureau and CSIRO, checks the data on temperature, extreme heat, ocean acidification, rainfall and a host of other measures.
Braganza, the climate services manager at the bureau, calls it “checking the vital signs of Australia’s climate”.
Those signs indicate that the country is becoming hotter and more dangerous – and the temperature trends will only worsen in the future.
Here are five charts from the biannual report that tell the story.
Temperatures are rising
Readings from the bureau’s network of weather stations shows the continent has now warmed by 1.51C since high-quality records started in 1910. Nine of the warmest years on record have occurred since 2013.
But the chart also compares computer models of the climate to actual observations, matching the trend closely, and showing temperatures will increase to 2040.
“This warming [to 2040] is largely now locked in, and it’s due to greenhouse gases that have already accumulated in the atmosphere,” Braganza said.
Extremely hot days are becoming more frequent
The bureau’s temperature observations show a clear trend across towards extremely hot days – that is, days when the average temperature for the continent was in the top 1% of hottest on record.
Braganza said that up to the 1970s these extremely hot days were rare.
“This is a really big change in the frequency of extreme heat across the continent,” he said.
“We know heatwaves are becoming longer and the intensity is increasing and they are becoming more frequent.
“The rate of change points to how rapidly our climate system is changing. The climate of the 1980s and 1990s is very different to what we are experiencing today.”
Dr Jaci Brown, research manager at CSIRO, said: “It’s not just a little bit hotter. These are long heatwaves and it’s not cooling down overnight.”
Oceans are warming
The world’s oceans have soaked up about 90% of the extra heat caused by global warming and, off Australia’s coastline, temperatures derived from satellites and in-water gauges show warming all around the continent.
The highest levels of ocean warming in the last four decades are in the Coral Sea, the waters off Tasmania’s east and the south-east of the country.
The report also shows heavy rain downpours have intensified, and Braganza said this was partly down to the rising ocean temperatures and the fact a warming atmosphere can hold more moisture to fall as rain.
Marine heatwaves are happening more often, threatening ecosystems such as the Great Barrier Reef, the report said, as well as damaging kelp and seagrass and causing marine species to shift.
The warming along the east coast has seen more than 100 marine species extend their range south, including the destructive long-spined sea urchin that are devastating kelp and seagrass habitats.
Carbon dioxide emissions, mostly from burning official fuels, have also made the oceans around Australia about 30% more acidic since the end of the 19th century, the report said.
Bushfire risk is worsening
Most of Australia is now seeing more days each year where bushfire conditions are among the worst 10% on record, with some regions seeing as many as 25 more days of dangerous fire weather.
To calculate the risk, a forest fire danger index has been developed that combines temperature, wind speed, humidity, rainfall and the flammability of fuel on the ground.
Prof David Bowman, director of the Fire Centre at the University of Tasmania, said bushfires would continue to worsen under climate change, with longer fire seasons, larger burned areas, degrading forests, loss of ancient ecosystems, chronic smoke pollution and loss of homes and businesses.
“Soon, bushfire insurance will be unaffordable,” he said. “A frightening consequence of loss of bushfire insurance is increased deaths as people heroically try to save their homes by not evacuating.”
Dr Grant Williamson, also at the University of Tasmania, said the increase in dangerous fire weather meant fewer days available for hazard reduction burns. “Fire risk is increasing, and our opportunity for risk reduction is decreasing,” he said.
Greenhouse gas emissions are increasing
The CSIRO has been recording the amount of greenhouse gases in the atmosphere, including CO2 and methane, from a monitoring station at Kennaook-Cape Grim since 1976.
In the 1980s, CO2 concentrations went up by 14 parts per million but, in the 2000s, it rose by 23.
The report shows that in Australia, between 2010 and 2019, fossil fuel burning released an average of 455m tonnes of CO2 a year. Emissions caused from burning the fossil fuels exported from Australia added a further 1055m tonnes a year to the atmosphere, the report shows.
“It’s increasingly recognised internationally that it will be very hard to keep temperatures to 1.5C given the time we have left to reduce, however there is still time to keep temperatures to 2C,” Braganza said.
“Keeping your emissions down as much as you can gives you a chance to bring temperatures back from overshooting 1.5C this century.”
