Country is heating more rapidly than the global average, with a rise of 4C expected by 2100, Bureau of Meteorology says

This article is more than 6 months old

This article is more than 6 months old

The summer just finished was Australia’s second-hottest on record, with the temperature 1.88C above average, the Bureau of Meteorology says.

The only hotter summer on record was the previous year, which was 2.14C above average. Temperatures this summer were above average across almost the entire country.

Dr Blair Trewin, a senior climatologist with the bureau, said the hot summer, which was marked by the unprecedented bushfire crisis that devastated communities and wildlife in much of the country, was part of a long-term warming trend that had seen the country warm by 1.4C since 1910. Most of that warming has come since 1950.

Trewin said: “That tells us the baseline is higher, and with that you have a higher risk of high extremes like we have seen in the past two summers. Our baseline expectation now is for warmer than average summers, and other seasons more generally.”

The heat records are relative to the long-term average for the years between 1961 and 1990.

The bureau’s summer report came as its officials told a Senate estimates hearing in Canberra that Australia is heating more rapidly than the global average.

Karl Braganza, the head of climate monitoring, was asked how much Australia was projected to warm, given a scientific analysis involving the World Meteorological Organisation last year found average global temperatures were expected to rise between 2.9C and 3.4C by 2100 under commitments put forward by national governments as part of the Paris agreement.

Braganza said the increase in Australia would be expected to be “closer to 4C” heating than the global average under that scenario, assuming countries did not do more than promised in Paris.

Adam Bandt, the Greens leader, said the government was undertaking no planning for the possibility of 4C warming in Australia. “Australia saw this horrific bushfire season with just over one degree of warming. We’re hurtling towards 4C and it’s only going to get worse from here,” he said.

This summer saw many more heat records broken than cool records. The bureau data shows 43 sites in NSW broke high temperature records but only five sites saw record lows. In Queensland, there were 10 heat records broken across different monitoring stations, but only one record for cool weather.

The 2018-19 summer also saw below average rainfall across the country, with western NSW, south-western Queensland and the Top End particularly dry. Some areas, including Western Australia’s west coast, and parts of the east coast, saw above average rainfall.

The second hottest summer comes after the bureau declared 2019 the hottest and driest year on record.

Data from the Australian Bureau of Meteorology shows 2019 was the hottest year on record. Data from the Australian Bureau of Meteorology shows 2019 was the hottest year on record.

Trewin said the summer could be characterised as a season “of two halves”.

“We had December and the first few days of January, which was extremely hot almost nationwide, and extremely dry. Those heat extremes in December and early January were quite exceptional,” he said.

That exceptional heat included 17 and 18 December, when on two consecutive days Australia recorded its hottest day on record. The national average temperature on 18 December was 41.9C – one whole degree hotter than the previous day.

December 2019 also delivered the worst conditions for bushfires on a record going back to 1950.

Several records were broken for warmest summer nights in NSW, Victoria and Queensland. On 1 February, nighttime temperatures in the rural area of Condobolin, west of Dubbo, NSW, did not drop below 34.7C.

Australia records worst December fire conditions after its hottest, driest year Read more

Aside from climate change, there were natural drivers of the heat in the early part of the summer. Trewin said in December and early January, the weather patterns were influenced by a strong Indian Ocean Dipole that had dragged moisture away from the continent and a “strongly negative Southern Annular Mode”.

But as both these systems moved into a neutral phase, the rest of January and February was less extreme.

Rainfall for January and February was slightly above average, Trewin said, but the extreme dry of December meant that across the three months rainfall was below average.

But 10 February still delivered record rainfall for some parts of NSW. At Taralga, 100km west of Wollongong, the town had its wettest summer day on record with 197mm beating the previous record of 130mm, set in 1885.

While the bureau’s report does not cover ocean temperatures, the hot summer has also seen the build-up of heat stress on the Great Barrier Reef, with scientists fearing a third mass coral bleaching event in the past five years if temperatures don’t fall in the next few days.