Australia is already experiencing an increase in extreme conditions from climate change and more sophisticated modelling is allowing scientists to pinpoint humans' contribution to the wilder weather, the Bureau of Meteorology and CSIRO said.
The fourth State of the Climate report found Australia's mean surface temperature has risen by about 1 degree since 1910, rainfall patterns are shifting away from the nation's south, and there is a marked increase in heatwaves and extreme fire weather days.
The state of our climate in 2016: Australia is already experiencing an increase in extreme conditions from climate change - and it's projected to get worse.
"Climate change is happening now and it's having a tangible impact on Australia," Karl Braganza, manager of the bureau's climate monitoring, said.
The fire season is now extending "by a matter of weeks on average", as warmer conditions arrive sooner and last longer over much of the country, he said.
In the future, as rising greenhouse gas levels drive increases in surface temperatures, the frequency of hot days including those bearing extreme fire weather will rise further, Dr Braganza said.
The biennial report adds to the growing body of evidence Australia's climate is changing, and comes days after CSIRO told Fairfax Media that levels of carbon dioxide – the most potent greenhouse gas – are rising at a record annual rate.
Warming waters
While surface temperatures fluctuate sharply – driven by the El Nino-La Nina cycle – the report focuses on the increasing proof that the oceans are heating up.
"The oceans really provide us with the most reliable indicator of how the globe as a whole is warming," said Steve Rintoul, interim director of the Climate Science Centre at the CSIRO.
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| More frequent, more prolonged and more intensive heatwaves are already being recorded across Australia as the climate warms. Photo: Leigh Henningham |
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| Most of the heat the earth has gained has gone into the oceans. Photo: Peter Rae |
Even so, the trend for surface temperatures is also clear.
The chances of very warm monthly maximum temperatures have risen more than five-fold for the 2001-15 period compared with the baseline 1951-80 period, with a similar rise in abnormal minimum temperatures. See chart below.)
"In the last one-two decades, as that distribution shifts further to the right ... you have a noticeable increase in extremes," Dr Braganza said.
The changes of extreme heat events – often accompanied by worsening
fire weather – have also increased markedly in recent decades.
For instance, 2013 – the nation's hottest year on record – had 28 days that were in the top 1 per cent for mean temperatures for their respective month. The bureau counted that many extreme heat days over the entire first 31 years of its existence. (See chart below).
An innovation from previous reports is the evidence that humans' contribution to extreme weather can now be quantified.
Researchers used climate and weather models to examine the extremely warm October-November 2014 period, when daytime temperature anomalies were almost 2.5 degrees above average. Using 1960-like levels of greenhouse gases, Australia would have been warm but not record breaking.
"We know that climate change changes the odds of these extreme
events, and what is new is the ability quantify the contribution to a
particular event from human-driven climate change," Dr Rintoul said.
A similar study of September 2013, another record breaker, found global warming's contributed 15 per cent.
Recent research has added to the understanding of other trends, such as the drying out of southern Australia during the growing season.
South-west Western Australia, for instance, has seen its May-July rainfall drop almost 20 per cent since 1970, as storm tracks shift southwards, taking the rain with them.
For south-eastern Australia, the drop is less pronounced – at 11 per cent over the April-October period – but still leading to a sharp slide in stream flows.
"Areas of southern Australia will probably spend more time in drought [in the future]", Dr Braganza said. "But when the rain does fall, it's likely to be heavier than it was in the past."
Tropical cyclones are reducing in frequency – a trend that is likely to continue – although their intensity is expected to rise later this century.
While wind speed is one issue, rising sea levels and heavier deluges mean the impact of the tropical tempests is likely to worsen even if they don't strengthen, Dr Braganza said.
Links
The chances of very warm monthly maximum temperatures have risen more than five-fold for the 2001-15 period compared with the baseline 1951-80 period, with a similar rise in abnormal minimum temperatures. See chart below.)
"In the last one-two decades, as that distribution shifts further to the right ... you have a noticeable increase in extremes," Dr Braganza said.
For instance, 2013 – the nation's hottest year on record – had 28 days that were in the top 1 per cent for mean temperatures for their respective month. The bureau counted that many extreme heat days over the entire first 31 years of its existence. (See chart below).
An innovation from previous reports is the evidence that humans' contribution to extreme weather can now be quantified.
Researchers used climate and weather models to examine the extremely warm October-November 2014 period, when daytime temperature anomalies were almost 2.5 degrees above average. Using 1960-like levels of greenhouse gases, Australia would have been warm but not record breaking.
A similar study of September 2013, another record breaker, found global warming's contributed 15 per cent.
Recent research has added to the understanding of other trends, such as the drying out of southern Australia during the growing season.
South-west Western Australia, for instance, has seen its May-July rainfall drop almost 20 per cent since 1970, as storm tracks shift southwards, taking the rain with them.
For south-eastern Australia, the drop is less pronounced – at 11 per cent over the April-October period – but still leading to a sharp slide in stream flows.
"Areas of southern Australia will probably spend more time in drought [in the future]", Dr Braganza said. "But when the rain does fall, it's likely to be heavier than it was in the past."
Tropical cyclones are reducing in frequency – a trend that is likely to continue – although their intensity is expected to rise later this century.
While wind speed is one issue, rising sea levels and heavier deluges mean the impact of the tropical tempests is likely to worsen even if they don't strengthen, Dr Braganza said.
Links
- 'Milestone': Global greenhouse gas levels accelerate past key marker
- Million new jobs in prospect by 2040 even as emissions dive: study
- Bureau of Meteorology: State of the Climate 2016
- CSIRO: State of the Climate 2016
- State of the Climate 2016 summary video
- Climate Change in Australia
- State of the Climate 2012
- Ocean and climate research has come a long way in thirty years
- As Australia lurches from drought to floods, temperatures continue to rise
- What’s causing Australia’s heat wave?
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