06/03/2020

(AU) After A Summer Of Extremes, Here’s What To Expect This Autumn

The Conversation -  |  |  | 

Dan Peled/AAP/Dave Hunt
The past Australian summer was a season of two contrasting halves. So did the midsummer weather change make a dent in the drought, and is it likely to continue through autumn?
The first half of summer was exceptionally hot, dry and dusty. Parts of eastern and southern Australia were engulfed by significant bushfires, and smoke haze covered large areas.
In the second half of the season, tropical moisture at times extended into southern Australia, producing well above-average rainfall for some areas. This was great news for many, but some parts of the country missed out. Other areas need follow-up falls over the coming months to ease the long-term dry, and inland water storages increased only slightly.
The autumn outlook suggests warmer-than-average temperatures for most of the country. There is also a slightly increased chance of wetter-than-average conditions in parts of southern Australia, indicating some areas could see a gradual easing of the drought conditions.
The first half of summer brought widespread bushfires to much of Australia’s southeast. DAN HIMBRECHTS/AAP
What happened this summer?
Summer 2019-20 was the nation’s second hottest in 110 years of records, driven in part by Australia’s hottest December on record in 2019. Warmth across much of the tropical north and east persisted into January and February. Summer nights were second-warmest on record.
Total summer rainfall was closer to normal – 8% below the long-term average. But the rainfall figures hide the significant shift in the climate mid-way through the season.
Australia experienced very warm and dry conditions in the lead-up to summer. With a delayed onset of the monsoon moving into the southern hemisphere, heat built across northern and central Australia from the start of December and was drawn south by weather systems.
Australia had its hottest day on record on December 18, with a nationwide average temperature of 41.88℃. This was far above the previous record of 40.32℃ set on January 7, 2013.
Six other days in December 2019 also exceeded this previous record. To put this in context, the Australia-wide average maximum temperature has exceeded 40℃ for more days in the past two summers than in the preceding 110 years combined.
The hottest temperature recorded this summer was at Nullabor, South Australia, on December 19, when it reached 49.9℃.
Averaged across the continent, December maximum temperatures were 4.15℃ above average - the previous December record was 2.41℃ above average, set in 2018.

Bureau of Meteorology/The Conversation, CC BY-ND
Then the rains came
Early January brought a noticeable change to the weather, with the first tropical cyclones of the season and the belated arrival of the monsoon.
Tropical cyclones Blake and Claudia brought heavy rain to much of the Top End and northern and central parts of Western Australia, while the east coast saw heavy falls in northern New South Wales and southeast Queensland.
February brought more tropical moisture to the continent and another two cyclones—Damien and Esther.
Despite this, temperatures across the north remained very warm. The monsoon did not arrive until January 18, some three weeks later than normal, though almost a week earlier than the previous year. Even after the monsoon arrived it was sporadic, so did little to temper the heat.
The Darwin River Dam (Darwin’s main water storage) dropped to 54% capacity - the result of two relatively dry wet seasons in a row.
In contrast, in southern parts of Australia, February felt milder than normal. After Melbourne had three days over 40℃ in December – the most in December since 1897 - it had no days at all over 35℃ in February. This last happened in 1994.

Bureau of Meteorology/The Conversation, CC BY-ND
What’s driving all this?
The abrupt change in weather patterns mid-season can be attributed to changes in two key Australian climate drivers: a strong positive phase of the Indian Ocean Dipole (IOD), and a negative phase of the Southern Annular Mode (SAM).
A positive IOD typically brings drier weather to much of southern, central and northern Australia. The 2019 positive IOD was the strongest since 1997 and affected large parts of the country (and eastern Africa) during the second half of the year. Normally such an event ends with the movement of the Asian monsoon into the southern hemisphere in late spring/early summer, but in 2019–20 this movement occurred about a month later than usual.
The delayed arrival of the Australian monsoon was likely related to the strength of the IOD itself, which prevented the monsoon’s southward shift.
The negative SAM typically brings drier and hotter than average weather to much of southeast and eastern Australia in spring and summer. It was triggered by a sudden warming of the stratosphere above Antarctica, identified in early September. This rare event affected Australian climate from October to December.
Both negative SAM and positive IOD are known to enhance the likelihood of increased springtime heatwaves and fire weather in southeast Australia.
In addition to these events, Australia’s changing climate underpinned the drier and warmer weather across southern Australia in winter and spring.
Climate drivers originating in the Indian Ocean and Antarctica can increase the chance of spring heatwaves in Australia. BIANCA DE MARCHI/AAP
What to expect in autumn
Rain has eased the dry in some places, but more is needed. Most heavy rain was recorded east of the Great Dividing Range, while larger totals west of the range generally fell in regions that didn’t feed into water storages, or where soils were so dry there was little runoff into storages.
While Sydney’s water storages rose from 42% to 81% during the second half of summer, storages in the northern Murray—Darling Basin only rose from 6% to 12% - similar to levels at the height of the Millennium drought.
And while some areas had good summer rainfall, others missed out. Western NSW and southwest Queensland endured another dry summer.
The autumn outlook suggests parts of southern Australia have a slightly increased chance of being wetter-than-average, while scattered parts of the north may see a drier end to the northern wet season. Autumn days are likely to be warmer than average for most of the country, except for parts of southern Australia, suggesting evaporation will remain above average.
This outlook would indicate some areas could see a gradual easing of the drought conditions.

Bureau of Meteorology/The Conversation, CC BY-ND


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(AU) Matt Canavan’s Bushfire Climate Skepticism Disproved As Studies Point To Human Impact

New Daily - Cait Kelly

There's been debate over whether the summer bushfires can be linked to manmade climate change. Now international scientists say they can prove it.


Two research papers released Thursday morning are further highlighting how humans contribute to the climate crisis, with scientists in one of the new studies saying they can prove Australia’s latest bushfire disaster is linked to man-made climate change.
The study by an international team of scientists at World Weather Attribution found man-made climate change had increased the bushfire risk by 30 per cent due to a lack of rainfall and higher temperatures in 2019, compared with 30 years ago.
“We’re very sure that is a definite number we can scientifically defend,” lead researcher Jan van Oldenborgh wrote.
It comes just a day after Nationals Senator Matt Canavan criticised Australian scientists after questioning the CSIRO over whether it could prove climate change had played a role in this summer’s fire weather.
While the newly-released report is yet to be peer reviewed, its release is significant because it addresses specific attribution – that is, it demonstrates links between climate change and a particular disaster.
Researchers wrote that the devastating early bushfire season was much greater than that predicted by traditional climate modelling. Australian heatwaves were also found to be 1-2 Celsius hotter and 10 times more likely to occur than in 1990.
“We can therefore only conclude that anthropogenic climate change has made a hot week like the one in December 2019 more likely by at least a factor of two,” the study wrote.
Further analysis released on Thursday shows a decade of insufficient political action on climate change means nations must now do four times the work to stop the planet warming 2  degrees above pre-industrial levels.
To meet the goals set in the Paris Agreement, we either need to do four times the work or the same in one-third of the time, research led by Dr Niklas Höhne of the NewClimate Institute and first published in the science journal Nature has found.
“The past decade of political failure on climate change has cost us all dear. It has shrunk the time left for action by two-thirds,” Dr Höhne said.
“In 2010, the world thought it had 30 years to halve global emissions of greenhouse gases. Today, we know that this must happen in 10 years to minimise the effects of climate change.”
The picture is bleak. And made worse by the fact the world is a long way off meeting the Paris requirements – we’re currently heading for 3 degrees of warming.



“The gap is so huge that governments, the private sector and communities need to switch into crisis mode, make their climate pledges more ambitious, and focus on early and aggressive action,” he wrote.
“We do not have another 10 years.”
By analysing all 10 editions of the annual Emissions Gap Report – which examines what countries have pledged to do, and what they’re actually doing – the group found global annual greenhouse gas emissions have increased by 14 per cent, quickly becoming a ticking time bomb.
Had serious climate action begun in 2010, the cuts required to meet the emissions levels for 2  degrees would have been around two per cent, per year, on average up to 2030.
Instead, emissions increased.
Consequently, the required cuts from 2020 are now more than seven per cent, per year, on average for 1.5  degrees (close to three per cent for 2  degrees).
“Although many reports, scientists and policymakers continue to discuss rises of 2 degrees, it must be emphasised that, in 2018, the Intergovernmental Panel on Climate Change reported that warming of more than 1.5  degrees would be disastrous,” he wrote.
Two degrees might not sound like a lot, but the consequences will be significant.
We can expect more intense storms, searing heatwaves, severe bushfire seasons and longer droughts.
More than 50 per cent of the world’s beaches will be lost by 2100.
If we don’t quickly reduce emissions, more than half the world’s beaches will be gone by 2100, and there will be mass extinction of animals and coral reefs.
Climate Council senior researcher Tim Baxter said Australia was on the front line of climate change.
“We know that at two degrees, the Great Barrier Reef will more or less not be a thing any more,” he said.
“With two degrees, you’re talking about mass bleaching happening at the frequencies it’s unlikely to recover from. Even at 1.5 degrees, it’s getting difficult.
“We know that sea levels will rise. There’s some uncertainty about how much, but we know when they rise there’s a bigger storm surge, so it goes further and further up the beach, so more homes are impacted.
“What we can say with absolute certainty, is that with the recent drought, the fires, then floods, we’ve seen what climate change looks like, and we’re talking about one-degree warming now.”
The consequences are alarming and Australia urgently needs to limit its contribution, Dr Höhne wrote.
“Countries are not even on track to achieve their now plainly inadequate 2015 pledges.
“Of the G20 countries, seven (Australia, Brazil, Canada, Japan, South Korea, South Africa and the United States) need to implement existing policy or roll out new measures.”
We can expect more storms, severe bushfire seasons and longer droughts. Photo: Getty
Although challenging, there are signs of hope, the analysis showed.
“There are lessons to be learnt from places such as Costa Rica, Shenzhen in China and Copenhagen that have made strides through the use of renewable energy and electrified transport,” Dr Höhne said.
“The United Kingdom (together with 75 other parties) and California have at least set ambitious goals to become carbon neutral, which might send signals to industry even before supporting policies are implemented.
“Meanwhile, 26 banks have stopped directly financing new coal-fired power plants.”
Although it was clear from the science that Australia, the world’s 14th biggest emitter, was not doing enough federally – there is action coming out of the states and territories, Mr Baxter said.
“Australia is one of the sunniest and one of the windiest countries on the planet. We are blessed with every resource needed for carbonisation,” he said.
“We have the solutions for at least 80 per cent, it’s just a matter of finding leadership that can bring that about.
“It doesn’t have to come from the federal government, you’ve got states who are stepping up. They’re not quite doing it enough but … they’re taking steps.”
In November, countries will meet in Glasgow for critical talks on limiting emissions and how they’re going to achieve the Paris Agreement.

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(AU) Climate Change Made 'Really Scary' Fire Extremes A Third More Likely

Sydney Morning Herald - Peter Hannam

Australia's extreme bushfire season was at least 30 per cent more likely than a century ago because of climate change, and the risks of a repeat will rise four-fold if global temperatures exceed a two-degree increase.
The World Weather Attribution group, an international collaboration including Australian scientists, used peer-reviewed methods to assess whether human-induced global warming altered the likelihood of bushfires of the intensity experienced during the 2019-20 summer.
Fire and Rescue NSW firefighters escape flames from the Gospers Mountain fire north-west of Sydney in mid-December 2019. Credit: Nick Moir

The scientists examined the probability of extreme heat and drought and a fire weather index as severe as those just experienced compared with Australia's climate of about 1900.
The bushfires drew international attention in part because of the "unprecedented nature of this event", with millions of hectares burned, 5900 residential and public structures destroyed and at least 34 people killed directly.
"It was really scary to see such extreme conditions in such a country as well prepared as Australia," said Maarten van Aalst, a researcher with the Red Cross Red Crescent Climate Centre in The Hague, Netherlands, and one of the researchers.
Previous studies of Australian heat had identified a clear influence of climate change, including the 2012-13 summer.
The recent heat again offered a clear climate change signal, with temperatures driven higher in heatwaves that are 1-2 degrees hotter than 1900, the researchers found. The record-breaking temperatures during one week in December - which smashed previous Australia-wide daily maximums - were 10 times more likely a century earlier, they said.
Identifying climate change's role for the drought was more difficult. The scientists did not find an attributable climate change trend in either extreme annual drought or the driest month of the September-February fire season.
A bushfire burning south of Canberra in early February brought another round of heavy smoke and fire threat to the nation's capital. Credit: Alex Ellinghausen

However, the climate influence was clear for the broader fire weather index, arguably before summer had begun.
The Bureau of Meteorology identified record high values during spring for almost 60 per cent of the country using its accumulated forest fire danger index.
Using a modified Canadian fire weather index that better accommodated wind speeds, the researchers found a trend towards higher risks since at least 1979.
They estimate the probability of an index as high as recorded during the recent summer had increased by at least 30 per cent - and as much as 80 per cent - since 1900 as a result of anthropogenic climate change.
"We think it could be much higher" than 30 per cent, said Geert Jan van Oldenborgh from the Royal Netherlands Meteorological Institute, and another of the researchers.
Climate models "are bad at capturing small-scale extremes, or extremes that depend on small-scale processes," Professor van Oldenborgh said.
"This is partly resolution, but in the case of heat extremes these depend strongly on factors like land use, irrigation, urbanisation, air pollution and other non-climate factors that are often not represented in climate models, and if they are have large uncertainties."
Australia has warmed about 1.4 degrees over the past century, or faster than the global rise of about 1 degree. With a global temperature rise of 2 degrees, the weather conditions behind the recent fires would be at least four times more common than in 1900, research found.
Taking the higher end of the model range estimate that the recent fires had been made 80 per cent more likely than 1900, the projection for conditions in a 2-degree world was for an eight-fold increase in similar fire weather than without the background climate change, Friederike Otto, from Oxford University's Environmental Change Institute, said.
Dr Otto cautioned, though, the higher estimates were "very uncertain due to the model deficiencies".
However, the world's weak emissions reduction efforts leave temperatures on course to rise 4.1-4.8 degrees by 2100 compared with pre-industrial levels, Climate Action Tracker estimates.
While the attribution study did not examine fire weather risks associated with a 4-degree warmer world, there is "no reason to assume" fire threats won't continue to climb, Dr Otto said.
Mogo on the NSW South Coast was among the towns hard hit by fires around New Year's Day. Credit: James Brickwood
 
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