2018-19 was Australia’s hottest summer on record, with a warm autumn likely too


File 20190228 150702 1t8sa4f.jpg?ixlib=rb 1.1
Dirty water from Queensland’s historic flooding, triggered by weeks of exceptional monsoon rains earlier in the year.
NASA Worldview/EPA

David Jones, Australian Bureau of Meteorology; Lynette Bettio, Australian Bureau of Meteorology, and Skie Tobin, Australian Bureau of Meteorology

Australian summers are getting hotter. Today marks the end of our warmest summer on record, setting new national temperature records. Worsening drought, locally significant flooding, damaging bushfires, and heatwaves capped a summer of extremes.

As we look to autumn, warmer temperatures overall and below average rainfall – especially in eastern parts of the country – are likely.

Australian summer mean temperature anomalies against the 1961–1990 average.
Bureau of Meteorology



Read more:
The stubborn high-pressure system behind Australia’s record heatwaves


Very hot…

The starkest feature of this summer was the record warmth. The national average temperature is expected to be about 2.1℃ above average, and will easily beat the previous record high set in summer 2012-13 (which was 1.28℃ warmer than average).

Very low rainfall accompanied the record heat of summer. At the national scale, each month was notably dry, and total summer rainfall was around 30% below average; the lowest for summer since 1982–83. The monsoon onset was delayed in Darwin until the 23rd of January (the latest since 1972–73) and typical monsoonal weather was absent for most of summer.

Preliminary summer 2018–19 mean temperature deciles.
Bureau of Meteorology

In December 2018 Australia saw its highest mean, maximum and minimum temperatures on record (monthly averages, compared to all other Decembers). Notable heatwaves affected the north of Australia at the start of the month, spreading to the west and south during the second half of December. Temperatures peaked at 49.3℃ at Marble Bar in Western Australia on the 27th, with mid-to-high 40s extending over larger areas.

The heat continued into January, which set a national monthly mean temperature record at 2.91℃ above the 1961–1990 average. Heatwave conditions which had emerged in December persisted, with a prolonged warm spell and numerous records set. Eight of the ten hottest days for the nation occurred during the month, while a minimum temperature of 36.6℃ at Wanaaring (Borrona Downs) in western New South Wales on the 26th set a new national minimum temperature record.

Temperatures moderated a little in the east of the country for February, partly in response to flooding rainfall in tropical Queensland. Even so, the national mean temperature will come in around 1.4℃ above average, making this February likely to be the fourth or fifth warmest on record.

…and very dry

Australia has seen dry summers before and many of these have been notably hot. The summers of 1972–73 and 1982–83 – which featured mean temperatures 0.90℃ and 0.92℃ above average, respectively – both came during the latter stages of significant droughts, and were both records at the time.

As the State of the Climate 2018 report outlines, Australia has warmed by just over 1℃ since 1910, with most warming occurring since 1950. This warming means global and Australian climate variability sits on top of a higher average temperature, which explains why 2018-19 was warmer again.

A major rain event affected tropical Queensland during late January to early February, associated with a slow-moving monsoonal low. Some sites had a year’s worth of rain in a two-week period, including Townsville Airport which had 1,257mm in ten days. Many Queenslanders affected by this monsoonal low went from drought conditions to floods in a matter of days. Flooding was severe and continues to affect rivers near the Gulf of Carpentaria, as well as some inland rivers which flow towards Kati Thanda–Lake Eyre.

Preliminary summer 2018–19 rainfall deciles.
Bureau of Meteorology

The outlook for autumn

Spring 2018 saw a positive Indian Ocean Dipole which faded in early summer. At the start of summer sea surface temperature anomalies in the central Pacific exceeded 0.8℃, which is the typical threshold for El Niño affecting the oceans, but these declined as summer progressed. Combined with a lack of coupling between the atmosphere and ocean, the El Niño–Southern Oscillation remained neutral, though normal rainfall patterns shifted to oceans to the north and east, leaving Australia drier as a result.

As we move into autumn, the El Niño–Southern Oscillation and Indian Ocean Dipole tend to have less influence at this time of year. The onset of new Indian Ocean Dipole or El Niño/La Niña events typically happens in late autumn or winter/spring.

Over recent years, autumn rainfall has also become less reliable, with declines in cool season rainfall in the southeast and southwest. Temperatures are also rising, in a local expression of the global warming trend.




Read more:
Explainer: El Niño and La Niña


The Bureau’s outlook for autumn shows high probabilities that day and night-time temperatures will remain above average for most of the country. We expect to see continued below-average rainfall in much of the east, where drought is currently widespread.

Looking to the winter, the Bureau’s ENSO Wrap-Up suggests the Pacific Ocean is likely to remain warmer than average. The potential for an El Niño remains, with approximately a 50% chance of El Niño developing during the southern hemisphere autumn or winter, twice the normal likelihood.

Rainfall outlook for autumn 2019.
Bureau of Meteorology


For more information watch BOM’s March–May 2019 Climate and Water Outlook video and subscribe to receive Climate Information emails.The Conversation

David Jones, Climate Scientist, Australian Bureau of Meteorology; Lynette Bettio, Senior Climatologist, Australian Bureau of Meteorology, and Skie Tobin, Climatologist, Australian Bureau of Meteorology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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How climate change can make catastrophic weather systems linger for longer


Steve Turton, CQUniversity Australia

Many parts of Australia have suffered a run of severe and, in some cases, unprecedented weather events this summer. One common feature of many of these events – including the Tasmanian heatwave and the devastating Townsville floods – was that they were caused by weather systems that parked themselves in one place for days or weeks on end.

It all began with a blocking high – so-called because it blocks the progress of other nearby weather systems – in the Tasman Sea throughout January and early February.

This system prevented rain-bearing cold fronts from moving across Tasmania, and led to prolonged hot dry northwesterly winds, below-average rainfall and scorching temperatures.




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Meanwhile, to the north, an intense monsoon low sat stationary over northwest Queensland for 10 days. It was fed on its northeastern flank by extremely saturated northwesterly winds from Indonesia, which converged over the greater northeast Queensland area with strong moist trade winds from the Coral Sea, forming a “convergence zone”.

Ironically, these trade winds originated from the northern flank of the blocking high in the Tasman, deluging Queensland while leaving the island state parched.

Unusually prolonged

Convergence zones along the monsoon trough are not uncommon during the wet season, from December to March. But it is extremely rare for a stationary convergence zone to persist for more than a week.

Could this pattern conceivably be linked to global climate change? Are we witnessing a slowing of our weather systems as well as more extreme weather?

There does seem to be a plausible link between human-induced warming, slowing of jet streams, blocking highs, and extreme weather around the world. The recent Tasman Sea blocking high can be added to that list, along with other blocking highs that caused unprecedented wildfires in California and an extreme heatwave in Europe last year.

There is also a trend for the slowing of the forward speed (as opposed to wind speed) of tropical cyclones around the world. One recent study showed the average forward speeds of tropical cyclones fell by 10% worldwide between 1949 and 2016. Meanwhile, over the same period, the forward speed of tropical cyclones dropped by 22% over land in the Australian region.

Climate change is expected to weaken the world’s circulatory winds due to greater warming in high latitudes compared with the tropics, causing a slowing of the speed at which tropical cyclones move forward.

Obviously, if tropical cyclones are moving more slowly, this can leave particular regions bearing the brunt of the rainfall. In 2017, Houston and surrounding parts of Texas received unprecedented rainfall associated with the “stalling” of Hurricane Harvey.

Townsville’s floods echoed this pattern. Near the centre of the deep monsoon low, highly saturated warm air was forced to rise due to colliding winds, delivering more than a year’s worth of rainfall to parts of northwest Queensland in just a week.

The widespread rain has caused significant rises in many of the rivers that feed into the Gulf of Carpentaria and the Great Barrier Reef lagoon, and some runoff has made it into the Channel Country and will eventually reach Lake Eyre in South Australia. Unfortunately, little runoff has found its way into the upper reaches of the Darling River system.

Satellite images before (right) and after (left) the floods in northwest Queensland.
Courtesy of Japan Meteorological Agency, Author provided

Huge impacts

The social, economic and environmental impacts of Australia’s recent slow-moving weather disasters have been huge. Catastrophic fires invaded ancient temperate rainforests in Tasmania, while Townsville’s unprecedented flooding has caused damage worth more than A$600 million and delivered a A$1 billion hit to cattle farmers in surrounding areas.

Townsville’s Ross River, which flows through suburbs downstream from the Ross River Dam, has reached a 1-in-500-year flood level. Some tributaries of the dam witnessed phenomenal amounts of runoff, reliably considered as a 1-in-2,000-year event

Up to half a million cattle are estimated to have died across the area, a consequence of their poor condition after years of drought, combined with prolonged exposure to water and wind during the rain event.




Read more:
Queensland’s floods are so huge the only way to track them is from space


Farther afield, both Norfolk Island and Lord Howe Island – located under the clear skies associated with the blocking high – have recorded exceptionally low rainfall so far this year, worsening the drought conditions caused by a very dry 2018. These normally lush subtropical islands in the Tasman Sea are struggling to find enough water to supply their residents’ and tourists’ demands.

Many parts of Australia have tolerated widespread extreme weather events this year, including some records. This follows a warm and generally dry 2018. In fact, 9 of the 10 warmest years on record in Australia have occurred since 2005, with only 1998 remaining from last century with reliable records extending back to 1910. Steady warming of our atmosphere and oceans is directly linked to more extreme weather events in Australia and globally.

If those extreme weather events travel more slowly across the landscape, their effects on individual regions could be more devastating still.The Conversation

Steve Turton, Adjunct Professor of Environmental Geography, CQUniversity Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Ice melt in Greenland and Antarctica predicted to bring more frequent extreme weather



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A new climate model combines data on ice loss from both polar regions for the first time.
Mark Brandon, CC BY-ND

Nick Golledge, Victoria University of Wellington

Last week, rivers froze over in Chicago when it got colder than at the North Pole. At the same time, temperatures hit 47℃ in Adelaide during the peak of a heatwave.

Such extreme and unpredictable weather is likely to get worse as ice sheets at both poles continue to melt.

Our research, published today, shows that the combined melting of the Greenland and Antarctic ice sheets is likely to affect the entire global climate system, triggering more variable weather and further melting. Our model predictions suggest that we will see more of the recent extreme weather, both hot and cold, with disruptive effects for agriculture, infrastructure, and human life itself.

We argue that global policy needs urgent review to prevent dangerous consequences.




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We finally have the rulebook for the Paris Agreement, but global climate action is still inadequate


Accelerated loss of ice

Even though the goal of the Paris Agreement is to keep warming below 2℃ (compared to pre-industrial levels), current government pledges commit us to surface warming of 3-4℃ by 2100. This would cause more melting in the polar regions.

Already, the loss of ice from ice sheets in Antarctica and Greenland, as well as mountain glaciers, is accelerating as a consequence of continued warming of the air and the ocean. With the predicted level of warming, a significant amount of meltwater from polar ice would enter the earth’s oceans.

The West Antarctic Ice Sheet is considered more vulnerable to melting, but East Antarctica , once thought to be inert, is now showing increasing signs of change.
Nick Golledge, CC BY-ND

We have used satellite measurements of recent changes in ice mass and have combined data from both polar regions for the first time. We found that, within a few decades, increased Antarctic melting would form a lens of freshwater on the ocean surface, allowing rising warmer water to spread out and potentially trigger further melting from below.

In the North Atlantic, the influx of meltwater would lead to a significant weakening of deep ocean circulation and affect coastal currents such as the Gulf Stream, which carries warm water from the tropics into the North Atlantic. This would lead to warmer air temperatures in Central America, Eastern Canada and the high Arctic, but colder conditions over northwestern Europe on the other side of the Atlantic.

Recent research suggests that tipping points in parts of the West Antarctic Ice Sheet may have already been passed. This is because most of the ice sheet that covers West Antarctica rests on bedrock far below sea level – in some areas up to 2 kilometres below.




Read more:
How Antarctic ice melt can be a tipping point for the whole planet’s climate


Bringing both poles into one model

It can be a challenge to simulate the whole climate system because computer models of climate are usually global, but models of ice sheets are typically restricted to just Antarctica or just Greenland. For this reason, the most recent Intergovernmental Panel of Climate Change (IPCC) assessment used climate models that excluded ice sheet interactions.

Global government policy has been guided by this assessment since 2013, but our new results show that the inclusion of ice sheet meltwater can significantly affect climate projections. This means we need to update the guidance we provide to policy makers. And because Greenland and Antarctica affect different aspects of the climate system, we need new modelling approaches that look at both ice sheets together.

When the edges of the West Antarctic Ice Sheet start to recede, they retreat into deeper and deeper water and the ice begins to float more easily.
Mark Brandon, CC BY-ND

Seas rise as ice melts on land

Apart from the impact of meltwater on ocean circulation, we have also calculated how ongoing melting of both polar ice caps will contribute to sea level. Melting ice sheets are already raising sea level, and the process has been accelerating in recent years.

Our research is in agreement with another study published today, in terms of the amount that Antarctica might contribute to sea level over the present century. This is good news for two reasons.

First, our predictions are lower than one US modelling group predicted in 2016. Instead of nearly a metre of sea level rise from Antarctica by 2100, we predict only 14-15cm.

Second, the agreement between the two studies and also with previous projections from the IPCC and other modelling groups suggests there is a growing consensus, which provides greater certainty for planners. But the regional pattern of sea level rise is uneven, and islands in the southwest Pacific will most likely experience nearly 1.5 times the amount of sea level rise that will affect New Zealand.

While some countries, including New Zealand, are making progress on developing laws and policies for a transition towards a low-carbon future, globally policy is lagging far behind the science.

The predictions we make in our studies underline the increasingly urgent need to reduce greenhouse gas emissions. It might be hard to see how our own individual actions can save polar ice caps from significant melting. But by making individual choices that are environmentally sustainable, we can persuade politicians and companies of the desire for urgent action to protect the world for future generations.The Conversation

Nick Golledge, Associate Professor of Glaciology, Victoria University of Wellington

This article is republished from The Conversation under a Creative Commons license. Read the original article.

When extreme weather wipes out wildlife, the fallout can last for years


Sean Maxwell, The University of Queensland and James Watson, The University of Queensland

The recent heatwaves have proved deadly to many Australian animals, from feral horses to flying foxes.

And it’s not just heatwaves that can cause mass die-offs. Last year, flooding rain wiped out entire Antarctic penguin colonies, while drought has previously caused mass mangrove diebacks around the Gulf of Carpentaria.

These events generate headlines, but what about the aftermath? And are these catastrophic events part of a wider pattern?




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Killer climate: tens of thousands of flying foxes dead in a day


Our research describes how species have responded to extreme weather events over the past 70 years. These responses can tell us a great deal about how species are likely to cope with change in the frequency and intensity of extreme events in coming years.

We reviewed 517 studies, dating back to 1941 and conducted throughout the world, that examined how birds, mammals, fish, amphibians, reptiles, invertebrates or plants have responded to droughts, cyclones, floods, heatwaves, and cold snaps.

We found more than 100 cases of dramatic population declines. In a quarter of these cases, population numbers showed no sign of recovery long after the event. And in most cases, extreme events reduced populations of common species that play an important role in maintaining ecosystem integrity.

For example, extreme drought in the 2000s drove massive population declines of invertebrate freshwater species across Australia’s Murray-Darling Basin, and populations of buffalo, waterbuck, and kudu along the Zambezi River in Zimbabwe suffered severe and persistent declines following droughts in the 1980s.

We also found 31 cases of populations completely disappearing after an extreme event. Large populations of lizards and spiders were eradicated after Hurricane Lilli struck the Bahamas in 1996, for example. These populations had begun to recover one year after Lilli, but in half of all the cases of local population extinction, the species was still absent years or decades after exposure to an extreme event.

Negative responses were the most commonly reported, and also included habitat loss, declines in species numbers, and declines in reproductive fitness after an extreme event. These impacts clearly pose a serious risk to the longevity of many species, and to threatened species in particular. Kosciuszko National Park, for example, is a stronghold for the endangered northern corroboree frog, but 42% of its breeding sites in the park were rendered unusable by severe drought conditions throughout the 2000s.

Is there an upside?

Alongside the many negative impacts, we also found a larger‐than‐expected number of positive or neutral responses to extreme events (21% of all responses). This is a reminder that natural disturbances from extreme events often play a crucial role in the natural dynamics of an ecosystem.

Unfortunately, however, in many cases it was invasive species that benefited from extreme events. Flooding in southern Minnesota in 2004, for example, led to the rapid incursion of invasive green sunfish into streams, and cyclones accelerated the invasion of sweet pittosporum in Jamaican rainforests in the 1990s.

Cases of extreme events benefiting threatened species were uncommon, but included rainforest frogs becoming less susceptible to a fungal pathogen, chytrid fungus, after cyclones reduced rainforest canopy cover.

We also identified a range of “ambiguous” responses, including changes in diet or foraging behaviour, and changes in the types of species inhabiting a study area. Changes in invertebrate communities were particularly prevalent (87 cases). In 18 of these cases, the changes were long-lasting. However, most of the studies we reviewed lasted less than one year, and did not monitor for long-term recovery following an extreme event. This limits our ability to assess the long-term implications of extreme events on the species composition of ecosystems.

Avoiding future impacts

The one failsafe option for helping species cope with extreme events is to retain intact habitats, as these are the places where species are most resilient to extreme events. Intact habitats are contiguous areas of water or native vegetation that often span various altitudes, temperatures and rainfall patterns. These places can also act as important refuges for species that rely on long breaks between extreme events to recover.

Where intact habitat protection is not possible, restoring land or seascapes can also help species to adapt to extreme events. For example, long-term restoration efforts (that is, those that will be effective for at least 15 years) in brackish marshes help plant and animal communities cope with drought events.

Ecological restoration that helps species to adapt to extreme events can also benefit humans too. For instance, coastal communities can use oyster reefs or seagrass beds to guard against flooding.




Read more:
Ecosystems across Australia are collapsing under climate change


Climate change has already increased the intensity and frequency of extreme events across the world, and the trend is expected to accelerate in the future. Recognising the importance of planning for extreme events is essential for helping species cope with climate change. Building resilience to extreme events may also provide an opportunity to reduce the vulnerability of humans too.

Governments, local councils, and local communities are under increasing pressure to plan for extreme climate events. We now need similar recognition of the importance of extreme events in threatened species planning efforts. Right now, this planning is virtually non-existent, and that needs to change.The Conversation

Sean Maxwell, Postdoctoral fellow, The University of Queensland and James Watson, Professor, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Australia’s 2018 in weather: drought, heat and fire


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Queensland’s ‘unprecedented’ bushfires were part of a year of extremes.
RACQ CQ/AAP

Karl Braganza, Australian Bureau of Meteorology

Last year was a time of exceptional weather and record-breaking heat according to the Bureau of Meteorology’s annual climate statement, which was released last night.

The Bureau issued four Special Climate Statements relating to “extreme” and “abnormal” heat, and reported a number of broken climate records.

One of the headline stories for the year was drought across eastern Australia — centred on New South Wales, but also affecting Victoria, eastern South Australia and southern Queensland.


Bureau of Meteorology

With the whole of NSW declared in drought during the latter half of 2018, this drought will be recorded as one of the more significant in Australia’s history, ranking alongside the Millennium, 1960s, World War Two and Federation Droughts. Of those historic droughts, only the Millennium Drought saw similar, accompanying high temperatures.

The below-average rainfall has persisted for around two years across much of NSW and adjacent regions. The drought conditions were particularly severe in the recent spring period, with low rainfall, persistently high temperatures, and record high evaporation.

This exceptionally dry period was influenced by sea surface temperatures to the west of the continent. Perhaps fortuitously, a developing El Niño in the Pacific Ocean failed to mature in the second half of the year. An El Niño would have typically exerted a further drying influence on eastern Australia.




Read more:
Australia moves to El Niño alert and the drought is likely to continue


The dry conditions in eastern states were severe enough to see Australia record its lowest September rainfall on record, and the second-lowest on record for any month — behind April 1902, during the prolonged Federation Drought. Over 2018, Australia’s annual rainfall was 11% below average, and the lowest recorded since 2005, during the Millennium Drought.

In contrast, above-average rainfall was recorded across parts of the tropical north, and most significantly in the Kimberley, consistent with recent trends of increasing rainfall in that region.

The drought conditions were exacerbated by record or near-record temperatures across many parts of the country. It was Australia’s third warmest year on record, behind 2013 and 2005. Daytime maximum temperatures were the warmest on record for NSW and Victoria, and second-warmest for South Australia, the Northern Territory and Australia as a whole.


Bureau of Meteorology

Persistent dry conditions through winter are typically associated with low soil moisture and heatwaves in the following spring and summer, and 2018 followed this pattern — with the added contribution of a warming climate.

The year ended with some record-breaking heat events. Perhaps the most significant of these was the extreme heat along the central and northern Queensland coast in late November and early December, which saw maximum daytime temperatures of 42.6 °C in Cairns and 44.9 °C in Proserpine on the 26th of November.

These temperatures, combined with persistent dry conditions in the preceding months, saw catastrophic fire weather and bushfires along 600km of the Queensland coast, an event that fire agencies have called unprecedented for the state.




Read more:
Sydney storms could be making the Queensland fires worse


The year ended with a burst of heat over the Christmas-New Year period, with temperatures at least 10 degrees warmer than average across southern South Australia, most of Victoria and southern NSW, leading to Australia’s warmest December on record.


Subscribe to receive Bureau Climate Information emails.The Conversation

Karl Braganza, Climate Scientist, Australian Bureau of Meteorology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Summer forecast: scorching heat and heightened bushfire risk


Catherine Ganter, Australian Bureau of Meteorology

Large parts of Australia are facing a hotter and drier summer than average, according to the Bureau of Meteorology’s summer outlook.

Drier than average conditions are likely for much of northern Australia. Most of the country has at least an 80% chance of experiencing warmer than average day and night-time temperatures.

The threat of bushfire will remain high, with few signs of the sustained rain needed to reduce fire risk or make a significant dent in the ongoing drought.

Expect extreme heat

Large parts of Western Australia, most of Queensland and the Top End of the Northern Territory are expected to be drier than usual. Further south, the rest of the country shows no strong push towards a wetter or drier than average summer, which is a change for parts of the southeast compared to recent months.


Bureau of Meteorology

Queensland has already seen some extraordinary record-breaking heat in recent days, with summer yet to truly begin. With the summer outlook predicting warmer days and nights, combined with recent dry conditions and our long-term trend of increasing temperatures, some extreme highs are likely this summer.


Bureau of Meteorology

All of this means above-normal bushfire potential in eastern Australia, across New South Wales, Victoria and Queensland. The bushfire outlook, also released today, notes that rain in areas of eastern Australia during spring, while welcome, was not enough to recover from the long-term dry conditions. The current wet conditions across parts of coastal New South Wales will help, but it will not take long once hot and dry conditions return for vegetation to dry out.




Read more:
Sydney storms could be making the Queensland fires worse


What about El Niño?

The Bureau is currently at El Niño ALERT, which means a roughly 70% chance of El Niño developing this season.




Read more:
Australia moves to El Niño alert and the drought is likely to continue


However, not all the ducks are lined up. While ocean temperatures have already warmed to El Niño levels, to declare a proper “event” there must also be a corresponding response in the atmosphere to reinforce the ocean – this hasn’t happened yet.

That said, climate models expect this event to arrive in the coming months. The outlook has factored in that chance, and the conditions predicted are largely consistent with what we would expect during El Niño. In summer, this includes drier weather in parts of northern Australia, and warmer summer days.

Once an El Niño is in place, weather systems across southern Australia tend to be more mobile. This can mean shorter but more intense heatwaves in Victoria and southern South Australia. However, in New South Wales and Queensland, El Niño is associated with both longer and more intense heat waves.

The exact reason why the states are affected differently is complicated, but relates to the fast-moving cold fronts and troughs that sweep through Victoria and South Australia in the summertime, creating cool changes. These weather systems don’t influence areas further north so when hot air arrives, it takes longer to clear.




Read more:
Drought, wind and heat: when fire seasons start earlier and last longer


The heavy rains seen in parts of eastern Australia in October and November have provided some welcome short-term relief to drought-stricken farmers, but longer-term rainfall relief has not arrived yet. If El Niño arrives, this widespread relief may only be on the cards in autumn.The Conversation

Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology

This article is republished from The Conversation under a Creative Commons license. Read the original article.