El Niño has rapidly become stronger and stranger, according to coral records


Mandy Freund, University of Melbourne; Ben Henley, University of Melbourne; David Karoly, CSIRO; Helen McGregor, University of Wollongong, and Nerilie Abram, Australian National University

The pattern of El Niño has changed dramatically in recent years, according to the first seasonal record distinguishing different types of El Niño events over the last 400 years.

A new category of El Niño has become far more prevalent in the last few decades than at any time in the past four centuries. Over the same period, traditional El Niño events have become more intense.

This new finding will arguably alter our understanding of the El Niño phenomenon. Changes to El Niño will influence patterns of precipitation and temperature extremes in Australia, Southeast Asia and the Americas.

Some climate model studies suggest this recent change in El Niño “flavours” could be due to climate change, but until now, long-term observations were limited.




Read more:
Explainer: El Niño and La Niña


Our paper, published in Nature Geoscience today, fills this gap using coral records to reconstruct El Niño event types for the past 400 years.

Central Pacific El Niño event frequency relative to Eastern Pacific El Niño event frequency over the past four centuries, expressed as the number of events in 30-year sliding windows.
Author provided

What is El Niño?

El Niño describes an almost year-long warming of the surface ocean in the tropical Pacific. These warming events are so extreme and powerful that their impacts are felt around the globe.

During strong El Niño events, Australia and parts of Asia often receive much less rainfall than during normal years. The opposite applies to the western parts of the Americas, where the stronger rising motion over unusually warm ocean waters often results in heavy rainfall, causing massive floods. At the same time many of the hottest years on record across the globe coincide with El Niño events.

El Niño and its global impacts. Schematic of idealised atmospheric and sea surface temperature conditions during Central (top left) and Eastern Pacific events (top right). Annual global temperature anomalies (lower panel) show the familiar upward trend due to climate change. Many of the hottest years on record coincide with El Niño events.
NOAA National Centers for Environmental information, Climate at a Glance: Global Time Series

The reason for such far-reaching influences on weather is the changes El Niño causes in atmospheric circulation. In normal years, a massive circulation cell, called the Walker circulation, moves air along the equator across the tropical Pacific.




Read more:
500 years of drought and flood: trees and corals reveal Australia’s climate history


Warmer waters during El Niño events disrupt or even reverse this circulation pattern. The type of atmospheric disruption and the climate impacts this causes depend in particular on where the warm waters of El Niño are located.

The new ‘flavour’ of El Niño

A new “flavour” of El Niño is now recognised in the tropical Pacific. This type of El Niño is characterised by warm ocean temperatures in the Central Pacific, rather than the more typical warming in the far Eastern Pacific near the South American coast, some 10,000km away.

Although not as strong as the Eastern Pacific version, the Central Pacific El Niño is clearly observed in recent decades, including in 2014-15 and most recently in 2018-19. Over most of the last 400 years, El Niño events happened roughly at the same rate in the Central and Eastern Pacific.

Differences between Central and Eastern Pacific El Niño events and their associated drought impacts.

By the end of the 20th century, though, our research shows a sudden change: a sharp increase of Central Pacific El Niño events becomes evident. At the same time, the number of conventional Eastern Pacific events stayed relatively low, but the three most recent Eastern-type events (in 1982-83, 1997-98 and 2015-16) were unusually strong.

Using coral to unlock the past

Our understanding of the new Central Pacific flavour of El Niño is hindered by the fact that El Niño events happen only every 2-7 years. So during our lifetime we can observe only a handful of events.

This isn’t enough to really understand Central Pacific El Niño, and whether they are becoming more common.

That’s why we look at corals from the tropical Pacific. The corals started growing decades to centuries before we began routinely measuring the climate with instruments. The corals are an excellent archive of changes in water conditions they experience as they grow, including ocean changes related to El Niño. We combined the information from a network of coral records that preserve seasonal histories.

At a seasonal timescale, we can see the characteristic patterns of past El Niño events in the chemistry of the corals. These patterns tell us which El Niño is which over the last 400 years. It is in this continuous picture of past El Niños obtained from coral archives that we found a clear picture of an unusual recent change in the Pacific’s El Niño flavours.

Underwater drilling of corals off Christmas Island (underwater team: Jennie Mallela, Oscar Branson; surface team: Jessica Hargreaves, Nerilie Abram).
Jason Turl, Nerilie Abram

Why do we care?

This extraordinary change in El Niño behaviour has serious implications for societies and ecosystems around the world. For example, the most recent Eastern-Pacific El Niño event in 2015-2016 triggered disease outbreaks across the globe. With the impacts of climate change continuing to unfold, many of the hottest years on record also coincide with El Niño events.




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


What’s more, the Pacific Ocean is currently lingering in an El Niño state. With these confounding events, many people around the world are wondering what extreme weather will be inflicted upon them in the months and years to come.

Our new record opens a door to understanding past changes of El Niño, with implications for the future too. Knowing how the different types of El Niño have unfolded in the past will mean we are better able to model, predict and plan for future El Niños and their widespread impacts.The Conversation

Mandy Freund, PhD Researcher, University of Melbourne; Ben Henley, Research Fellow in Climate and Water Resources, University of Melbourne; David Karoly, Leader, NESP Earth Systems and Climate Change Hub, CSIRO; Helen McGregor, ARC Future Fellow, University of Wollongong, and Nerilie Abram, ARC Future Fellow, Research School of Earth Sciences; Chief Investigator for the ARC Centre of Excellence for Climate Extremes, Australian National University

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.

Will the arrival of El Niño mean fewer mosquitoes this summer?



File 20181105 74787 xceqwb.jpg?ixlib=rb 1.1
A hot summer will mean wetlands dry out faster than ever, so how will pest mosquitoes respond?
Cameron Webb (NSW Health Pathology), Author provided

Cameron Webb, University of Sydney

Once the warm weather arrives, you know mosquitoes won’t be far behind. Spring heatwaves associated with the impending arrival of El Niño to the east coast of Australia may mean we’ll get an early taste of summer, but what about mosquitoes? Does a long, hot summer mean fewer annoying buzzing and biting beasts bothering us whenever we spend time outdoors?

Where do mosquitoes come from?

Mosquitoes are complex animals. Like all insects, they thrive in warm weather, but they need more than just heat, they need water.

Mosquitoes lay their eggs on or around water. Without it, they cannot complete their life cycle. Mosquito “wrigglers” hatch out from eggs and spend a week or so swimming about before emerging and flying off in search of blood. Depending on where the water is, whether it is wetlands, puddles or water-filled containers, different kinds of mosquitoes will be present.

There are hundreds of different mosquitoes in Australia. Some like salty water, some like fresh. Some need pristine conditions while some will tolerate filthy water trapped at the bottom of a septic tank.

Because mosquitoes rely on water, rainfall plays a critical role in determining how many mosquitoes will be buzzing about this summer.




Read more:
Health Check: why mosquitoes seem to bite some people more


A hot, dry summer must mean fewer mosquitoes?

The likelihood that an El Niño will bring drier and warmer conditions to eastern Australia this summer is increasing. The latest predictions from the Bureau of Meteorology are that there is a 70% chance an El Nino will occur this year, about three times more than usual.

At first, this may seem like good news for those averse to mosquito bites, but don’t pack away the repellent just yet.

While floods bring mosquitoes, and often outbreaks of mosquito-borne disease, drought will knock out almost all mosquitoes. It is true that the ongoing dry conditions across inland areas of Australia will ensure mosquito populations remain low, but that doesn’t mean mosquitoes will disappear completely.




Read more:
The worst year for mosquitoes ever? Here’s how we find out


Water doesn’t just come from rain

While a lack of rain will keep many wetlands dry, that isn’t the case for our coastal wetlands. Some of the worst pest mosquitoes in Australia are found in our mangroves, saltmarshes and sedgelands.

Mosquitoes, like the saltmarsh mosquito, Aedes vigilax, love wetlands regularly flooded by high tides. The eggs of this mosquito, laid in moist wetland mud, survive long periods of dry conditions. Once covered by tides, these hatch, complete development within a week, and emerge in extraordinary numbers to fly kilometres away into nearby communities to bite and spread disease-causing pathogens such as Ross River virus.

Not only have these mosquitoes found a way to survive without rain, they thrive in hot and dry conditions. Without substantial rainfall, the pools and ponds in the wetlands dry completely, killing off any fish or other aquatic predators, ensuring perfect conditions once the next series of tides comes flooding in. The arrival of El Niño may be bad news for lots of wetland wildlife, but it isn’t all bad news for mosquitoes.

The saltmarsh mosquito, Aedes vigilax, is one of the most important pest mosquitoes in coastal regions of Australia and has adapted to thrive in hot and dry conditions.
Stephen Doggett (NSW Health Pathology)

Bringing mosquitoes home

Much has been made of the impact of heatwaves on human health. It may also inadvertently increase health risks in metropolitan regions of Australia. A shortage of water increases the need to conserve and store water around the backyard. Unfortunately, that also means creating a home for mosquitoes.

One of the most widespread mosquitoes in the country, a mosquito that has probably bitten almost every Australian, is the backyard mosquito Aedes notoscriptus. This mosquito is found in water-filled containers around the backyard, from drains and roof gutters to rainwater tanks and bird baths. While you’d think hot and dry conditions will impact this mosquito, think about the extra effort we’re taking to store water around the home. If your rainwater tank isn’t properly screened or you’re keeping uncovered bins and buckets around the backyard filled with water, you’ll be providing a home for mosquitoes.

The debate about the impact of a changing climate on mosquitoes and mosquito-borne disease often focuses on the spread of tropical diseases into warming temperate regions. The truth is it may be the way humans respond to a changing climate through water-saving measures around the home that could increase mosquito impacts in urban areas. This also may bring a risk of exotic mosquitoes to our suburbs, which could transmit more serious mosquito-borne pathogens such as dengue, chikungunya and Zika viruses.

While some parts of Australia will have fewer annoying mozzies this summer, don’t be complacent about taking steps to avoid mosquito bites. Choose and use the right insect repellents and reduce opportunities for mosquitoes to move into your backyard by covering up water-holding containers.The Conversation

Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney

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

El Niño in the Pacific has an impact on dolphins over in Western Australia



File 20171006 9797 1for0lt
Leaping bottlenose dolphins.
Kate Sprogis/MUCRU, Author provided

Kate Sprogis, Murdoch University; Fredrik Christiansen, Murdoch University; Lars Bejder, Murdoch University, and Moritz Wandres, University of Western Australia

Indo-Pacific bottlenose dolphins (Tursiops aduncus) are a regular sight in the waters around Australia, including the Bunbury area in Western Australia where they attract tourists.

The dolphin population here, about 180km south of Perth, has been studied quite intensively since 2007 by the Murdoch University Cetacean Unit. We know the dolphins here have seasonal patterns of abundance, with highs in summer/autumn (the breeding season) and lows in winter/spring.

But in winter 2009, the dolphin population fell by more than half.

A leaping bottlenose dolphin.
Kate Sprogis/MUCRU, Author provided

This decrease in numbers in WA could be linked to an El Niño event that originated far away in the Pacific Ocean, we suggest in a paper published today in Global Change Biology. The findings could have implications for future sudden drops in dolphin numbers here and elsewhere.


Read more: Tackling the kraken: unique dolphin strategy delivers dangerous octopus for dinner


A Pacific event

The El Niño Southern Oscillation (ENSO) results from an interaction between the atmosphere and the tropical Pacific Ocean. ENSO periodically fluctuates between three phases: La Niña, Neutral and El Niño.

During our study from 2007 to 2013, there were three La Niña events. There was one El Niño event in 2009, with the initial phase in winter being the strongest across Australia.

The blue vertical line shows the decline in dolphin numbers (d) during the 2009 El Niño event.
Kate Sprogis, Author provided

Coupled with El Niño, there was a weakening of the Leeuwin Current, the dominant ocean current off WA. There was also a decrease in sea surface temperature and above average rainfall.

ENSO is known to affect the strength of the south-ward flowing Leeuwin Current.

During La Niña, easterly trade winds pile warm water on the western side of the Pacific Ocean. This westerly flow of warm water across the top of Australia through the Indonesian Throughflow results in a stronger Leeuwin Current.

During El Niño, trade winds weaken or reverse and the pool of warm water in the Pacific Ocean gathers on the eastern side of the Pacific Ocean. This results in a weaker Indonesian Throughflow across the top of Australia and a weakening in strength of the Leeuwin Current.

A chart showing sea surface temperature (SST) anomalies off Western Australia. Note the extremes for the moderate El Niño in 2009 (blue rectangle), and the strong La Niña in 2011 (red rectangle)
Moritz Wandres, Author provided

The strength and variability of the Leeuwin Current coupled with ENSO affects species biology and ecology in WA waters. This includes the distribution of fish species, the transport of rock lobster larvae, the seasonal migration of whale sharks and even seabird breeding success.

The question we asked then was whether ENSO could affect dolphin abundance?

What happened during the El Niño?

These El Niño associated conditions may have affected the distribution of dolphin prey, resulting in the movement of dolphins out of the study area in search of adequate prey elsewhere.

A surfacing bottlenose dolphin.
Kate Sprogis/MUCRU, Author provided

This is similar to what happens for seabirds in WA. During an El Niño event with a weakened Leeuwin Current, the distribution of prey changes around seabird’s breeding colonies resulting in a lower abundance of important prey species, such as salmon.

This in turn negatively impacts seabirds, including a decrease in reproductive output and changes in foraging.

In southwestern Australia, the amount of rainfall is strongly connected to sea surface temperature. When the water temperature in the Indian Ocean decreases, the region receives higher rainfall during winter.

High levels of rainfall contribute to terrestrial runoff and alters freshwater inputs into rivers and estuaries. The changes in salinity influences the distribution and abundance of dolphin prey.

This is particularly the case for the river, estuary, inlet and bay around Bunbury. Rapid changes in salinity during the onset of El Niño may have affected the abundance and distribution of fish species.

In 2009, there was also a peak in strandings of dead bottlenose dolphins in WA (between 1981-2010), but the cause of this remains unknown.

Of these strandings, in southwest Australia, there was a peak in June that coincided with the onset of the 2009 El Niño.

Specifically, in the Swan River, Perth, there were several dolphin deaths, with some resident dolphins that developed fatal skin lesions that were enhanced by the low-salinity waters.

What does all this mean?

Our study is the first to describe the effects of climate variability on a coastal, resident dolphin population.

A group of bottlenose dolphins.
Kate Sprogis/MUCRU, Author provided

We suggest that the decline in dolphin abundance during the El Niño event was temporary. The dolphins may have moved out of the study area due to changes in prey availability and/or potentially unfavourable water quality conditions in certain areas (such as the river and estuary).


Read more: Explainer: El Niño and La Niña


Long-term, time-series datasets are required to detect these biological responses to anomalous climate conditions. But few long-term datasets with data collected year-round for cetaceans (whales, dolphins and porpoises) are available because of logistical difficulties and financial costs.

Continued long-term monitoring of dolphin populations is important as climate models provide evidence for the doubling in frequency of extreme El Niño events (from one event every 20 years to one event every ten years) due to global warming.

The ConversationWith a projected global increase in frequency and intensity of extreme weather events (such as floods, cyclones), coastal dolphins may not only have to contend with increasing coastal human-related activities (vessel disturbance, entanglement in fishing gear, and coastal development), but also have to adapt to large-scale climatic changes.

Kate Sprogis, Research associate, Murdoch University; Fredrik Christiansen, Postdoctoral Research Fellow, Murdoch University; Lars Bejder, Professor, Cetacean Research Unit, Murdoch University, Murdoch University, and Moritz Wandres, Oceanographer PhD Student, University of Western Australia

This article was originally published on The Conversation. Read the original article.

Meet El Niño’s cranky uncle that could send global warming into hyperdrive


Ben Henley, University of Melbourne; Andrew King, University of Melbourne; Chris Folland, Met Office Hadley Centre; David Karoly, University of Melbourne; Jaci Brown, CSIRO, and Mandy Freund, University of Melbourne

You’ve probably heard about El Niño, the climate system that brings dry and often hotter weather to Australia over summer.

You might also know that climate change is likely to intensify drought conditions, which is one of the reasons climate scientists keep talking about the desperate need to reduce greenhouse gas emissions, and the damaging consequences if we don’t.

El Niño is driven by changes in the Pacific Ocean, and shifts around with its opposite, La Niña, every 2-7 years, in a cycle known as the El Niño Southern Oscillation or ENSO.

But that’s only part of the story. There’s another important piece of nature’s puzzle in the Pacific Ocean that isn’t often discussed.

It’s called the Interdecadal Pacific Oscillation, or IPO, a name coined by a study which examined how Australia’s rainfall, temperature, river flow and crop yields changed over decades.

Since El Niño means “the boy” in Spanish, and La Niña “the girl”, we could call the warm phase of the IPO “El Tío” (the uncle) and the negative phase “La Tía” (the auntie).

These erratic relatives are hard to predict. El Tío and La Tía phases have been compared to a stumbling drunk. And honestly, can anyone predict what a drunk uncle will say at a family gathering?

What is El Tío?

Like ENSO, the IPO is related to the movement of warm water around the Pacific Ocean. Begrudgingly, it shifts its enormous backside around the great Pacific bathtub every 10-30 years, much longer than the 2-7 years of ENSO.

The IPO’s pattern is similar to ENSO, which has led climate scientists to think that the two are strongly linked. But the IPO operates on much longer timescales.

We don’t yet have conclusive knowledge of whether the IPO is a specific climate mechanism, and there is a strong school of thought which proposes that it is a combination of several different mechanisms in the ocean and the atmosphere.

Despite these mysteries, we know that the IPO had an influence on the global warming “hiatus” – the apparent slowdown in global temperature increases over the early 2000s.

Global temperatures are on the up, but the IPO affects the rate of warming.
Author provided, data from NOAA, adapted from England et al. (2014) Nat. Clim. Change

Temperamental relatives

When it comes to global temperatures we know that our greenhouse gas emissions since the industrial revolution are the primary driver of the strong warming of the planet. But how do El Tío and La Tía affect our weather and climate from year to year and decade to decade?

Superimposed on top of the familiar long-term rise in global temperatures are some natural bumps in the road. When you’re hiking up a massive mountain, there are a few dips and hills along the way.

Several recent studies have shown that the IPO phases, El Tío and La Tía, have a temporary warming and cooling influence on the planet.

Rainfall around the world is also affected by El Tío and La Tía, including impacts such as floods and drought in the United States, China, Australia and New Zealand.

In the negative phase of the IPO (La Tía) the surface temperatures of the Pacific Ocean are cooler than usual near the equator and warmer than usual away from the equator.

Since about the year 2000, some of the excess heat trapped by greenhouse gases has been getting buried in the deep Pacific Ocean, leading to a slowdown in global warming over about the last 15 years. It appears as though we have a kind auntie, La Tía perhaps, who has been cushioning the blow of global warming. For the time being, anyway.

The flip side of our kind auntie is our bad-tempered uncle, El Tío. He is partly responsible for periods of accelerated warming, like the period from the late 1970s to the late 1990s.

The IPO has been in its “kind auntie” phase for well over a decade now. But the IPO could be about to flip over to El Tío. If that happens, it is not good news for global temperatures – they will accelerate upwards.

Models getting better

One of the challenges to climate science is to understand how the next decade, and the next couple of decades, will unravel. The people who look after our water and our environment want to know things like how fast our planet will warm in the next 10 years, and whether we will have major droughts and floods.

To do this we can use computer models of Earth’s climate. In our recently published paper in Environmental Research Letters, we evaluated how well a large number of models from around the world simulate the IPO. We found that the models do surprisingly well on some points, but don’t quite simulate the same degree of slow movement (the stubborn behaviour) of El Tío and La Tía that we observe in the real world.

But some climate models are better at simulating El Tío and La Tía. This is useful because it points the way to better models that could be used to understand the next few decades of El Tío, La Tía and climate change.

However, more work needs to be done to predict the next shift in the IPO and climate change. This is the topic of a new set of experiments that are going to be part the next round of climate model comparisons.

With further model development and new observations of the deep ocean available since 2005, scientists will be able to more easily answer some of these important questions.

Whatever the case, cranky old El Tío is waiting just around the corner. His big stick is poised, ready to give us a massive hiding: a swift rise in global temperatures over the coming decades.

And like a big smack, that would be no laughing matter.

The Conversation

Ben Henley, Research Fellow in Climate and Water Resources, University of Melbourne; Andrew King, Climate Extremes Research Fellow, University of Melbourne; Chris Folland, Science Fellow, Met Office Hadley Centre; David Karoly, Professor of Atmospheric Science, University of Melbourne; Jaci Brown, Senior Research Scientist, CSIRO, and Mandy Freund, PhD student, University of Melbourne

This article was originally published on The Conversation. Read the original article.

Australia’s climate in 2016 – a year of two halves as El Niño unwound


Blair Trewin, Australian Bureau of Meteorology

For Australia’s climate, 2016 was a year of two halves. The year started with one of the strongest El Niño events on record in place in the Pacific Ocean, and the opening months of 2016 were generally hot and dry, especially in northern and eastern Australia.

From May onwards there was a dramatic change in the pattern, with heavy rain and flooding a regular feature of the middle months of the year.

Overall temperatures were the fourth warmest on record in 2016, capping off Australia’s hottest decade. We track these events and more in the Bureau of Meteorology’s annual climate summary released today.

Dry to start

At the start of 2016, many parts of Australia were significantly affected by drought. Long-term drought had existed since 2012 through much of inland Queensland and adjacent northern areas of New South Wales, while shorter-term drought affected Tasmania, central and western Victoria, and parts of South Australia.

While some rain fell between January and April in these areas, it was generally not enough to have much impact on the rainfall deficiencies. Tasmania was hit especially hard, with low water storages restricting hydroelectric production, and long-lived and extensive bushfires in central and western parts of the state a feature of the summer period.

January to April, normally the wettest time of the year across Australia’s far north, was also much drier than normal with rainfall well below average in the Kimberley, the Northern Territory Top End, and on Cape York Peninsula.

It was the least active Australian tropical cyclone season since comprehensive satellite records began in 1970, with only three cyclones in the region, none of them severe, and only one of which made landfall.

The rains are here

Widespread heavy rains began in May – something well predicted by seasonal forecast models – as the El Niño ended and conditions in the Indian Ocean became very favourable for Australian rainfall, with unusually warm waters between Western Australia and Indonesia. Each month from May to September was wetter than average across most of the continent, with heavy rains extending into areas such as inland Queensland where the winter is normally the driest time of the year.

The wet conditions culminated in September, when nationally averaged rainfall was nearly three times the average. It was the wettest September on record for New South Wales and the Northern Territory, and in the top four wettest for every state except Western Australia and Tasmania.

May to September was the wettest on record over Australia, with some locations in inland New South Wales breaking previous records for the period by nearly 200 millimetres. Rainfall returned to more normal levels in eastern mainland Australia from October onwards, although Tasmania remained wet, and a tropical low brought widespread heavy rains extending from the Kimberley south through central Australia as far south as South Australia and Victoria in the year’s final days.

Despite flood damage in places and some rain-affected harvests, the wet conditions were generally positive for agriculture. They also led to large increases in water storage levels in many areas, especially in the Murray-Darling Basin and in Tasmania.

Flooding and storms were also a feature of this period. In early June, an East Coast Low affected almost the whole east coast from southern Queensland southwards.

Northern Tasmania saw some of its most severe flooding on record, and the Sydney region suffered significant coastal erosion with some property damage. The heavy September rains led to major flooding on several inland rivers, particularly the Lachlan River in central New South Wales, and went on to produce the highest flood since the early 1990s on the Murray River in South Australia as the waters moved downstream.

An intense low-pressure system in South Australia at the end of September caused major wind and flood damage there. In Tasmania, which had further flooding in November, the seven months from May to November were the wettest on record, after the seven months from October 2015 to April 2016 had been the driest on record.

Over Australia as a whole, it was the 17th wettest year on record with rainfall 17% above the long-term average. Tasmania had its second-wettest year on record, despite the dry start, and South Australia its fourth-wettest. Below-average rainfalls in 2016 were largely confined to parts of the northern tropics, coastal areas of southern Queensland and northern New South Wales, and some parts of coastal Western Australia. Heavy rains in the year’s final week were enough to lift Adelaide to its second-wettest year on record, while Uraidla, in the Adelaide Hills, had the largest annual rainfall total at any South Australian site since 1917.

The heat is on

It was the fourth-warmest year on record for Australia, with temperatures 0.87℃ above average nationally, 0.33℃ short of the record set in 2013.

The year got off to a very warm start; it was the warmest autumn on record for Australia, and the first half of the year was also the warmest on record, although there were no individual heatwaves on the scale of those experienced in 2013 or 2014.

The second half of the year was less warm. During the wet months in mid-year, heavy cloud cover led to cool days but warm nights, then a cool October resulted in spring temperatures almost exactly matching the long-term average. A warm start and cooler finish is typical of a post-El Niño year as rainfall typically changes from below to above average.

It was the warmest year on record in many parts of the northern tropics, along much of the east coast, and in parts of Tasmania. Darwin, Brisbane, Sydney and Hobart all had their warmest year on record. The warmth on land in these coastal areas was matched by warmth in the oceans.

Sea surface temperatures in the Australian region were the warmest on record, with the first half of the year especially warm. The record warm waters contributed to extensive coral bleaching on the Great Barrier Reef, and also affected fisheries in Tasmania.

Temperatures were closer to average in other parts of the country, including inland areas of the eastern states, South Australia and most of Western Australia. In a few parts of southern Western Australia, which had its coldest winter since 1990, temperatures in 2016 were slightly below average (one of only a handful of land areas in the world where this was the case), and there was some frost damage to crops in what was otherwise a very productive year for Australia’s grain-growers.

2016 continues a sequence of years with Australian temperatures well above average. While 2016 did not set a record, the last four years all rank in Australia’s six warmest, and the last ten years have been Australia’s warmest on record. 2016 is also almost certain to be the hottest year on record globally.

The Conversation

Blair Trewin, Climate scientist, Australian Bureau of Meteorology

This article was originally published on The Conversation. Read the original article.