The North American heatwave shows we need to know how climate change will change our weather


NASA

Christian Jakob, Monash University and Michael Reeder, Monash UniversityEight days ago, it rained over the western Pacific Ocean near Japan. There was nothing especially remarkable about this rain event, yet it made big waves twice.

First, it disturbed the atmosphere in just the right way to set off an undulation in the jet stream – a river of very strong winds in the upper atmosphere – that atmospheric scientists call a Rossby wave (or a planetary wave). Then the wave was guided eastwards by the jet stream towards North America.

Along the way the wave amplified, until it broke just like an ocean wave does when it approaches the shore. When the wave broke it created a region of high pressure that has remained stationary over the North American northwest for the past week.

This is where our innocuous rain event made waves again: the locked region of high pressure air set off one of the most extraordinary heatwaves we have ever seen, smashing temperature records in the Pacific Northwest of the United States and in Western Canada as far north as the Arctic. Lytton in British Columbia hit 49.6℃ this week before suffering a devastating wildfire.

What makes a heatwave?

While this heatwave has been extraordinary in many ways, its birth and evolution followed a well-known sequence of events that generate heatwaves.

Heatwaves occur when there is high air pressure at ground level. The high pressure is a result of air sinking through the atmosphere. As the air descends, the pressure increases, compressing the air and heating it up, just like in a bike pump.

Sinking air has a big warming effect: the temperature increases by 1 degree for every 100 metres the air is pushed downwards.

The North American heatwave has seen fires spread across the landscape.
NASA

High-pressure systems are an intrinsic part of an atmospheric Rossby wave, and they travel along with the wave. Heatwaves occur when the high-pressure systems stop moving and affect a particular region for a considerable time.

When this happens, the warming of the air by sinking alone can be further intensified by the ground heating the air – which is especially powerful if the ground was already dry. In the northwestern US and western Canada, heatwaves are compounded by the warming produced by air sinking after it crosses the Rocky Mountains.

How Rossby waves drive weather

This leaves two questions: what makes a high-pressure system, and why does it stop moving?

As we mentioned above, a high-pressure system is usually part of a specific type of wave in the atmosphere – a Rossby wave. These waves are very common, and they form when air is displaced north or south by mountains, other weather systems or large areas of rain.




Read more:
We’ve learned a lot about heatwaves, but we’re still just warming up


Rossby waves are the main drivers of weather outside the tropics, including the changeable weather in the southern half of Australia. Occasionally, the waves grow so large that they overturn on themselves and break. The breaking of the waves is intimately involved in making them stationary.

Importantly, just as for the recent event, the seeds for the Rossby waves that trigger heatwaves are located several thousands of kilometres to the west of their location. So for northwestern America, that’s the western Pacific. Australian heatwaves are typically triggered by events in the Atlantic to the west of Africa.

Another important feature of heatwaves is that they are often accompanied by high rainfall closer to the Equator. When southeast Australia experiences heatwaves, northern Australia often experiences rain. These rain events are not just side effects, but they actively enhance and prolong heatwaves.

What will climate change mean for heatwaves?

Understanding the mechanics of what causes heatwaves is very important if we want to know how they might change as the planet gets hotter.

We know increased carbon dioxide in the atmosphere is increasing Earth’s average surface temperature. However, while this average warming is the background for heatwaves, the extremely high temperatures are produced by the movements of the atmosphere we talked about earlier.

So to know how heatwaves will change as our planet warms, we need to know how the changing climate affects the weather events that produce them. This is a much more difficult question than knowing the change in global average temperature.

How will events that seed Rossby waves change? How will the jet streams change? Will more waves get big enough to break? Will high-pressure systems stay in one place for longer? Will the associated rainfall become more intense, and how might that affect the heatwaves themselves?




Read more:
Explainer: climate modelling


Our answers to these questions are so far somewhat rudimentary. This is largely because some of the key processes involved are too detailed to be explicitly included in current large-scale climate models.

Climate models agree that global warming will change the position and strength of the jet streams. However, the models disagree about what will happen to Rossby waves.

From climate change to weather change

There is one thing we do know for sure: we need to up our game in understanding how the weather is changing as our planet warms, because weather is what has the biggest impact on humans and natural systems.

To do this, we will need to build computer models of the world’s climate that explicitly include some of the fine detail of weather. (By fine detail, we mean anything about a kilometre in size.) This in turn will require investment in huge amounts of computing power for tools such as our national climate model, the Australian Community Climate and Earth System Simulator (ACCESS), and the computing and modelling infrastructure projects of the National Collaborative Research Infrastructure Strategy (NCRIS) that support it.

We will also need to break down the artificial boundaries between weather and climate which exist in our research, our education and our public conversation.The Conversation

Christian Jakob, Professor in Atmospheric Science, Monash University and Michael Reeder, Professor, School of Earth, Atmosphere and Environment, Monash University

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

Three weeks without electricity? That’s the reality facing thousands of Victorians, and it will happen again


James Ross/AAP

Anthony Richardson, RMIT UniversityLast week’s storm system wreaked havoc across Victoria. Some 220,000 households and businesses lost power, and residents in the hills on Melbourne’s fringe were warned yesterday it might not be restored for three weeks.

The extreme weather severely damaged the poles and powerlines that distribute electricity, particularly in the Mount Dandenong area. Senior AusNet official Steven Neave said of the region this week, “we basically have no network left, the overhead infrastructure is pretty much gone. It requires a complete rebuild”.

That leaves about 3,000 customers without electricity for weeks, in the heart of winter. The loss of power also cut mobile phone and internet services and reportedly allowed untreated water to enter drinking supplies.

So, could this disaster have been avoided? And under climate change, how can we prepare for more events like this?

fallen tree on powerlines
Fallen trees brought down power lines across Melbourne.
Daniel Pockett/AAP

An uncertain future

The Mount Dandenong area is heavily forested, and the chance of above-ground power infrastructure being hit by falling trees is obviously high.

Without electricity, people cannot turn on lights, refrigerate food or medications, cook on electric stoves or use electric heaters. Electronic banking, schooling and business activities are also badly disrupted. For vulnerable residents, in particular, the implications are profound.

Such disruptions are hard to avoid, at least while the electricity network is above ground. Good management, however, can prevent some trees coming down in storms.

The more pertinent question is: how can we prepare for such an event in the future?

Scientists warn such extreme weather will increase in both frequency and severity as climate change accelerates. The Australian Energy Market Operator is acutely aware of this, warning climate change poses “material risks to individual assets, the integrated energy system, and society”.

However, it’s challenging to predict exactly how future heatwaves, storms, bushfires and floods will affect the power network. As AEMO notes, many climate models related to storms and cyclones involve an element of unpredictability. So, plans to make the electricity system more resilient must address this uncertainty.

As researchers have noted, there is no “one future” to prepare for – we must be ready for many potential eventualities.




Read more:
Victoria’s wild storms show how easily disasters can threaten our water supply


tree fallen on house
Under climate change, extreme weather is predicted to become more severe.
Daniel Pockett/AAP

Yallourn – the bigger problem?

Meanwhile, in Victoria’s LaTrobe Valley, a situation at the Yallourn coal-fired power station which may have even greater consequences for electricity supplies.

A coal mine wall adjacent to the station is at risk of collapse after flooding in the Morwell River caused it to crack. If the wall is breached and the mine is flooded, as happened in 2012, there will be no coal to power the station and almost a quarter of Victoria’s power supply could be out for months.

Victoria’s energy needs are increasingly supplied by renewables. However, losing Yallourn’s generation capacity would reduce the capacity of the network to adapt to other possible disruptions.

If further disruptions seem unlikely, it’s worth noting the Callide Power Station in Queensland is still operating at reduced capacity after a recent fire.




Read more:
An act of God, or just bad management? Why trees fall and how to prevent it


power plant with chimneys
A wall adjacent to the Yallourn power plant may collapse.
Julian Smith/AAP

Look beyond the immediate crisis

The Victorian government has offered up to A$1,680 per week, for up to three weeks, to help families without power buy supplies and find alternative accommodation.

Welfare groups say the assistance could be improved. They have called for changes to make it quicker and easier for people to access money, cash injections to frontline charities and more temporary accommodation facilities for displaced people and their pets.

While no doubt needed, these are all reactive responses targeted at those without electricity. When any system is disrupted, however, the effects can be widespread and felt long after the initial problem has been addressed.

Take dairy farmers in Gippsland, for example, who could not milk their cows without electricity. Cows must be milked regularly or else they stop producing milk – they cannot be “switched back on” when electricity is restored. Longer-term assistance may well be required for farmers facing such ripple effects.

And as welfare groups have noted, power companies should support affected customers over the long-term, with electricity discounts, deferrals and payment plans.




Read more:
No food, no fuel, no phones: bushfires showed we’re only ever one step from system collapse


Sign reading 'power and shower'
Relief centres offer affected residents a hot shower and electricity access, but longer-term solutions are also needed.
Daniel Pockett/AAP

A call for backup

So, what else can be done to prepare for future power disruptions? Those with backup options, such as portable fuel-powered generators, or off-grid household batteries connected to solar panels, will undoubtedly be more resilient in such events.

These are examples of “system redundancy”, providing alternative electricity until the network is restored.

But it costs money to invest in household batteries or a generator that may never be used. Resilience is often a function of wealth, and the less well-off risk being left behind.

Certainly, governments can act to make society as a whole more resilient to power outages. For example, mobile phone towers have backup battery life of just 24 hours. As Victoria’s Emergency Management Commissioner Andrew Crisp said this week, extending that is something authorities “need to look at”.

Power and communications infrastructure could be moved underground to protect it from storms. While such a move would be expensive, it has been argued not doing so will lead to greater long-term costs under a changing climate.

The recent challenges at Yallourn and Callide show the risks inherent in a centralised electricity network dominated by coal.

Certainly, integrating renewable energy sources into the power network comes with its own challenges. However, expanding energy storage such as batteries, or shifting to small, community-level microgrids will go a long way to improving the resilience of the system.

This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. It is supported by a philanthropic grant from the Paul Ramsay Foundation. Find the series here.The Conversation

Anthony Richardson, Researcher and Teacher, Centre for Urban Research, RMIT University

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

How rain, wind, heat and other heavy weather can affect your internet connection


Gordonekoff / Shutterstock

James Jin Kang, Edith Cowan University and Paul Haskell-Dowland, Edith Cowan UniversityWhen your Netflix stream drops out in the middle of a rainstorm, can you blame the wild weather?

Quite possibly. The weather can affect the performance of your internet connection in a variety of ways.

This can include issues such as physical damage to the network, water getting into electrical connections, and wireless signal interference. Some types of connection are more vulnerable to weather than others.

The behaviour of other humans in response to the weather can also have an effect on your connection.

How rain can affect your internet connection

Internet connections are much more complicated than the router and cables in our homes. There are many networking devices and cables and connections (of a variety of types and ages) between our homes and the websites we are browsing.

How do we connect to the Internet?

An internet connection may involve different kinds of physical link, including the copper wiring used in the old phone network and more modern fibre optic connections. There may also be wireless connections involved, such as WiFi, microwave and satellite radio.

Example of multi-layered internet access.
Ferran, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Rain can cause physical damage to cables, particularly where telecommunication networks are using old infrastructure.

ADSL-style connections, which use the old phone network, are particularly vulnerable to this type of interference. Although many Australians may be connected to the National Broadband Network (NBN), this can still run (in part) through pre-existing copper wires (in the case of “fibre to the node” or “fibre to the cabinet” connections) rather than modern optical fibres (“fibre to the home”).

Different types of NBN connection.
Riick, CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/, via Wikimedia Commons

Much of the internet’s cabling is underground, so if there is flooding, moisture can get into the cables or their connectors. This can significantly interfere with signals or even block them entirely, by reducing the bandwidth or causing an electrical short-circuit.

But it isn’t just your home connection that can be impacted. Wireless signals outside the home or building can be affected by rainfall as water droplets can partially absorb the signal, which may result in a lower level of coverage.

Even once the rain stops, the effects can still be felt. High humidity can continue to affect the strength of wireless signals and may cause slower connection speeds.

Copper cables and changed behaviour

If you are using ADSL or NBN for your internet connection, it is likely copper phone cables are used for at least some of the journey. These cables were designed to carry voice signals rather than data, and on average they are now more than 35 years old.

Only around 18% of Australian homes have the faster and more reliable optical-fibre connections.

There is also a behaviour factor. When it rains, more people might decide to stay indoors or work from home. This inevitably leads to an increase in the network usage. When a large number of people increase their internet usage, the limited bandwidth available is rapidly consumed, resulting in apparent slowdowns.




Read more:
How to boost your internet speed when everyone is working from home


This is not only within your home, but is also aggregated further up the network as your traffic is joined by that from other homes and eventually entire cities and countries.

Heatwaves and high winds

In Australia, extreme cold is not usually a great concern. Heat is perhaps a more common problem. Our networking devices are likely to perform more slowly when exposed to extreme heat. Even cables can suffer physical damage that may affect the connection.

Imagine your computer fan is not running and the device overheats — it will eventually fail. While the device itself may be fine, it is likely the power supply will struggle in extremes. This same issue can affect the networking equipment that controls our internet connection.

Satellite internet services for rural users can be susceptible to extreme weather, as the satellite signals have to travel long distances in the air.

Radio signals are not usually affected by wind, but hardware such as satellite dishes can be swayed, vibrated, flexed or moved by the wind.

Most of the time, human behaviour is the main cause

For most users, the impact of rain will be slight – unless they are physically affected by a significant issue such as submerged cables, or they are trying to use WiFi outside during a storm.

So, can weather affect your internet connection? Absolutely.

Will most users be affected? Unlikely.

So if your favourite Netflix show is running slow during in rainy weather, it’s most likely that the behaviour of other humans is to blame — holed up indoors and hitting the internet, just like you.




Read more:
Internet traffic is growing 25% each year. We created a fingernail-sized chip that can help the NBN keep up


The Conversation


James Jin Kang, Lecturer, Computing and Security, Edith Cowan University and Paul Haskell-Dowland, Associate Dean (Computing and Security), Edith Cowan University

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

Cyclone Seroja just demolished parts of WA – and our warming world will bring more of the same


Bureau of Meteorology

Jonathan Nott, James Cook UniversityTropical Cyclone Seroja battered parts of Western Australia’s coast on Sunday night, badly damaging buildings and leaving thousands of people without power. While the full extent of the damage caused by the Category 3 system is not yet known, the event was unusual.

I specialise in reconstructing long-term natural records of extreme events, and my historic and prehistoric data show cyclones of this intensity rarely travel as far south as this one did. In fact, it has happened only 26 times in the past 5,000 years.

Severe wind gusts hit the towns of Geraldton and Kalbarri – towns not built to withstand such conditions.

Unfortunately, climate change is likely to mean disasters such as Cyclone Seroja will become more intense, and will be seen further south in Australia more often. In this regard, Seroja may be a timely wake-up call.

Seroja: bucking the cyclone trend

Cyclone Seroja initially piqued interest because as it developed off WA, it interacted with another tropical low, Cyclone Odette. This rare phenomenon is known as the Fujiwhara Effect.

Cyclone Seroja hit the WA coast between the towns of Kalbarri and Gregory at about 8pm local time on Sunday. According to the Bureau of Meteorology it produced wind gusts up to 170 km/hour.

Seroja then moved inland north of Geraldton, weakening to a category 2 system with wind gusts up to 120 km/hour. It then tracked further east and has since been downgraded to a tropical low.

The cyclone’s southward track was historically unusual. For Geraldton, it was the first Category 2 cyclone impact since 1956. Cyclones that make landfall so far south on the WA coast are usually less intense, for several reasons.

First, intense cyclones draw their energy from warm sea surface temperatures. These temperatures typically become cooler the further south of the tropics you go, depleting a cyclone of its power.

Second, cyclones need relatively low speed winds in the middle to upper troposphere – the part of the atmosphere closest to Earth, where the weather occurs. Higher-speed winds there cause the cyclone to tilt and weaken. In the Australian region, these higher wind speeds are more likely the further south a cyclone travels.

Third, most cyclones make landfall in the northern half of WA where the coast protrudes far into the Indian Ocean. Cyclones here typically form in the Timor Sea and move southward or south-west away from WA before curving southeast, towards the landmass.

For a cyclone to cross the coast south of about Carnarvon, it must travel a considerable distance towards the south-west into the Indian Ocean. This was the case with Seroja – winds steered it away from the WA coast before they weakened, allowing the cyclone to curve back towards land.

Reading the ridges

My colleagues and I have devised a method to estimate how often and where cyclones make landfall in Australia.

As cyclones approach the coast, they generate storm surge – abnormal sea level rise – and large waves. The surge and waves pick up sand and shells from the beaches and transport them inland, sometimes for several hundred metres.

These materials are deposited into ridges which stand many metres above sea level. By examining these ridges and geologically dating the materials within them, we can determine how often and intense the cyclones have been over thousands of years.




Read more:
Our new model shows Australia can expect 11 tropical cyclones this season


At Shark Bay, just north of where Seroja hit the coast, a series of 26 ridges form a “ridge plain” made entirely of one species of a marine cockle shell (Fragum eragatum). The sand at beaches near the plain are also made entirely of this shell.

The ridge record shows over the past 5,000 years, cyclones of Seroja’s intensity, or higher, have crossed the coast in this region about every 190 years – so about 26 times. Some 14 of these cyclones were more intense than Seroja.

The record shows no Category 5 cyclones have made landfall here over this time. The ridge record prevents us from knowing the frequency of less intense storms. But Bureau of Meteorology cyclone records since the early 1970s shows only a few crossed the coast in this region, and all appear weaker than Seroja.

Emergency services crews in the WA town of Geraldton, preparing ahead of the arrival of Tropical Cyclone Seroja
Emergency services crews in the WA town of Geraldton, preparing ahead of the arrival of Tropical Cyclone Seroja – an event rarely seen this far south.
Department of Fire and Emergency Services WA

Cyclones under climate change

So why does all this matter? Cyclones can kill and injure people, damage homes and infrastructure, cause power and communication outages, contaminate water supplies and more. Often, the most disadvantaged populations are worst affected. It’s important to understand past and future cyclone behaviour, so communities can prepare.

Climate change is expected to alter cyclone patterns. The overall number of tropical cyclones in the Australian region is expected to decrease. But their intensity will likely increase, bringing stronger wind and heavier rain. And they may form further south as the Earth warms and the tropical zone expands poleward.

This may mean cyclones of Seroja’s intensity are likely to become frequent, and communities further south on the WA coast may become more prone to cyclone damage. This has big implications for coastal planning, engineering and disaster management planning.

In particular, it may mean homes further south must be built to cope with stronger winds. Storm surge may also worsen, inundating low-lying coastal land.

Global climate models are developing all the time. As they improve, we will gain a more certain picture of how tropical cyclones will change as the planet warms. But for now, Seroja may be a sign of things to come.




Read more:
Wetlands have saved Australia $27 billion in storm damage over the past five decades


This article is part of Conversation series on the nexus between disaster, disadvantage and resilience. Read the rest of the stories here.The Conversation

Jonathan Nott, Professor of Physical Geography, James Cook University

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

Even after the rains, Australia’s environment scores a 3 out of 10. These regions are struggling the most


Shutterstock

Albert Van Dijk, Australian National University; Marta Yebra, Australian National University, and Shoshana Rapley, Australian National UniversityImproved weather conditions have pulled Australia’s environment out of its worst state on record, but recovery remains partial and precarious, new research reveals.

Each year, we collate a vast number of measurements on the state of our environment. The data are collected in many different ways – including satellites, field stations and surveys – then combined to produce an overall national score.

A year ago, after prolonged drought and devastating bushfires, Australia’s environment scored a shocking 0.8 out of ten. Our new research shows nature started its long road to recovery in 2020, especially in New South Wales and Victoria. Some of the regions with the poorest scores have high levels of social disadvantage, which risks being further entrenched by environmental disasters such as drought, bushfire and heatwaves.

Nationally, Australia’s environmental condition score increased by 2.6 points last year, to reach a (still very low) score of 3.2. But overall conditions across large swathes of the country remain poor.

Environmental Condition Score for 2020 by state and territory.
ANU Fenner School

Scores rising but still in the red

From a long list of environmental indicators we report on, seven are selected to calculate an overall score for each region, as well as nationally.

These indicators – high temperatures, river flows, wetlands, soil health, vegetation condition, growth conditions and tree cover – are chosen because they allow a comparison against previous years. See the graphic below to find the score for your region.

The largest improvements occurred in NSW and Victoria thanks to good rains. The poorest conditions occurred in the Northern Territory and Western Australia, where there was little solace from dry conditions.

Comparing local government areas, the best conditions occurred in Nillubik Shire on the northern edge of Melbourne. In contrast, the worst conditions occurred in Katherine in the Northern Territory and in the Shire of Ngaanyatjarraku in remote WA.



@media only screen and (max-width: 450px) {
iframe.box {display:none}
}
@media only screen and (min-width: 451px) and (max-width: 1460px) {
iframe.box {display:block}
}

From drought to rain

2020 started as badly as 2019 ended – with extreme temperatures, drought and fires, especially in Australia’s southeast. The Sydney suburb of Penrith was the hottest place on Earth on January 4 and, following the bushfires, Canberra had the most dangerous air quality in the world for several days. Clearly, climate change is already affecting our cities and nature.

By the end of summer, the high temperatures also caused another mass coral bleaching in the Great Barrier Reef – the third such event in five years.

Only in February-March did the weather turn, providing good and in some areas very plentiful rains – for example along the NSW coast. Later in the year officials declared an La Niña event – an ocean circulation pattern that normally encourages rainfall in Australia.

While rainfall was not extraordinarily high, it lifted most regions in eastern Australia out of extreme drought. Some parts of northern and western Australia missed out, however, and in some areas the drought deepened.

Taken as an average over the year and over the country, rainfall was 10% above the average for the previous two decades. The number of hot days – those reaching 35℃ – was 11% or nine days more than the 20-year average.

Values for 15 environmental indicators in 2020, expressed as the change from average 2000-2019 conditions. Similar to national economic indicators, they provide a summary but also hide regional variations, complex interactions and long-term context.
ANU Fenner School

The improved rainfall helped replenish dried soils, and national average soil moisture was close to average. Growth conditions for the NSW wheatbelt were the best in many years and tree cover increased in northern and eastern Australia.

The rain refilled many dams and reservoirs, especially in Canberra and Sydney. It also made some eastern rivers flow again, including the Darling River in NSW. But with such dry starting conditions, wetlands in inland eastern Australia filled only modestly and waterbird numbers remained low.

Drought persisted across large swathes of inland northern and western Australia, where in some parts, vegetation growth conditions were the worst in decades. And the surplus rain was often not enough to reach wetlands, which continued to shrink.




Read more:
Wake up, Mr Morrison: Australia’s slack climate effort leaves our children 10 times more work to do


New shoots in forest after fire
Signs of life: some parts of Australia have benefited from recent rain.
Shutterstock

Bushfires: few but locally severe

Fire activity in vast areas of inland Australia was very low, because a run of dry years did not leave much dry grass to burn.

Nationally, the total area burnt was 17 million hectares – 90% below the 20-year average. This led to 80 million tonnes of carbon emissions (43% below average).

Fire activity was not low everywhere. In southeast Australia, fires in southern NSW, East Gippsland and the ACT severely damaged forests and other ecosystems as well as people and property.

The full ecological damage of the Black Summer fires was not entirely apparent in 2020. That’s partly because COVID-19 restrictions made the situation difficult to assess.

The fires burned more than 80% of the habitat of 30 threatened species, and may have been the death blow for several. Food shortages and feral cats further reduced populations of surviving animals in the burnt ecosystems.

But some wildlife proved unexpectedly resilient. For example, a great effort by citizen scientists showed frogs rebounded well after the rains.

Another 15 species were added to the Threatened Species List in 2020. In good news, three species were removed from the list, including two species of tree frogs that recovered from the global chytrid fungus.




Read more:
5 remarkable stories of flora and fauna in the aftermath of Australia’s horror bushfire season


Stopping the slow train wreck

The accelerating impacts of climate change will not stop here. New records will inevitably be broken. Heat, drought and fire will again damage our environment and lives. Some ecosystems will be lost forever. But even worse outcomes can be avoided – if the world can rein in greenhouse gas pollution.

There’s cause for cautious optimism. International pressure may force the Morrison government’s hand on climate action. Several states and territories have already taken decisive climate action. Low-emission energy and transport are advancing quickly. As individuals we can fly and drive less, get solar panels and divest from fossil fuel companies.

In the meantime, we must adapt to inevitable climate change and reduce other pressures on our ecosystems. Citizen scientists have proven essential in monitoring how individual species are faring – so download that app and enjoy nature even more. And plant a few trees to help nature along.

Finally, pressure your local, state and national politicians. Ask them: how are you addressing vegetation loss, invasive pests and over-extraction from rivers? If you don’t like the answer, tell them, or try to vote them out.

With greater urgency and some luck, there is still much to be salvaged.

The full report and a video summary are available here.




Read more:
Our turtle program shows citizen science isn’t just great for data, it makes science feel personal


This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. You can read the rest of the stories here.The Conversation

Albert Van Dijk, Professor, Water and Landscape Dynamics, Fenner School of Environment & Society, Australian National University; Marta Yebra, Associate Professor in Environment and Engineering, Australian National University, and Shoshana Rapley, Research assistant, Australian National University

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

After the floods, stand by for spiders, slugs and millipedes – but think twice before reaching for the bug spray


Lukas Koch / AAP

Caitlyn Forster, University of Sydney; Dieter Hochuli, University of Sydney, and Eliza Middleton, University of SydneyRecord-breaking rain has destroyed properties across New South Wales, forcing thousands of people to evacuate and leaving hundreds homeless.

Humans aren’t the only ones in trouble. Many of the animals that live with and around us are also heading for higher ground as the floodwaters rise.

Often small creatures — especially invertebrates like spiders, cockroaches and millipedes — will seek refuge in the relatively dry and safe environments of people’s houses. While this can be a problem for the human inhabitants of the house, it’s important to make sure we don’t add to the ecological impact of the flood with an overzealous response to these uninvited guests.

Warragamba Dam in southwestern Sydney has been spilling a Sydney Harbour’s worth of water each day during the rains.
Eliza Middleton, Author provided

What floods do to ecosystems

Floods can have a huge impact on ecosystems, triggering landslides, increasing erosion, and introducing pollutants and soil into waterways. One immediate effect is to force burrowing animals out of their homes, as they retreat to safer and drier locations. Insects and other invertebrates living in grass or leaf litter around our homes are also displaced.

Burrowing invertebrates come to the surface during floods, providing food for opportunistic birds.
Dieter Hochuli, Author provided

Snakes have reportedly been “invading” homes in the wake of the current floods. Spiders too have fled the rising waters. Heavy rain can flood the burrows of the Australian funnelweb, one of the world’s most venomous spiders.

Some invertebrates will boom; others may plummet

Rain increases greenery, which can support breeding booms of animals such as mosquitoes, locusts, and snails.

Even species that don’t thrive after floods are likely to become more visible as they flock to our houses for refuge. But an apparent short-term increase in numbers may conceal a longer story of decline.




Read more:
After the floods come the mosquitoes – but the disease risk is more difficult to predict


After periods of flooding, the abundance of invertebrates can fall by more than 90% and the number of different species in an area significantly drops. This has important implications for the recovery of an ecosystem, as many of the ground dwelling invertebrates displaced by floods are needed for soil cycling and decomposition.

So before you reach for the bug spray, consider the important role these animals play in our ecosystem.

What to do with the extra house guests?

If your house has been flooded, uninvited creatures taking shelter in your house are probably one of the smaller issues you are facing.

Once the rain subsides, cleaning in and around your property will help reduce unwanted visitors. Inside your house, you may see an increase in cockroaches, which flourish in humid environments. Ventilating the house to dry out any wet surfaces can help get rid of cockroach infestations, and filling crevices can also deter unwanted visitors.




Read more:
Floods leave a legacy of mental health problems — and disadvantaged people are often hardest hit


In the garden, you may see an increase in flies in the coming weeks and months as they lay eggs in rotting plants. Consider removing any fruit and vegetables in the garden that may rot.

Mosquitoes are also one to watch as they lay eggs in standing water. Some species pose a risk of diseases such as Ross River virus. To prevent unwanted mozzies, make sure to empty things that have filled with rainwater, such as buckets and birdbaths.

If you do encounter one of our more dangerous animals in your home, such as venomous snakes and spiders, do not handle them yourself. If you find an injured or distressed snake, or are concerned about snakes in your house, call your local wildlife group who will be able to relocate them for you.

Just like the floods, which will subside as the water moves on, the uninvited gathering of animals is a temporary event. Most visitors will quickly disperse back to more appropriate habitat when the weather dries, and their usual homes are available again.

You may see an increase in slugs in your local area after rainy conditions.
Eliza Middleton @smiley_lize

Don’t sweat the small stuff

While many of the impacts of floods are our own making, through poor planning and development in flood-prone areas, effective design of cities and backyards can mitigate the risks of floods. Vegetation acts as a “sponge” for stormwater, and appropriate drainage allows water to flow through more effectively. Increasing backyard vegetation also provides extra habitat for important invertebrate species, including pollinators and decomposers.




Read more:
Not ‘if’, but ‘when’: city planners need to design for flooding. These examples show the way


With severe weather events on the rise, it is important to understand how ecosystems respond to, and recover from natural disasters. If invertebrates are unable to perform vital ecosystem functions, such as soil cycling, decomposition, and pollination, ecosystems may struggle to return to their pre-flood state. If the ecosystems don’t recover, we may see prolonged booms of nuisance pests such as mosquitoes.

A few temporary visitors are are a minor inconvenience in comparison to the impacts floods have on the environment, infrastructure and the health and well-being of people impacted. So while it may seem like a bit of a creepy inconvenience, maybe we should let our house guests stay until the flood waters go down.The Conversation

Caitlyn Forster, PhD Candidate, School of Life and Environmental Sciences, University of Sydney; Dieter Hochuli, Professor, School of Life and Environmental Sciences, University of Sydney, and Eliza Middleton, Laboratory Manager, School of Life and Environmental Sciences, University of Sydney

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

Climate explained: how particles ejected from the Sun affect Earth’s climate


Earth’s magnetic field protects us from the solar wind, guiding the solar particles to the polar regions.
SOHO (ESA & NASA)

Annika Seppälä


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz


When the Sun ejects solar particles into space, how does this affect the Earth and climate? Are clouds affected by these particles?

When we consider the Sun’s influence on Earth and our climate, we tend to think about solar radiation. We are acutely aware of the skin-burning dangers of ultraviolet, or UV, radiation.

But the Sun is an active star. It also continuously releases what is known as “solar wind”, made up of charged particles, largely protons and electrons, that travel at speeds of hundreds of kilometres per hour.

Some of these particles that reach Earth are guided into the polar atmosphere by our magnetic field. As a result, we can see the southern lights, aurora australis, in the southern hemisphere, and the northern equivalent, aurora borealis.

Aurora Australis
Aurora australis observed above southern New Zealand.
Shutterstock/Fotos593

This visible manifestation of solar particles entering Earth’s atmosphere is a constant reminder there is more to the Sun than sunlight. But the particles have other effects as well.




Read more:
Why is the sun’s atmosphere so hot? Spacecraft starts to unravel our star’s mysteries


Solar particles and ozone

When solar particles enter the atmosphere, their high energies ionise neutral atmospheric nitrogen and oxygen molecules, which make up 99% of the atmosphere. This “energetic particle precipitation”, named because it’s like a rain of particles from space, is a major source of ionisation in the polar atmosphere above 30km altitude — and it sets off a chain of reactions that produces chemicals that facilitate the destruction of ozone.

The impact of solar particles on atmospheric ozone was first observed in 1969. Since the early 2000s, thanks to new kinds of satellite observations, we have seen growing evidence that solar particles play an important part in influencing polar ozone. During particularly active times, when the Sun releases large amounts of particles into space, up to 60% of ozone at altitudes above 50km can be depleted. The effect can last for weeks.

Lower down in the atmosphere, below 50km, solar particles are important contributors to the year-to-year variability in polar ozone levels, often through indirect pathways. Here, solar particles again contribute to ozone loss, but a recent discovery showed they also help curb some of the depletion in the Antarctic ozone hole.

How ozone affects the climate

Most of the ozone in the atmosphere resides in a thin layer at altitudes of 20-25km — the “ozone layer”.

But ozone is everywhere in the atmosphere, from the Earth’s surface to altitudes above 100km. It is a greenhouse gas and plays a key role in heating and cooling the atmosphere, which makes it critical for climate.

In the southern hemisphere, changes in polar ozone are known to influence regional climate conditions.

Satellite image of Earth's atmosphere
Solar particles ionise nitrogen and oxygen molecules in the atmosphere, which leads to other chemical reactions that contribute to ozone destruction.
Shutterstock/PunyaFamily

Its depletion above Antarctica had a cooling effect, which in turn pulled the westerly wind jet that circles the continent closer. As the Antarctic hole recovers, this wind belt can meander further north and affect rainfall patterns, sea-surface temperatures and ocean currents. The Southern Annular Mode describes this north-south movement of the wind belt that circles the southern polar region.

Ozone is important for future climate predictions, not only in the thin ozone layer, but throughout the atmosphere. It is crucial we understand the factors that influence ozone variability, be it man-made or natural like the Sun.

The Sun’s direct influence

The link between solar particles and ozone is reasonably well established, but what about any direct effects solar particles may have on the climate?

We have observational evidence that solar activity influences regional climate variability at both poles. Climate models also suggest such polar effects link to larger climate patterns (such as the Northern and Southern Annular Modes) and influence conditions in mid-latitudes.

The details are not yet well understood, but for the first time the influence of solar particles on the climate system will be included in climate simulations used for the upcoming Intergovernmental Panel on Climate Change (IPCC) assessment.




Read more:
Solar weather has real, material effects on Earth


Through solar radiation and particles, the Sun provides a key energy input to our climate system. While these do vary with the Sun’s 11-year cycle of magnetic activity, they can not explain the recent rapid increase in global temperatures due to climate change.

We know rising levels of greenhouse gases in the atmosphere are pushing up Earth’s surface temperature (the physics have been known since the 1800s). We also know human activities have greatly increased greenhouse gases in the atmosphere. Together these two factors explain the observed rise in global temperatures.

What about clouds?

Clouds are much lower in the atmosphere than where most solar particles penetrate. Particles know as galactic cosmic rays (coming from the centre of our galaxy rather than the Sun) may be linked to cloud formation.

It has been suggested cosmic rays could influence the formation of condensation nuclei, which act as “seeds” for clouds. But recent research at the CERN nuclear research facility suggests the effects are insignificant.

This doesn’t rule out some other mechanisms for cosmic rays to affect cloud formation, but thus far there is little supporting evidence.The Conversation

Annika Seppälä, Senior Lecturer in Geophysics

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

What is a 1 in 100 year weather event? And why do they keep happening so often?


Andy Pitman, UNSW; Anna Ukkola, UNSW, and Seth WestraPeople living on the east coast of Australia have been experiencing a rare meteorological event. Record-breaking rainfall in some regions, and very heavy and sustained rainfall in others, has led to significant flooding.

In different places, this has been described as a one in 30, one in 50 or one in 100 year event. So, what does this mean?

What is a 1 in 100 year event?

First, let’s clear up a common misunderstanding about what a one in 100 year event means. It does not mean the event will occur exactly once every 100 years, or that it will not happen again for another 100 years.

For meteorologists, the one in 100 year event is an event of a size that will be equalled or exceeded on average once every 100 years. This means that over a period of 1,000 years you would expect the one in 100 year event would be equalled or exceeded ten times. But several of those ten times might happen within a few years of each other, and then none for a long time afterwards.




Read more:
Explainer: was the Sydney storm ‘once-in-a-century’?


Ideally, we would avoid using the phrase “one in 100 year event” because of this common misunderstanding, but the term is so widespread now it is hard to change. Another way to think about what a one in 100 year event means is that there is a 1% chance of an event of at least that size in any given year. (This is known as an “annual exceedance probability”.)

How common are 1 in 100 year events?

Many people are surprised by the feeling that one in 100 year events seem to happen much more often than they might expect. Although a 1% probability might sound pretty rare and unlikely, it is actually more common than you might think. There are two reasons for this.

First, for a given location (such as where you live), a one in 100 year event would be expected to occur on average once in 100 years. However, across all of Australia you would expect the one in 100 year event to be exceeded somewhere far more often than once in a century!

In much the same way, you might have a one in a million chance of winning the lottery, but the chance someone wins the lottery is obviously much higher.

Second, while a one in 100 year flood event might have a 1% chance of occurring in a given year (hence it’s referred to as a “1% flood”), the chance is much higher when looking at longer time periods. For example, if you have a house designed to withstand a 1% flood, this means over the course of 70 years there’s a roughly 50% chance the house would be flooded at some point during this time! Not the best odds.

How well do we know how often flood events occur?

Incidents like these 1% annual exceedance probability events are often referred to as “flood planning levels” or “design events”, because they are commonly used for a range of urban planning and engineering design applications. Yet this presupposes we can work out exactly what the 1% event is, which sounds simpler than it is in practice.

First of all, we use historical data to estimate the one in 100 year event, but Australia has only about 100 years of reliable meteorological observations, and even shorter records of river flow in most locations. We know for sure this 100-year record does not contain the largest possible events that could occur in terms of rainfall, drought, flood and so on. We have data from indirect paleoclimate evidence pointing to much larger events in the past.




Read more:
Sydney storm: are extreme rains and flash floods increasing?


So a 1% event is by no means a “worst case” scenario, and some of the evidence from paleoclimate data suggests the climate has been very different in the deep past.

Second, estimating the one in 100 year event using historical data assumes the underlying conditions are not changing. But in many parts of the world, we know rainfall and streamflow are changing, leading to a changing risk of flooding.

Moreover, even if there was no change in rainfall, changes to flood risk can occur due to a host of other factors. Increased flood risk can result from land clearing or other changes in the vegetation in a catchment, or changes in catchment management.

Increased occurrence of flooding can also be associated with poor planning decisions that locate settlements on floodplains. This means a one in 100 year event estimated from past observations could under- or indeed overestimate current flood risk.

A third culprit for influencing how often a flood occurs is climate change. Global warming is unquestionably heating the oceans and the atmosphere and intensifying the hydrological cycle. The atmosphere can hold more water in a warmer world, so we would expect to see rainfall intensities increasing.

Extreme rainfall events are becoming more extreme across parts of Australia. This is consistent with theory, which suggests we will see roughly a 7% increase in rainfall per degree of global warming.

Australia has warmed on average by almost 1.5℃, implying about 10% more intense rainfall. While 10% might not sound too dramatic, if a city or dam is designed to cope with 100mm of rain and it is hit with 110mm, it can be the difference between just lots of rain and a flooded house.

So what does this mean in practice?

Whether climate change “caused” the current extreme rainfall over coastal New South Wales is difficult to say. But it is clear that with temperatures and heavy rainfall events becoming more extreme with global warming, we are likely to experience one in 100 year events more often.

We should not assume the events currently unfolding will not happen again for another 100 years. It’s best to prepare for the possibility it will happen again very soon.




Read more:
Droughts and flooding rains: it takes three oceans to explain Australia’s wild 21st-century weather


The Conversation


Andy Pitman, Director of the ARC Centre of Excellence for Climate System Science, UNSW; Anna Ukkola, ARC DECRA Fellow, UNSW, and Seth Westra, Associate Professor, School of Civil, Environmental and Mining Engineering

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