What Greenland’s record-breaking rain means for the planet


Willow Hallgren, Griffith UniversityFor three days this month, 7 billion tonnes of rain fell across Greenland — the largest amount since records began in 1950. It’s also the first time since then that rain, not snow, fell on Greenland’s highest peak.

This is alarming. Greenland’s ice sheet is the second largest on the planet (after Antarctica) and any rain falling on its surface accelerates melting. By August 15, the amount of ice lost was seven times greater than is normal for mid-August.

This is just the latest extreme climate event on the island, which sits in the North Atlantic Ocean. In a single day in July this year, the amount of ice that melted in Greenland would have covered the US state of Florida with 5 centimetres of water. And last October, research showed ice in Greenland is melting faster than at any other time in the past 12,000 years.

Melting in Greenland threatens to significantly hamper humanity’s efforts to mitigate climate change. That’s because, after a certain point, it may create catastrophic “feedback loops”. Let’s look at the issue in more detail.

Rising temperatures in the Arctic

Greenland’s vast ice sheet comprises almost 1.7 million square kilometres of glacial land ice. It covers most of the territory and contains enough ice to raise sea levels by more than 7 metres if melted.

The Greenland and Antarctica ice sheets lost a combined 6.4 trillion tonnes of ice between 1992 and 2017. Melting in Greenland has contributed to 60% (17.8 millimetres) of the Earth’s overall sea-level rise due to melting ice sheets, even though Greenland is much smaller than Antarctica.

This may be partly because half of Greenland’s melting is the result of rising air temperatures, which cause surface melting. In Antarctica, most ice loss is from ocean water melting glaciers that spill from land into the sea. And the rate of ice loss in both Greenland and Antarctica is accelerating — increasing sixfold since the 1990s.

Rain falling on ice exacerbates this process. So what’s behind the recent unprecedented weather?

Temperatures in the Arctic are rising twice as quickly as the rest of the planet for a number of reasons, including changes in cloud cover and water vapour, the reflectivity of the surface, and how weather systems transport energy from the tropics to the polar regions. This has made extreme weather events more common.




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Climate explained: why is the Arctic warming faster than other parts of the world?


In recent years in Greenland, rain has fallen further north, and more rain has fallen in winter. This is not normal for these regions, which usually get snow, not rain, in below-freezing temperatures.

This month’s rain is the result of warm, moist air flowing up from south-west of Greenland and remaining for several days. In the morning of August 14, temperatures at the 3,216-metre summit of Greenland’s ice sheet surpassed freezing point, peaking at 0.48℃. Rain fell on the summit for several hours that morning and on August 15.

This was particularly shocking given the above-freezing temperatures occurred so late in Greenland’s normally short summer. At this time of year, large areas of bare ice are exposed from a lack of snow, which leads to greater runoff of rainwater and meltwater into the oceans.

Temperatures rarely surpass freezing at Greenland’s highest point.
Shutterstock

When melting is self-reinforcing

Rainfall makes the ice sheet more prone to surface melt since it exacerbates the so-called “ice-albedo positive feedback”. In other words, the melting reinforces itself.

When rain falls, its warmth can melt snow, exposing the underlying darker ice, which absorbs more sunlight. This increases temperatures at the surface, leading to more melting.

Unfortunately, this isn’t the only positive feedback loop destabilising the Greenland ice sheet.

The “positive melt-elevation feedback” is another, where the lower height of the ice sheet leads to faster melting because higher temperatures occur at lower altitudes.

Also worrying is when higher temperatures cause coastal glaciers to thin, allowing more ice to slip into the sea. This both speeds up the rate of glacier flow towards the sea and lowers the ice surface, exposing it to warmer air temperatures and, in turn, increasing melting.

The rate of ice loss in both Greenland and Antarctica is accelerating.
Shutterstock

What does this mean for the planet?

These positive feedbacks can lead to tipping points — abrupt and irreversible changes in the climate system after a certain threshold is reached. We are more likely to reach these tipping points as emissions increase and global temperatures rise.

While the science on tipping points is still emerging, the most recent report from the Intergovernmental Panel on Climate Change said they cannot be ruled out. The report identified likely tipping points such as widespread Arctic sea-ice melting and the thawing of methane-rich permafrost.




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Recent studies show what humanity may be up against. A study from May this year showed a substantial part of the Greenland ice sheet is either at, or about to reach, a tipping point where melting will accelerate, even if global warming is stopped. Scientists are concerned reaching this point may trigger a cascade effect, leading to other tipping points being reached.

Melted ice from both the Arctic Ocean and Greenland have caused an influx of freshwater into the North Atlantic Ocean. This has contributed to the slowing of a system of crucial ocean currents, which carry warm water from the tropics into the colder North Atlantic. This current, called the Atlantic Meridional Overturning Circulation (AMOC), has slowed by 15% since the 1950s.

If the AMOC slows down any further, the consequences for the planet could be profound. It could destabilise the West African monsoon, cause more frequent drought in the Amazon rainforest and accelerate ice loss in Antarctica.

An existential threat

The rising likelihood of tipping points being reached beyond 1.5℃ of warming represents a potential, looming existential threat to human civilisation. However, even if we’ve already crossed some tipping points, as some scientists suggest, how fast the impacts unfold is still within our control.

If we limit global warming to 1.5℃ this century, we give ourselves longer to adapt to heating already locked into the Earth’s system. But the window is rapidly closing; estimates indicate we may reach the crucial 1.5℃ threshold as soon as the mid-2030s.

The message for humanity is urgent: hard science, not cloying political spin, needs to dictate climate action in the coming years. As with COVID-19, listening to the scientists gives us the best hope of saving the planet.




Read more:
When Greenland was green: rapid global warming 55 million years ago shows us what the future may hold


The Conversation


Willow Hallgren, Adjunct Research Fellow, Centre for Planetary Health and Food Security, Griffith University

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

Forget massive seawalls, coastal wetlands offer the best storm protection money can buy


shutterstock.

Robert Costanza, Crawford School of Public Policy, Australian National UniversityCoastal communities around the world are facing increasing threats from tropical cyclones. Climate change is causing rising sea levels and bigger, more frequent storms.

Many coastal communities are pondering what to do. Should they build massive seawalls in a bid to protect existing infrastructure? Do they give up on their current coastal locations and retreat inland? Or is there another way?

In the US, the US Army Corps of Engineers has proposed building a 20-foot high giant seawall to protect Miami, the third most populous metropolis on the US east coast. The US$6 billion proposal is tentative and at least five years off, but sure to be among many proposals in the coming years to protect coastal communities from storms.




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But seawalls are expensive to build, require constant maintenance and provide limited protection.

Consider China, which already has a huge number of seawalls built for storm protection. A 2019 study analysed the impact of 127 storms on China between 1989 and 2016.

Coastal wetlands were far more cost effective in preventing storm damages. They also provided many other ecosystem services that seawalls do not.

How wetlands reduce storm effects

Coastal wetlands reduce the damaging effects of tropical cyclones on coastal communities by absorbing storm energy in ways that neither solid land nor open water can.

The mechanisms involved include decreasing the area of open water (fetch) for wind to form waves, increasing drag on water motion and hence the amplitude of a storm surge, reducing direct wind effects on the water surface, and directly absorbing wave energy.

Wetland vegetation contributes by decreasing surges and waves and maintaining shallow water depths that have the same effect. Wetlands also reduce flood damages by absorbing flood waters caused by rain and moderating their effects on built-up areas.

Coastal wetlands can absorb storm energy in ways neither solid land nor open water can.
Coastal wetlands can absorb storm energy in ways neither solid land nor open water can.
Shutterstock

In 2008 I and colleagues estimated coastal wetlands in the US provided storm protection services worth US$23 billion a year.

Our new study estimates the global value of coastal wetlands to storm protection services is US$450 billion a year (calculated at 2015 value) with 4,600 lives saved annually.

To make this calculation, we used the records of more than 1,000 tropical cyclones since 1902 that caused property damage and/or human casualties in 71 countries. Our study took advantage of improved storm tracking, better global land-use mapping and damage-assessment databases, along with improved computational capabilities to model the relationships between coastal wetlands and avoided damages and deaths from tropical cyclones.

The 40 million hectares of coastal wetlands in storm-prone areas provided an average of US$11,000 per hectare a year in avoided storm damages.




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Rising seas allow coastal wetlands to store more carbon


Pacific nations benefit most

The degree to which coastal wetlands provide storm protection varies between countries (and within countries). Key factors are storm probability, amount of built infrastructure in storm-prone areas, if wetlands are in storm-prone areas, and coastal conditions.

The top five countries in terms of annual avoided damages (all in 2015 US dollar values) are the United States (US$200 billion), China (US$157 billion), the Philippines (US$47 billion), Japan (US$24 billion) and Mexico (US$15 billion).

In terms of lives saved annually, the top five are: China (1,309); the Philippines (976); the United States (469)l India (414); and Bangladesh (360).

Floodwaters inundate Manila suburbs in November 2020 following Typhoon Vamco.
Floodwaters inundate Manila suburbs in November 2020 following Typhoon Vamco.
Ace Morandante/Malacanang Presidential Photographers Division/AP

Other ecosystem services

Coastal wetlands also provide other valuable ecosystem services. They provide nursery habitat for many commercially important marine species, recreational opportunities, carbon sequestration, management of sediment and nutrient run-off, and many other valuable services.

In 2014 I and colleagues estimated the value of other ecosystem services provided by wetlands (over and above storm protection) at about $US 135,000 a hectare a year.

But land-use changes, including the loss of coastal wetlands, has been eroding both services. Since 1900 the world has lost up to 70% of its wetlands (Davidson, 2014).

Preserving and restoring coastal wetlands is a very cost-effective strategy for society, and can significantly increase well-being for humans and the rest of nature.

With the frequency and intensity of tropical cyclones and other extreme weather events projected to further increase, the value of coastal wetlands will increase in the future. This justifies investing much more in their conservation and restoration.The Conversation

Robert Costanza, Professor and VC’s Chair, Crawford School of Public Policy, Australian National University

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

A wet winter, a soggy spring: what is the negative Indian Ocean Dipole, and why is it so important?


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Nicky Wright, University of Sydney; Andréa S. Taschetto, UNSW, and Andrew King, The University of MelbourneThis month we’ve seen some crazy, devastating weather. Perth recorded its wettest July in decades, with 18 straight days of relentless rain. Overseas, parts of Europe and China have endured extensive flooding, with hundreds of lives lost and hundreds of thousands of people evacuated.

And last week, Australia’s Bureau of Meteorology officially declared there is a negative Indian Ocean Dipole — the first negative event in five years — known for bringing wet weather.

But what even is the Indian Ocean Dipole, and does it matter? Is it to blame for these events?

What is the Indian Ocean Dipole?

The Indian Ocean Dipole, or IOD, is a natural climate phenomenon that influences rainfall patterns around the Indian Ocean, including Australia. It’s brought about by the interactions between the currents along the sea surface and atmospheric circulation.

It can be thought of as the Indian Ocean’s cousin of the better known El Niño and La Niña in the Pacific. Essentially, for most of Australia, El Niño brings dry weather, while La Niña brings wet weather. The IOD has the same impact through its positive and negative phases, respectively.

Positive IODs are associated with an increased chance for dry weather in southern and southeast Australia. The devastating Black Summer bushfires in 2019–20 were linked to an extreme positive IOD, as well as human-caused climate change which exacerbated these conditions.

Negative IODs tend to be less frequent and not as strong as positive IOD events, but can still bring severe climate conditions, such as heavy rainfall and flooding, to parts of Australia.

The Indian Ocean Dipole (IOD) index, used to track the variability of the Indian Ocean Dipole. An event occurs after the index crosses the threshold for 8 weeks.
Bureau of Meteorology

The IOD is determined by the differences in sea surface temperature on either side of the Indian Ocean.

During a negative phase, waters in the eastern Indian Ocean (near Indonesia) are warmer than normal, and the western Indian Ocean (near Africa) are cooler than normal.




Read more:
Explainer: El Niño and La Niña


This causes more moisture-filled air to flow towards Australia, favouring wind pattern changes in a way that promotes more rainfall to southern parts of Australia. This includes parts of Western Australia, South Australia, Victoria, NSW and the ACT.

Generally, IOD events start in late autumn or winter, and can last until the end of spring — abruptly ending with the onset of the northern Australian monsoon.

The negative phase of the Indian Ocean Dipole.
Bureau of Meteorology

Why should we care?

We probably have a wet few months ahead of us.

The negative IOD means the southern regions of Australia are likely to have a wet winter and spring. Indeed, the seasonal outlook indicates above average rainfall for much of the country in the next three months.

In southern Australia, a negative IOD also means we’re more likely to get cooler daytime temperatures and warmer nights. But just because we’re more likely to have a wetter few months doesn’t mean we necessarily will — every negative IOD event is different.

Rainfall outlooks for August–October suggest that large parts of Australia will likely experience above-median rainfall.
Bureau of Meteorology, CC BY

While the prospect of even more rain might dampen some spirits, there are reasons to be happy about this.

First of all, winter rainfall is typically good for farmers growing crops such as grain, and previous negative IOD years have come with record-breaking crop production.

In fact, negative IOD events are so important for Australia that their absence for prolonged periods has been blamed for historical multi-year droughts in the past century over southeast Australia.

Negative IOD years can also bring better snow seasons for Australians. However, the warming trend from human-caused climate change means this signal isn’t as clear as it was in the past.

A negative IOD may mean a better snow season in the High Country.
Shutterstock

It’s not all good news

This is the first official negative IOD event since 2016, a year that saw one of the strongest negative IOD events on record. It resulted in Australia’s second wettest winter on record and flooding in parts of NSW, Victoria, and South Australia.

The 2016 event was also linked to devastating drought in East Africa on the other side of the Indian Ocean, and heavy rainfall in Indonesia.

Thankfully, current forecasts indicate the negative IOD will be a little milder this time, so we hopefully won’t see any devastating events.

The number of Indian Ocean Dipole events (per 30 years) based on climate models.
Modified from Abram et al. (2020)

Is the negative IOD behind the recent wet weather?

It’s too early to tell, but most likely not.

While Perth is experiencing one of its wettest Julys on record, the southwest WA region has historically been weakly influenced by negative IODs.

Negative IODs tend to be associated with moist air flow and lower atmospheric pressure further north and east than Perth, such as Geraldton to Port Hedland.

Outside of Australia, there has been extensive flooding in China and across Germany, Belgium, and The Netherlands.

It’s still early days and more research is needed, but these events look like they might be linked to the Northern Hemisphere’s atmospheric jet stream, rather than the negative IOD.

The jet stream is like a narrow river of strong winds high up in the atmosphere, formed when cool and hot air meet. Changes in this jet stream can lead to extreme weather.

What about climate change?

The IOD — as well as El Niño and La Niña — are natural climate phenomena, and have been occurring for thousands of years, before humans started burning fossil fuels. But that doesn’t mean climate change today isn’t having an effect on the IOD.




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Why drought-busting rain depends on the tropical oceans


Scientific research is showing positive IODs — linked to drier conditions in eastern Australia — have become more common. And this is linked to human-caused climate change influencing ocean temperatures.

Climate models also suggest we may experience more positive IOD events in future, including increased chances of bushfires and drought in Australia, and fewer negative IOD events. This may mean we experience more droughts and less “drought-breaking” rains, but the jury’s still out.

When it comes to the recent, devastating floods overseas, scientists are still assessing how much of a role climate change played.

But in any case, we do know one thing for sure: rising global temperatures from climate change will cause more frequent and severe extreme events, including the short-duration heavy rainfalls associated with flooding, and heatwaves.

To avoid worse disasters in our future, we need to cut emissions drastically and urgently.




Read more:
You may have heard the ‘moon wobble’ will intensify coastal floods. Well, here’s what that means for Australia


The Conversation


Nicky Wright, Research Fellow, University of Sydney; Andréa S. Taschetto, Associate Professor, UNSW, and Andrew King, ARC DECRA fellow, The University of Melbourne

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

You may have heard the ‘moon wobble’ will intensify coastal floods. Well, here’s what that means for Australia


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Mark Gibbs, Australian Institute of Marine ScienceExtreme floods this month have been crippling cities worldwide. This week in China’s Henan province, a year’s worth of rain fell in just three days. Last week, catastrophic floods swept across western Germany and parts of Belgium. And at home, rain fell in Perth for 17 days straight, making it the city’s wettest July in 20 years.

But torrential rain isn’t the only cause of floods. Many coastal towns and cities in Australia would already be familiar with what are known as “nuisance” floods, which occur during some high tides.

A recent study from NASA and the University of Hawaii suggests even nuisance floods are set to get worse in the mid-2030s as the moon’s orbit begins another phase, combined with rising sea levels from climate change.

The study was conducted in the US. But what do its findings mean for the vast lengths of coastlines in Australia and the people who live there?

A triple whammy

We know average sea levels are rising from climate change, and we know small rises in average sea levels amplify flooding during storms. From the perspective of coastal communities, it’s not if a major flood will occur, it’s when the next one will arrive, and the next one after that.

But we know from historical and paleontological records of flooding events that in many, if not most, cases the coastal flooding we’ve directly experienced in our lifetimes are simply the entrée in terms of what will occur in future.

Flooding is especially severe when a storm coincides with a high tide. And this is where NASA and the University of Hawaii’s new research identified a further threat.

Researchers looked at the amplification phase of the natural 18.6-year cycle of the “wobble” in the moon’s orbit, first identified in 1728.

The orbit of the moon around the sun is not quite on a flat plane (planar); the actual orbit oscillates up and down a bit. Think of a spinning plate on a stick — the plate spins, but also wobbles up and down.




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When the moon is at particular parts of its wobbling orbit, it pulls on the water in the oceans a bit more. This means for some years during the 18.6-year cycle, some high tides are higher than they would have otherwise been.

This results in increases to daily tidal rises, and this, in turn, will exacerbate coastal flooding, whether it be nuisance flooding in vulnerable areas, or magnified flooding during a storm.

View of Earth from the Moon
The moon’s orbit isn’t on a flat plane. It oscillates up and down, like a plate would when it spins on a stick.
Shutterstock

A major wobble amplification phase will occur in the mid-2030s, when climate change will make the problem become severe in some cases.

The triple whammy of the wobble in the moon’s orbit, ongoing upwards creep in sea levels from ocean warming, and more intense storms associated with climate change, will bring the impacts of sea-level rise earlier than previously expected — in many locations around the world. This includes in Australia.

So what will happen in Australia?

The locations in Australia where tides have the largest range, and will be most impacted by the wobble, aren’t close to the major population centres. Australia’s largest tides are close to Broad Sound, near Hay Point in central Queensland, and Derby in the Kimberley region of Western Australia.

However, many Australian cities host suburbs that routinely flood during larger high tides. Near my home in Meanjin (Brisbane), the ocean regularly backs up through the storm water drainage system during large high tides. At times, even getting from the front door to the street can be challenging.

Derby, WA, has one of the biggest tidal ranges in Australia.
Shutterstock

Some bayside suburbs in Melbourne are also already exposed to nuisance flooding. But a number of others that are not presently exposed may also become more vulnerable from the combined influence of the moon wobble and climate change — even when the weather is calm. High tide during this lunar phase, occurring during a major rainfall event, will result in even greater risk.




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High-tide flood risk is accelerating, putting coastal economies at risk


In high-income nations like Australia, sea-level rise means increasing unaffordability of insurance for coastal homes, followed by an inability to seek insurance cover at all and, ultimately, reductions in asset values for those unable or unwilling to adapt.

The prognosis for lower-income coastal communities that aren’t able to adapt to sea-level rise is clear: increasingly frequent and intense flooding will make many aspects of daily life difficult to sustain. In particular, movement around the community will be challenging, homes will often be inundated, unhealthy and untenable, and the provision of basic services problematic.

What do we do about it?

While our hearts and minds continue to be occupied by the pandemic, threats from climate change to our ongoing standard of living, or even future viability on this planet, haven’t slowed. We can pretend to ignore what is happening and what is increasingly unstoppable, or we can proactively manage the increasing threat.

Some coastal communities, such as in Melbourne’s bayside suburbs, may experience flooding, even if they never have before.
Shutterstock

Thankfully, approaches to adapting the built and natural environment to sea-level rise are increasingly being applied around the world. Many major cities have already embarked on major coastal adaptation programs – think London, New York, Rotterdam, and our own Gold Coast.

However, the uptake continues to lag behind the threat. And one of the big challenges is to incentivise coastal adaptation without overly impacting private property rights.




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For flood-prone cities, seawalls raise as many questions as they answer


Perhaps the best approach to learning to live with water is led by the Netherlands. Rather than relocating entire communities or constructing large barriers like sea walls, this nation is finding ways to reduce the overall impact of flooding. This includes more resilient building design or reducing urban development in specific flood retention basins. This means flooding can occur without damaging infrastructure.

There are lessons here. Australia’s adaptation discussions have often focused on finding the least worst choice between constructing large seawalls or moving entire communities — neither of which are often palatable. This leads to inaction, as both options aren’t often politically acceptable.

The seas are inexorably creeping higher and higher. Once thought to be a problem for our grandchildren, it is becoming increasingly evident this is a challenge for the here and now. The recently released research confirms this conclusion.




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The Conversation


Mark Gibbs, Principal Engineer: Reef Restoration, Australian Institute of Marine Science

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

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.




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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.

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


Ian Wright, Western Sydney UniversityThe wild storms that recently raged across eastern Victoria caused major property and environmental damage, and loss of lives. They’ve also triggered serious water contamination incidents.

Yarra Valley Water issued an urgent health warning to not to drink tap water — not even if it’s boiled — in three affected suburbs: Kalista, Sherbrooke and The Patch.

So what caused this incident? Yarra Valley Water says the severe weather led to an equipment failure, with potentially unsafe water entering the drinking water system.

I spoke to the water authority about the nature of the contamination, and they did not provide any more detail. But based on my three decades of experience in the water industry, I can offer some insight into how disasters create contamination crises, and Australia’s vulnerabilities.

Does boiling water help?

Despite recent health warnings, it’s worth pointing out that Australia’s water supply is generally safe and reliable, with few exceptions. Still, this is hardly the first time disasters have disrupted water supply, whether from droughts, storms and floods, or bushfires.

For example, the Black Summer bushfires damaged water supply infrastructure for many communities, such as in Eden and Boydtown on the south coast of New South Wales. The Bega Valley Shire Council issued a boil water notice, as the loss of electricity stopped chlorinating the water supply, which is needed to maintain safe disinfection levels.

Boil water alerts indicate harmful pathogens may be present in the water, and you should boil water for at least one minute to kill them.




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Better boil ya billy: when Australian water goes bad


In inland and remote communities, drinking water contamination can be more common and very difficult to resolve.

For example, many remote Western Australian towns have chronic water quality problems, with drinking water often failing to meet Australian standards. And in 2015, the WA Auditor General reported the water in many Indigenous communities contains harmful contaminants, such as uranium and nitrates.

The source of this contamination is often naturally occurring chemical compounds in the local geology of ground water supplies.

One of the biggest contamination incidents in Australia occurred in August and September in 1998. A series of extreme wet weather events after a long drought triggered the contamination of Sydney’s drinking water with high levels of protozoan parasites, which can cause serious diseases such as gastroenteritis or cryptosporidiosis. It resulted in boil water alerts across much of the Sydney metropolitan area.

But what makes this latest incident in Victoria so concerning is that authorities have warned even boiling will not reduce contamination. This suggests contamination may be due to the presence of a harmful chemical, or high levels of sediment particles.

Sediment in water — measured as “turbidity” — can be hazardous because these particles can hold other contaminants, or even shield pathogens from disinfection.

Yarra Valley Water’s advice for the affected suburbs is to avoid using water in any cooking, making ice, brushing teeth or mixing baby formula, and for people to take care not to ingest water in the shower or bath. Emergency drinking water is being supplied by Yarra Valley Water in some locations.

So why do disasters threaten our drinking water?

This latest incident is another reminder that our drinking water is vulnerable to disruption from extreme weather.

This is almost certain to continue, and worsen, as the the Bureau of Meterology’s State of the Climate 2020 report predicts more extreme weather — including drought, heatwaves, bushfires, storms, and floods — in Australia’s future.

As these disasters become more frequent and extreme under climate change, impacts on water supplies across Australia are likely to become more destructive.

A good example of how this can unfold was the impact on Canberra’s water supply after the destructive 2003 bushfires.

Fire burned most of the region’s Cotter River catchments, which hold three dams. After fires went out, massive storms eroded the weakened ground, and washed ash, soil and organic debris into the storage reservoirs. It took years for the water supply system to fully recover.

Physical damage to water infrastructure is also a big risk, as modern water supplies are large and complex. For example, a fallen tree could break open the roof of a sealed water storage tank, exposing water to the elements.

Interruptions of electrical supplies after extreme weather are also common, leading to failures of water supply technology. This, for instance, could stop a water pump from operating, or break down the telemetry system which helps control operations.

As difficult as these hits to Australia’s water security are, and will be in future, it’s even more problematic in the developing world, which may not have the resources to recover.

How can we withstand these challenges?

To maintain optimal water quality, we must protect the integrity of water catchments — areas where water is collected by the natural landscape.

For example, damaging logging operations along steep slopes in Melbourne’s biggest water catchment threatens to pollute the city’s drinking water because it increases the risk of erosion during storms.




Read more:
Logging must stop in Melbourne’s biggest water supply catchment


There’s also merit in Australian cities investing in advanced treatment of wastewater for reuse, rather than build infrequently used desalination plants for when there’s drought.

Australia could follow the US state of California which has ambitious targets to reuse more than 60% of its sewage effluent.

And it’s completely safe — Australia has developed guidelines to ensure recycled water is treated and managed to operate reliably and protect public health.




Read more:
Why does some tap water taste weird?


If you’re concerned about water quality from the tap and haven’t received any alerts, you might just not like its taste. If in doubt, contact you local water supplier.


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. You can read the rest of the stories here.The Conversation

Ian Wright, Senior Lecturer in Environmental Science, Western Sydney University

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