Why 2℃ of global warming is much worse for Australia than 1.5℃


Andrew King, University of Melbourne; Ben Henley, University of Melbourne, and David Karoly, University of Melbourne

Australia is a land of extremes. We’ve experienced all manner of climate extremes over the past few years, from heatwaves (both on land and over the Great Barrier Reef), to droughts and flooding rains. The Conversation

We can already link some of these recent extreme events to climate change. But for others, the link is less clear.

So far we have had about 1℃ of global warming above the average pre-industrial climate. So how will extreme weather events change with more warming in the future? Will they become more frequent? Will they become more severe?

We have investigated these questions in our new research, published today in Nature Climate Change.

Climate targets

The Paris Agreement, brokered in 2015, committed the world’s governments to:

Holding the increase in the global average temperature to well below 2℃ above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5℃ above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.

It is vital that we understand how climate extremes in Australia might change if we limit global warming to either 1.5℃ or 2℃, and what the implications might be of pursuing the more lenient target rather than the more ambitious one.

In our study we used state-of-the-art climate model simulations to examine the changing likelihood of different climate extremes under four different scenarios: a natural world without any human-caused climate change; the world of today; a 1.5℃ warmer world; and a 2℃ warmer one.

Heat extremes are here to stay

First, we looked at hot Australian summers, like the record-breaking “angry summer” of 2012-13.

We already knew that human influences on the climate had increased the likelihood of hot summers. Our results show that this trend would continue with future warming. In fact, in a world of 2℃ global warming, even an average summer would outstrip those historically hot ones like 2012-13.

Australian summer temperatures are strongly related to the El Niño-Southern Oscillation, with hot summers more likely to occur during El Niño events, and cooler ones during La Niña episodes.

In the past, a summer as hot as 2012-13 would have been very unlikely during a La Niña. But our modelling predicts that with either 1.5℃ or 2℃ of global warming, we could expect similarly angry summers to occur during both El Niño and La Niña periods.

We already know that the sea surface temperatures associated with mass bleaching of much of the Great Barrier Reef in early 2016 would have been virtually impossible without climate change. If the world continues to warm to either the 1.5℃ or 2℃ levels, very warm seas like we saw early last year would become the norm.

High sea temperatures linked to coral bleaching in Great Barrier Reef will become more likely in a warmer world.
Author provided

In fact, our research suggests that with 2℃ of global warming, the future average sea temperatures around the Great Barrier Reef would be even hotter than the extremes observed around the time of the 2016 bleaching.

Less change for heavy rains and droughts

In December 2010 Queensland was devastated by severe flooding following very heavy rainfall. Our analysis suggests that this kind of event is highly unusual, and may well continue to be so. There isn’t a clear signal for an increase or decrease in those events with ongoing climate warming.

Natural climate variability seems to play a greater role than human-driven climate change (at least below the 2℃ threshold) when it comes to influencing Australian heavy rainfall events.

The Millennium Drought across southeast Australia led to water shortages and crop failures. Drought is primarily driven by a lack of rainfall, but warmer temperatures can exacerbate drought impacts by increasing evaporation.

Our results showed that climate change is increasing the likelihood of hot and dry years like we saw in 2006 across southeast Australia. At 1.5℃ and 2℃ of global warming these events would probably be more frequent than they are in today’s world.

Heat extremes are much more common at 2℃ than 1.5℃
Author provided

Not a lost cause

It is clear that Australia is going to suffer from more frequent and more intense climate extremes as the world warms towards (and very likely beyond) the levels described in the Paris Agreement.

If we miss these targets, the warming will continue and the extremes we experience in Australia are going to be even worse.

With either 1.5℃ or 2℃ global warming, we will see more extremely hot summers across Australia, more frequent marine heatwaves of the kind that can cause bleaching of the Great Barrier Reef, and probably more frequent drought conditions too.

The more warming we experience, the worse the impacts will be. The solution is clear. To limit global warming, the world’s nations need to reduce their greenhouse gas emissions – fast.

Andrew King, Climate Extremes Research Fellow, University of Melbourne; Ben Henley, Research Fellow in Climate and Water Resources, University of Melbourne, University of Melbourne, and David Karoly, Professor of Atmospheric Science, University of Melbourne

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

Why do some graziers want to retain, not kill, dingoes?



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Australia has a complex relationship with the dingo.
Angus Emmott, Author provided

Euan Ritchie, Deakin University

Vast, ancient, nutrient-poor, with wild swings between droughts, floods and fires: this describes much of the Australian continent. Livestock grazing and farming in such a land is certainly not without its challenges. The Conversation

Where we’ve failed to work with the local conditions, we see barren plains, dust storms, the extinction of native species, and the repossession of properties by banks, among many ills.

But such a dire picture is far from universal, and belies the fact that many who live on the land are also among our most innovative land managers. Many projects offer potential benefits for livestock production and the environment alike, but without support progress may be hindered.

Putting dingoes to work

One of the most contentious examples involves encouraging dingoes. Many pastoral areas require land managers to take “all reasonable and practical steps” to manage the risk of dingoes, which are classed as pest animals.

But a growing body of research argues that dingoes can be effective at controlling kangaroo and feral goat populations, especially on cattle stations.

A Western Australian couple, David Pollock and Frances Jones, were recently featured on Australian Story for their decision to regenerate their property, Wooleen, by de-stocking, encouraging local flora and fauna, and investing in ecotourism.

Their neighbours, including sheep graziers whose stock are vulnerable to dingoes, feel this is an irresponsible decision. Graziers have a mandate to control dingoes (“wild dogs”, to many) and dingo-domestic dog hybrids — which can’t be easily and reliably distinguished in the wild.

Dingoes are known to be very effective at controlling kangaroo populations.
Angus Emmott

While the impacts and merits of encouraging dingoes in sheep country are hotly debated, their role in the management of cattle stations is much better understood. But restrictive legislation and the stigma attached to dingoes are frustrating for those who see them as having a vital ecological and economic role for their properties.

Queensland grazier Angus Emmott writes that his beef cattle enterprise, Noonbah station, has benefited from leaving dingoes and kangaroos alone:

We run a beef cattle enterprise in the top end of the Queensland channel country, southwest of Longreach. As a part of our management plan, we leave the dingoes and the ’roos alone. We see a range of benefits to our operation.

When the dingoes don’t have their social structure disrupted by poison baiting, trapping and shooting, only the apex bitch breeds, once a year at most. These family groups have strictly defined ranges, and they kill or chase off other wild dogs or dingoes that intrude. They also keep kangaroos down to very low numbers, which is a huge benefit in regards to pasture growth and being able to rest our paddocks. The dingoes also keep down feral pig, cat and fox numbers.

Yes, dingoes do take some of our calves, but the benefits of pasture growth and feral animal control result in a net benefit of better land condition and a greater dollar return. Dingoes also benefit biodiversity conservation and soil condition. We acknowledge this management model does not work in sheep country, including for some of our nearby neighbours, and in these cases we need to look at different forms of management, such as fencing and/or companion and guardian animals.

Research supports the financial benefits of this approach in certain circumstances. Some studies have found that, perversely, taking lethal action against dingoes can increase the incidence of attacks on stock and boost the population of herbivores that compete with cattle for pasture.

Solutions for protecting livestock against attack, such as guardian dogs, are also at hand and may be considerably cheaper than constructing and maintaining extensive predator-proof fences. Livestock guardian dogs have been shown to be effective in numerous locations across Australia, on large and small grazing properties. But investment from state and federal government (and related agencies) aimed at encouraging such innovation has been lacking.

Kangaroos can become very abundant following rain and without control by dingoes.
Angus Emmott

Working with the land

Regardless of whether graziers take the drastic steps seen at Wooleen, now is the time to reflect on the direction of Australia’s land management.

If we’re to overcome the many challenges we face, including the impacts of climate change on food production, then we need to support the bold new thinking emerging from rural and regional Australia, and our scientific institutions.

Such ideas could include making better use of native animals – better suited to Australian conditions – as sources of meat, and reforming land use legislation to allow new industries.

Seeing some of the worst land degradation first hand it’s easy to think that it’s all too hard and that environmental repair will take decades, if not centuries. This can invite inertia and apathy, the enemies of positive change.

But the stories of Wooleen, Noonbah and other innovators show us what is possible. Science has helped demonstrate ecological repair can happen faster and to a greater extent than many might appreciate.

Big changes certainly carry risks, and these must be managed carefully, but new and sometimes brave ideas will always improve our understanding of the land. Whatever the outcome, such knowledge helps guide better decisions for more sustainable grazing, farming and bio-diverse conservation.


Euan Ritchie would like to acknowledge the contribution of Angus Emmott to this article.

Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University

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

The Sydney Barrier Reef: engineering a natural defence against future storms


Rob Roggema, University of Technology Sydney

The risk of more severe storms and cyclones in the highly urbanised coastal areas of Newcastle, Sydney and Wollongong might not be acute, but it is a real future threat with the further warming of the southern Pacific Ocean. One day a major storm – whether an East Coast Low or even a cyclone – could hit Sydney. The Conversation

With higher ocean temperatures killing and bleaching coral along the Great Barrier Reef to the north, we could also imagine where the right temperatures for a coral reef would be in a warmer climate. Most probably, this would be closer to the limits of the low latitudes, hence in front of the Sydney metro area.

We should then consider whether it is possible to help engineer a natural defence against storms, a barrier reef, should warming oceans make conditions suitable here.

Ocean warming trend is clear

The oceans are clearly warming at an alarming rate, with the unprecedented extent and intensity of coral bleaching events a marker of rising temperatures. After the 2016-2017 summer, coral bleaching affected two-thirds of the Great Barrier Reef.

On the other side of the Pacific, sea surface temperatures off Peru’s northern coast have risen 5-6℃ degrees above normal. Beneath the ocean surface, the warming trend is consistent too.

The East Australian Current keeps the waters around Lord Howe Island warm enough to sustain Australia’s southernmost coral reef. The waters off Sydney are just a degree or two cooler.

With the East Australian Current now extending further south, the warming of these south-eastern coastal waters might be enough in a couple of decades for Nemo to swim in reality under Sydney Harbour Bridge.

This shift in ocean temperatures is expected to drive strong storms and inland floods, according to meteorologists.

On top of this, when we plot a series of maps since 1997 of cyclone tracks across the Pacific, it shows a slight shift to more southern routes. These cyclones occur only in the Tasman Sea and way out from the coast, but, still, there is a tendency to move further south. The northern part of New Zealand recently experienced the impacts this could have.

Think big to prepare for a big storm

If we would like to prevent what Sandy did to New York, we need to think big.

If we don’t want a storm surge entering Parramatta River, flooding the low-lying areas along the peninsulas, if we don’t want flash-flooding events as result of river discharges, if we don’t want our beaches to be washed away, if we want to keep our property along the water, and if we want to save lives, we’d better prepare to counter these potential events through anticipating their occurrence.

The coast is the first point where a storm impacts the city. Building higher and stronger dams have proven to be counterproductive. Once the dam breaks or overflows the damage is huge. Instead we should use the self-regenerating defensive powers nature offers us.

Thinking big, we could design a “Sydney Barrier Reef”, which allows nature to regenerate and create a strong and valuable coast.

The first 30-40 kilometres of the Pacific plateau is shallow enough to establish an artificial reef. The foundations of this new Sydney Barrier Reef could consist of a series of concrete, iron or wooden structures, placed on the continental shelf, just beneath the water surface. Intelligently composed to allow the ocean to bring plants, fish and sand to attach to those structures, it would then start to grow as the base for new coral.

This idea has not been tested for the Sydney continental flat yet. But in other parts of the world experiments with artificial reefs seem promising. At various sites, ships, metro carriages and trains seem to be working as the basis for marine life to create a new underworld habitat

The Sydney Barrier Reef will have the following advantages:

  1. Over decades a natural reef will grow. Coral will develop and a new ecosystem will emerge.

  2. This reef will protect the coast and create new sandbanks, shallow areas and eventually barrier islands, as the Great Barrier Reef has done.

  3. It will increase the beach area, because the conditions behind the reef will allow sediments to settle.

  4. It creates new surfing conditions as a result of the sandbanks.

  5. It will protect Sydney from the most severe storm surges as it breaks the surge.

  6. It will present a new tourist attraction of international allure.

Let’s create a pilot project as a test. Let’s start to design and model the pilot to investigate what happens in this particular location. Let’s simulate the increase of temperature over time and model the impact of a cyclone.

Let’s create, so when Sandy hits Sydney, we will be better protected.

Rob Roggema, Professor of Sustainable Urban Environments, University of Technology Sydney

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