Chris Turney's Blog

Sydney declares a climate emergency ��� what does that mean in practice? Chris Turney, UNSW

Late on Monday night, the City of Sydney became the second state capital in Australia (after Hobart a week earlier) to officially declare a climate emergency. With climate change considered a threat to human life, Sydney councillors unanimously supported a motion put forward by Lord Mayor Clover Moore to mobilise city resources to reduce carbon emissions and minimise the impact of future change.

The decision sees Sydney join a variety of local and national governments around the world, in a movement that is increasingly gaining momentum. In total, some 658 local governments around the world have made the same declaration, with the UK and Canada committing their national governments to the global movement in just the past two months.

An official declaration of climate emergency puts a government on a ���wartime mobilisation��� that places climate change at the centre of policy and planning decisions.

Read more: UK becomes first country to declare a 'climate emergency'

While interpretations differ on what a ���climate emergency��� means in practice, governments have established a range of measures to help meet the targets set by the Paris climate agreement. Under this agreement, 197 countries have pledged to limit global temperature rise to less than 2��� above pre-industrial levels, and ideally no more than 1.5���.

With 2018 having brought all manner of record-breaking climate extremes, and global average temperatures projected to reach 3.2��� above the pre-industrial average based on current national pledges and targets for greenhouse emissions, Sydney���s recognition of a national emergency is both highly appropriate and also a major turning-point for Australia.

Although a signatory to the Paris Agreement, Australia���s greenhouse emissions have risen over the past four years since the repeal of the carbon price. With Australian emissions most notably increasing around transport, the United Nations climate discussions currently being held in Bonn have raised concerns over the nation���s ability to meet its Paris commitments.

Economic impacts

With the global cost of inaction on climate change projected to reach a staggering US$23 trillion a year by the end of the century (equivalent to around five 2008 global financial crises every year), several nations are already ramping up their Paris Agreement commitments ahead of schedule. The UK recently announced its intention to be carbon-neutral by 2050.

Australia is particularly vulnerable to the future financial costs of climate change, with economic models suggesting losses of A$159 billion a year through the impact of sea level rise and drought-driven collapses in agricultural productivity. The cost for each household has been put at about A$14,000.

Read more: Cutting cities' emissions does have economic benefits ��� and these ultimately outweigh the costs

After Sydney���s declaration, 150 faith leaders on Tuesday signed an open letter endorsing the decision, and describing the climate issue as a moral challenge that transcends religious belief. They have called for an urgent mobilisation to reach 100% renewable energy by the year 2030, and for an end to the approval of any new coal and gas projects, including Adani���s controversial Carmichael coal mine in Queensland.

The recent court ruling against the proposed Rocky Hill coal mine in the New South Wales Hunter Valley ��� a decision made partly on climate grounds ��� could mark a crucial turning point in the fortunes of future mining projects.

Read more: Landmark Rocky Hill ruling could pave the way for more courts to choose climate over coal

As part of its emergency declaration, Sydney has also called on the federal government to establish a ���just transition authority��� to support Australians currently employed in fossil fuel industries. This is an urgent issue and a crucial part of the transition to a low-emissions economy.

A major nationwide training program will be needed to help re-skill the estimated 8,000 people who work in fossil-fuelled electricity production, and to help fill the tens of thousands of new jobs in renewable energy-related fields.

With the scale of change required to decarbonise the global economy and hopefully avoid a 2��� warmer world, the need to support communities across Australia and overseas will likely become an increasing challenge for governments around the world. Putting ourselves on an emergency footing could help provide precisely the impetus we need.

This article was amended on June 28, 2019, to acknowledge that Hobart was the first Australian state capital to declare a climate emergency, not Sydney as originally stated.

Chris Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW

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

Sydney declares a climate emergency – what does that mean in practice? Chris Turney, UNSW

Late on Monday night, the City of Sydney became the second state capital in Australia (after Hobart a week earlier) to officially declare a climate emergency. With climate change considered a threat to human life, Sydney councillors unanimously supported a motion put forward by Lord Mayor Clover Moore to mobilise city resources to reduce carbon emissions and minimise the impact of future change.

The decision sees Sydney join a variety of local and national governments around the world, in a movement that is increasingly gaining momentum. In total, some 658 local governments around the world have made the same declaration, with the UK and Canada committing their national governments to the global movement in just the past two months.

An official declaration of climate emergency puts a government on a “wartime mobilisation” that places climate change at the centre of policy and planning decisions.

Read more: UK becomes first country to declare a 'climate emergency'

While interpretations differ on what a “climate emergency” means in practice, governments have established a range of measures to help meet the targets set by the Paris climate agreement. Under this agreement, 197 countries have pledged to limit global temperature rise to less than 2℃ above pre-industrial levels, and ideally no more than 1.5℃.

With 2018 having brought all manner of record-breaking climate extremes, and global average temperatures projected to reach 3.2℃ above the pre-industrial average based on current national pledges and targets for greenhouse emissions, Sydney’s recognition of a national emergency is both highly appropriate and also a major turning-point for Australia.

Although a signatory to the Paris Agreement, Australia’s greenhouse emissions have risen over the past four years since the repeal of the carbon price. With Australian emissions most notably increasing around transport, the United Nations climate discussions currently being held in Bonn have raised concerns over the nation’s ability to meet its Paris commitments.

Economic impacts

With the global cost of inaction on climate change projected to reach a staggering US$23 trillion a year by the end of the century (equivalent to around five 2008 global financial crises every year), several nations are already ramping up their Paris Agreement commitments ahead of schedule. The UK recently announced its intention to be carbon-neutral by 2050.

Australia is particularly vulnerable to the future financial costs of climate change, with economic models suggesting losses of A$159 billion a year through the impact of sea level rise and drought-driven collapses in agricultural productivity. The cost for each household has been put at about A$14,000.

Read more: Cutting cities' emissions does have economic benefits – and these ultimately outweigh the costs

After Sydney’s declaration, 150 faith leaders on Tuesday signed an open letter endorsing the decision, and describing the climate issue as a moral challenge that transcends religious belief. They have called for an urgent mobilisation to reach 100% renewable energy by the year 2030, and for an end to the approval of any new coal and gas projects, including Adani’s controversial Carmichael coal mine in Queensland.

The recent court ruling against the proposed Rocky Hill coal mine in the New South Wales Hunter Valley – a decision made partly on climate grounds – could mark a crucial turning point in the fortunes of future mining projects.

Read more: Landmark Rocky Hill ruling could pave the way for more courts to choose climate over coal

As part of its emergency declaration, Sydney has also called on the federal government to establish a “just transition authority” to support Australians currently employed in fossil fuel industries. This is an urgent issue and a crucial part of the transition to a low-emissions economy.

A major nationwide training program will be needed to help re-skill the estimated 8,000 people who work in fossil-fuelled electricity production, and to help fill the tens of thousands of new jobs in renewable energy-related fields.

With the scale of change required to decarbonise the global economy and hopefully avoid a 2℃ warmer world, the need to support communities across Australia and overseas will likely become an increasing challenge for governments around the world. Putting ourselves on an emergency footing could help provide precisely the impetus we need.

This article was amended on June 28, 2019, to acknowledge that Hobart was the first Australian state capital to declare a climate emergency, not Sydney as originally stated.

Chris Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW

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

UK becomes first country to declare a 'climate emergency' Days of protest by Extinction Rebellion have brought parts of London to a standstill. Shutterstock Chris Turney, UNSW

On Wednesday night a bipartisan UK Parliament passed an extraordinary measure: a national declaration of an Environment and Climate Emergency.

The UK is the first national government to declare such an emergency. The decision marks a renewed sense of urgency in tackling climate change, following a visit to Parliament by teenage activist Greta Thunberg , the broadcast of David Attenborough’s documentary Climate Change: The Facts and 11 days of protest by environmental group Extinction Rebellion that paralysed parts of London.

Read more: Extinction Rebellion: disruption and arrests can bring social change

There are now some 49 million people living under national, city and local declarations of a climate emergency around the world.

Extinction Rebellion protesters surround a boat blocking Oxford Circus, London. Kevin J. Frost/Shutterstock What is a climate emergency?

While there is no precise definition of what constitutes action to meet such an emergency, the move has been likened to putting the country on a “war footing”, with climate and the environment at the very centre of all government policy, rather than being on the fringe of political decisions.

The UK are legally committed to a 80% reduction in carbon emissions by 2050 (relative to their 1990 levels) and was recently recognised as one of just 18 developed economies that have driven down carbon dioxide emissions over the last decade.

Some city and local councils have set out their climate emergency policies to become carbon zero by 2030 built around renewable energy supplies, more energy-efficient housing and a host of other measures. Yesterday’s decision in Parliament implies further national reductions and investment in this space.

Read more: The terror of climate change is transforming young people's identity

Counting down to 2030

The year 2030 is an important target. In spite of what climate contrarians might voice very loudly, five of our planet’s warmest years on record have occurred since 2010, whilst 2018 experienced all manner of climate extremes that broke numerous global records.

It’s sobering to realise that, because the oceans are a major sink of heat, the estimated 40-year delay in the release of this energy back into the atmosphere means the conditions of the last decade are in part a consequence of our pollution from the 1970s.

With the planet to experience further warming from the heat held by the oceans, there is increasing international focus on meeting the United Nation’s Paris Agreement which was signed by 197 countries in 2016. This ground-breaking agreement has the ambitious global aim of preventing global temperatures from reaching 2˚C above pre-industrial levels (the late nineteenth century) by 2100, and ideally should be no more than 1.5˚C.

Declaring an emergency was one of the demands from the Extinction Rebellion protest put to the UK government. Shutterstock

A report by the Intergovernmental Panel on Climate Change (the IPCC) has suggested that meeting this target means annual global carbon emissions must effectively halve between now and 2030, and then fall to zero by 2050. This is a target the UK opposition party Labour are now calling for.

More recent studies suggest even more ambitious cuts may be required.

The cost of inaction

Research in Australia has investigated the cost to the global economy if the Paris Agreement is not met and the world hits 4˚C warmer.

The values are eye-watering: an estimated US$23 trillion a year over the long-term. This has been likened to the world experiencing four to six global financial crises on the scale of 2008 every year.

In Australia, the cost would be on the order of A$159 billion a year, with most of the losses caused by drought-driven collapses in agricultural productivity and sea level rise. The expense to each Australian household has been put at the order of A$14,000.

The declaration of climate emergency by the UK comes at a crucial time in Australia, just two weeks out from a federal election. While the major parties have made public statements of support for the Paris Agreement, it remains unclear whether current and former leaders are fully aware of their obligations.

Read more: Climate change forced these Fijian communities to move – and with 80 more at risk, here's what they learned

At a time when politicians discuss the need to “live within our means” when it comes to national finances, this does not appear to translate to the environment when we’re considering future generations.

Instead we seem to be caught in a debate surrounding the costs of action rather than inaction. The next generation of Australian voters certainly don’t seem confident about political commitments to their future as they hold their third national school strike tomorrow.

The welcome announcement from the UK is a major step in the right direction and potentially a watershed moment for a more sustainable global future. Is it too much to hope Australia could follow next?

Chris Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW

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

Australia���s epic story: a tale of amazing people, amazing creatures and rising seas We have so much more to learn about Australia. Shutterstock/Lev Savitskiy Michael Bird, James Cook University ; Alan Cooper, University of Adelaide ; Chris Turney, UNSW ; Darren Curnoe, UNSW ; Lynette Russell, Monash University , and Sean Ulm, James Cook University

The Australian continent has a remarkable history ��� a story of isolation, desiccation and resilience on an ark at the edge of the world.

It is a story of survival, ingenuity, and awe-inspiring achievements over many years.

Shortly after the dinosaurs died out 65 million years ago, Australia was torn from the supercontinent of Gondwana by immense tectonic forces and began its long, lonely, journey north towards the equator.

The lush temperate forests of Gondwana slowly disappeared as the Australian landmass pushed north, preserving a snapshot of faunal life from a much earlier evolutionary time.

Read more: A new species of marsupial lion tells us about Australia's past

This antipodean ark carried a bizarre cargo of marsupials who were spared the fate of their kin on other continents who were decimated by the rise of placental mammals.

Collision course

By about 5 million years ago the slow-motion collision of Australia into the Pacific and Indian tectonic plate began to push-up the now four-kilometre high mountains of central New Guinea.

This collision also formed the small stepping stones of islands across the Wallace Line which almost, but never quite, connected Australia to Asia through the Indonesian archipelago. They will meet in another 20 million years or so and Australia will become a vast appendix of the Asian landmass.

At the beginning of the Pleistocene period around 2.8 million years ago, global climate began to cycle dramatically between glacial periods, or ice ages, and interglacials, the warm phases between them. As the ice sheets waxed and waned over these cycles, each lasting between 50,000 and 100,000 years, sea levels rose and fell by up to 125 metres.

At times of lower sea level Australia, New Guinea and Tasmania were joined to form the single continent we know as Sahul.

A wide brown land

While remnants of the Gondwanan forests persisted in cooler and wetter parts like Tasmania and high in the Australian Alps, the continent became a wide brown land of desert, grassland and savanna; of droughts and flooding rains.

Fast forward to 130,000 years ago to a period scientists call the last interglacial ��� the stretch of time between the last two ice ages. This was a time when Australia���s climate and landscape looked a like lot it does today.

Sea levels were perhaps a few metres higher and marsupial megafauna ruled the land.

An impression of a giant lizard, Megalania, stalks a herd of migrating Diprotodon, while a pair of massive megafaunal kangaroos look on. Laurie Beirne

Kangaroos that could browse on leaves growing on trees three metres from the ground, three ton wombat-like Diprotodons and giant flightless birds the size of a moa (Genyornis newtonii) foraged across the landscape. These monsters became meals for the carnivorous marsupial lion (Thylacoleo carniflex) and the 4.5m long venomous goanna Megalania.

A strange menagerie indeed had evolved on the evolutionary ark that became Australia!

Meandering rivers channelled monsoon rains from the north into Australia���s vast arid centre. Kati-Thanda (Lake Eyre) was 25 metres deep and joined up with Lake Frome and other smaller basins to create a massive inland water body the size of Israel, with a volume equivalent to 700 Sydney harbours.

When sea levels dropped

Over the next 70,000 years or so the ice slowly began to build up on Antarctica and in the northern Hemisphere. As a result, sea levels dropped, exposing huge areas of once drowned land as Australia once more joined its island neighbours to form the enlarged continent of Sahul.

About this time a new kind of placental mammal ��� Homo sapiens ��� had begun to move out of Africa, and would eventually make its home across Asia.

Around 74,000 years ago, the Mt Toba volcano���s supereruption ��� the largest in the last 2 million years ��� spread 800 cubic kilometres of volcanic ash and debris widely across Asia.

Read more: The origin of 'us': what we know so far about where we humans come from

By plunging the planet into a long volcanic winter, Mt Toba may have delayed human ancestors making their way out of Africa to our doorstep. However, sometime before 50,000 years ago Homo sapiens finally reached Southeast Asia.

Along the way they ignored or joined with earlier evolutionary cousins including Homo erectus, Homo neanderthalensis, Homo floresiensis (the ���hobbit���), the new kid on the block Homo luzonensis, and the enigmatic Denisovans.

And so, the most potent placental mammal to ever walk the earth was now poised to enter a continent dominated by ancient marsupial giants ��� Sahul.

The first Australians

Making landfall on Sahul was no easy task and says much about the capabilities of the first people who entered the continent; the first Australians.

Even with sea level 70 metres lower than today the journey by any route involved at least six island hops followed by a final open ocean crossing of around 100 kilometres before Australia could be reached.

Of course, this is science���s story; for many Indigenous Australians their ancestors have always been here.

The peopling of Sahul didn���t happen by chance. Genetic research suggests hundreds to thousands of people must have purposely made the crossing. The success of these mariners speaks much of their abilities as also demonstrated by their rock art, jewellery, advanced stone tool technologies, watercraft construction and burial rituals, in the region, all before 40,000 years ago.

The time of human arrival has been progressively pushed back over the last few decades. It���s now widely accepted that humans first made landfall on Sahul by 50,000 years ago, or perhaps even as early as 65,000 years ago.

Read more: Buried tools and pigments tell a new history of humans in Australia for 65,000 years

Excavations through many layers at a site in the Northern Territory. Dominic O Brien/Gundjeihmi Aboriginal Corporation

It���s also clear that once people arrived, they settled the continent very rapidly. In only a few thousand years people were living from the western desert coasts to the highly productive (now dry) Willandra Lakes in western New South Wales.

Once every nook and cranny was occupied movement became restricted ��� Aboriginal people stayed on their particular country, literally, for the next 50,000 years.

Read more: DNA reveals Aboriginal people had a long and settled connection to country

What happened to the megafauna?

The impact that human arrival had on the marsupial continent of Sahul remains hotly contested. Many have argued that people wiped out the megafauna within a few thousand years of arriving.

But there���s now clear evidence that some megafauna lived on beyond this time. If landfall was at 65,000 years, it would show that people and megafauna coexisted for a very long time.

There���s also a body of opinion that suggests climate change, as the world headed into the last ice age, wiped out populations of megafauna already under stress.

The large inland lakes, in total about the size of England, began to dry out from around 50,000 years ago. This drying has been ascribed to natural climate change and human modification of the environment through burning and the hunting of megafauna.

Read more: Climate change wiped out Australia's megafauna

Sahul, during the last ice age (beginning 30,000 years ago and peaking 20,000 years ago) was cold ��� around 5 degrees colder ��� and much drier than present. Sea level was 125 metres lower and, as a consequence the continent was almost 40% larger than it is today.

Shifting sand dunes expanded over much of the arid interior, ice caps and glaciers expanded over interior Tasmania, the southern highlands of New South Wales and along the mountainous spine of New Guinea.

Strong winds carried dust from the now dry interior lake basins southeast into the Tasman Sea and northwest into the Indian Ocean. A large brackish inland sea, bigger than Tasmania, occupied the Gulf of Carpentaria.

Humans and animals alike retreated into locations where water and food were more assured in a broader inhospitable landscape ��� some perhaps around the coastal fringes of Sahul.

When sea levels rise again

Ten thousand years later and everything began to rapidly change again. From shortly after 20,000 years ago global climate began to warm and the planet���s ice sheets began to collapse. The water flooded back into the oceans and sea-levels began to rise, at times up to a whopping 1.5 centimetres per year.

Australia���s coastline has moved before thanks to changes in sea level. Flickr/Travellers travel photobook, CC BY

In some parts of Sahul this shifted the coastline inland by 20 metres or more in a given year. This radical reconfiguration of the coastline went on for thousands of years with a significant impact on Aboriginal societies.

Read more: Australia's coastal living is at risk from sea level rise, but it's happened before

This history is recorded today in Aboriginal oral histories of coastal flooding and migration from this time. As sea level rise squeezed people into a rapidly shrinking landmass, population density rose and in turn may have ushered in a new era of social, technological and economic change in Aboriginal societies.

Sea level rise severed the connections to Tasmania and New Guinea for the final time, reaching a peak about 1-2 metres above modern levels some 8,000 years ago, thereafter stabilising slowly to pre-twentieth century levels.

Climate settled into a pattern broadly similar to present, with the last few thousand years seeing increased intensity of the El Nino-La Nina climate cycles leading to the boom and bust cycles we live with today.

Over the last 10,000 years, Aboriginal populations increased, possibly in the later stages with the help of the recent placental mammal import, the dingo.

When Europeans invaded Sahul���s ancient shores, one blink of an eye ago, there were perhaps more than 1,000,000 people in 250 language groups across the continent.

They had not only survived, but thrived, on the driest inhabited continent on earth for 50,000 years or more.

What an epic story! And there is so much more to learn.

Michael Bird, ARC Laureate Fellow, JCU Distinguished Professor, ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University; Alan Cooper, Director, Australian Centre for Ancient DNA, ARC L:aureate Fellow, ARC CoE Biodiversity and Heritage CI, University of Adelaide; Chris Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW; Darren Curnoe, Associate Professor and Chief Investigator, ARC Centre of Excellence for Australian Biodiversity and Heritage, University of New South Wales, UNSW; Lynette Russell, Professor of Indigenous Studies at Monash University, and Deputy Director of the ARC Centre of Excellence for Australian Biodiversity and Heritage, Monash University, and Sean Ulm, Deputy Director, ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University

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

Australia’s epic story: a tale of amazing people, amazing creatures and rising seas We have so much more to learn about Australia. Shutterstock/Lev Savitskiy Michael Bird, James Cook University ; Alan Cooper, University of Adelaide ; Chris Turney, UNSW ; Darren Curnoe, UNSW ; Lynette Russell, Monash University , and Sean Ulm, James Cook University

The Australian continent has a remarkable history — a story of isolation, desiccation and resilience on an ark at the edge of the world.

It is a story of survival, ingenuity, and awe-inspiring achievements over many years.

Shortly after the dinosaurs died out 65 million years ago, Australia was torn from the supercontinent of Gondwana by immense tectonic forces and began its long, lonely, journey north towards the equator.

The lush temperate forests of Gondwana slowly disappeared as the Australian landmass pushed north, preserving a snapshot of faunal life from a much earlier evolutionary time.

Read more: A new species of marsupial lion tells us about Australia's past

This antipodean ark carried a bizarre cargo of marsupials who were spared the fate of their kin on other continents who were decimated by the rise of placental mammals.

Collision course

By about 5 million years ago the slow-motion collision of Australia into the Pacific and Indian tectonic plate began to push-up the now four-kilometre high mountains of central New Guinea.

This collision also formed the small stepping stones of islands across the Wallace Line which almost, but never quite, connected Australia to Asia through the Indonesian archipelago. They will meet in another 20 million years or so and Australia will become a vast appendix of the Asian landmass.

At the beginning of the Pleistocene period around 2.8 million years ago, global climate began to cycle dramatically between glacial periods, or ice ages, and interglacials, the warm phases between them. As the ice sheets waxed and waned over these cycles, each lasting between 50,000 and 100,000 years, sea levels rose and fell by up to 125 metres.

At times of lower sea level Australia, New Guinea and Tasmania were joined to form the single continent we know as Sahul.

A wide brown land

While remnants of the Gondwanan forests persisted in cooler and wetter parts like Tasmania and high in the Australian Alps, the continent became a wide brown land of desert, grassland and savanna; of droughts and flooding rains.

Fast forward to 130,000 years ago to a period scientists call the last interglacial — the stretch of time between the last two ice ages. This was a time when Australia’s climate and landscape looked a like lot it does today.

Sea levels were perhaps a few metres higher and marsupial megafauna ruled the land.

An impression of a giant lizard, Megalania, stalks a herd of migrating Diprotodon, while a pair of massive megafaunal kangaroos look on. Laurie Beirne

Kangaroos that could browse on leaves growing on trees three metres from the ground, three ton wombat-like Diprotodons and giant flightless birds the size of a moa (Genyornis newtonii) foraged across the landscape. These monsters became meals for the carnivorous marsupial lion (Thylacoleo carniflex) and the 4.5m long venomous goanna Megalania.

A strange menagerie indeed had evolved on the evolutionary ark that became Australia!

Meandering rivers channelled monsoon rains from the north into Australia’s vast arid centre. Kati-Thanda (Lake Eyre) was 25 metres deep and joined up with Lake Frome and other smaller basins to create a massive inland water body the size of Israel, with a volume equivalent to 700 Sydney harbours.

When sea levels dropped

Over the next 70,000 years or so the ice slowly began to build up on Antarctica and in the northern Hemisphere. As a result, sea levels dropped, exposing huge areas of once drowned land as Australia once more joined its island neighbours to form the enlarged continent of Sahul.

About this time a new kind of placental mammal – Homo sapiens – had begun to move out of Africa, and would eventually make its home across Asia.

Around 74,000 years ago, the Mt Toba volcano’s supereruption — the largest in the last 2 million years – spread 800 cubic kilometres of volcanic ash and debris widely across Asia.

Read more: The origin of 'us': what we know so far about where we humans come from

By plunging the planet into a long volcanic winter, Mt Toba may have delayed human ancestors making their way out of Africa to our doorstep. However, sometime before 50,000 years ago Homo sapiens finally reached Southeast Asia.

Along the way they ignored or joined with earlier evolutionary cousins including Homo erectus, Homo neanderthalensis, Homo floresiensis (the ‘hobbit’), the new kid on the block Homo luzonensis, and the enigmatic Denisovans.

And so, the most potent placental mammal to ever walk the earth was now poised to enter a continent dominated by ancient marsupial giants – Sahul.

The first Australians

Making landfall on Sahul was no easy task and says much about the capabilities of the first people who entered the continent; the first Australians.

Even with sea level 70 metres lower than today the journey by any route involved at least six island hops followed by a final open ocean crossing of around 100 kilometres before Australia could be reached.

Of course, this is science’s story; for many Indigenous Australians their ancestors have always been here.

The peopling of Sahul didn’t happen by chance. Genetic research suggests hundreds to thousands of people must have purposely made the crossing. The success of these mariners speaks much of their abilities as also demonstrated by their rock art, jewellery, advanced stone tool technologies, watercraft construction and burial rituals, in the region, all before 40,000 years ago.

The time of human arrival has been progressively pushed back over the last few decades. It’s now widely accepted that humans first made landfall on Sahul by 50,000 years ago, or perhaps even as early as 65,000 years ago.

Read more: Buried tools and pigments tell a new history of humans in Australia for 65,000 years

Excavations through many layers at a site in the Northern Territory. Dominic O Brien/Gundjeihmi Aboriginal Corporation

It’s also clear that once people arrived, they settled the continent very rapidly. In only a few thousand years people were living from the western desert coasts to the highly productive (now dry) Willandra Lakes in western New South Wales.

Once every nook and cranny was occupied movement became restricted – Aboriginal people stayed on their particular country, literally, for the next 50,000 years.

Read more: DNA reveals Aboriginal people had a long and settled connection to country

What happened to the megafauna?

The impact that human arrival had on the marsupial continent of Sahul remains hotly contested. Many have argued that people wiped out the megafauna within a few thousand years of arriving.

But there’s now clear evidence that some megafauna lived on beyond this time. If landfall was at 65,000 years, it would show that people and megafauna coexisted for a very long time.

There’s also a body of opinion that suggests climate change, as the world headed into the last ice age, wiped out populations of megafauna already under stress.

The large inland lakes, in total about the size of England, began to dry out from around 50,000 years ago. This drying has been ascribed to natural climate change and human modification of the environment through burning and the hunting of megafauna.

Read more: Climate change wiped out Australia's megafauna

Sahul, during the last ice age (beginning 30,000 years ago and peaking 20,000 years ago) was cold – around 5 degrees colder – and much drier than present. Sea level was 125 metres lower and, as a consequence the continent was almost 40% larger than it is today.

Shifting sand dunes expanded over much of the arid interior, ice caps and glaciers expanded over interior Tasmania, the southern highlands of New South Wales and along the mountainous spine of New Guinea.

Strong winds carried dust from the now dry interior lake basins southeast into the Tasman Sea and northwest into the Indian Ocean. A large brackish inland sea, bigger than Tasmania, occupied the Gulf of Carpentaria.

Humans and animals alike retreated into locations where water and food were more assured in a broader inhospitable landscape – some perhaps around the coastal fringes of Sahul.

When sea levels rise again

Ten thousand years later and everything began to rapidly change again. From shortly after 20,000 years ago global climate began to warm and the planet’s ice sheets began to collapse. The water flooded back into the oceans and sea-levels began to rise, at times up to a whopping 1.5 centimetres per year.

Australia’s coastline has moved before thanks to changes in sea level. Flickr/Travellers travel photobook, CC BY

In some parts of Sahul this shifted the coastline inland by 20 metres or more in a given year. This radical reconfiguration of the coastline went on for thousands of years with a significant impact on Aboriginal societies.

Read more: Australia's coastal living is at risk from sea level rise, but it's happened before

This history is recorded today in Aboriginal oral histories of coastal flooding and migration from this time. As sea level rise squeezed people into a rapidly shrinking landmass, population density rose and in turn may have ushered in a new era of social, technological and economic change in Aboriginal societies.

Sea level rise severed the connections to Tasmania and New Guinea for the final time, reaching a peak about 1-2 metres above modern levels some 8,000 years ago, thereafter stabilising slowly to pre-twentieth century levels.

Climate settled into a pattern broadly similar to present, with the last few thousand years seeing increased intensity of the El Nino-La Nina climate cycles leading to the boom and bust cycles we live with today.

Over the last 10,000 years, Aboriginal populations increased, possibly in the later stages with the help of the recent placental mammal import, the dingo.

When Europeans invaded Sahul’s ancient shores, one blink of an eye ago, there were perhaps more than 1,000,000 people in 250 language groups across the continent.

They had not only survived, but thrived, on the driest inhabited continent on earth for 50,000 years or more.

What an epic story! And there is so much more to learn.

Michael Bird, ARC Laureate Fellow, JCU Distinguished Professor, ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University; Alan Cooper, Director, Australian Centre for Ancient DNA, ARC L:aureate Fellow, ARC CoE Biodiversity and Heritage CI, University of Adelaide; Chris Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW; Darren Curnoe, Associate Professor and Chief Investigator, ARC Centre of Excellence for Australian Biodiversity and Heritage, University of New South Wales, UNSW; Lynette Russell, Professor of Indigenous Studies at Monash University, and Deputy Director of the ARC Centre of Excellence for Australian Biodiversity and Heritage, Monash University, and Sean Ulm, Deputy Director, ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University

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

How a change in climate wiped out the 'Siberian unicorn' An artist’s impression of Siberian unicorns (Elasmotherium) walking in the steppe grass on a cloudy day. Shutterstock/Elenarts Kieren Mitchell, University of Adelaide ; Adrian Lister, Natural History Museum ; Alan Cooper, University of Adelaide , and Chris Turney, UNSW

A mysterious shaggy giant species of rhinoceros – named the Siberian unicorn due to its enormous single horn – turns out to have survived in western Russia until just 36,000 years ago, according to research published today in Nature Ecology & Evolution. This extinction date means that the Siberian unicorn’s final days were shared with early modern humans and Neanderthals.

Previously, little was known about the creature thought to have become extinct more than 200,000 years ago. But genetic analysis and radiocarbon dating have begun to reveal many aspects of how it lived, and when it died out.

A key finding is that the Siberian unicorn did not become extinct due to modern human hunting, nor even the peak of the last Ice Age starting around 25,000 years ago.

Read more: China's legalisation of rhino horn trade: disaster or opportunity?

Instead, it succumbed to a more subtle change in climate that reduced grassland from eastern Europe to China.

Our new results show that the Siberian unicorn was reliant on these grasslands and, unlike other species in the area such as the saiga antelope, was unable to adapt to change.

The ‘Siberian unicorn’

The Siberian unicorn (Elasmotherium) had a single large horn, estimated at up to a metre in length. It was one of many diverse rhino species that once existed.

In addition to the extinct woolly rhinoceros (which is still found as frozen mummies), there are five species of living rhino. All of these creatures are now sadly in trouble, including the white rhino (near threatened), the Javan rhino (critically endangered), and the Sumatran rhino (critically endangered).

The loss of the Siberian unicorn provides a valuable case study displaying the poor resilience of rhinos to environmental change.

The animal we worked on was found in modern-day Russia, though its range also extended to areas that now include Kazakhstan, Mongolia, and northern China, where it inhabited a steppe-like habitat dominated by grasses and herbs.

The Siberian unicorn shared this environment with the saiga antelope, and other Ice Age species including the woolly rhino and mammoth.

But most evidence to date suggested that the Siberian unicorn became extinct 200,000 years ago, while the woolly rhino and mammoth became extinct around 13,000 and 4,000 years ago, respectively.

So why did the Siberian unicorn become extinct while other species that lived in the same habitat held on for thousands of years longer or, like the saiga, still survive today?

Saiga antelope at the Stepnoi Sanctuary, Russia. Its impressive nose acts as a dust-filter and reverse-cycle air-conditioner, minimising water loss in dry environments. Wikimedia/Andrey Giljov, CC BY-SA A smoking gun

A few unconfirmed pieces of evidence have recently suggested that the Siberian unicorn survived until closer to the present, much like the woolly rhinoceros. So we surveyed the age of 23 bone samples of the animal held in museum collections in Russia and the UK.

Rather than 200,000 years, new dating found the Siberian unicorn actually became extinct as recently as just 36,000 years ago.

Next we considered how it might have become extinct at this time.

Climate change seems a likely contender – but 36,000 years is well before the height of the Ice Age, which occurred 20,000-25,000 years ago.

But this date does match the timing of a pronounced change towards cooler summers across Northern Europe and Asia. This seasonal change resulted in grasses and herbs becoming more sparse, and an increase in tundra plant species such as mosses and lichens.

A vulnerable specialist

So why did a change in climate 36,000 years ago drive the Siberian unicorn extinct, but not the woolly rhinoceros or the saiga?

To answer this question, our study took fossil bones from the Siberian unicorn, woolly rhino, and saiga, and looked at the nitrogen and carbon they contained – as differences in these elements reflect an animal’s diet.

We found that before 36,000 years ago the saiga and the Siberian unicorn behaved very similarly, eating grass almost exclusively. After this point, the carbon and nitrogen in saiga bones showed a major dietary shift towards other plant types.

Read more: Ancient fish evolved in shallow seas – the very places humans threaten today

But shifting from a grass diet proved too difficult for the Siberian unicorn, with its special folded wear-resistant teeth and a low-slung head right at grass height. Relatives such as the woolly rhino had always eaten a more balanced array of plants, and were much less impacted by a change in habitat.

Importantly, the change in climate that drove the Siberian unicorn extinct was actually much less pronounced than those which occurred during the Ice Age that followed. Or the changes that we will face in the near future.

The story of the Siberian unicorn is a timely reminder that even subtle changes in plant distributions can have devastating knock-on effects for large animal species.

Worryingly, this is a dire risk for many animals, such as the Siberian unicorn’s surviving cousins, which thanks to humans already have heavily restricted ranges.

Kieren Mitchell, Postdoctoral Research Associate, Australian Centre for Ancient DNA (ACAD) & Centre for Australian Biodiversity and Heritage (CABAH), University of Adelaide; Adrian Lister, Research Leader, Natural History Museum; Alan Cooper, Director, Australian Centre for Ancient DNA, University of Adelaide, and Chris Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW

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

Will 2018 be the year of climate action? Victorian London's 'Great Stink' sewer crisis might tell us Chris Turney, UNSW

In the late 19th century, the irrepressible Mark Twain is reputed to have said in a speech:

Everybody talks about the weather but nobody does anything about it.

He’s said to have borrowed that quote from a friend, but if Twain were alive today he would no doubt have more to say on the subject. In a time when we are becoming increasingly accustomed to extremes in the climate system, the events of this year have risen above the background noise of political turmoil to dominate the global headlines.

While global leadership in dealing with climate change may be depressingly limited, I can’t help but wonder if 2018 will be the year our global tribe feels threatened enough to act.

Encouragingly, there may be a historical (and largely unknown) precedent for tackling climate change: Victoria London’s handling of the “Great Stink”, where growth had turned the River Thames into an open sewer.

Read more: Lowy Institute Poll shows Australians' support for climate action at its highest level in a decade

Climate system extremes

2018 is breaking all manner of records.

In January, the eastern USA and western Europe fell under persistent frigid Arctic conditions brought about by a weakening of the polar vortex.

Six months later, the north has been experiencing exceptional hemispheric-wide summer warming and drought, most likely amplified by a weakening of Atlantic Ocean circulation – the latter (ironically) being expressed by unusually cool surface ocean waters.

In recent weeks, Florence, Mangkhut and Helene have become the latest household names to mark a succession of storms battering the USA, Asia and Europe this year.

Closer to home, New South Wales is now suffering a state-wide drought, along with other regions in Australia. Early wildfires and the threat of more to come has resulted in the earliest government total fire ban on record.

As the crisis deepens, it’s worth reflecting on Victorian London’s “Great Stink” sewage problem - where things finally got so bad that authorities were forced to accept evidence, reject sceptics, and act.

A ‘deadly sewer’

In the Victorian age, London’s growth had turned the River Thames into an open sewer. Conditions were so bad they inspired many to write on the risks to public health.

‘The silent highwayman’, an 1858 cartoon from Punch magazine, commenting on the deadly levels of pollution in the River Thames. Wikimedia, CC BY

Charles Dickens provided a lurid description in Little Dorrit, describing the Thames as a “deadly sewer” while the scientist Michael Faraday wrote to The Times of London that:

if we neglect this subject, we cannot expect to do so with impunity; nor ought we to be surprised if, ere many years are over, a hot season give us sad proof of the folly of our carelessness.

An 1855 cartoon from Punch Magazine in which Michael Faraday gives his card to ‘Father Thames’, commenting on Faraday gauging the river’s ‘degree of opacity’. Wikimedia

In 1854, medic John Snow demonstrated the source of cholera in the London suburb of Soho was a local water pump. To test his ideas, officials removed the handle on the pump, and the number of cases all but disappeared.

Sewage sceptics

But there was an intransigence about meeting the threat. Ignoring scientific evidence, “sewage sceptics” held the view that poor air quality – so called “miasma”– was the cause of the frequent outbreaks of cholera and other diseases.

They convinced the government to reject the evidence, considering there to be “no reason to adopt this belief”. The scale of the sewage problem in London was considered too large to be solved, possibly encouraged by political pressure from the thriving water industry that delivered direct to those who could afford it. For several more years, this view persisted.

That was until the year of the “Great Stink”.

The ‘Great Stink’ arrives

In the summer heatwave of 1858, the Thames’ sewage turned noses across London. Conditions were so bad, teams of men were employed to shovel lime at the many sewage outlets into the capital’s river in a vain attempt to stop the smell.

Even the national legislators were not spared, with the windows of the Houses of Parliament covered in lime-soaked sack cloths. Serious thought was even given to relocating government outside London, at least until the air had cleared. The conditions created a heady stench that cut through the politically charged rhetoric of the day, and forced a rethink.

Within nine years of the “Great Stink”, the 900-kilometre London Sewage Network was constructed - an engineering marvel of the Victorian age. The politicians at the time weren’t immediately convinced the new infrastructure would help public health but the disappearance of disease accepted as the norm for the capital convinced even the most ardent of sceptics. No one talks about miasma as a real thing anymore.

The Great Stink of 1858 overturned beliefs founded on misinformation. A challenge considered impossible, was solved.

Our generation’s ‘Great Stink’

Fast forward 160 years and the recent spate of climate headlines is on the back of an increasing trend towards greater extremes, with all the associated human, environmental, and financial costs.

In August of this year, the Actuaries Climate Index – which monitors changes in sea level rise and climate extremes for the North American insurance industry since the 1960s – reported that the five-year moving average reached a new high in 2017. This year promises to continue the trend and is no single outlier.

Will 2018 be the year when the world does something about climate change?

Will 2018 be our generation’s “Great Stink”?

Read more: While nations play politics, cities and states are taking up the climate challenge

Chris Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW

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

Anthropocene began in 1965, according to signs left in the world's 'loneliest tree' Pavla Fenwick, Author provided Chris Turney, UNSW ; Jonathan Palmer, UNSW , and Mark Maslin, UCL

On Campbell Island in the Southern Ocean, some 400 miles south of New Zealand, is a single Sitka spruce. More than 170 miles from any other tree, it is often credited as the “world’s loneliest tree”. Planted in the early 20th century by Lord Ranfurly, governor of New Zealand, the tree’s wood has recorded the radiocarbon produced by above ground atomic bomb tests – and its annual layers show a peak in 1965, just after the tests were banned. The tree therefore gives us a potential marker for the start of the Anthropocene.

But why 1965? The 1960s is a decade forever associated with the hippie movement and the birth of the modern environmentalism, a sun-blushed age in which the Apollo moon landings gave us the iconic image of a fragile planet framed against a desolate lunar surface. It was also a time when the world was fast globalising, with rapid industrialisation and economic growth driving population expansion and a massive increase in our impact on the environment.

This postwar period has been called the “Great Acceleration”. So the question we’re interested in is whether this step change in human activity left an indelible mark on our planet, one which, if we disappeared today, would still leave a permanent signature in the geological record.

If traces of nuclear testing were present even on Campbell Island then the bombs must have had a truly global impact. Turney et al, Author provided

The concept of a human-dominated geological epoch has been around since the 19th century, but the idea that we have created an Anthropocene has recently become more popular in the face of long-term global changes in the environment far beyond what may be considered “natural”. While humans have long had an impact on the planet at the local and even continental level, the scale of modern change is sufficiently large that geologists are considering the evidence to recognise the Anthropocene officially in the geological timescale. They have set the scientific community a major challenge to find a global-wide environmental marker or “golden spike” that represents this crucial change.

‘Small boy’ nuclear test in Nevada, July 1962. US National Nuclear Security Administration

A major contender for defining the start of the Anthropocene Epoch is the peak in radioactive elements produced from above ground thermonuclear bomb tests, the majority of which occurred at the height of the Cold War in the early-1960s. The problem from a geologist’s point of view is most of the records of this spike in radioactivity (for example preserved in lake sediments and the annual growth of tree-rings) have been reported from the Northern Hemisphere where the majority of the tests took place. To demonstrate a truly global human impact requires a signal from a remote, pristine location in the Southern Hemisphere that occurs at the same time as the north. This is where our new study comes in.

Sampling the World’s Loneliest Tree.

In the journal Scientific Reports we publish a new record that identifies a radioactive signal preserved from exactly this sort of place: Campbell Island, a rare piece of real estate in the depths of the Southern Ocean.

During the Australasian Antarctic Expedition 2013-2014 we undertook scientific sampling across the island to get a better handle on the scale of environmental change in this most remote of locations. The solitary Sitka spruce is in the southern part of the island. The species is found naturally along the west coast of North America from Alaska to California – it is only in the Southern Hemisphere because humans transplanted it there.

Levels of radiocarbon recorded on Campbell Island peaked in late 1965. Turney et al, Author provided

Nonetheless, the Campbell Island tree is growing exceptionally well – at a rate five to ten times faster than surrounding native shrubs – which gave us plenty of data to work with. Detailed analysis of the tree’s year-by-year growth shows the peak in radioactive elements took place sometime between October and December 1965, which coincides with the same signal in the Northern Hemisphere. This spruce has demonstrated unequivocally that humans have left an impact on the planet, even in the most pristine of environments, that will be preserved in the geological record for tens of millennia and beyond.

Our research promises to reignite the debate around when humans really became a geological superpower. Should we define the Anthropocene by when humanity invented the technology to make themselves extinct? If so, then the nuclear bomb spike recorded in the loneliest tree on the planet suggests it began in 1965.

Chris Turney, ARC Centre of Excellence for Australian Biodiversity and Heritage, University of New South Wales, UNSW; Jonathan Palmer, Research Fellow, School of Biological, Earth and Environmental Sciences., UNSW, and Mark Maslin, Professor of Palaeoclimatology, UCL

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

Anthropocene began in 1965, according to signs left in the world's 'loneliest tree' Pavla Fenwick, Author provided Chris Turney, UNSW ; Jonathan Palmer, UNSW , and Mark Maslin, UCL

On Campbell Island in the Southern Ocean, some 400 miles south of New Zealand, is a single Sitka spruce. More than 170 miles from any other tree, it is often credited as the “world’s loneliest tree”. Planted in the early 20th century by Lord Ranfurly, governor of New Zealand, the tree’s wood has recorded the radiocarbon produced by above ground atomic bomb tests – and its annual layers show a peak in 1965, just after the tests were banned. The tree therefore gives us a potential marker for the start of the Anthropocene.

But why 1965? The 1960s is a decade forever associated with the hippie movement and the birth of the modern environmentalism, a sun-blushed age in which the Apollo moon landings gave us the iconic image of a fragile planet framed against a desolate lunar surface. It was also a time when the world was fast globalising, with rapid industrialisation and economic growth driving population expansion and a massive increase in our impact on the environment.

This postwar period has been called the “Great Acceleration”. So the question we’re interested in is whether this step change in human activity left an indelible mark on our planet, one which, if we disappeared today, would still leave a permanent signature in the geological record.

If traces of nuclear testing were present even on Campbell Island then the bombs must have had a truly global impact. Turney et al, Author provided

The concept of a human-dominated geological epoch has been around since the 19th century, but the idea that we have created an Anthropocene has recently become more popular in the face of long-term global changes in the environment far beyond what may be considered “natural”. While humans have long had an impact on the planet at the local and even continental level, the scale of modern change is sufficiently large that geologists are considering the evidence to recognise the Anthropocene officially in the geological timescale. They have set the scientific community a major challenge to find a global-wide environmental marker or “golden spike” that represents this crucial change.

‘Small boy’ nuclear test in Nevada, July 1962. US National Nuclear Security Administration

A major contender for defining the start of the Anthropocene Epoch is the peak in radioactive elements produced from above ground thermonuclear bomb tests, the majority of which occurred at the height of the Cold War in the early-1960s. The problem from a geologist’s point of view is most of the records of this spike in radioactivity (for example preserved in lake sediments and the annual growth of tree-rings) have been reported from the Northern Hemisphere where the majority of the tests took place. To demonstrate a truly global human impact requires a signal from a remote, pristine location in the Southern Hemisphere that occurs at the same time as the north. This is where our new study comes in.

Sampling the World’s Loneliest Tree.

In the journal Scientific Reports we publish a new record that identifies a radioactive signal preserved from exactly this sort of place: Campbell Island, a rare piece of real estate in the depths of the Southern Ocean.

During the Australasian Antarctic Expedition 2013-2014 we undertook scientific sampling across the island to get a better handle on the scale of environmental change in this most remote of locations. The solitary Sitka spruce is in the southern part of the island. The species is found naturally along the west coast of North America from Alaska to California – it is only in the Southern Hemisphere because humans transplanted it there.

Levels of radiocarbon recorded on Campbell Island peaked in late 1965. Turney et al, Author provided

Nonetheless, the Campbell Island tree is growing exceptionally well – at a rate five to ten times faster than surrounding native shrubs – which gave us plenty of data to work with. Detailed analysis of the tree’s year-by-year growth shows the peak in radioactive elements took place sometime between October and December 1965, which coincides with the same signal in the Northern Hemisphere. This spruce has demonstrated unequivocally that humans have left an impact on the planet, even in the most pristine of environments, that will be preserved in the geological record for tens of millennia and beyond.

Our research promises to reignite the debate around when humans really became a geological superpower. Should we define the Anthropocene by when humanity invented the technology to make themselves extinct? If so, then the nuclear bomb spike recorded in the loneliest tree on the planet suggests it began in 1965.

Chris Turney, ARC Centre of Excellence for Australian Biodiversity and Heritage, University of New South Wales, UNSW; Jonathan Palmer, Research Fellow, School of Biological, Earth and Environmental Sciences., UNSW, and Mark Maslin, Professor of Palaeoclimatology, UCL

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

Why remote Antarctica is so important in a warming world Chris Fogwill, Keele University ; Chris Turney, UNSW , and Zoe Robinson, Keele University

Ever since the ancient Greeks speculated a continent must exist in the south polar regions to balance those in the north, Antarctica has been popularly described as remote and extreme. Over the past two centuries, these factors have combined to create, in the human psyche, an almost mythical land – an idea reinforced by tales of heroism and adventure from the Edwardian golden age of “heroic exploration” and pioneers such as Robert Falcon Scott, Roald Amundsen and Ernest Shackleton.

Recent research, however, is casting new light on the importance of the southernmost continent, overturning centuries of misunderstanding and highlighting the role of Antarctica in how our planet works and the role it may play in a future, warmer world.

Heroic exploration, 1913. wiki

What was once thought to be a largely unchanging mass of snow and ice is anything but. Antarctica holds a staggering amount of water. The three ice sheets that cover the continent contain around 70% of our planet’s fresh water, all of which we now know to be vulnerable to warming air and oceans. If all the ice sheets were to melt, Antarctica would raise global sea levels by at least 56m.

Where, when, and how quickly they might melt is a major focus of research. No one is suggesting all the ice sheets will melt over the next century but, given their size, even small losses could have global repercussions. Possible scenarios are deeply concerning: in addition to rising sea levels, meltwater would slow down the world’s ocean circulation, while shifting wind belts may affect the climate in the southern hemisphere.

In 2014, NASA reported that several major Antarctic ice streams, which hold enough water to trigger the equivalent of a one-and-a-half metre sea level rise, are now irreversibly in retreat. With more than 150m people exposed to the threat of sea level rise and sea levels now rising at a faster rate globally than any time in the past 3,000 years, these are sobering statistics for island nations and coastal cities worldwide.

An immediate and acute threat

Recent storm surges following hurricanes have demonstrated that rising sea levels are a future threat for densely populated regions such as Florida and New York. Meanwhile the threat for low-lying islands in areas such as the Pacific is immediate and acute.

Much of the continent’s ice is slow sliding towards the sea. R Bindschadler / wiki

Multiple factors mean that the vulnerability to global sea level rise is geographically variable and unequal, while there are also regional differences in the extremity of sea level rise itself. At present, the consensus of the IPPC 2013 report suggests a rise of between 40 and 80cm over the next century, with Antarctica only contributing around 5cm of this. Recent projections, however, suggest that Antarctic contributions may be up to ten times higher.

Studies also suggest that in a world 1.5-2°C warmer than today we will be locked into millennia of irreversible sea level rise, due to the slow response time of the Antarctic ice sheets to atmospheric and ocean warming.

We may already be living in such a world. Recent evidence shows global temperatures are close to 1.5°C warmer than pre-industrial times and, after the COP23 meeting in Bonn in November, it is apparent that keeping temperature rise within 2°C is unlikely.

So we now need to reconsider future sea level projections given the potential global impact from Antarctica. Given that 93% of the heat from anthropogenic global warming has gone into the ocean, and these warming ocean waters are now meeting the floating margins of the Antarctic ice sheet, the potential for rapid ice sheet melt in a 2°C world is high.

In polar regions, surface temperatures are projected to rise twice as fast as the global average, due to a phenomenon known as polar amplification. However, there is still hope to avoid this sword of Damocles, as studies suggest that a major reduction in greenhouse gases over the next decade would mean that irreversible sea level rise could be avoided. It is therefore crucial to reduce CO₂ levels now for the benefit of future generations, or adapt to a world in which more of our shorelines are significantly redrawn.

This is both a scientific and societal issue. We have choices: technological innovations are providing new ways to reduce CO₂ emissions, and offer the reality of a low-carbon future. This may help minimise sea level rise from Antarctica and make mitigation a viable possibility.

Given what rising sea levels could mean for human societies across the world, we must maintain our longstanding view of Antarctica as the most remote and isolated continent.

Chris Fogwill, Professor of Glaciology and Palaeoclimatology, Keele University; Chris Turney, Professor of Earth Sciences and Climate Change, UNSW, and Zoe Robinson, Reader in Physical Geography and Sustainability/Director of Education for Sustainability, Keele University

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