Australia: La Nina


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Extreme weather leads to public health crises – so health and climate experts must work together


Aparna Lal, Australian National University and Rebecca Colvin, Australian National University

This year has seen a number of extreme weather events around the globe, from hurricanes in the Americas to devastating flooding in South Asia. The loss of lives, homes and livelihoods are made worse by subsequent disease outbreaks: after the South Asian floods, more than 12,000 cases of watery diarrhoea were reported in Bangladesh. Presumably, many more cases are unreported.

As our climate changes, severe weather events (especially intense rainfall) will become the “new normal”. The connection between climate and disease is well established, even in less extreme situations.


Read more: Irma and Harvey: very different storms, but both affected by climate change


This makes it vital that our meteorologists, climate scientists and health systems work closely together. Particularly, health professionals should make better use of weather forecasts to proactively manage disease risk. Climate outlooks – with a longer-term perspective than weather forecasts – can also help with long-range tactical and strategic planning.

The link between climate change and disease

Climate change projections consistently indicate increased climate variability. A more variable climate creates conditions for the spread and control of infectious disease. In particular, changes in the intensity and duration of rain can help spread pathogens through water.

Both floods and droughts can increase waterborne infections, either when clean and dirty water mix during floods, or through inadequate storage and concentration of toxic organisms when water is scarce.


Read more: Flooding from Hurricane Harvey causes a host of public health concerns


These risks are not restricted to countries with limited resources. In Australia, fluctuations in the sea surface temperatures in the Indian Ocean (a phenomenon shown by the “Indian Ocean Dipole”) are linked to spikes in rates of waterborne diseases like cryptosporidiosis, which cause gastrointestinal illness.

NSW Health documents, obtained earlier this year by the ABC, reveal that more than 100,000 NSW residents were issued protective boil-water alerts in the past five years. These residents lived in areas where pathogens like cryptosporidium were found in unfiltered drinking water pumped from rivers, lakes and dams. A more variable climate can increase these risks.

Research suggests we can improve public health outcomes by integrating both climate dynamics and the impact on human health into our management of natural water resources.

We need integrated climate and health systems

Traditional disease surveillance systems rely on early detection of illnesses as they occur, not predicting them before they happen. But outbreaks that follow extreme events are already underway before authorities are notified.

The close relationship between climate signals and some waterborne diseases suggest that advances in numerical weather forecasting and climate science present new opportunities for public health officials.


Read more: How satellites can help control the spread of diseases such as Zika


Forecasting based on climate variables is well established in crop disease management and ecosystem conservation.

Recent technological advancements, such as real-time predictions of disease outbreaks, highlight great potential for forecasting to be used for human health benefit ahead of extreme weather events.

Collaboration is key

At present, health professionals and climate forecasters generally operate separately from each other, as very distinct professions. This can make it very difficult for researchers, public servants and service providers to work effectively together.

Our experience at the ANU Climate Change Institute has taught us that an important early step to fostering cooperation is helping individuals build relationships.


Read more: We’ve got to stop meeting like this


It’s important to create opportunities for people from different sectors to come together so they can exchange knowledge and make personal connections. Emphasising that health and climate experts have many shared goals can help encourage new cross-sector networks and a sense of a shared professional identity. (And realistically, one of the most important things you can do to promote productive exchanges is feed people well.)

There’s a real opportunity to integrate health and climate knowledge bases. This could be what’s known as a “boundary object”: something that can be meaningfully interpreted by people with different training and backgrounds, which helps to span the “boundary” between these sectors or disciplines.

We stand to gain from integration across climate and health

As our understanding of climate patterns grows, there are more opportunities for the health sector to take advantage of sophisticated modelling and prediction.

This is particularly true if disease surveillance and climate and weather forecasting can be combined to assess health risks ahead of extreme weather events, rather than during or after the fact.

The ConversationBy fostering collaboration and the integration of the health and climate sectors, we can improve our capacity to respond to the health risks posed by climate change.

Aparna Lal, Research Fellow, Australian National University and Rebecca Colvin, Knowledge Exchange Specialist, Australian National University

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

The Madhouse Effect: this is how climate denial in Australia and the US compares


David Schlosberg, University of Sydney

This article is part of an ongoing series from the Post-Truth Initiative, a Strategic Research Excellence Initiative at the University of Sydney. The series examines today’s post-truth problem in public discourse: the thriving economy of lies, bullshit and propaganda that threatens rational discourse and policy.

The project brings together scholars of media and communications, government and international relations, physics, philosophy, linguistics, and medicine, and is affiliated with the Sydney Social Sciences and Humanities Advanced Research Centre (SSSHARC), the Sydney Environment Institute and the Sydney Democracy Network.


Michael Mann is well known for his classic “hockey stick” work on global warming, for the attacks he has long endured from climate denialists, and for the good fight of communicating the environmental and political realities of climate change.

Mann’s work, including his recent book The Madhouse Effect, has helped me, as a dual US-Australian citizen, think about the similarities and differences between the US and Australia as we respond to what has been called the climate change denial machine.

In both countries, the denialists and distortionists have undermined public knowledge, public policy, new economic development opportunities, and the very value of the environment. Climate policy is being built upon alternative facts, fake news, outright lies, PR spin and industry-written talking points.

From the carbon industry capture of the two major parties, to the Abbott-Turnbull government parroting industry talking points, to coal industry lobbyists as government energy advisers, to the outright idiotic conspiracy pronouncements of senators funded and advised by the US-based denial machine, the Madhouse Effect is in full force in Australia.


Further reading: New coal plants wouldn’t be clean, and would cost billions in taxpayer subsidies


How we can expose and counter this denialist machine? To partly lay out the task, I will discuss three points of contrast between the US and Australia.

Political culture

There is a key difference between the two countries’ political cultures. As much as the denialists have determined Australian energy and climate policy, they have not been as successful, yet, at undermining deep-seeded respect in Australian culture for the common good, for science, for expertise and knowledge.

I left the US at the start of 2011. Living in Arizona, I had experienced the full weight of the racism, the white nationalism, the anti-intellectual, anti-education, anti-fact atmosphere that has since spread all the way to the White House.

I used to tell people I left because Arizona had simply become anti-enlightenment. Folks really didn’t get it, until now, when it is the attitude that rules the country.

Shortly after I arrived in Australia, the then-prime minister, Tony Abbott, led an attack on the work of economist Ross Garnaut. Abbott slammed Garnaut’s 2011 report as anti-democratic. The report had simply pointed out the cost of climate inaction and the viability of putting a price on carbon.

Later, Abbott doubled down and dismissed the quality of Australian economists as a whole. Other denialists went further – Garnaut was called a fascist and was subject to the kind of attacks Mann is well familiar with.

Surprisingly to me, a good part of the public seemed appalled by Abbott’s trashing of an academic. This was seen an attack not just on a carbon price, or a policy recommendation, but on science and knowledge as a whole.

And there was the chief scientist on TV, defending the academy – and that’s when I learned Australia actually had a chief scientist, to whom the media paid attention. This is not something we had in Arizona.

Abbott wound up backing down from the worst of the criticism. The whole series of events illustrated to me, a new Australian, that there is a strong cultural norm here that supports science, that respects expertise and that understands that real knowledge should be used to inform good policy in the public interest.

It wasn’t a one-time event. Last year, when the government fired climate scientists at CSIRO, there was another huge public backlash. The government had to step back a bit, both on the actual science to be done and the radical agenda change away from science for the public good.

And again, when the government wanted to support the dubious work of Bjorn Lomborg, that caused an outcry from both the university sector and the public. Even though the government wound up paying more than A$600,000 on what The Australian called his “vanity book project”, they couldn’t import him and plant him at any Australian university.


Further reading: The Australian Consensus Centre: what are the costs and benefits to UWA?


As Mann says, the main issue in implementing good, sound climate policy is no longer simply the science. The main issue is the cultural understanding of, and respect for the role of science in informing political decisions.

That’s not to say there are no attacks on science – clearly, these continue (such as the recent challenges to normal Bureau of Meteorology practices). But, overall, climate denialists and their enablers are outnumbered outliers in Australia, rather the norm.

The power of the carbon industry

My second point of comparison is not quite as positive.

The problem in Australia is less a culture turning against the Enlightenment, and more the direct political power and influence of the carbon industry. This is most evident not just in our poor emissions and climate policies, but also in the fact the Australian government is hell-bent on sabotaging an entire industrial sector.

I honestly do not understand how the sabotage of the renewables industry in Australia – an all-out attack on a clearly promising and innovative sector – is not treated as a form of industrial treason.

We have had a set of politicians, under the influence of a dying industry, undermining one of the most promising areas of our own economy. They do so for the sole benefit of carbon diggers, at the expense of the rest of Australia, of the next generation and of the planet.

And the justification for this is all based on falsehoods and lies, straight from the PR team of the carbon industry. We hear arguments for energy security, energy poverty and clean coal; we hear that renewables undermine the reliability of the grid. It’s all absolute bullshit.


Further reading: On the origins of environmental bullshit


But, again, even here I think there is some hope. We have seen, over the last few years, an incredible coalition grow – one focused on the end of carbon mining, on protecting communities, on creating real jobs, and on supporting renewables.

Once-unthinkable coalitions of farmers and Aboriginal communities are fighting new mines, new attacks on sacred and fertile land and water.

We have intensive household investment in rooftop solar – and as the feed-in tariffs are undermined, those folks will increasingly invest in battery storage. And we’re finally seeing states move in this direction, with increasing development of utility-scale renewable and storage projects. As hard as the federal government and its allies resist, renewables are growing and the public supports this – even conservative voters.

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This industry will be the innovator, the job creator, the future of this country’s energy system. That is a movement – a transformation – that now seems inevitable even in the face of the carbon industry, its political allies and their outright attacks on innovation.


Further reading: The solar panel and battery revolution: how will your state measure up?


Impacts and adaptation

There is one other important point to make in comparing the US and Australia – and maybe it is the most dire.

All of this talk, about the science, about the power of the denialist machine, about post-truth and the sabotage of renewables, is all about one side of the climate issue: emissions.

The other side, which is crucial to us here in Australia, is how we adapt to the climate change the denialist machine has baked into our future. This nice stable period of the last 10,000 years, the Holocene, in which humanity has evolved, built our cities, our infrastructure, our supply chains, the expectations of our everyday lives – is over.

Climate change means change, and Australia is already facing it in more severe ways than the US.

So adaptation is the next battle, and it must be just. We know who benefits from denialism and the sabotage of renewables. And it is pretty straightforward who will be harmed most if we don’t plan for coming change. We know who dies in heatwaves, for example – the poor, the elderly, those who live alone, those without resources.

This is happening right here. The Rockefeller-funded Resilient Sydney project found that the number one chronic stress is increasing health services demand, which is crucial to resilience in Western Sydney during heatwaves. If we don’t attend to that, vulnerable people will continue to die every time it heats up.


Further reading: How people can best make the transition to cool future cities


Australia needs to face up to adaptation planning on a large scale – rather than cut funds to the good work already being done. We need to focus on giving those most vulnerable to climate change a fair go by looking after their needs first.

One promising step is that the Sydney Environment Institute, with colleagues in Planetary Health and Public Health at the University of Sydney, are establishing a new research hub for NSW OEH on the Health and Social Impacts of Climate Change.

We have also partnered with Resilient Sydney to examine the actual experience of communities in shock events – the impacts on people and how policy responses can be improved. This work is all about adapting to the complex impacts of climate change in fair and just ways.

Overall, then, yes, Australia has industry-led denialists creating a madhouse effect, just as Mann writes about in the US.

But my hope is that we can use our broad political culture of respect for science and for the fair go to resist denialism and the coal profiteers, to implement a post-carbon energy transformation, and adapt fairly and justly to the inevitable changes the denial industry has locked in here.


Michael Mann is taking part in a panel discussion, The Madhouse Effect: What is Stopping Action on Climate Change?, from 6.30-8pm on Wednesday, August 16, as part of the Sydney Science Festival. This article is an edited and revised version of comments given in response to Mann’s February 8 talk on The Madhouse Effect, organised by the University of Sydney’s Sydney Environment Institute.

Michael Mann’s talk about The Madhouse Effect, and the response by David Schlosberg.

You can read other pieces in the post-truth series here.

The ConversationThe Democracy Futures series is a joint global initiative between The Conversation and the Sydney Democracy Network. The project aims to stimulate fresh thinking about the many challenges facing democracies in the 21st century.

David Schlosberg, Professor of Environmental Politics and Co-Director Sydney Environment Institute, University of Sydney

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

Two new books show there’s still no goodbye to messy climate politics


Marc Hudson, University of Manchester

As atmospheric carbon dioxide concentrations rise, so too does the number of books telling us what the consequences are, and what we can do. Two more have been released in the past few weeks – Anna Krien’s brilliant Quarterly Essay The Long Goodbye: Coal, Coral and Australia’s Climate Deadlock, and the worthy Climate Wars by Labor’s shadow environment minister Mark Butler. Both deserve a wide audience.

Krien, author of Into the Woods: The Battle for Tasmania’s Forests has a sharp eye for the right anecdote and a brilliant turn of phrase. Her reportage can be spoken of in the same breath as Elizabeth Kolbert’s seminal Field Notes from a Catastrophe. She has read extensively (I for one was not familiar with the Myxocene – the age of slime) and in researching her latest essay has clocked up thousands of miles as she dives on the Great Barrier Reef and travels inland to areas that will be affected by the proposed coal mine developments in the Galilee Basin.

Krien offers valuable insights into issues such as coal firm Adani’s negotiations with traditional owners, the battles over coal seam gas, and Port Augusta’s rocky transition from coal to – possibly – renewables. She talks to “ordinary” people, weaving their perspectives into the story while not losing sight of the climate deadlock in her title – the ongoing fight within the Liberal and National parties over climate and energy policy.

In one of many telling phrases she writes of the “Stockholm syndrome built on donations, royalties, taxes and threats” that bedevils Australian politics, pointing out that the fate that befell Kevin Rudd still looms large in the collective political memory. In the end, she returns to the Great Barrier Reef, and her final paragraphs pack an emotional punch that will stay with the reader for a long time.

My only quibble with Krien’s fastidious reporting is that, unlike previous Quarterly Essays, there are no footnotes. But maybe that’s only really an issue for nerds like me.

This is Quarterly Essay 66. Number 33 was Guy Pearse’s equally alarming Quarry Vision. In years to come, perhaps Quarterly Essay 99 might explain how we continued not to take action, as the consequences of climate change piled ever higher around us. Or how – alongside unexpected technological breakthroughs – we began finally to race against our nemesis, our own hubris. Time will tell.

Mark Butler is aiming to do something else besides just telling us about climate politics: as a shadow minister he is setting out Labor’s stall for the next federal election, whenever that might be.

Butler was climate minister in Rudd’s second, brief, government. In 2015-16 he undertook extensive consultations with business, community groups, academics and other “stakeholders” (surely everyone in the world is a stakeholder when it comes to the climate?). His book is essentially an extended advert for that process and its outcomes.

Butler’s prose is solid, and occasionally stolid, as he throws fact after report after statistic at the reader. However, he generally seeks to strike a constructive balance between “problem” and “solution”. There are only a few short chapters on the climate policy mess, with the bulk of the book concentrating on what a future Labor government proposes to do about it.

Inevitably, Butler is more critical of his political rivals, the Liberals and the Greens, than of his own party. You wouldn’t know from reading this book that it was Paul Keating’s Labor government who first began to use economic modelling to argue against emissions reductions, or that it was a Labor government who, in 1995, refused to institute a small carbon tax that would fund renewable energy.

Butler is also, oddly, flat-out wrong when he writes that former Labor minister Graham Richardson persuaded Prime Minister Bob Hawke to agree a 20% emissions reduction target before the 1990 federal election. It was actually his colleague Ros Kelly, in October 1990, and the “commitment” was carefully hedged.

These historical details matter, because we need to be able to hold politicians (and even ex-politicians) to account over their climate pledges. But many readers will nevertheless be more interested in what Butler says a Labor government will do, rather than what previous Labor governments didn’t.

Butler obliges, giving us chapters on “Labor’s clean power plan”, “Manufacturing and mining in a low-carbon world”, and “Low-carbon communities”. Occasionally he raises thorny problems (refugees, the coal industry) without really grappling with them. Given the ugly history around these issues (and the political Stockholm Syndrome identified by Krien), this is perhaps unsurprising.

Curiously, both books make a similar omission: they contain very little on the failures of policymakers and social movement organisations in the period from 2006 to 2012. In 2015, at the Labor Party’s national conference, I asked panellists – Butler was one – what had gone wrong during this time, which encompassed Kevin Rudd’s first prime ministership – in light of the fact that we had known about climate change since the late 1980s.

The other panellists gave thoughtful, sometimes self-critical answers. Butler kept schtum. Yet the question is worth asking if we are to avoid history repeating itself, this time as farce. We need smart people – and Krien and Butler are among them – to be asking how citizens can exert sustained pressure on existing governments and to build capacity to keep holding governments’ feet to the fire until they really and truly take climate policy seriously instead of just using it to score points and kill careers.

Ultimately, anyone interested in the future of Australia – and the future of climate policy – should read both of these books carefully. While Krien’s has some immediate use, its greater function will be something we can pull out of a time capsule to explain to young people 20 years hence that we knew exactly what was coming and what we had to do. It will help them understand why we didn’t do it.

The ConversationButler’s book will serve well over the next five years, as citizens try to hold a putative Labor government to its fine (if still inadequate) promises on the great moral challenge of our generation.

Marc Hudson, PhD Candidate, Sustainable Consumption Institute, University of Manchester

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

Can property survive the great climate transition?



File 20170711 5989 eviovx
Property is under threat, physically and conceptually, from climate change.
.Martin./flickr, CC BY-ND

Louise Crabtree, Western Sydney University

This is one of a series of articles to coincide with the 2017 Ecocity World Summit in Melbourne.


As we become an increasingly urban species, urban resilience is emerging as a big deal. The idea is generating a lot of noise about how to develop or retrofit cities that can deal with the many challenges before us, or consume less energy in the transition to post-carbon economies.

There is ample activity aimed at making this happen, including through designing and building ecocities, and calls such as that of the Transition Towns movement, which suggests substantial changes to our ways of life might be both necessary and inevitable.

In all of this, very little has been said about the elephant in the urban living room – property. Property systems are the codification of our relationship to place and the way in which many of us make a claim to place, including a roof over our heads.

If our cities are to become more resilient and sustainable, our systems of property need to come along for the ride.

Static property rights will be tested

Western systems of property law assume property is delineated and static: the property holder has invested (often substantial) financial resources to secure a claim to that neatly identified parcel of land and/or buildings. Further, the property owner expects to make a nice economic return on their parcel.

Unfortunately, the future doesn’t look neatly delineated or static. Many researchers and practitioners tell us the future might not look like anything we’ve ever seen. Some say we are reaching a tipping point, after which the rules we have constructed will no longer apply or be of use.

As some property is washed out to sea, much may become too hot to live in, and what remains may be subject to relentless and increasing waves of migration and instability.

In the face of such calamity, how then might we – as a big, inclusive “we” – talk about and demonstrate our relationship to place? Will we be able to do that without seeing the emergence of metaphorical or actual fortresses?

Models that allow for change

These are live questions. There are no easy answers, but there are places where we might start.

Models such as rolling easements offer one way to handle property that is in flux. Rolling easements are a form of property that recognises that the coast is a dynamic landscape and allows for the coastline of wetlands to migrate inland as sea levels rise.

These sound promising in their capacity to balance private and public interests in property, but their potential has not yet been tested in areas of urban development, such as housing.

Echoing the potential mobility and flexibility of rolling easements are diverse housing tenures that can dislocate the right to reside in place from exclusionary, proprietary title to an individual, speculative housing “asset”.

Examples include housing co-operatives and community land trusts. So far, these have proven effective in delivering a range of affordable and flexible housing options, but still ultimately rely on an understanding that property is static.

So, how might we conceptualise and identify dynamic models of housing that can change with our cities?

Mobility studies are starting to talk about home as mobile and fluid, while resilience theory is recognising the importance of a sense of place. Resilience theory also tells us that complex systems are best governed by collaborative, flexible, learning mechanisms.

The combination of more fluid understandings of home and more sensitive ideas of place may offer a framework for thinking about how we occupy cities through complex challenges and in the face of uncertainty – including how to accommodate the need for mobility and flexibility.

Indigenous inspiration

Living in colonised landscapes tells us it might be time to rethink which way around the “ownership” dynamic works in property relationships.

That is, if we are to think about and create property systems that are as dynamic as the landscapes we occupy, we might need to start thinking about ourselves as belonging to and answerable to the land, not the other way around.

We might also need to start thinking about our claims not being static but dependent on the web of relationships we are entwined in, including with non-humans. Some say that First Peoples might have a grasp of property dynamics that is more suited to the times we are entering.

So, making cities green might be the easy part. It remains to be seen whether property law and property systems are up to the task of transition.


The ConversationYou can read other articles in the series here. The Ecocity World Summit is being hosted by the University of Melbourne, Western Sydney University, the Victorian government and the City of Melbourne in Melbourne from July 12-14.

Louise Crabtree, Senior Research Fellow, Institute for Culture and Society, Western Sydney University

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

Why the climate is more sensitive to carbon dioxide than weather records suggest



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A new paper improves our estimate of the climate’s sensitivity to carbon dioxide.
NASA/Wikimedia Commons

Andrew Glikson, Australian National University

One of the key questions about climate change is the strength of the greenhouse effect. In scientific terms this is described as “climate sensitivity”. It’s defined as the amount Earth’s average temperature will ultimately rise in response to a doubling of atmospheric carbon dioxide levels.

Climate sensitivity has been hard to pin down accurately. Climate models give a range of 1.5-4.5℃ per doubling of CO₂, whereas historical weather observations suggest a smaller range of 1.5-3.0℃ per doubling of CO₂.

In a new study published in Science Advances, Cristian Proistosescu and Peter J. Huybers of Harvard University resolve this discrepancy, by showing that the models are likely to be right.

According to their statistical analysis, historical weather observations reveal only a portion of the planet’s full response to rising CO₂ levels. The true climate sensitivity will only become manifest on a time scale of centuries, due to effects that researchers call “slow climate feedbacks”.

Fast and slow

To understand this, it is important to know precisely what we mean when we talk about climate sensitivity. So-called “equilibrium climate sensitivity”, or slow climate feedbacks, refers to the ultimate consequence of climate response – in other words, the final effects and environmental consequences that a given greenhouse gas concentration will deliver.

These can include long-term climate feedback processes such as ice sheet disintegration with consequent changes in Earth’s surface reflection (albedo), changes to vegetation patterns, and the release of greenhouse gases such as methane from soils, tundra or ocean sediments. These processes can take place on time scales of centuries or more. As such they can only be predicted using climate models based on prehistoric data and paleoclimate evidence.

On the other hand, when greenhouse gas forcing rises at a rate as high as 2–3 parts per million (ppm) of CO₂ per year, as is the case during the past decade or so, the rate of slow feedback processes may be accelerated.

Measurements of atmosphere and marine changes made since the Industrial Revolution (when humans first began the mass release of greenhouse gases) capture mainly the direct warming effects of CO₂, as well as short-term feedbacks such as changes to water vapour and clouds.

A study led by climatologist James Hansen concluded that climate sensitivity is about 3℃ for a doubling of CO₂ when considering only short-term feedbacks. However, it’s potentially as high as 6℃ when considering a final equilibrium involving much of the West and East Antarctic ice melting, if and when global greenhouse levels transcend the 500-700ppm CO₂ range.

This illustrates the problem with using historical weather observations to estimate climate sensitivity – it assumes the response will be linear. In fact, there are factors in the future that can push the curve upwards and increase climate variability, including transient reversals that might interrupt long-term warming. Put simply, temperatures have not yet caught up with the rising greenhouse gas levels.

Prehistoric climate records for the Holocene (10,000-250 years ago), the end of the last ice age roughly 11,700 years ago, and earlier periods such as the Eemian (around 115,000-130,000 years ago) suggest equilibrium climate sensitivities as high as 7.1-8.7℃.

So far we have experienced about 1.1℃ of average global warming since the Industrial Revolution. Over this time atmospheric CO₂ levels have risen from 280ppm to 410ppm – and the equivalent of more than 450ppm after factoring in the effects of all the other greenhouse gases besides CO₂.

Estimate of climate forcing for 1750-2000.
Author provided

Crossing the threshold

Climate change is unlikely to proceed in a linear way. Instead, there is a range of potential thresholds, tipping points, and points of no return that can be crossed during either warming or transient short-lived cooling pauses followed by further warming.

The prehistoric records of the cycles between ice ages, namely intervening warmer “interglacial” periods, reveal several such events, such as the big freeze that suddenly took hold about 12,900 years ago, and the abrupt thaw about 8,200 years ago.

In the prehistoric record, sudden freezing events (called “stadial events”) consistently follow peak interglacial temperatures.

Such events could include the collapse of the Atlantic Mid-Ocean Circulation (AMOC), with consequent widespread freezing associated with influx of extensive ice melt from the Greenland and other polar ice sheets. The influx of cold ice-melt water would abort the warm salt-rich AMOC, leading to regional cooling such as is recorded following each temperature peak during previous interglacial periods.

Over the past few years cold water pools south of Greenland have indicated such cooling of the North Atlantic Ocean. The current rate of global warming could potentially trigger the AMOC to collapse.

A collapse of the AMOC, which climate “sceptics” would no doubt welcome as “evidence of global cooling”, would represent a highly disruptive transient event that would damage agriculture, particularly in the Northern Hemisphere. Because of the cumulative build-up of greenhouse gases in the atmosphere such a cool pause is bound to be followed by resumed heating, consistent with IPCC projections.

The growth in the cold water region south of Greenland, heralding a possible collapse of the Atlantic Mid-Ocean Circulation.
Author provided

Humanity’s release of greenhouse gases is unprecedented in speed and scale. But if we look far enough back in time we can get some clues as to what to expect. Around 56 million years ago, Earth experienced warming by 5-8℃ lasting several millennia, after a sudden release of methane-triggered feedbacks that caused the CO₂ level rise to around 1,800ppm.

The ConversationYet even that sudden rise of CO₂ levels was lower by a large factor than the current CO₂ rise rate of 2-3ppm per year. At this rate, unprecedented in Earth’s recorded history of the past 65 million years (with the exception of the consequences of asteroid impacts), the climate may be entering truly uncharted territory.

Andrew Glikson, Earth and paleo-climate scientist, Australian National University

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