Scientists still don’t know how far melting in Antarctica will go – or the sea level rise it will unleash


Chen Zhao, University of Tasmania and Rupert Gladstone, University of LaplandThe Antarctic ice sheet is the largest mass of ice in the world, holding around 60% of the world’s fresh water. If it all melted, global average sea levels would rise by 58 metres. But scientists are grappling with exactly how global warming will affect this great ice sheet.

This knowledge gap was reflected in the latest report from the Intergovernmental Panel on Climate Change (IPCC). It contains projections from models in which important processes affecting the ice sheets, known as feedbacks and tipping points, are absent because scientific understanding is lacking.

Projected sea level rise will have widespread effects in Australia and around the world. But current projections of ice sheet melt are so wide that developing ways for societies to adapt will be incredibly expensive and difficult.

If the world is to effectively adapt to sea level rise with minimal cost, we must quickly address the uncertainty surrounding Antarctica’s melting ice sheet. This requires significant investment in scientific capacity.

Tourists photograph beachside homes damaged by storm
Australia is vulnerable to sea level rise and associated storm surge, such as this scene at a Sydney beach in 2016.
David Moir/AAP

The great unknown

Ice loss from the Antarctic and Greenland ice sheets was the largest contributor to sea level rise in recent decades. Even if all greenhouse gas emissions ceased today, the heat already in the ocean and atmosphere would cause substantial ice loss and a corresponding rise in sea levels. But exactly how much, and how fast, remains unclear.

Scientific understanding of ice sheet processes, and of the variability of the forces that affect ice sheets, is incredibly limited. This is largely because much of the ice sheets are in very remote and harsh environments, and so difficult to access.

This lack of information is one of the main sources of uncertainty in the models used to estimate ice mass loss.

At the moment, quantifying how much the Greenland and Antarctic ice sheets will contribute to sea level rise primarily involves an international scientific collaboration known as the “Ice Sheet Model Intercomparison Project for CMIP6”, or ISMIP6, of which we are part.

The project includes experts in ice sheet and climate modelling and observations. It produces computer simulations of what might happen if the polar regions melt under different climate scenarios, to improve projections of sea level rise.

The project also investigates ice sheet–climate feedbacks. In other words, it looks at how processes in the oceans and atmosphere will affect the Antarctic and Greenland ice sheets, including whether the changes might cause them to collapse – leading to large and sudden increases in sea level.




Read more:
Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month


a melting glacier
Ice loss from sheets in Antarctic and Greenland were the biggest contributor to sea-level rise in recent decades.
John McConnico/AP

Melting from below

Research has identified so-called “basal melt” as the most significant driver of Antarctic ice loss. Basal melt refers to the melting of ice shelves from underneath, and in the case of Antarctica, interactions with the ocean are thought to be the main cause. But gathering scientific observations beneath ice shelves is a major logistical challenge, leading to a dearth of data about this phenomenon.

This and other constraints mean the rate of progress in ice sheet modelling has been insufficient to date, and so active ice sheet models are not included in climate models.

Scientists must instead make projections using the ice sheet models in isolation. This hinders scientific attempts to accurately simulate the feedback between ice and climate.

For example, it creates much uncertainty in how the interaction between the ocean and the ice shelf will affect ice mass loss, and how the very cold, fresh meltwater will make its way back to global oceans and cause sea level rise, and potentially disrupt currents.

Despite the uncertainties ISMIP6 is dealing with, it has published a series of recent research including a key paper published in Nature in May. This found if the world met the Paris Agreement target of limiting global warming to 1.5℃ this century, land ice melt would cause global sea level rise of about 13cm by 2100, in the most optimistic scenario. This is compared to a rise of 25cm under the world’s current emissions-reduction pledges.

The study also outlines a pessimistic, but still plausible, basal melt scenario for Antarctica in which sea levels could be five times higher than in the main scenarios.

The breadth of such findings underpinned sea level projections in the latest IPCC report. The Antarctic ice sheet once again represented the greatest source of uncertainty in these projections.

The below graph shows the IPCC’s latest sea level projections. The shaded area reflects the large uncertainties in models using the same basic data sets and approaches. The dotted line reflects deep uncertainty about tipping points and thresholds in ice sheet stability.

IPCC reports are intended to guide global policy-makers in coming years and decades. But the uncertainties about ice melt from Antarctica limit the usefulness of projections by the IPCC and others.




Read more:
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The IPCC’s projections for global average sea level change in metres, relative to 1900.
IPCC

Dealing with uncertainty

Future sea level rise poses big challenges such as human displacement, infrastructure loss, interference with agriculture, a potential influx of climate refugees, and coastal habitat degradation.

It’s crucial that ice sheet models are improved, tested robustly against real-world observations, then integrated into the next generation of international climate models – including those being developed in Australia.

International collaborations such as NECKLACE and RISE are seeking to coordinate international effort between models and observations. Significant investment across these projects is needed.

Sea levels will continue rising in the coming decades and centuries. Ice sheet projections must be narrowed down to ensure current and future generations can adapt safely and efficiently.


The authors would like to acknowledge the contributions of Dr Ben Galton-Fenzi, Dr Rupert Gladstone, Dr Thomas Zwinger and David Reilly to the research from which this article draws.The Conversation

Chen Zhao, Research associate, University of Tasmania and Rupert Gladstone, Adjunct professor, University of Lapland

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

How much will our oceans warm and cause sea levels to rise this century? We’ve just improved our estimate


Jakob Weis, University of Tasmania, Author provided

Kewei Lyu, CSIRO; John Church, UNSW, and Xuebin Zhang, CSIROKnowing how much sea levels are likely to rise during this century is vital to our understanding of future climate change, but previous estimates have generated wide ranges of uncertainty. In our research, published today in Nature Climate Change, we provide an improved estimate of how much our oceans are going to warm and its contribution to sea level rise, with the help of 15 years’ worth of measurements collected by a global array of autonomous underwater sampling floats.

Our analysis shows that without dramatic reductions in greenhouse gas emissions, by the end of this century the upper 2,000 metres of the ocean is likely to warm by 11-15 times the amount of warming observed during 2005-19. Water expands as it gets warmer, so this warming will cause sea levels to rise by 17-26 centimetres. This is about one-third of the total projected rise, alongside contributions from deep ocean warming, and melting of glaciers and polar ice sheets.

Ocean warming is a direct consequence of rising greenhouse gas concentrations in the atmosphere as a result of our burning of fossil fuels. This results in an imbalance between the energy arriving from the Sun, and the energy radiated out into space. About 90% of the excess heat energy in the climate system over the past 50 years is stored in the ocean, and only about 1% in the warming atmosphere.

Warming oceans cause sea levels to rise, both directly via heat expansion, and indirectly through melting of ice shelves. Warming oceans also affect marine ecosystems, for example through coral bleaching, and play a role in weather events such as the formation of tropical cyclones.

Systematic observations of ocean temperatures began in the 19th century, but it was only in the second half of the 20th century that enough observations were made to measure ocean heat content consistently around the globe.

Since the 1970s these observations indicate an increase in ocean heat content. But these measurements have significant uncertainties because the observations have been relatively sparse, particularly in the southern hemisphere and at depths below 700m.

To improve this situation, the Argo project has deployed a fleet of autonomous profiling floats to collect data from around the world. Since the early 2000s, they have measured temperatures in the upper 2,000m of the oceans, and sent the data via satellite to analysis centres around the world.

These data are of uniform high quality and cover the vast majority of the open oceans. As a result, we have been able to calculate a much better estimate of the amount of heat accumulating in the world’s oceans.

Global distribution of Argo floats.
Argo project

The global ocean heat content continued to increase unabated during the temporary slowdown in global surface warming in the beginning of this century. This is because ocean warming is less affected than surface warming by natural yearly fluctuations in climate.




Read more:
Ocean depths heating steadily despite global warming ‘pause’


Current observations, future warming

To estimate future ocean warming, we need to take the Argo observations as a basis and then use climate models to project them into the future. But to do that, we need to know which models are in closest agreement with new, more accurate direct measurements of ocean heat provided by the Argo data.

The latest climate models, used in last month’s landmark report by the Intergovernmental Panel on Climate Change, all show ocean warming over the period of available Argo observations, and they project that warming will continue in the future, albeit with a wide range of uncertainties.

Ocean warming magnitudes from latest climate model simulations and Argo observations.




Read more:
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By comparing the Argo temperature data for 2005-19 with the simulations generated by models for that period, we used a statistical approach called “emergent constraint” to reduce uncertainties in model future projections, based on information about the ocean warming we know has already occurred. These constrained projections then provided an improved estimate of how much heat energy will accumulate in the oceans by the end of the century.

By 2081–2100, under a scenario in which global greenhouse emissions continue on their current high trajectory, we found the upper 2,000m of the ocean is likely to warm by 11-15 times the amount of warming observed during 2005-19. This corresponds to 17–26cm of sea level rise from ocean thermal expansion.

Climate models can also make predictions based on a range of different future greenhouse gas emissions. Strong emissions reductions, consistent with bringing surface global warming to within about 2℃ of pre-industrial temperatures, would reduce the projected warming in the upper 2,000m of the ocean by about half — that is, between five and nine times the ocean warming already seen in 2005-19.

This would equate to 8-14cm of sea level rise due to thermal expansion. Of course, reducing emissions so as to hit the more ambitious Paris target of 1.5℃ surface warming would reduce these impacts even further.

Other factors linked to sea levels

There are several other factors that will also drive up sea levels, besides the heat influx into the upper oceans investigated by our research. There is also warming of the deep ocean below 2,000m, which is still under-sampled in the current observing system, as well as the effects of melting from glaciers and polar ice sheets.

This indicates that even with strong policy action to reduce greenhouse gas emissions, the oceans will continue to warm and sea levels will continue to rise well after surface warming is stabilised, but at a much reduced rate, making it easier to adapt to the remaining changes. Cutting greenhouse gas emissions earlier rather than later will be more effective at slowing ocean warming and sea level rise.




Read more:
If we stopped emitting greenhouse gases right now, would we stop climate change?


Our improved projection is founded on a network of ocean observations that are far more extensive and reliable than anything available before. Sustaining the ocean observing system into the future, and extending it to the deep ocean and to areas not covered by the present Argo program, will allow us to make more reliable climate projections in the future.The Conversation

Kewei Lyu, Postdoctoral Researcher in Ocean and Climate, CSIRO; John Church, Chair Professor, Climate Change Research Centre, UNSW, and Xuebin Zhang, Principal Research Scientist, CSIRO

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

‘How high above sea level am I?’ If you’ve googled this, you’re likely asking the wrong question — an expert explains


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Shayne McGregor, Monash University; Nerilie Abram, Australian National University, and Ruth Reef, Monash UniversityThe latest report from the United Nations Intergovernmental Panel on Climate Change is confronting. It finds global mean sea levels rose by about 20 centimetres between 1901 and 2018. In fact, sea levels have risen faster over the last hundred years than any time in the last 3,000 years.

This acceleration is expected to continue. A further 15-25cm of sea level rise is expected by 2050, with little sensitivity to greenhouse gas emissions between now and then. Beyond 2050, however, the amount of sea level rise will largely depend on our future emissions.

In a low-emissions scenario, we can expect sea levels to rise to about 38cm above the 1995–2014 average by the year 2100. In a high-emissions scenario this is expected to more than double to 77cm.

In either case, who will feel the effects of sea level rise? And how much does your location’s height above sea level really matter? It’s a question a lot of you have been googling since the report’s release. But the answer isn’t straightforward.




Read more:
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Sea level rise isn’t uniform

Since satellites began measuring sea surface height almost three decades ago we have learned sea level rise is not uniform across the globe.

The map on the left in this video shows daily sea level variations since 1993, while the curve on the right shows the month-by-month global mean sea level.

In fact, sea levels can vary quite substantially on a year-to-year and decade-to-decade basis. However, we know much of this regional variability is driven by surface wind changes — and will typically decrease over long periods.

So while the IPCC report’s projections are for global mean sea level for the year 2100, most coastal locations will experience a sea level rise within 20% of the projections (which are subject to change beyond 2050 depending on global emissions).

Flood zones and drainage

Elevation above the high tide is an important factor in determining how at risk a particular location is of experiencing flooding due to sea level rise.

In low elevation coastal zones, physical distance to the coast and certain topographic features in the area such as sand dunes, wetlands and human built structures like levies and flood walls can act as a buffer to sea level rise.

That said, current and projected sea level rise may still pose a significant risk to regions with these buffers, as there are many ways by which sea level rise can lead to flooding.

For instance, as sea levels rise water from the sea can inundate storm water drainage systems and end up flooding inland regions with elevations below (or which will eventually be below) sea level. This is because drainage largely depends on gravity, and some storm water systems don’t have flood gates to stop water entering from the ocean.

Here we see Bobbin Head in NSW flood during a king tide. This problem will become more pronounced as sea levels rise and will require clever engineering solutions, such as drainage pumps to push water back out to sea.

There are also cases where man-made features intended to help protect people from sea level impacts can be breached, resulting in flooding. One prominent example was the New Orleans flooding that occurred during Hurricane Katrina, when the man-made flood levee system suffered many failures

The tidal range around Australia varies from less than 1m in some parts such as southwest Australia, to more than 8m in other parts such as the northwest.

The tidal range in an area determines how quickly flooding impacts will increase as sea levels rise. If two regions have the same elevation, as the high tide rises past the regions’ elevation, the region with a smaller tidal range will likely struggle with more flooding and for longer than the region with a larger tidal range.

Beach erosion increases risk

Yet all of the above hasn’t considered the fact our beaches are naturally mobile systems which respond to change. This is why the relationship between an assets elevation above the high tide mark and risk of flooding is less straightforward at low elevation coastal zones — where 11% of Australia’s population lives.

When sea levels rise, the shape of the coastline changes with it and can move inland to a great extent. If sea levels rise by 1m, the coast can erode inland by 1km or more. This can potentially create risk for properties even if they are currently above the height of the projected sea level rise.

Australia has many retreating coastlines, often forming striking erosional landforms such as The Great Ocean Road region.




Read more:
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However, the response of the coastline can also be moderated by natural and human factors. In some regions, coastal elevation is actually increasing due to sediment being deposited, or tectonic uplift raising the coast as fast (or even faster) than rising sea levels.

In Australia, this is especially pronounced in estuaries with a riverine supply of sediments and where vegetation such as mangroves, saltmarshes and dune vegetation help collect sediment in their root systems.

We know sea level rise is with us for the long haul. And it’s now inevitable we will have to adapt to changes along our coasts. We’re already using a number of approaches to counteract projected sea level rise in Australia, including:

  • sand renourishment of beaches
  • the formation of more seagrass, saltmarsh and mangrove habitats
  • construction of seawalls and other hard coastal protection measures.

But it’s important to note we still have a choice for how much and how quickly sea levels will rise beyond 2050. So perhaps, instead of googling your current elevation, a more pragmatic approach would be to think of what you can do to help protect your own coasts and reduce your carbon footprint.The Conversation

Shayne McGregor, Associate professor, Monash University; Nerilie Abram, Chief Investigator for the ARC Centre of Excellence for Climate Extremes; Deputy Director for the Australian Centre for Excellence in Antarctic Science, Australian National University, and Ruth Reef, Associate Professor, School of Earth Atmosphere and Environment, Monash University

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

Rising seas and melting glaciers: these changes are now irreversible, but we have to act to slow them down


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Nick Golledge, Te Herenga Waka — Victoria University of Wellington

After three years of writing and two weeks of virtual negotiations to approve the final wording, the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) confirms that changes are happening in Earth’s climate across every continent and every ocean.

My contribution was as one of 15 lead authors to a chapter about the oceans, the world’s icescapes and sea level change — and this is where we are now observing changes that have become irreversible over centuries, and even millennia.


Read more: This is the most sobering report card yet on climate change and Earth’s future. Here’s what you need to know


Overall, the world is now 1.09℃ warmer than it was during the period between 1850 and 1900. The assessment shows the ocean surface has warmed slightly less, by about 0.9℃ as a global average, than the land surface since 1850, but about two-thirds of the ocean warming has taken place during the last 50 years.

Underwater canyon in the Pacific ocean.
The world’s oceans are warming and acidifying. Shutterstock/Damsea

We concluded that it is virtually certain the heat content of the ocean will continue to increase for the rest of the current century, and will likely continue until at least 2300, even under low-emissions scenarios.

We also concluded that carbon dioxide emissions are the main driver of acidification in the open ocean and that this has been increasing faster than any time in at least 26,000 years.

We can also say with high confidence that oxygen levels have dropped in many ocean regions since the mid-20th century and that marine heatwaves have doubled in frequency since 1980, also becoming longer and more intense.

Past greenhouse gas emissions, since 1750, mean we are now committed to future ocean warming throughout this century. The rate of change depends on our future emissions, but the process itself is now irreversible on centennial to millennial time scales.

Glacier calving on the Antarctic Peninsula.
A warming ocean is melting ice from below in West Antarctica. Shutterstock/Steve Allen

Ice loss in Antarctica

All this heat is bad news for the area I work in: Antarctica. With a warming ocean, the Antarctic ice sheet is left vulnerable to melting because so much of it rests on bedrock below sea level.

As the ocean warms and the ice sheet melts, sea level goes up around the world. We have very high confidence that the ice lost from West Antarctica in recent decades has exceeded any gain in mass from snowfall. We are also confident this loss has largely been due to increased melting of ice below sea level, driven by warming ocean water.

 

 

 

This melting has allowed the acceleration and thinning of grounded ice further inland — and this is what contributes to sea level rise. On the other side of the world, the Greenland ice sheet has also been losing mass over recent decades, but in Greenland this is principally due to warmer air, rather than warming ocean water.


Read more: If warming exceeds 2°C, Antarctica’s melting ice sheets could raise seas 20 metres in coming centuries


It is virtually certain that the melting of the two great ice sheets, in Greenland and Antarctica, as well as the many thousands of glaciers around the world, will continue to raise sea levels globally for the rest of the current century.

By 2100, we project global mean sea level to be between 0.4m (for the lowest emission scenario, in which CO₂ emissions would have to drop to net zero by 2050) and 0.8m (for the highest emissions scenario) above the 1995–2014 average. How high the seas rise this century clearly depends on how much and how quickly we manage to cut greenhouse gas emissions.

The time to act is now

There are processes at play which we still cannot fully capture in computer models, mostly because they take place over periods of time longer than we have direct (satellite-based) observations for. In Antarctica, some of these uncertain processes could greatly accelerate the loss of ice, and potentially add one metre to the projected sea level by 2100.

Whether or not this worst-case scenario plays out or not remains uncertain, but what is increasingly beyond doubt is that global mean sea level will continue to rise for centuries to come. The magnitude of this depends very much on the extent to which we are able, collectively, to reduce greenhouse gas emissions right now.

Ocean ways against a coastal city.
Globally, the seas will continue to rise for centuries to come. Shutterstock/JivkoM

The scientific updates in our AR6 chapter are in line with those from previous assessments. That’s encouraging, because every assessment report brings in new authors with different expertise. The fact the scientific conclusions remain consistent reflects the overwhelming agreement within the global scientific community.

For our chapter, we have assessed 1500 research papers, but across the entire AR6, over 14,000 publications were considered, with an emphasis on recent research that hasn’t been assessed in previous IPCC reports.

The report has been scrutinised carefully at every stage of its evolution, attracting nearly 80,000 individual review comments from experts all over the world. Every single comment had to be addressed by the author team, with written responses provided and any changes to the text carefully noted and tracked.

What changes with each assessment is the clarity of the trends we are observing, and the increasing urgency with which we must act. While some aspects of AR6 are new, the underlying message remains the same. The longer we wait, the more devastating the consequences.

Click here to read more of The Conversation’s coverage of the IPCC reportThe Conversation

Nick Golledge, Professor of Glaciology, Te Herenga Waka — Victoria University of Wellington

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

Managed retreat of settlements remains a tough call even as homes flood and coasts erode


Tayanah O’Donnell, Australian National UniversityIt is no joke that New South Wales residents are in the midst of their fourth “one in 100 year” event since January 2020. Much of the Australian east coast continues to experience heavy rainfall, strong winds and abnormally high tides. All will make the current floods worse.

As climate tipping points are reached and the Earth’s systems begin to buckle under the strain, the need for considered adaptation strategies is overwhelmingly clear. One of these strategies is for human settlements to retreat from areas most at risk, whether from floods or bushfires. While something needs to be done to ensure future generations do not suffer catastrophic consequences, managed retreat is a complex tool.

These strategic decisions in the next five to ten years will be challenging. And these decisions really matter: where and how do we build residential areas that can cope with a climate-changed world?




Read more:
Yes, Australia is a land of flooding rains. But climate change could be making it worse


What is managed retreat?

Managed retreat can be defined as “purposeful, co-ordinated movement of people and assets out of harm’s way”. Managed retreat more often refers to the retreat of existing development out of harm’s way. Planned retreat is usually the preferred phrasing for new development that is planned for possible future relocation.

Both planned and managed retreat are focused on the permanent relocation of people and assets, as opposed to the evacuations we are seeing now.

Managed retreat is experiencing a resurgence in scientific literature as the impacts of climate change become increasingly frequent, severe and more obvious. These impacts bring with them a recognition of the need for adaptation even as we urgently reduce greenhouse gas emissions.

Of course, relocating away from high-risk locations is not an entirely new concept. However, managed retreat in response to a changing climate is not only complex, but also has a lot of political baggage. The complexity spans legal, financial, cultural and logistical factors among others: the political baggage seemingly associated with effective climate action in Australia often hinders governments’ abilities to respond properly.

Societies around the world need to grapple with the reality that managed retreat will become a suite of tools to respond to crisis. Insurers will not always be available, and the costs to governments (and therefore to you, the taxpayer) of responding to increasing rates of disasters, irrespective of insurance, will continue to grow exponentially.




Read more:
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Responding to events after the fact is an unsustainable model of adaptation. There is, too, a need to acknowledge settlement needs and historical built environment legacies that have put significant state infrastructure in harm’s way.

Managing difficult trade-offs

We know trade-offs need to be made between what we protect and what we let go in suburban floodplain areas.

Legal machanisms to force people and assets to move can and must be thoughtful. The implementation of managed retreat in urbanised areas faces multiple hurdles. These include:




Read more:
Coastal law shift from property rights to climate adaptation is a landmark reform


It is wrong to see managed retreat as the panacea for climate risk and development in vulnerable locations. In many cases, once development is in place, it can be more appealing to some to protect an at-risk area rather than work towards managed retreat. Even where managed retreat has been successful, as in the case of the flood-prone township of Grantham, it was not without pain.

There are also other, more basic needs, such as having land available where people can relocate.

Working out highest and best use of land

There are ways that land can be used for its highest and best use at a point in time. For example, tools like easements can enable vulnerable land to be used, subject to event-based or time-based trigger-point thresholds. Once these thresholds are reached, the land is put to some other use. The advantage of these machanisms, especially for new development, is that owners are clear about the risks from the start.

This still leaves us with hard decisions about responding to at-risk current developments. Putting off these hard decisions and leaving them for future decision-makers will result in a huge injustice, because there will be catastrophe as Earth’s tipping points are passed. Development decisions made now will determine the impacts on our children and grandchildren.

Urban development decisions for both new and existing development in this coming decade demand courage and leadership. If we accept that Australian cities will continue to expand and increase in density, then we have some serious questions to ask ourselves. What kind of future do we want?

Some areas should simply not be developed.




Read more:
‘Climigration’: when communities must move because of climate change


There is a risk that an over-reliance on managed retreat will over-simplify the challenge of working out what to do about development in at-risk locations. There is a clear need to separate out what to do about current and past developments, and how to approach new developments.

The latter is easy – do not rebuild residential homes in at-risk areas. Governments should repurpose these zones for uses that permit nature-based solutions to the need to adapt to climate change.

Current development is much more complex. In some cases, managed retreat – done thoughtfully and considerately – will be the only option.The Conversation

Tayanah O’Donnell, Honorary Senior Lecturer, Australian National University

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

Worried about Earth’s future? Well, the outlook is worse than even scientists can grasp



Daniel Mariuz/AAP

Corey J. A. Bradshaw, Flinders University; Daniel T. Blumstein, University of California, Los Angeles, and Paul Ehrlich, Stanford University

Anyone with even a passing interest in the global environment knows all is not well. But just how bad is the situation? Our new paper shows the outlook for life on Earth is more dire than is generally understood.

The research published today reviews more than 150 studies to produce a stark summary of the state of the natural world. We outline the likely future trends in biodiversity decline, mass extinction, climate disruption and planetary toxification. We clarify the gravity of the human predicament and provide a timely snapshot of the crises that must be addressed now.

The problems, all tied to human consumption and population growth, will almost certainly worsen over coming decades. The damage will be felt for centuries and threatens the survival of all species, including our own.

Our paper was authored by 17 leading scientists, including those from Flinders University, Stanford University and the University of California, Los Angeles. Our message might not be popular, and indeed is frightening. But scientists must be candid and accurate if humanity is to understand the enormity of the challenges we face.

Girl in breathing mask attached ot plant in container
Humanity must come to terms with the future we and future generations face.
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Getting to grips with the problem

First, we reviewed the extent to which experts grasp the scale of the threats to the biosphere and its lifeforms, including humanity. Alarmingly, the research shows future environmental conditions will be far more dangerous than experts currently believe.

This is largely because academics tend to specialise in one discipline, which means they’re in many cases unfamiliar with the complex system in which planetary-scale problems — and their potential solutions — exist.

What’s more, positive change can be impeded by governments rejecting or ignoring scientific advice, and ignorance of human behaviour by both technical experts and policymakers.

More broadly, the human optimism bias – thinking bad things are more likely to befall others than yourself – means many people underestimate the environmental crisis.

Numbers don’t lie

Our research also reviewed the current state of the global environment. While the problems are too numerous to cover in full here, they include:

  • a halving of vegetation biomass since the agricultural revolution around 11,000 years ago. Overall, humans have altered almost two-thirds of Earth’s land surface

  • About 1,300 documented species extinctions over the past 500 years, with many more unrecorded. More broadly, population sizes of animal species have declined by more than two-thirds over the last 50 years, suggesting more extinctions are imminent




Read more:
What is a ‘mass extinction’ and are we in one now?


  • about one million plant and animal species globally threatened with extinction. The combined mass of wild mammals today is less than one-quarter the mass before humans started colonising the planet. Insects are also disappearing rapidly in many regions

  • 85% of the global wetland area lost in 300 years, and more than 65% of the oceans compromised to some extent by humans

  • a halving of live coral cover on reefs in less than 200 years and a decrease in seagrass extent by 10% per decade over the last century. About 40% of kelp forests have declined in abundance, and the number of large predatory fishes is fewer than 30% of that a century ago.

State of the Earth's environment
Major environmental-change categories expressed as a percentage relative to intact baseline. Red indicates percentage of category damaged, lost or otherwise affected; blue indicates percentage intact, remaining or unaffected.
Frontiers in Conservation Science

A bad situation only getting worse

The human population has reached 7.8 billion – double what it was in 1970 – and is set to reach about 10 billion by 2050. More people equals more food insecurity, soil degradation, plastic pollution and biodiversity loss.

High population densities make pandemics more likely. They also drive overcrowding, unemployment, housing shortages and deteriorating infrastructure, and can spark conflicts leading to insurrections, terrorism, and war.




Read more:
Climate explained: why we need to focus on increased consumption as much as population growth


Essentially, humans have created an ecological Ponzi scheme. Consumption, as a percentage of Earth’s capacity to regenerate itself, has grown from 73% in 1960 to more than 170% today.

High-consuming countries like Australia, Canada and the US use multiple units of fossil-fuel energy to produce one energy unit of food. Energy consumption will therefore increase in the near future, especially as the global middle class grows.

Then there’s climate change. Humanity has already exceeded global warming of 1°C this century, and will almost assuredly exceed 1.5 °C between 2030 and 2052. Even if all nations party to the Paris Agreement ratify their commitments, warming would still reach between 2.6°C and 3.1°C by 2100.

people walking on a crowded street
The human population is set to reach 10 billion by 2050.
Shutterstock

The danger of political impotence

Our paper found global policymaking falls far short of addressing these existential threats. Securing Earth’s future requires prudent, long-term decisions. However this is impeded by short-term interests, and an economic system that concentrates wealth among a few individuals.

Right-wing populist leaders with anti-environment agendas are on the rise, and in many countries, environmental protest groups have been labelled “terrorists”. Environmentalism has become weaponised as a political ideology, rather than properly viewed as a universal mode of self-preservation.

Financed disinformation campaigns against climate action and forest protection, for example, protect short-term profits and claim meaningful environmental action is too costly – while ignoring the broader cost of not acting. By and large, it appears unlikely business investments will shift at sufficient scale to avoid environmental catastrophe.

Changing course

Fundamental change is required to avoid this ghastly future. Specifically, we and many others suggest:

  • abolishing the goal of perpetual economic growth

  • revealing the true cost of products and activities by forcing those who damage the environment to pay for its restoration, such as through carbon pricing

  • rapidly eliminating fossil fuels

  • regulating markets by curtailing monopolisation and limiting undue corporate influence on policy

  • reigning in corporate lobbying of political representatives

  • educating and empowering women across the globe, including giving them control over family planning.

A coal plant
The true cost of environmental damage should be borne by those responsible.
Shutterstock

Don’t look away

Many organisations and individuals are devoted to achieving these aims. However their messages have not sufficiently penetrated the policy, economic, political and academic realms to make much difference.

Failing to acknowledge the magnitude and gravity of problems facing humanity is not just naïve, it’s dangerous. And science has a big role to play here.

Scientists must not sugarcoat the overwhelming challenges ahead. Instead, they should tell it like it is. Anything else is at best misleading, and at worst potentially lethal for the human enterprise.




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Mass extinctions and climate change: why the speed of rising greenhouse gases matters


The Conversation


Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University; Daniel T. Blumstein, Professor in the Department of Ecology and Evolutionary Biology and the Institute of the Environment and Sustainability, University of California, Los Angeles, and Paul Ehrlich, President, Center for Conservation Biology, Bing Professor of Population Studies, Stanford University

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

Pacific Islands must stop relying on foreign aid to adapt to climate change, because the money won’t last



Patrick Nunn, Author provided

Patrick D. Nunn, University of the Sunshine Coast and Roselyn Kumar, University of the Sunshine Coast

The storm of climate change is approaching the Pacific Islands. Its likely impact has been hugely amplified by decades of global inertia and the islands’ growing dependency on developed countries.

The background to this situation is straightforward. For a long time, richer developed countries have been underwriting the costs of climate change in poorer developing countries, leaving them reliant on Western solutions to their climate-related issues.




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But as rising sea water continues to encroach on these low-lying Pacific islands, inundating infrastructure and even cemeteries, it’s clear almost every externally sponsored attempt at climate adaptation has failed here.

And as the costs of adaptation in richer countries escalate, this funding support to developing countries will likely taper out in future.

We’ve researched climate change adaptation in the Pacific for more than 50 years. We argue this trend is not merely unsustainable, but also dangerous. Pacific Island nations must start drawing from traditional knowledge to adapt to climate change, rather than continue to rely on foreign funds.

The ruins of a sea wall on a coastline.
High waves destroyed this sea wall on Majuro Atoll (Marshall Islands).
Patrick Nunn, Author provided

Western solutions don’t always work

On a global scale, climate adaptation strategies have largely been either ineffective or unsustainable.

This is especially the case in non-Western contexts, where Western science continues to be privileged. In the Pacific Islands, this is often because these Western strategies invariably subordinate, even ignore, funding recipients’ culturally grounded worldviews.

A good example is the desire of foreign donors to build hard structures, such as sea walls, to protect eroding coasts. This is the preferred strategy in richer nations.

However it does not embrace nature-based solutions such as replanting coastal mangroves, which can be more readily sustained in poorer contexts.

A likely scenario

The availability of external financial assistance means developing countries have become more dependent on their richer counterparts for climate change adaptation.

For example, between 2016 and 2019, Australia provided A$300 million to help Pacific Island nations adapt to climate change, committing to a further $500 million to 2025. This left little need or incentive for these countries to fund their own adaptation needs.




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But imagine this climate change scenario. Ten years from now, unprecedented rainfall is dumped on Australia’s east coast over a prolonged period. Several cities become flooded and remain so for weeks.

In the aftermath, the Australian government scrambles to make recently flooded areas liveable once more. They build a series of massive coastal dikes – structures to prevent the rising sea from flooding populated areas.

The cost is exorbitant and unanticipated – like COVID-19 – so the government will look for ways to shuffle money around. This may well include reducing financial aid for climate change adaptation in poorer countries.

Plunging international aid

Economic modelling shows nations will incur massive costs this century to adapt to climate change within their own borders. So it’s almost inevitable wealthier countries will rethink the extent of their assistance to the developing world.

A chart showing the projected adaptation aid to the Pacific Islands.
Recent and projected Australian GDP and adaptation aid to Pacific Island.
countries.

Patrick Nunn, Author provided

In fact, even before the pandemic, Australia’s foreign aid budget was projected to decrease in real terms by nearly 12% from 2020 to 2023.

These factors do not bode well for developing countries, which will be facing higher climate adaptation costs and dwindling foreign aid assistance.




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Building autonomy with ‘cashless adaptation’

Leaders of developing countries should anticipate this situation now, and reverse their growing dependence on outside assistance.

For example, rural communities in regions like the Pacific Islands could revive their use of “cashless adaptation”. This means developing ways of adapting livelihoods to climate change that cost nothing.

These methods include the intentional planting of surplus crops, the use of traditional methods of food preservation and water storage, the use of free locally-available materials and labour for constructing sea defences. And it perhaps even includes the recognition that living along coastal fringes exposes you unnecessarily to weather-related change.

Prior to globalisation, this is how it was for decades, even centuries, in places like the rural Pacific islands. Then, adaptation to a changing environment was sustained by cooperation with one another and the use of freely available materials, not with cash.

Researchers have also argued for such “looking forward to the past” strategies regarding Hawaii’s climate adaptation.

And research from last year in Fiji showed more rural communities still have and use a stock of traditional methods for anticipating and withstanding disasters, such as flood and drought.




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We can take this argument further. Perhaps it’s time for Pacific Island nations to rediscover traditional medicines, at least for primary health care, to supplement western medicine.

Greater production and consumption of locally grown foods, over imported foods, is also an important and valuable transformation.

The future of the developing world

A hut with a large pointed roof, built with local materials.
Dirak faluw (‘men’s house’) at Wanyaan Village on Yap (Micronesia) was.
constructed by community labour using local-available materials.

Roselyn Kumar, Author provided

The need for nations to adapt to unanticipated phenomena like climate change and COVID-19 encourages de-globalisation – including that countries depend less on cross-border aid and economic activity. So it seems inevitable that under current global circumstances, smaller economies will be forced to become more efficient and self-reliant.

Restoring traditional adaptation strategies would not only drive effective and sustainable climate change adaptation, but also would restore residents’ beliefs in their own time-honoured ways of coping with environmental shocks.

This not only means finding ways to reduce costs through cashless adaptation, but also to explore radical ways of reducing dependency and increasing autonomy. An appeal to past practice, and traditional ways of coping, is well worth considering.The Conversation

Patrick D. Nunn, Professor of Geography, School of Social Sciences, University of the Sunshine Coast and Roselyn Kumar, , University of the Sunshine Coast

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

Unwelcome sea change: new research finds coastal flooding may cost up to 20% of global economy by 2100



Darren Pateman/AAP

Ebru Kirezci, University of Melbourne and Ian Young, University of Melbourne

Over the past two weeks, storms pummelling the New South Wales coast have left beachfront homes at Wamberal on the verge of collapse. It’s stark proof of the risks climate change and sea level rise pose to coastal areas.

Our new research published today puts a potential price on the future destruction. Coastal land affected by flooding – including high tides and extreme seas – could increase by 48% by 2100. Exposed human population and assets are also estimated to increase by about half in that time.

Under a scenario of high greenhouse gas emissions and no flood defences, the cost of asset damage could equate up to 20% of the global economy in 2100.

Without a dramatic reduction in greenhouse gas emissions, or a huge investment in sea walls and other structures, it’s clear coastal erosion will devastate the global economy and much of the world’s population.

In Australia, we predict the areas to be worst-affected by flooding are concentrated in the north and northeast of the continent, including around Darwin and Townsville.

Man cleans up after Townsville flood
A clean-up after flooding last year in Townsville, an Australian city highly exposed to future sea level rise.
Dan Peled/AAP

Our exposed coasts

Sea levels are rising at an increasing rate for two main reasons. As global temperatures increase, glaciers and ice sheets melt. At the same time, the oceans absorb heat from the atmosphere, causing the water to expand. Seas are rising by about 3-4 millimetres a year and the rate is expected to accelerate.

These higher sea levels, combined with potentially more extreme weather under climate change, will bring damaging flooding to coasts. Our study set out to determine the extent of flooding, how many people this would affect and the economic damage caused.




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We combined data on global sea levels during extreme storms with projections of sea level rises under moderate and high-end greenhouse gas emission scenarios. We used the data to model extreme sea levels that may occur by 2100.

We combined this model with topographic data (showing the shape and features of the land surface) to identify areas at risk of coastal flooding. We then estimated the population and assets at risk from flooding, using data on global population distribution and gross domestic product in affected areas.

Homes at Collaroy in Sydney damaged by storm surge
Many coastal homes, such as these at Sydney’s Collaroy beach, are exposed to storm surge damage.
David Moir/AAP

Alarming findings

So what did we find? One outstanding result is that due to sea level rise, what is now considered a once-a-century extreme sea level event could occur as frequently as every ten years or less for most coastal locations.

Under a scenario of high greenhouse gas emissions and assuming no flood defences, such as sea walls, we estimate that the land area affected by coastal flooding could increase by 48% by 2100.




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This could mean by 2100, the global population exposed to coastal flooding could be up to 287 million (4.1% of the world’s population).

Under the same scenario, coastal assets such as buildings, roads and other infrastructure worth up to US$14.2 trillion (A$19.82 trillion) could be threatened by flooding.

This equates to 20% of global gross domestic product (GDP) in 2100. However this worst-case scenario assumes no flood defences are in place globally. This is unlikely, as sea walls and other structures have already been built in some coastal locations.

In Australia, areas where coastal flooding might be extensive include the Northern Territory, and the northern coasts of Queensland and Western Australia.

Elsewhere, extensive coastal flooding is also projected in:
– southeast China
– Bangladesh, and India’s states of West Bengal and Gujurat
– US states of North Carolina, Virginia and Maryland
– northwest Europe including the UK, northern France and northern Germany.

A woman struggles through floodwaters in Bangladesh
Bangladesh is among the nations most exposed to coastal flooding this century.
SOPA

Keeping the sea at bay

Our large-scale global analysis has some limitations, and our results at specific locations might differ from local findings. But we believe our analysis provides a basis for more detailed investigations of climate change impacts at the most vulnerable coastal locations.

It’s clear the world must ramp up measures to adapt to coastal flooding and offset associated social and economic impacts.

This adaptation will include building and enhancing coastal protection structures such as dykes or sea walls. It will also include coastal retreat – allowing low-lying coastal areas to flood, and moving human development inland to safer ground. It will also require deploying coastal warning systems and increasing flooding preparedness of coastal communities. This will require careful long-term planning.

All this might seem challenging – and it is. But done correctly, coastal adaptation can protect hundreds of millions of people and save the global economy billions of dollars this century.




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The Conversation


Ebru Kirezci, PhD candidate, University of Melbourne and Ian Young, Kernot Professor of Engineering, University of Melbourne

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