Antarctica has lost 3 trillion tonnes of ice in 25 years. Time is running out for the frozen continent

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As the world prevaricates over climate action, Antarctica’s future is shrouded in uncertainty.
Hamish Pritchard/British Antarctic Survey

Steve Rintoul, CSIRO and Steven Chown, Monash University

Antarctica lost 3 trillion tonnes of ice between 1992 and 2017, according to a new analysis of satellite observations. In vulnerable West Antarctica, the annual rate of ice loss has tripled during that period, reaching 159 billion tonnes a year. Overall, enough ice has been lost from Antarctica over the past quarter-century to raise global seas by 8 millimetres.

What will Antarctica look like in the year 2070, and how will changes in Antarctica impact the rest of the globe? The answer to these questions depends on choices we make in the next decade, as outlined in our accompanying paper, also published today in Nature.

Read more:
Ocean waves and lack of sea ice can trigger Antarctic ice shelves to disintegrate

Our research contrasts two potential narratives for Antarctica over the coming half-century – a story that will play out within the lifetimes of today’s children and young adults.

While the two scenarios are necessarily speculative, two things are certain. The first is that once significant changes occur in Antarctica, we are committed to centuries of further, irreversible change on global scales. The second is that we don’t have much time – the narrative that eventually plays out will depend on choices made in the coming decade.

Change in Antarctica has global impacts

Despite being the most remote region on Earth, changes in Antarctica and the Southern Ocean will have global consequences for the planet and humanity.

For example, the rate of sea-level rise depends on the response of the Antarctic ice sheet to warming of the atmosphere and ocean, while the speed of climate change depends on how much heat and carbon dioxide is taken up by the Southern Ocean. What’s more, marine ecosystems all over the world are sustained by the nutrients exported from the Southern Ocean to lower latitudes.

From a political perspective, Antarctica and the Southern Ocean are among the largest shared spaces on Earth, regulated by a unique governance regime known as the Antarctic Treaty System. So far this regime has been successful at managing the environment and avoiding discord.

However, just as the physical and biological systems of Antarctica face challenges from rapid environmental change driven by human activities, so too does the management of the continent.

Antarctica in 2070

We considered two narratives of the next 50 years for Antarctica, each describing a plausible future based on the latest science.

In the first scenario, global greenhouse gas emissions remain unchecked, the climate continues to warm, and little policy action is taken to respond to environmental factors and human activities that affect the Antarctic.

Under this scenario, Antarctica and the Southern Ocean undergo widespread and rapid change, with global consequences. Warming of the ocean and atmosphere result in dramatic loss of major ice shelves. This causes increased loss of ice from the Antarctic ice sheet and acceleration of sea-level rise to rates not seen since the end of the last glacial period more than 10,000 years ago.

Warming, sea-ice retreat and ocean acidification significantly change marine ecosystems. And unrestricted growth in human use of Antarctica degrades the environment and results in the establishment of invasive species.

Under the high-emissions scenario, widespread changes occur by 2070 in Antarctica and the Southern Ocean, with global impacts.
Rintoul et al. 2018. Click image to enlarge.

In the second scenario, ambitious action is taken to limit greenhouse gas emissions and to establish policies that reduce human pressure on Antarctica’s environment.

Under this scenario, Antarctica in 2070 looks much like it does today. The ice shelves remain largely intact, reducing loss of ice from the Antarctic ice sheet and therefore limiting sea-level rise.

An increasingly collaborative and effective governance regime helps to alleviate human pressures on Antarctica and the Southern Ocean. Marine ecosystems remain largely intact as warming and acidification are held in check. On land, biological invasions remain rare. Antarctica’s unique invertebrates and microbes continue to flourish.

Antarctica and the Southern Ocean in 2070, under the low-emissions (left) and high-emissions (right) scenarios. Each of these systems will continue to change after 2070, with the magnitude of the change to which we are committed being generally much larger than the change realised by 2070.
Rintoul et al. 2018. Click image to enlarge.

The choice is ours

We can choose which of these trajectories we follow over the coming half-century. But the window of opportunity is closing fast.

Global warming is determined by global greenhouse emissions, which continue to grow. This will commit us to further unavoidable climate impacts, some of which will take decades or centuries to play out. Greenhouse gas emissions must peak and start falling within the coming decade if our second narrative is to stand a chance of coming true.

If our more optimistic scenario for Antarctica plays out, there is a good chance that the continent’s buttressing ice shelves will survive and that Antarctica’s contribution to sea-level rise will remain below 1 metre. A rise of 1m or more would displace millions of people and cause substantial economic hardship.

Under the more damaging of our potential scenarios, many Antarctic ice shelves will likely be lost and the Antarctic ice sheet will contribute as much as 3m of sea level rise by 2300, with an irreversible commitment of 5-15m in the coming millennia.

The ConversationWhile challenging, we can take action now to prevent Antarctica and the world from suffering out-of-control climate consequences. Success will demonstrate the power of peaceful international collaboration and show that, when it comes to the crunch, we can use scientific evidence to take decisions that are in our long-term best interest.

The choice is ours.

Steve Rintoul, Research Team Leader, Marine & Atmospheric Research, CSIRO and Steven Chown, Professor of Biological Sciences, Monash University

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


Ocean waves and lack of sea ice can trigger Antarctic ice shelves to disintegrate

Luke Bennetts, University of Adelaide; Rob Massom, and Vernon Squire

Large waves after the loss of sea ice can trigger Antarctic ice shelf disintegration over a period of just days, according to our new research.

With other research also published today in Nature showing that the rate of annual ice loss from the vulnerable Antarctic Peninsula has quadrupled since 1992, our study of catastrophic ice shelf collapses during that time shows how the lack of a protective buffer of sea ice can leave ice shelves, already weakened by climate warming, wide open to attack by waves.

Read more:
Antarctica has lost 3 trillion tonnes of ice in 25 years. Time is running out for the frozen continent

Antarctica is covered by an ice sheet that is several kilometres thick in places. It covers an area of 14 million square kilometres – roughly twice the size of Australia. This ice sheet holds more than 90% of the world’s ice, which is enough to raise global mean sea level by 57 metres.

As snow falls and compacts on the ice sheet, the sheet thickens and flows out towards the coast, and then onto the ocean surface. The resulting “ice shelves” (and glacier tongues) buttress three-quarters of the Antarctic coastline. Ice shelves act as a crucial braking system for fast-flowing glaciers on the land, and thus moderate the ice sheet’s contribution to sea-level rise.

In the southern summer of 2002, scientists monitoring the Antarctic Peninsula (the northernmost part of mainland Antarctica) by satellite witnessed a dramatic ice shelf disintegration that was stunning in its abruptness and scale. In just 35 days, 3,250 square km of the Larsen B Ice Shelf (twice the size of Queensland’s Fraser Island) shattered, releasing an estimated 720 billion tonnes of icebergs into the Weddell Sea.

This wasn’t the first such recorded event. In January 1995, roughly 1,500 square km of the nearby Larsen A Ice Shelf suddenly disintegrated after several decades of warming and years of gradual retreat. To the southwest, the Wilkins Ice Shelf suffered a series of strikingly similar disintegration events in 1998, 2008 and 2009 — not only in summer but also in two of the Southern Hemisphere’s coldest months, May and July.

These sudden, large-scale fracturing events removed features that had been stable for centuries – up to 11,500 years in the case of Larsen B. While ice shelf disintegrations don’t directly raise sea level (because the ice shelves are already floating), the removal of shelf ice allows the glaciers behind them to accelerate their discharge of land-based ice into the ocean – and this does raise sea levels. Previous research has shown that the removal of Larsen B caused its tributary glaciers to flow eight times faster in the year following its disintegration.

Read more:
Cold and calculating: what the two different types of ice do to sea levels

The ocean around ice shelves is typically covered by a very different (but equally important) type of ice, called sea ice. This is formed from frozen seawater and is generally no more than a few metres thick. But it stretches far out into the ocean, doubling the area of the Antarctic ice cap when at its maximum extent in winter, and varying in extent throughout the year.

The response of Antarctic sea ice to climate change and variability is complex, and differs between regions. Around the Antarctic Peninsula, in the Bellingshausen and northwestern Weddell seas, it has clearly declined in extent and annual duration since satellite monitoring began in 1979, at a similar rate to the Arctic’s rapidly receding sea ice.

The Southern Ocean is also host to the largest waves on the planet, and these waves are becoming more extreme. Our new study focuses on “long-period” swell waves (with swells that last up to about 20 seconds). These are generated by distant storms and carry huge amounts of energy across the oceans, and can potentially flex the vulnerable outer margins of ice shelves.

The earliest whalers and polar pioneers knew that sea ice can damp these waves — Sir Ernest Shackleton reported it in his iconic book South!. Sea ice thus acts as a “buffer” that protects the Antarctic coastline, and its ice shelves, from destructive ocean swells.

Strikingly, all five of the sudden major ice shelf disintegrations listed above happened during periods when sea ice was abnormally low or even absent in these regions. This means that intense swell waves crashed directly onto the vulnerable ice shelf fronts.

The straw that broke the camel’s back

The Antarctic Peninsula has experienced particularly strong climate warming (roughly 0.5℃ per decade since the late 1940s), which has caused intense surface melting on its ice shelves and exacerbated their structural weaknesses such as fractures. These destabilising processes are the underlying drivers of ice shelf collapse. But they do not explain why the observed disintegrations were so abrupt.

Our new study suggests that the trigger mechanism was swell waves flexing and working weaknesses at the shelf fronts in the absence of sea ice, to the point where they calved away the shelf fronts in the form of long, thin “sliver-bergs”. The removal of these “keystone blocks” in turn led to the catastrophic breakup of the ice shelf interior, which was weakened by years of melt.

Our research thus underlines the complex and interdependent nature of the various types of Antarctic ice – particularly the important role of sea ice in forming a protective “buffer” for shelf ice. While much of the focus so far has been on the possibility of ice shelves melting from below as the sea beneath them warms, our research suggests an important role for sea ice and ocean swells too.

The edge of an ice shelf off the Antarctic Peninsula, with floating sea ice beyond (to the left in this image).
NASA/Maria Jose Vinas

In July 2017 an immense iceberg broke away from the Larsen C Ice Shelf, just south of Larsen B, prompting fears that it could disintegrate like its neighbours.

Our research suggests that four key factors will determine whether it does: extensive flooding and fracturing across the ice shelf; reduced sea ice coverage offshore; extensive fracturing of the ice shelf front; and calving of sliver-bergs.

Read more:
Don’t worry about the huge Antarctic iceberg – worry about the glaciers behind it

If temperatures continue to rise around the Antarctic, ice shelves will become weaker and sea ice less extensive, which would imply an increased likelihood of future disintegrations.

However, the picture is not that clear-cut, as not all remaining ice shelves are likely to respond in the same way to sea ice loss and swell wave impacts. Their response will also depend on their glaciological characteristics, physical setting, and the degree and nature of surface flooding. Some ice shelves may well be capable of surviving prolonged absences of sea ice.

The ConversationIrrespective of these differences, we need to include sea ice and ocean waves in our models of ice sheet behaviour. This will be a key step towards better forecasting the fate of Antarctica’s remaining ice shelves, and how much our seas will rise in response to projected climate change over coming decades. In parallel, our new findings underline the need to better understand and model the mechanisms responsible for recent sea ice trends around Antarctica, to enable prediction of likely future change in the exposure of ice shelves to ocean swells.

Luke Bennetts, Lecturer in applied mathematics, University of Adelaide; Rob Massom, Leader, Sea Ice Group, Antarctica & the Global System program, Australian Antarctic Division and Antarctic Climate and Ecosystems CRC, and Vernon Squire, Deputy Vice-Chancellor Academic, Professor of Applied Mathematics

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

Why methane should be treated differently compared to long-lived greenhouse gases

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Livestock is a significant source of methane, a potent but short-lived greenhouse gas.
from, CC BY-SA

Dave Frame, Victoria University of Wellington; Adrian Henry Macey, Victoria University of Wellington, and Myles Allen, University of Oxford

New research provides a way out of a longstanding quandary in climate policy: how best to account for the warming effects of greenhouse gases that have different atmospheric lifetimes.

Carbon dioxide is a long-lived greenhouse gas, whereas methane is comparatively short-lived. Long-lived “stock pollutants” remain in the atmosphere for centuries, increasing in concentration as long as their emissions continue and causing more and more warming. Short-lived “flow pollutants” disappear much more rapidly. As long as their emissions remain constant, their concentration and warming effect remain roughly constant as well.

Our research demonstrates a better way to reflect how different greenhouse gases affect global temperatures over time.

Cost of pollution

The difference between stock and flow pollutants is shown in the figure below. Flow pollutant emissions, for example of methane, do not persist. Emissions in period one, and the same emissions in period two, lead to a constant (or roughly constant) amount of the pollutant in the atmosphere (or river, lake, or sea).

With stock pollutants, such as carbon dioxide, concentrations of the pollutant accumulate as emissions continue.

Flow and stock pollutants over time. In the first period, one unit of each pollutant is emitted, leading to one unit of concentration. After each period, the flow pollutant decays, while the stock pollutant remains in the environment.
provided by author, CC BY

The economic theory of pollution suggests different approaches to greenhouse gases with long or short lifetimes in the atmosphere. The social cost (the cost society ought to pay) of flow pollution is constant over time, because the next unit of pollution is just replacing the last, recently decayed unit. This justifies a constant price on flow pollutants.

In the case of stock pollutants, the social cost increases with constant emissions as concentrations of the pollutant rise, and as damages rise, too. This justifies a rising price on stock pollutants.

Read more:
Cows exude lots of methane, but taxing beef won’t cut emissions

A brief history of greenhouse gas “equivalence”

In climate policy, we routinely encounter the idea of “CO₂-equivalence” between different sorts of gases, and many people treat it as accepted and unproblematic. Yet researchers have debated for decades about the adequacy of this approach. To summarise a long train of scientific papers and opinion pieces, there is no perfect or universal way to compare the effects of greenhouse gases with very different lifetimes.

This point was made in the first major climate report produced by the Intergovernmental Panel on Climate Change (IPCC) way back in 1990. Those early discussions were loaded with caveats: global warming potentials (GWP), which underpin the traditional practice of CO₂-equivalence, were introduced as “a simple approach … to illustrate the difficulties inherent in the concept”.

The problem with developing a concept is that people might use it. Worse, they might use it and ignore all the caveats that attended its development. This is, more or less, what happened with GWPs as used to create CO₂-equivalence.

The science caveats were there, and suggestions for alternatives or improvements have continued to appear in the literature. But policymakers needed something (or thought they did), and the international climate negotiations community grasped the first option that became available, although this has not been without challenges from some countries.

Better ways to compare stocks and flows

An explanation of the scientific issues, and how we address them, is contained in this article by Michelle Cain. The approach in our new paper shows that modifying the use of GWP to better account for the differences between short- and long-lived gases can better link emissions to warming.

Under current policies, stock and flow pollutants are treated as being equivalent and therefore interchangeable. This is a mistake, because if people make trade-offs between emissions reductions such that they allow stock pollutants to grow while reducing flow pollutants, they will ultimately leave a warmer world behind in the long term. Instead, we should develop policies that address methane and other flow pollutants in line with their effects.

Then the true impact of an emission on warming can be easily assessed. For countries with high methane emissions, for example from agriculture, this can make a huge difference to how their emissions are judged.

For a lot of countries, this issue is of secondary importance. But for some countries, particularly poor ones, it matters a lot. Countries with a relatively high share of methane in their emissions portfolios tend to be either middle-income countries with large agriculture sectors and high levels of renewables in their electricity mix (such as much of Latin America), or less developed countries where agricultural emissions dominate because their energy sector is small.

This is why we think the new research has some promise. We think we have a better way to conceive of multi-gas climate targets. This chimes with new possibilities in climate policy, because under the Paris Agreement countries are free to innovate in how they approach climate policy.

Improving the environmental integrity of climate policy

This could take several forms. For some countries, it may be that the new approach provides a better way of comparing different gases within a single-basket approach to greenhouse gases, as in an emissions trading scheme or taxation system. For others, it could be used to set separate but coherent emissions targets for long- and short-lived gases within a two-basket approach to climate policy. Either way, the new approach means countries can signal the centrality of carbon dioxide reductions in their policy mix, while limiting the warming effect of shorter-lived gases.

The new way of using global warming potentials demonstrably outperforms the traditional method in a range of emission scenarios, providing a much more accurate indication of how stock and flow pollutants affect global temperatures. This is especially so under climate mitigation scenarios.

Well designed policies would assist sectoral fairness within countries, too. Policies that reflect the different roles of stock and flow pollutants would give farmers and rice growers a more reasonable way to control their emissions and reduce their impact on the environment, while still acknowledging the primacy of carbon dioxide emissions in the climate change problem.

The ConversationAn ideal approach would be a policy that aimed for zero emissions of stock pollutants such as carbon dioxide and low but stable (or gently declining) emissions of flow pollutants such as methane. Achieving both goals would mean that a farm, or potentially a country, can do a better, clearer job of stopping its contribution to warming.

Dave Frame, Professor of Climate Change, Victoria University of Wellington; Adrian Henry Macey, Senior Associate, Institute for Governance and Policy Studies; Adjunct Professor, New Zealand Climate Change Research Institute. , Victoria University of Wellington, and Myles Allen, Professor of Geosystem Science, Leader of ECI Climate Research Programme, University of Oxford

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

A bird’s eye view of New Zealand’s changing glaciers

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Small aircraft carry scientists high above the Southern Alps to survey glacier changes.
Hamish McCormick/NIWA, CC BY-SA

Andrew Lorrey, National Institute of Water and Atmospheric Research; Andrew Mackintosh, Victoria University of Wellington, and Brian Anderson, Victoria University of Wellington

Every March, glacier “watchers” take to the skies to photograph snow and ice clinging to high peaks along the length of New Zealand’s Southern Alps.

This flight needs to happen on cloud-free and windless days at the end of summer before new snow paints the glaciers white, obscuring their surface features.

Each year, at the end of summer, scientists monitor glaciers along New Zealand’s Southern Alps.

Summer of records

The summer of 2017-18 was New Zealand’s warmest on record and the Tasman Sea experienced a marine heat wave, with temperatures up to six degrees above normal for several weeks.

The loss of seasonal snow cover and older ice during this extreme summer brings the issue of human-induced climate change into tight focus. The annual flights have been taking place for four decades and the data on end-of-summer snowlines provide crucial evidence.

The disappearance of snow and ice for some of New Zealand’s glaciers is clear and irreversible, at least within our lifetimes. Many glaciers we survey now will simply vanish in the coming decades.

The Franz Josef glacier advanced during the 1980s and 1990s but is now retreating.
Andrew Lorrey/NIWA, CC BY-SA

Glaciers are a beautiful part of New Zealand’s landscape, and important to tourism, but they may not be as prominent in the future. This stored component of the freshwater resource makes contributions to rivers that are used for recreation and irrigation of farm land.

Meltwater flowing from glaciers around Aoraki/Mt Cook into the Mackenzie Basin feeds important national hydroelectricity power schemes. Seasonal meltwater from glaciers can partially mitigate the impacts of summer drought. This buffering capacity may become more crucial if the eastern side of New Zealand’s mountains become drier in a changing climate.

Pioneering glacier monitoring

When Trevor Chinn began studying New Zealand’s 3,000 or so glaciers in the 1960s, he realised monitoring all of them was impossible. He searched for cost-effective ways to learn as much as he could. This resulted in comprehensive glacier mapping and new snow and ice observations when similar work was dying out elsewhere. Mapping of all of the world’s glaciers – nearly 198,000 in total – was only completed in 2012, yet Trevor had already mapped New Zealand’s ice 30 years earlier.

Octogenarian Trevor Chinn still participates in the snowline flights every year to support younger scientists.
Dave Allen/NIWA, CC BY-SA

In addition, he wanted to understand how snow and ice changed from year to year. Trevor decided to do annual glacier photographic flights, looking for the end-of-summer snowlines – a feature about half way between the terminus and the top of a glacier where hard, blue, crevassed glacier ice usually gives way to the previous winter’s snow. The altitude of this transition is an indicator of the annual health of a glacier.

It was a visionary approach that provided a powerful and unique archive of climate variability and change in a remote South Pacific region, far removed from well-known European and North American glaciers. But what was hidden at the time was that New Zealand glaciers were about to undergo significant changes.

Trevor Chinn took part in this summer’s flight and said:

This year is the worst we’ve ever seen. There was so much melt over the summer that more than half the glaciers have lost all the snow they had gained last winter, plus some from the winter before, and there’s rocks sticking out everywhere. The melt-back is phenomenal.

New insights from old observations

The Southern Alps end-of-summer snowline photo archive, produced by the National Institute of Water and Atmospheric Research, is a remarkable long-term record. Our colleagues Lauren Vargo and Huw Horgan are leading the effort to harness this resource with photogrammetry to deliver precise (metre-scale) three-dimensional models of glacier changes since 1978, building directly on Trevor Chinn’s work.

Glaciers respond to natural variability and human-induced changes, and we suspect the latter has become more dominant for our region. During the 1980s and 1990s, while glaciers were largely retreating in other parts of the world, many in New Zealand were advancing. Our recent research shows this anomaly was caused by several concentrated cooler-than-average periods, with Southern Alps air temperature linked to Tasman Sea temperatures directly upwind.

The situation changed after the early 2000s, and we postulated whether more frequent high snowlines and acceleration of ice loss would occur. Since 2010, multiple high snowline years have been observed. In 2011, the iconic Fox Glacier (Te Moeka o Tuawe) and Franz Josef Glacier (Kā Roimata o Hine Hukatere) started a dramatic retreat – losing all of the ground that they regained in the 1990s and more.

In a series of ice collapses, New Zealand’s Fox Glacier retreated by around 300 m between January 2014 and January 2015.

Looking ahead by examining the past

How New Zealand’s glaciers will respond to human-induced climate change is an important question, but the answer is complicated. A recent study suggests human-induced climate warming since about 1990 has been the largest factor driving global glacier decline. For New Zealand, which is significantly influenced by regional variability of the surrounding oceans and atmosphere, the picture is less clear.

To assess how human-induced climate influences and natural variability affect New Zealand glaciers requires the use of climate models, snowline observations and other datasets. Our research team, with support from international colleagues, are doing just that to see how Southern Alps ice will respond to a range of future scenarios.

The ConversationContinuing the snowline photograph work will allow us to better identify climate change tipping points and warning signs for our water resources – and therefore better prepare New Zealand for an uncertain future.

Andrew Lorrey, Principal Scientist & Programme Leader of Climate Observations and Processes, National Institute of Water and Atmospheric Research; Andrew Mackintosh, Professor & Director of Antarctic Research Centre, expert on glaciers and ice sheets, Victoria University of Wellington, and Brian Anderson, Senior Research Fellow, Victoria University of Wellington

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.

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 slowly 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.

The ConversationGiven 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.

New Zealand’s productivity commission charts course to low-emission future

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According to a recent report, New Zealand will need to increase renewable electricity generation, plant more trees and continue switching to electric transport more rapidly to achieve its zero carbon goal by 2050.
from, CC BY-SA

Robert McLachlan, Massey University

New Zealand has set itself a target of becoming carbon-neutral by 2050.

A recent report issued by the New Zealand Productivity Commission has found that this is an achievable goal, even under modest forecasts of technological progress and increases in carbon price.

Read more:
A fresh start for climate change mitigation in New Zealand

Rising emissions

New Zealand already had a goal of reducing greenhouse gas emissions to 50% below 1990 levels by 2050. That target had been in place since 2002, but emissions continued to rise through the 2000s.

An emissions trading scheme, which began operating in 2008, failed to stop the increase. A flood of imported cars increased New Zealand’s vehicle fleet and its emissions by 20% in just the past four years. A “wall of timber”, expected after 2020 as existing plantations are harvested, would further greatly increase net emissions under current carbon accounting rules.

Agriculture is responsible for an unusually large proportion — just under 50% — of New Zealand’s emissions. These emissions were rising too, especially long-lived nitrous oxides released by effluent and synthetic fertilisers.

A key part of New Zealand’s plan to meet global obligations had always been international carbon trading. However, in the Ukraine hot air scandal, low-integrity carbon credits were imported at rock-bottom prices. International trading was therefore suspended in 2015.

Aiming for zero

The Paris climate agreement made New Zealand’s “50 by 50” target — which the country wasn’t on track to meet — look distinctly weak. It has now become clear that only zero net emissions can stabilise temperatures, at any level, in the long run.

Read more:
A new approach to emissions trading in a post-Paris climate

It was in this context that New Zealand’s previous government asked the Productivity Commission to examine the “opportunities and challenges of a transition to a lower net emissions economy”. A few months into their work, the government changed and the new climate change minister, the Greens’ James Shaw, reinforced the urgency of the inquiry by asking the commission to consider the possibility of a net zero target for 2050.

The resulting 500-page report, now available in draft form, is a huge and comprehensive piece of work. From the very beginning, the commission knew what they were up against, writing that:

…the shift from the old economy to a new, low-emissions, economy will be profound and widespread, transforming land use, the energy system, production methods and technology, regulatory frameworks and institutions, and business and political culture.

The impact of widespread consultation, evidence and research is clear throughout. Although it is only advice, the report is a valuable resource for all future work on emissions reduction. It joins a chorus of similar (but much less detailed) studies issued recently.

Cost of carbon

The report finds that the carbon price required to get to zero net emissions in 2050 is fairly modest. In one model, it rises from its present price of NZ$21/tonne to NZ$55 in 2030 and NZ$157 in 2050 — within the NZ$100-250 range of global estimates consistent with the goal of keeping global temperature rise below 2℃. In other words, New Zealand does not have an unusually difficult decarbonisation challenge.

Although the report covers all main aspects of society and economy, there are three big changes that stand out:

  • Transport must be electrified rapidly (in some models, nearly all light vehicles entering the fleet must be zero-emission by the early 2030s)

  • Huge numbers of trees – up to an extra 2.8 million hectares, tripling the current plantation estate – must be planted to absorb carbon dioxide. These trees have to go somewhere, probably on sheep and beef farms

  • A lot of new renewable electricity generation will be needed, nearly doubling the present capacity, which is already 85% renewable.

Emissions trading can work

The meat of the report is the policies and institutions required to support and drive the transition. Key among them is a revised emissions trading scheme. So far the scheme has failed to reduce domestic emissions because the price of carbon was too low. This was driven mainly by low international prices, sector exemptions (including agriculture), and policy uncertainty which left businesses and investors unclear about future rules and prices.

The commission’s key recommended fixes include the adoption of a falling cap on emissions (to drive up prices and guarantee emissions reductions); a rising price cap (to prevent shocks to the economy and political resistance from emitters); and a rising price floor (to provide confidence to investors in low-emission technologies). Indeed, California’s system includes all of these elements and is currently on track to reduce emissions to 40% below 1990 levels by 2030.

Besides the emissions trading scheme, the report argues that every sector needs its own strategy. For example, on transport, it recommends an emissions standard – something most other developed countries except Australia currently have. Without this, New Zealand risks becoming a dumping ground for high-emission vehicles that manufacturers cannot sell elsewhere. They also recommend a “feebate” scheme, in which vehicles entering the fleet either incur a fee (if they have above-average emissions) or receive a rebate.

Risks and opportunities

I see a few key risks. First, trade-exposed industries, such as agriculture and food and metal processing, need to get discounts on carbon prices to remain competitive. A future in which each global industry decarbonises in a coordinated way does not seem likely, but each industry in each country still needs an incentive to clean up. This aspect remains difficult to deal with. For example, the recommendation that agriculture should be fully phased into the ETS is far outside the political mainstream in New Zealand at the moment.

The falling cap on emissions is an absolutely vital component, but it remains a decision that could be subject to lobbying in the aftermath of some domestic or international crisis.

In none of the report’s scenarios do gross emissions fall by more than 43% by 2050. This is certainly achievable, and it is in line with what some countries are doing right now, but it means New Zealand is relying heavily on tree planting to get to net zero. This is not a long-term solution – eventually you run out of space to plant more trees.

Although the commission has cast its net wide, it does not encompass all views. Political scientist Bronwyn Hayward, perhaps influenced by Trumpism, sees a climate commission as just another panel of experts telling us what to do. Without a fundamental renewal of democracy, this risks a backlash. Naomi Klein goes even further and views neoliberalism as being in kahoots with the fossil fuel industry as the enemy, with the only hope being youth activism.

The ConversationShe might not be wrong. In New Zealand, the idea for a Zero Carbon Act did originate with a youth group, Generation Zero. Their campaign has led fairly directly to this detailed road map for a zero carbon future. The next step, a public consultation about the Zero Carbon Act itself, kicks off this month.

Robert McLachlan, Professor in Applied Mathematics, Massey University

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

Why blowing the 1.5C global warming goal will leave poor tropical nations sweating most of all

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Poor tropical nations are likely to feel the effects of climate change most acutely.

Andrew King, University of Melbourne and Luke Harrington, University of Oxford

Almost all of us are going to be worse off as climate change takes hold, whether through heatwaves, changing rainfall patterns, sea level rise, or damage to ecosystems. But it’s the world’s poorest people who will suffer the biggest disruptions to their local climate, as our new study, published in Geophysical Research Letters today, explains.

The Paris Agreement aims to keep global warming well below 2℃ above pre-industrial levels, and ideally no more than 1.5℃. Meeting the more ambitious 1.5℃ target will be extremely challenging, given that we have already had more than 1℃ of global warming so far, and global greenhouse emissions are still rising.

Read more:
Fossil fuel emissions hit record high after unexpected growth: Global Carbon Budget 2017

We examined the likely consequences of missing the 1.5℃ global warming target in terms of perceptible local climate change, by looking at the “signal-to-noise ratio”. The idea is that 1℃ of warming is more noticeable where there is very little variation in temperature (such as in Singapore, for example) compared with places where the temperature variations are much higher (like Melbourne). Where temperature variations are smaller less warming is needed before the change in climate becomes noticeable.

Read more:
Ground zero for climate change: the tropics were first to feel the definite effects in the 1960s

Society and ecosystems are adapted to the range of temperatures experienced in their location, so the signal-to-noise measure of climate change reflects this effect. In simple terms, it is a measure of how soon global warming will push the temperature beyond the normal bounds of variation at a given location. This will happen sooner in places where the weather doesn’t vary much, and later in places where it does.

Because global warming is likely to overshoot the ambitious Paris goal of 1.5℃, but perhaps not the more modest 2℃ goal, we looked in particular at the signal-to-noise ratio created by using state-of-the-art global climate model projections to move between 1.5℃ and 2℃ of global warming.

More perceptible warming is projected over the tropics than at higher latitudes.
CREDIT, Author provided

As expected, the signal-to-noise ratio is high in the tropics, where the variability in temperature is lower. This means that local temperature changes due to global warming will generally be felt more keenly in the tropics than at higher latitudes if the world exceeds the 1.5℃ Paris target.

The inequality of climate change

Next, we overlaid the signal-to-noise ratio data with population and gross domestic product (GDP) data to investigate the relationship between local climate change and wealth.

As the less economically developed areas of the world are predominantly in the tropics, and the more developed economies are at higher latitudes, we predict that the world’s wealthiest countries will experience less perceptible climate change than the poorest.

Locations in the poorest countries tend to experience greater local climate change.
Author provided

For example, we project that the people of the UK, the first country to industrialise and one of the world’s richest nations, would experience less than half the level of perceptible climate change, as measured by our signal-to-noise ratio, than the people of the Democratic Republic of Congo, one of the world’s poorest.

This means that if we do exceed the 1.5℃ Paris target, the countries that will face the biggest impact are those who are least to blame for creating the problem, and least equipped to deal with the resulting problems.

Read more:
Developing countries can prosper without increasing emissions

An impetus to act

Keeping global warming to modest levels, as signatories to the Paris Agreement have pledged to do, has many benefits compared with the alternative of a 3℃ or 4℃ warmer world. Previous research has shown that this would reduce the frequency of heat extremes and their impacts in many places around the world, and would reduce droughts and extreme rain events. There would be benefits for many of the world’s plant and animal species as well as entire ecosystems, including the Great Barrier Reef.

Limiting global warming also helps the poorest parts of the world develop. By reducing greenhouse gas emissions more rapidly the developed world would put less of the burden of climate change onto the developing world. This should incentivise stronger emissions reductions globally. The UN Sustainable Development Goals call for action to eradicate absolute poverty and reduce inequality. Our research underlines the fact that both of these goals, and others, depend implicitly on reining in global warming.

The ConversationUnfortunately, the alternative – and where our current emissions trajectory is taking us – is a warmer world in which the poorest and least culpable nations pay the biggest price.

Andrew King, Climate Extremes Research Fellow, University of Melbourne and Luke Harrington, Postdoctoral Research Assistant, Environmental Change Institute, University of Oxford

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