Lethal Heating: June 2017

30/06/2017

The World’s Tropical Zone Is Expanding, And Australia Should Be Worried

The Conversation - Steve Turton

‘Tropics’ may conjure images of sun-kissed islands, but the expanding tropical zone could bring drought and cyclones further south. Pedro Fernandes/Flickr, CC BY-SA

The Tropics are defined as the area of Earth where the Sun is directly overhead at least once a year — the zone between the Tropics of Cancer and Capricorn.
However, tropical climates occur within a larger area about 30 degrees either side of the Equator. Earth's dry subtropical zones lie adjacent to this broad region. It is here that we find the great warm deserts of the world.

Earth's bulging waistline
Earth's tropical atmosphere is growing in all directions, leading one commentator to cleverly call this Earth's "bulging waistline".
Since 1979, the planet's waistline been expanding poleward by 56km to 111km per decade in both hemispheres. Future climate projections suggest this expansion is likely to continue, driven largely by human activities – most notably emissions of greenhouse gases and black carbon, as well as warming in the lower atmosphere and the oceans.
If the current rate continues, by 2100 the edge of the new dry subtropical zone would extend from roughly Sydney to Perth.
As these dry subtropical zones shift, droughts will worsen and overall less rain will fall in most warm temperate regions.
Poleward shifts in the average tracks of tropical and extratropical cyclones are already happening. This is likely to continue as the tropics expand further. As extratropical cyclones move, they shift rain away from temperate regions that historically rely upon winter rainfalls for their agriculture and water security.
Researchers have observed that, as climate zones change, animals and plants migrate to keep up. But as biodiversity and ecosystem services are threatened, species that can't adjust to rapidly changing conditions face extinction.
In some biodiversity hotspots – such as the far southwest of Australia – there are no suitable land areas (only oceans) for ecosystems and species to move into to keep pace with warming and drying trends.
We are already witnessing an expansion of pests and diseases into regions that were previously climatically unsuitable. This suggests that they will attempt to follow any future poleward shifts in climate zones.
I recently drew attention to the anticipated impacts of an expanding tropics for Africa. So what might this might mean for Australia?

IPCC

Australia is vulnerable
Australia's geographical location makes it highly vulnerable to an expanding tropics. About 60% of the continent lies north of 30°S.
As the edge of the dry subtropical zone continues to creep south, more of southern Australia will be subject to its drying effects.
Meanwhile, the fringes of the north of the continent may experience rainfall and temperature conditions that are more typical of our northern neighbours.
The effects of the expanding tropics are already being felt in southern Australia in the form of declining winter rainfall. This is especially the case in the southwest and — to a lesser extent — the continental southeast.
Future climate change projections for Australia include increasing air and ocean temperatures, rising sea levels, more hot days (over 35℃), declining rainfall in the southern continental areas, and more extreme fire weather events.
For northern Australia, changes in annual rainfall remain uncertain. However, there is a high expectation of more extreme rainfall events, many more hot days and more severe (but less frequent) tropical cyclones and associated storm surges in coastal areas.

Dealing with climate change
Adaptation to climate change will be required across all of Australia. In the south the focus will have to be on adapting to projected drying trends. Other challenges include more frequent droughts, more warm spells and hot days, higher fire weather risk and rising sea levels in coastal areas.
The future growth of the north remains debatable. I have already pointed out the lack of consideration of climate change in the White Paper for the Development of Northern Australia.
The white paper neglects to explain how planned agricultural, mining, tourism and community development will adapt to projected changes in climate over coming decades — particularly, the anticipated very high number of hot days.
For example, Darwin currently averages 47 hot days a year, but under a high carbon emission scenario, the number of hot days could approach 320 per year by 2090. If the north is to survive and thrive as a significant economic region of Australia, it will need effective climate adaptation strategies. This must happen now — not at some distant time in the future.
This requires bipartisan support from all levels of government, and a pan-northern approach to climate adaptation. It will be important to work closely with industry and affected local and Indigenous communities across the north.
These sectors must have access to information and solutions drawn from interdisciplinary, "public good" research. In the face of this urgent need, CSIRO cuts to such research and the defunding of the National Climate Change Adaptation Research Facility should be ringing alarm bells.
As we enter uncharted climate territory, never before has public-good research been more important and relevant.

Links

Contributions To Sea-Level Rise Have Increased By Half Since 1993, Largely Because Of Greenland’s Ice

The Conversation - John Church | Christopher Watson | Matt King | Xianyao Chen | Xuebin Zhang

Water mass enters the ocean from glaciers such as this along the Greenland coast. NASA/JPL-Caltech

Contributions to the rate of global sea-level rise increased by about half between 1993 and 2014, with much of the increase due to an increased contribution from Greenland's ice, according to our new research.
Our study, published in Nature Climate Change, shows that the sum of contributions increased from 2.2mm per year to 3.3mm per year. This is consistent with, although a little larger than, the observed increase in the rate of rise estimated from satellite observations.
Globally, the rate of sea-level rise has been increasing since the 19th century. As a result, the rate during the 20th century was significantly greater than during previous millennia. The rate of rise over the past two decades has been larger still.
The rate is projected to increase still further during the 21st century unless human greenhouse emissions can be significantly curbed.
However, since 1993, when high-quality satellite data collection started, most previous studies have not reported an increase in the rate of rise, despite many results pointing towards growing contributions to sea level from the ice sheets of Greenland and Antarctica. Our research was partly aimed at explaining how these apparently contradictory results fit together.

Changes in the rate of rise
In 2015, we completed a careful comparison of satellite and coastal measurements of sea level. This revealed a small but significant bias in the first decade of the satellite record which, after its removal, resulted in a slightly lower estimate of sea-level rise at the start of the satellite record. Correcting for this bias partially resolved the apparent contradiction.
In our new research, we compared the satellite data from 1993 to 2014 with what we know has been contributing to sea level over the same period. These contributions come from ocean expansion due to ocean warming, the net loss of land-based ice from glaciers and ice sheets, and changes in the amount of water stored on land.
Previously, after around 2003, the agreement between the sum of the observed contributions and measured sea level was very good. Before that, however, the budget didn't quite balance.
Using the satellite data corrected for the small biases identified in our earlier study, we found agreement with the sum of contributions over the entire time from 1993 to 2014. Both show an increase in the rate of sea-level rise over this period.

The total observed sea-level rise is the sum of contributions from thermal expansion of the oceans, fresh water input from glaciers and ice sheets, and changes in water storage on land. IPCC

After accounting for year-to-year fluctuations caused by phenomena such as El Niño, our corrected satellite record indicates an increase in the rate of rise, from 2.4mm per year in 1993 to 2.9mm per year in 2014. If we used different estimates for vertical land motion to estimate the biases in the satellite record, the rates were about 0.4mm per year larger, changing from 2.8mm per year to 3.2mm per year over the same period.

Is the whole the same as the sum of the parts?
Our results show that the largest contribution to sea-level rise – about 1mm per year – comes from the ocean expanding as it warms. This rate of increase stayed fairly constant over the time period.
The second-largest contribution was from mountain glaciers, and increased slightly from 0.6mm per year to 0.9mm per year from 1993 to 2014. Similarly, the contribution from the Antarctic ice sheet increased slightly, from 0.2mm per year to 0.3mm per year.
Strikingly, the largest increase came from the Greenland ice sheet, as a result of both increased surface melting and increased flow of ice into the ocean. Greenland's contribution increased from about 0.1mm per year (about 5% of the total rise in 1993) to 0.85mm per year (about 25% in 2014).

Greenland's contribution to sea-level rise is increasing due to both increased surface melting and flow of ice into the ocean. NASA/John Sonntag, CC BY

The contribution from land water also increased, from 0.1mm per year to 0.25mm per year. The amount of water stored on land varies a lot from year to year, because of changes in rainfall and drought patterns, for instance. Despite this, rates of groundwater depletion grew whereas storage of water in reservoirs was relatively steady, with the net effect being an increase between 1993 and 2014.
So in terms of the overall picture, while the rate of ocean thermal expansion has remained steady since 1993, the contributions from glaciers and ice sheets have increased markedly, from about half of the total rise in 1993 to about 70% of the rise in 2014. This is primarily due to Greenland's increasing contribution.

What is the future of sea level?
The satellite record of sea level still spans only a few decades, and ongoing observations will be needed to understand the longer-term significance of our results. Our results also highlight the importance of the continued international effort to better understand and correct for the small biases we identified in the satellite data in our earlier study.
Nevertheless, the satellite data are now consistent with the historical observations and also with projected increases in the rate of sea-level rise.
Ocean heat content fell following the 1991 volcanic eruption of Mount Pinatubo. The subsequent recovery (over about two decades) probably resulted in a rate of ocean thermal expansion larger than from greenhouse gases alone. Thus the underlying acceleration of thermal expansion from human-induced warming may emerge over the next decade or so. And there are potentially even larger future contributions from the ice sheets of Greenland and Antarctica.
The acceleration of sea level, now measured with greater accuracy, highlights the importance and urgency of cutting greenhouse gas emissions and formulating coastal adaptation plans. Given the increased contributions from ice sheets, and the implications for future sea-level rise, our coastal cities need to prepare for rising sea levels.

Sea-level rise will have significant impacts on coastal communities and environments. Bruce Miller/CSIRO, CC BY

Links

World Has Three Years Left To Stop Dangerous Climate Change, Warn Experts

The Guardian - Fiona Harvey

Former UN climate chief Christiana Figueres among signatories of letter warning that the next three years will be crucial to stopping the worst effects of global warming

Former UN climate chief Christiana Figueres: "We stand at the doorway of being able to bend the emissions curve downwards by 2020." Photograph: Jason Alden/Getty Images

Avoiding dangerous levels of climate change is still just about possible, but will require unprecedented effort and coordination from governments, businesses, citizens and scientists in the next three years, a group of prominent experts has warned.
Warnings over global warming have picked up pace in recent months, even as the political environment has grown chilly with Donald Trump's formal announcement of the US's withdrawal from the Paris agreement. This year's weather has beaten high temperature records in some regions, and 2014, 2015 and 2016 were the hottest years on record.
But while temperatures have risen, global carbon dioxide emissions have stayed broadly flat for the past three years. This gives hope that the worst effects of climate change – devastating droughts, floods, heatwaves and irreversible sea level rises – may be avoided, according to a letter published in the journal Nature this week.
The authors, including former UN climate chief Christiana Figueres and Hans Joachim Schellnhuber of the Intergovernmental Panel on Climate Change, argue that the next three years will be crucial. They calculate that if emissions can be brought permanently lower by 2020 then the temperature thresholds leading to runaway irreversible climate change will not be breached.
Figueres, the executive secretary of the UN Framework Convention on Climate Change, under whom the Paris agreement was signed, said: "We stand at the doorway of being able to bend the emissions curve downwards by 2020, as science demands, in protection of the UN sustainable development goals, and in particular the eradication of extreme poverty. This monumental challenge coincides with an unprecedented openness to self-challenge on the part of sub-national governments inside the US, governments at all levels outside the US, and of the private sector in general. The opportunity given to us over the next three years is unique in history."
Schellnhuber, director of the Potsdam Institute for Climate Impact Research, added: "The maths is brutally clear: while the world can't be healed within the next few years, it may be fatally wounded by negligence [before] 2020."
Scientists have been warning that time is fast running out to stave off the worst effects of warming, and some milestones may have slipped out of reach. In the Paris agreement, governments pledged an "aspirational" goal of holding warming to no more than 1.5C, a level which it is hoped will spare most of the world's lowest-lying islands from inundation. But a growing body of research has suggested this is fast becoming impossible.
Paris's less stringent, but firmer, goal of preventing warming from exceeding 2C above pre-industrial levels is also in doubt.
The authors point to signs that the trend of upward emissions is being reversed, and to technological progress that promises lower emissions for the future. Renewable energy use has soared, creating a foundation for permanently lowering emissions. Coal use is showing clear signs of decline in key regions, including China and India. Governments, despite Trump's pronouncements, are forging ahead with plans to reduce greenhouse gases.
The authors called for political and business leaders to continue tackling emissions and meeting the Paris goals without the US. "As before Paris, we must remember that impossible is not a fact, it's an attitude," they wrote.
They set out six goals for 2020 which they said could be adopted at the G20 meeting in Hamburg on 7-8 July. These include increasing renewable energy to 30% of electricity use; plans from leading cities and states to decarbonise by 2050; 15% of new vehicles sold to be electric; and reforms to land use, agriculture, heavy industry and the finance sector, to encourage green growth.
Prof Gail Whiteman said the signs from technical innovation and economics were encouraging: "Climate science underlines the unavoidable urgency of our challenge, but equally important is the fact that the economic, technical and social analyses show that we can resoundingly rise to the challenge through collective action."
While the greenhouse gases poured into the atmosphere over the last two centuries have only gradually taken effect, future changes are likely to be faster, scientists fear. Johan Rockström of the Stockholm Resilience Centre said: "We have been blessed by a remarkably resilient planet over the past 100 years, able to absorb most of our climate abuse. Now we have reached the end of this era, and need to bend the global curve of emissions immediately, to avoid unmanageable outcomes for our modern world."

Links

29/06/2017

Climate Change Could Threaten Up To 2 Billion Refugees By 2100

Huffington Post - Alexander C. Kaufman

In this August 2016 photo, a family on a raft approaches a boat in a flooded area of Jamalpur, Bangladesh. Probal Rashid via Getty Images

Charles Geisler, a sociologist at Cornell University, spent much of his career researching where poor people go when rich corporations swoop in and buy the land out from under their feet.
But his focus began to shift in 2005, after observing how storm surges tainted farmland in Bangladesh with salt water. Later that year, Hurricane Katrina struck New Orleans, submerging communities once believed to be safe behind levees and dikes. As floodwaters inundated Vietnam’s Mekong Delta last year, Geisler’s new worldview came into sharp relief.

The rising sea, he surmised, is the one displacement force more powerful than greed.
Geisler began collating climate and demographic research, and came to a dire conclusion: By the year 2100, rising sea levels could force up to 2 billion people inland, creating a refugee crisis among one-fifth of the world’s population.
Worse yet, there won’t be many places for those migrants to go.
His findings appear in the July issue of the journal Land Use Policy.
“We have a pending crisis,” Geisler, a professor emeritus of development sociology at Cornell, told HuffPost. “This relocation and huge mass migration from the coastal zone, it’s going to take place in this century and the next century.”

To get the 2 billion figure, Geisler extrapolated from a 2015 study published in the journal PLOS One. That research predicted that by 2060, there would be some 1.4 billion people living in low-lying coastal regions at risk from sea level rise. Drawing from nearly a dozen other studies, Geisler and his co-author, the University of Kentucky climate researcher Ben Currens, modeled what he called a “rather extreme scenario.”

“The paper is the worst-case scenario,” Geisler said. “We looked for estimates in these various barriers to entry that were coming from the most draconian changes that could hit us from climate change and sea level rise.”
Geisler outlined three obstacles, or “barriers to entry,” to relocating people driven inland from their homes by rising seas. The first problem is that climate change isn’t just affecting coastal communities. Droughts and desertification could make areas safe from sea level rise uninhabitable at worst, and incapable of sustaining a large influx of migrants at best, Geisler said. The second issue is closely linked: If climate refugees flock to cities, increasing the urban sprawl into land once used to farm food, those metropoles could lose the ability to feed their inflated populations.
The third issue involves physical and legal barriers, meaning regions and municipalities might erect walls and post guards to prevent climate migrants from entering and settling down. Geisler dubbed this phenomenon the “no-trespass zone.”
Geisler warned that too much of the conversation around climate adaptation is focused on building sea walls, learning to live with regular flooding, and relocating communities inland, as has happened in Alaska. These limited ideas of “adaptation” could leave humanity woefully unprepared for a mass migration that Geisler said could dwarf the current refugee crisis in Europe, driven by war, poverty and drought-linked famine in regions south and east of the continent. At least 65.6 million people have fled their homes, and the United Nations estimates that 20 people are forcibly displaced every minute by war and persecution alone. Adding unfettered climate change to that mix threatens to yield human catastrophe on a scale that is difficult to describe without sounding bombastic.
The U.S. is particularly at risk. Millions of mainland Americans could be forced to flee inland, sending the populations of at least nine coastal states downward, according a University of Georgia study released in April. Texas alone could have to take in as many as 2.5 million internal migrants.

The rising sea, he surmised, is the one displacement force more powerful than greed.

“My hope is that this paper will reorient planners and policymakers who use the term ‘adaptation’ in a very narrow way,” Geisler said. “It’s used either to mean fortifying coastal structures to keep the sea off the land, or it’s used to refer to moving a population from a coastal zone in some organized way.”

There are better ways to prepare, he said. He pointed to four counties in South Florida that began sharing hydrological data and research on the rate of sea level rise, then drafted a joint evacuation plan. Dealing with the possible results of runaway climate change requires “transboundary” planning, he said.
“Climate change is going to be with us for a long time, and the coastal zone population is going to be overwhelming as it moves inland,” Geisler said. “How are we going to employ these people? Where are we going to house them? What energy sources are they going to need?”
“Bottom line: Far more people are going to be living on far less land, and land that is not as fertile and habitable and sustainable as the low-elevation coastal zone,” he added. “And it’s coming at us faster than we thought.”

Links

Climate Scientists Reveal Their Fears For The Future

ABC Lateline - Kerry Brewster

Climate scientists rarely speak publicly about their personal views. But in the wake of some extreme weather events in Australia, the specialists who make predictions about our climate reveal they're experiencing sometimes deep anxieties.

Transcript
DR SARAH PERKINS-KIRKPATRICK, RESEARCH FELLOW, UNSW CLIMATE CHANGE RESEARCH CENTRE: I think this one, it's one of my favourites.

KERRY BREWSTER: Four climate scientists at different stages in their lives and careers reveal the burden of knowing what predicted climate changes will bring.

PROF. KATRIN MEISSNER, DIRECTOR, UNSW CLIMATE CHANGE RESEARCH CENTRE: I think for years I was really living in two different worlds. I was a scientist at work who was just objectively looking at numbers, and, um, then over years starting to be more and more worried about my own life, but I separated it completely from my private life.
I think that was a little bit of a self-protection.
'That doesn't really work that well anymore. In the past few years, I carry this knowledge with me wherever I am.
That looks beautiful, Kaitlin! That looks amazing. Look at this.
My name is Katrin Meissner, I'm the director of the Climate Change Research Centre of the University of New South Wales.
I have been working in this field for the last 20 years and I have been mapping lots of concerning trends in that time.
Many people do not really understand how big a threat climate change is to humanity.
The changes that we see right now are much faster than anything we have seen in the climate history and that concerns me because it means that ecosystems might not be able to adapt.
It's going to be dramatic. It's going to be very dramatic.

SARAH PERKINS-KIRKPATRICK: I think one day in the last heatwave I measured 45 degrees outside in the shade in our front patio, and it was 39 on the inside. I was sleeping with wet towels on my legs to keep cool.
I'm Sarah Perkins-Kirkpatrick and I'm a research fellow at the University of New South Wales and when I look at is heatwaves, so how they have changed, why they have changed, what their changes will be in the future, how we measure them and the role of climate change behind the heatwaves.
I had conversations with my husband as these heatwaves were occurring in summer, going, "Are we doing the right thing? Is it right to bring kids into this world?" with me knowing how bad it's going to be.
There is so much wrong with climate change and there are so many impacts that we're already looked into that I can't change, that no-one can really change. It's going to be bad and it's almost why would you inflict that on someone?

JUSTIN OOGERS, PHD STUDENT, UNIVERSITY OF MELBOURNE: Okay, so that's where it's going to go.
My name is Justin Oogers, I'm doing a PhD at the University of Melbourne just looking at urban micro climate as it is now and looking at how we can improve it into the future.
We need to be able to plan our cities better, we need to be able to design them better, keeping in mind what's coming, keeping in mind these temperatures that are getting into the 50s in Melbourne, and often I can't believe that I'm saying that, but the computer models, all the research is telling us, this is what's coming.
Yeah, it's tragic. Whenever I talk to my wife about heatwaves, she gets scared of them and unfortunately I can't really give her any good news.
I have been married for about five years. Yes, we want children, but we're quite concerned about it, even scared of it.
Our parents both want us to have children and there's lot of joy that comes with having children, but at the same time, knowing what's coming with climate change, we have actually just been putting it off.

PROFESSOR DAVE GRIGGS, DIRECTOR, MONASH SUSTAINABLE DEVELOPMENT INSTITUTE: You can say you don't believe in gravity but the apple is still going to hit you on the head. You can say you don't believe in climate change but it's not going to stop it getting it hotter.
I think Australia is the most vulnerable developed country in the world to climate change.
My name is Professor David Griggs, I work at the Monash Sustainable Institute at Monash University.
My background is as a climate scientist and atmospheric physicist. In the past I had been the head of the intergovernmental panel on climate change, science working group secretariat. I have been director of the Hadley Centre for Climate Change which is the UK government research centre into climate change and I've been the vice-chair of the World Climate Research Programme.
I think we're heading into a future with a considerably greater warming than two degrees and when the world doesn't do something about it, that brings a whole range of emotions into play.
I mean, depression is what is clearly something, you know, you get days when you're down because you just, what you know and what you can see coming is not good.
For people living in Australia, it means that a lot of people will suffer and a lot of people will die.
The problem is nobody's death certificate will say this person died of climate change. It will say they will die of heat stress, or cardiac arrest or they died in a bushfire.

SARAH PERKINS-KIRKPATRICK: Climate scientists are under a lot of scrutiny. We get ridiculed a lot by certain people for being alarmists, by going too much into detail. Where in actual fact we're actually probably reservists and are very conservative in our estimates and make sure we're so sure of the numbers before we actually get them out there.
I don't like to scare people, but the future is not looking very good.

DAVE GRIGGS: I'm fortunate in that I live in Melbourne at the moment and Melbourne is one of the more climate adapted cities in Australia.
If I was living in Darwin or Brisbane, I would be seriously thinking about moving.
One of the important things about climate change when you think of it in the context of sustainable development...

KERRY BREWSTER: Among climate scientists the conversation is turning to their personal plans.

DAVE GRIGGS: We'll talk about where we're planning to retire to or where we're planning to move to, how we're planning to, you know, safeguard our families from, in the future.
And the consensus seems to be Tasmania. Tassie because it's the furthest south, it's the coolest.

SARAH PERKINS-KIRKPATRICK: We have thrown up the idea, you know, the potential if the opportunity came up is moving to Canberra. It's a city, it's got good infrastructure, it's got good employment opportunities.
Yes, it gets warm there and yes, it's a dry climate but the temperature doesn't get as hot as Sydney. Their night-time temperatures are a lot cooler and you can cope with extreme heat much better if you got cooler night-time temperatures to sleep.

JUSTIN OOGERS: For me and my wife, anywhere, maybe forced to move further south, and I'm sure that there's a lot of other people that are probably thinking the same thing.
My grandpa decided to move down to the coolest part of Australia. He's living on a boat south of Hobart and he's trying to drag me down to Tasmania. He's saying, "The University of Tasmania is down here. Should come down here", and I have often said to him I'd think about it.
My wife, she is a lot more keen to do it.

KATRIN MEISSNER: I find it really hard to decide on one particular region saying this one is going to be safe and we are just going to lock this one in.
I don't think there will be any safe places. I am, the impacts are going to be big.
So my approach is to be as mobile, as flexible as possible to be able to adapt to whatever is going to happen. My children are bilingual and we're working on a third language.
Both children have three passports, and they actually have the freedom to be able to study and work even in the European Union, or in Canada or in Australia.

KERRY BREWSTER: After scoping New Zealand and Tasmania, Professor Griggs has settled on his native England as a climate change retreat.

DAVE GRIGGS: London is over here on the right-hand side. So we're down here in the south-west with Devon and Cornwall.
This is the house. Just a traditional old English farm house built around 1800. That's my vegetable patch so that's where I can grow my own food.
I have certainly taken a look at this and looked at the climate projections and said yeah, that's going to be good for the next sort of 100 years or so.
When, some new fact comes in that makes me fearful, I think, well, at least, you know, I have done what I can to protect my family.
I can't protect them from changes in the global economy. I can't protect them from, you know, mass migrations, I can't protect them from, you know, some of the impacts that they are going to be, no matter where I move to and no matter where I buy my house, but I can do what I can.

Links

Guest Post: Is The Collapse Of The West Antarctic Ice Sheet Inevitable?

Carbon Brief - Prof Christina Hulbe* | Dr Christian Ohneiser*

Aerial view of Antarctica from NASA's IceBridge project, which has allowed scientists to determine that the West Antarctic Ice Sheet may be in irreversible decline. Credit: NASA.

In the late 1970s, glaciologist John Mercer was one of the first scientists to warn of “rapid deglaciation” of the West Antarctic Ice Sheet under human-caused warming. Other scientists, studying both modern Antarctica and the geologic record of its past, soon came to a similar conclusion.
Forty years on, with more observations and a better understanding of ice sheet processes, scientists have a clearer idea of how the ice sheet is changing. Yet different models still give different projections of when retreat of the West Antarctic Ice Sheet passes the point of no return.
So, is the eventual collapse of the West Antarctic Ice Sheet already inevitable? Model projections under low emissions scenarios suggest that ice sheet retreat could stabilise, but under medium and high scenarios, collapse is unstoppable.

Chain reaction
Ice sheets form where snow accumulates, densifies, and remains stored as ice on the land surface. Antarctica’s massive ice sheets sit astride the cold, windswept continental interior and funnel down towards the (relatively) warm ocean around the coast.
Where the ice meets the water, floating ice shelves form. These are seaward extensions of the ice sheet that connect land-based ice with relatively fast-changing parts of the climate system. Changing winds and warmer oceans bring warm water into contact with the floating ice, increasing the rate at which it melts.
Ocean-driven ice loss is already underway where the West Antarctic Ice Sheet flows into the Amundsen Sea. The best observations available indicate that relatively warm Circumpolar Deep Water has been able to intrude onto the Amundsen Sea continental shelf over the last few decades. The continental shelf is the area of seabed immediately surrounding a land mass, where the sea is relatively shallow compared to the open ocean beyond it.
The warmer-than-usual water increases the melt rate on the underside of floating ice shelves, causing them to thin. For the West Antarctic Ice Sheet, this thinning sets up a chain reaction that scientists think could be unstoppable.

The interdisciplinary and multi-institution Aotearoa New Zealand Ross Ice Shelf research programme aims to understand the processes and process interactions that determine how the ice shelf will respond to future warming. This field camp is in the middle of the ice shelf, about 350 km from Scott Base, at location selected to balance our interests in sub-ice oceanography, ice/atmosphere interaction, glaciology, and sedimentary records of the past. Later this year, we will return to the site with a hot water drill built at Victoria University of Wellington to bore through the ice to observe the ice/ocean interface directly, measure ocean properties, and sample sediments on the sea floor. Credit: Christina Hulbe.

‘Self-sustaining retreat’
In West Antarctica, most of the ice sheet rests on the seafloor, and the basin that it sits in grows deeper with distance from the coastline. This makes it particularly susceptible to a “self-sustaining retreat”.
The base of the ice sheet is below sea level, which means that the warm ocean can melt and thin the ice at the “grounding line” – the boundary between the grounded ice sheet and the floating ice shelf.
If we were to take only one measure of the well-being of the West Antarctic Ice Sheet, it would probably be the position of the grounding line. The position of the grounding line indicates the balance between water stored in the ice sheet and water returned to the sea. Processes acting at the grounding line can also drive the grounded ice to change.
Melting alone can cause grounding line retreat and sea level rise. But melting can also initiate something called the “marine ice sheet instability”. “Marine” because the base of the ice sheet is below sea level, and “instability” for the fact that once it starts, the retreat is self-sustaining.
Here’s how it works. If changes on the floating side cause ice on the grounded side to lift off from the seafloor and float, the grounding line will retreat. Because the ice flows more rapidly when it is floating than it did when grounded, the rate of ice flow near the grounding line will increase. Faster flow means thinning, which may in turn cause more ice to lift off and float. Because greater thickness also causes the ice to flow faster, grounding line retreat into the deep can also produce faster flow.
You can see this explained in the figure below.

Diagram showing why the West Antarctic Ice Sheet is particularly susceptible to runaway grounding line retreat. Source: Hulbe (2017).

Not whether ice sheets retreat, but how fast
It is not clear yet if this instability has already started along the Amundsen Sea coast. If it hasn’t, and if the ocean warming stops, the grounding line should balance out at a new location. If it has, the retreat will continue no matter what happens next.
Model predictions of the future of the ice sheet can vary by a factor of 10 or more for the same emissions scenarios. These differences depend on how the processes through which climate forces the ice to change are represented in the models. But the question isn’t whether or not climate change will drive ice sheet retreat, the question is how fast it will go, and the extent to which policy decisions to affect our carbon emissions can make a difference to the outcome.
Under medium and high emissions scenarios, the models agree that the West Antarctic Ice Sheet will eventually collapse. At the higher end, marine-based sections of the East Antarctic ice sheet also retreat. However, under low emissions scenarios – lower than our current pathway – retreat may be limited.
If the marine ice sheet instability has not been initiated, then once the warming stops, the rate of retreat declines and grounding lines stabilise. The implication is that wholesale loss of the West Antarctic Ice Sheet may not be inevitable. But the low-end ice sheet scenarios are not well understood and the more scientists study the geologic record of past ice sheet change, the more vulnerable the ice sheets appear to be.
Earth’s climate has been oscillating between relatively warm (interglacial) and relatively cold (glacial) conditions for the last five million years. Even before human influences on climate, those swings appear to have driven grounding line retreat deep into the West Antarctic Ice Sheet interior. Some of the warm swings were into what are called “super-interglacial” conditions. During these times, southern oceans were between 3C and 8C warmer than at present, the ice sheets were smaller, and global sea levels were higher than today.
The causes and timings of super-interglacials are not well understood and even the models most responsive to changing temperatures can’t reproduce the speed of ice loss. But these records make clear how sensitive the Antarctic ice sheets are to climate change, even before the extra kick from global warming. The record of the past never seems to yield less cause for concern.
The motto for early 21st Century cryospheric science should be “that happened faster than I thought it would.” Wherever we look, either in the past or in the present, we are challenged to keep up – in the ways we measure, theorise, project, and prepare for the future.

*Prof Christina Hulbe is geophysicist in the School of Surveying at the University of Otago in New Zealand
*Dr Christian Ohneiser is a paleoclimatologist in the Department of Geology at the same university.

Links

28/06/2017

Coral Reefs Could Be Gone In 30 Years

National Geographic - Laura Parker

World Heritage reefs will die of heat stress unless global warming is curbed, a new UN study finds.

A diver explores corals on the Great Barrier Reef off Australia, the largest living structure on Earth. PHOTOGRAPH BY DAVID DOUBILET, NATIONAL GEOGRAPHIC CREATIVE

The world's coral reefs, from the Great Barrier Reef off Australia to the Seychelles off East Africa, are in grave danger of dying out completely by mid-century unless carbon emissions are reduced enough to slow ocean warming, a new UNESCO study says.
And consequences could be severe for millions of people.
The decline of coral reefs has been well documented, reef by reef. But the new study is the first global examination of the vulnerability of the entire planet's reef systems, and it paints an especially grim picture. Of the 29 World Heritage reef areas, at least 25 of them will experience twice-per-decade severe bleaching events by 2040—a frequency that will "rapidly kill most corals present and prevent successful reproduction necessary for recovery of corals," the United Nations Educational, Scientific and Cultural Organization concluded. In some areas, that's happening already.

An aerial view of snorkel and dive boats at Sombrero coral reef system off the Florida Keys during spring extreme low tides. PHOTOGRAPH BY MIKE THEISS, NATIONAL GEOGRAPHIC CREATIVE

Divers swim past a reef wall teeming with fish. PHOTOGRAPH BY DAVID DOUBILET, NATIONAL GEOGRAPHIC CREATIVE

"These are spectacular places, many of which I've visited. Seeing the damage being wrought has just been heartbreaking," says Mark Eakin, a reef expert with the National Oceanic and Atmospheric Administration, and a lead author of the new report. "We're to the point now where caction is essential. It's urgent."

Mass Bleachings
By 2100, most reef systems will die, unless carbon emissions are reduced. Many others will be gone even sooner. "Warming is projected to exceed the ability of reefs to survive within one to three decades for the majority of the World Heritage sites containing corals reefs," the report says.
Reefs, often referred to as the rainforests of the oceans, occupy less than one percent of the ocean floor, but provide habitat for a million species, including a fourth of the world's fish. They also protect coastlines against erosion from tropical storms and act as a barrier to sea-level rise.

Giant soft coral, likely hundreds of years old, is rooted on a coral reef wall at a depth of 40 meters in New Caledonia. PHOTOGRAPH BY ENRIC SALA, NATIONAL GEOGRAPHIC

"It is terrifying to think of the repercussions of the global and large scale loss of reefs," says Ruth Gates, director of the Hawaii Institute of Marine Biology in Kaneohe, Hawaii. "The reduction in food supplies, the lack of coastal protection as the reef collapses and subsequent land erosion will make some places unlivable and people will have to move. And that's not even mentioning the collapse of reef-related tourism."
In the past three years, 25 reefs—which comprise three-fourths of the world's reef systems— experienced severe bleaching events in what scientists concluded was the worst-ever sequence of bleachings to date. The Great Barrier Reef was especially hard hit. Other reefs that experienced severe bleaching include the Seychelles, New Caledonia, 750 miles (1,210 kilometres) east of Australia, and the United States, off Hawaii and Florida.
"The last three years have been extremely depressing for me," Eakin, with NOAA, says. "We're seeing truly catastrophic damage to many reef systems around the world. The Great Barrier Reef damage we've seen is greater than anything we've seen in the past 20 years."

Humphead wrasse and other fish swimming in a coral reef Near Lord Howe Island, New South Wales, Australia. PHOTOGRAPH BY DAVID DOUBILET, NATIONAL GEOGRAPHIC CREATIVE

The consequences are already being felt by some people, and will quickly grow more severe, says Eakin's NOAA colleague and co-author Scott F. Heron. Low-lying islands such as Kiribati, a string of 33 coral atolls in the central Pacific Ocean, already see saltwater inundating freshwater drinking sources. Higher tides and crumbling reefs are causing more storm surges. Soon, loss of coral, especially when combined with global overfishing, will translate to fewer fish—and local protein shortages.
"These are real things that real people are experiencing," Heron says. "I've met these people. They've been to my house. This is happening."
Heron also notes that despite scepticism in some corners about climate change, even the crudest of models from two decades ago predicted just the type of reef damage seen today.
"If what the models projected back then has started to come true, even with all of their issues, then we should have good faith in the science of the current projections," Heron says. "And those projections say if we don't act there will be many, many serious impacts."

Saint Joseph Atoll, a nature reserve with a marine protected area in Seychelles Islands. PHOTOGRAPH BY THOMAS PESCHAK, NATIONAL GEORGAPHIC CREATIVE

Time To Act
Most World Heritage sites are managed locally to control pollutants from farm runoff or overfishing. Now, the "ubiquitous global threat" to reef systems has become so great, Eakin and Heron say, that local protections are not enough. They hope their new, bleak assessment will help the world's nations to realise that unless they move faster to reduce greenhouse gas emissions, these special places—and the people who rely on them—will suffer greatly, far sooner than expected.
"When someone needs help, the overwhelming majority of us will stretch ourselves to help out—it's a human trait. It's what makes us people," Heron adds. "That the people most impacted by these changes are not necessarily people we encounter in our day-to-day lives does not remove our responsibility to help them."

Links

'Long, Slow, Horrible': Former Defence Officers Warn Of Climate Impacts On National Security

Fairfax - Fergus Hunter

Former Defence Force officers, including a former chief of the Australian military, have warned that climate change will emerge as the defining security threat of the 21st century and urged governments to step up their responses accordingly.
The warnings come as the Senate convenes an inquiry into the national security implications of the environmental phenomenon, called by Greens senator Scott Ludlam. The government has dismissed the move, arguing it is unnecessary because of actions already being taken by the Defence Force.

Climate policy debate intensifies
Politicians from all sides have been very willing to share their thoughts on climate policy and the government's plan for a clean energy target.

But a former Defence Force chief, retired admiral Chris Barrie, says the overall response to the "existential threat" needs to be ramped up as Australia faces particular exposure to the consequences of extreme weather events, higher temperatures and sea level rises.
Mr Barrie said the world's governments were not on track to keep warming to 2 degrees celsius – the target laid out in the Paris climate accord – and said the impacts on humanity could be "long, slow, lingering and horrible".
"I think the climate change threat is pretty damn serious and we have fiddled around in terms of getting in place the right systems to head off the worst outcomes," he told Fairfax Media, calling for measured adaptation by the military and other sectors and rapid global reduction of emissions.
"The military have been working on it but their perspective is limited to responses to natural disasters and protecting bases. They are not at the forefront of heading off the challenge. That is the responsibility of the leadership at the very top and the community."
Experts have warned that Australia lies in a region described as "disaster alley", with booming populations that are exposed to cyclones, rising sea levels and extreme weather. These threats are predicted to worsen and unleash waves of climate refugees.
The 2016 Defence White Paper labelled climate change a "major challenge for countries in Australia's immediate region". Since then, Defence has established a climate security adviser in its upper echelons and factored in environmental planning and risk into its operations. They are also trying to reduce their greenhouse gas emissions.

Jackson Kiloe, the Premier of Taro in the Solomon Islands, standing where the shoreline used to be. Photo: Penny Stephens

"Climate change will see higher temperatures, increased sea-level rise and will increase the frequency and intensity of extreme weather events. These effects will exacerbate the challenges of population growth and environmental degradation, and will contribute to food shortages and undermine economic development," the white paper said.
Defence has also completed a study into the impact of sea level rise, flooding, storm surge and coastal erosion on bases and is conducting a similar analysis on the ability of training sites to continue under environmental upheaval.

Families internally displaced by drought arrive at makeshift camps in the Tabelaha area on the outskirts of Mogadishu, Somalia. Photo: AP

Retired army major Michael Thomas, now a senior fellow at the Centre for Climate and Security, said global warming increases the likelihood of instability in the region and further abroad, particularly for developing nations.
"I think it's the defining threat of this century. I can't think of any other threat that is transforming the planet on this level or scale. It's such a ubiquitous threat," he said.
"People might say terror is a threat and that's true but I don't think it's anywhere near what climate change is presenting itself as."
An often cited example of the environment as a "threat multiplier" is the severe, four-year drought that preceded the Syrian civil war, which has killed more than 400,000 people and displaced more than five million. The drought forced regional farmers and workers into the cities and created food shortages and political instability.
Mr Thomas praised the Defence Force for its work so far but said they had been handicapped by a decade of fraught political debates and policy uncertainty, comparing it to the unpredictable nature of national energy policy.
In a September 2016 address, Chief of Army Lieutenant General Angus Campbell warned that the 10 countries most at risk of sea level rise were in Australia's immediate region.
Lieutenant General Campbell compared the estimated cost of inaction, a 23 per cent hit to global GDP by 2100, to the cost of action, 1.6 per cent impact by 2050. He expressed fear that climate change was "the ultimate threat multiplier".

Links

Suing To Save The Climate: What To Do When Your Future’s At Risk And Your Government Doesn’t Care

Huffington Post - Kelly Rigg

New Zealand is the latest country to be sued for its failure to act on climate

Sarah Thomson

On June 8, U.S. District Judge Ann Aiken observed, "I have no doubt that the right to a climate system capable of sustaining human life is fundamental to a free and ordered society."
With these words, a case brought by a group of 21 young people against the government for failing to protect their right to a safe climate was granted permission to proceed to trial.
Her decision came nearly two years after the Urgenda Foundation sued the Dutch government and won – a decision which ordered the government to reduce emissions in line with scientific recommendations, by 25% from 1990 levels by 2020.
Although the governments of both countries are working to overturn these decisions, climate lawsuits are spreading rapidly around the world. Cases have been brought against the governments of Belgium, Switzerland, Norway, and Pakistan (not to mention countless others targeting corporate actors).
Next up is New Zealand, a country that is known for its ancient and spectacular natural landscapes and swaths of vast, untouched wilderness. But despite its pristine reputation, the country has a dirty secret: rising greenhouse gas emissions that make it one of the highest per capita emitters in the world, enabled by a woefully inadequate climate change policy.
That policy is about to come under sharp scrutiny in a court case being brought against the government by law student Sarah Thomson, which is due to be heard by a local court on June 26th.
Sarah claims that the government's inaction is completely out of step with the international scientific and political consensus regarding the steps needed to adequately respond to climate change.
It will be hard for the government to argue against her position.
After all, New Zealand is a part of this consensus: having accepted the findings of IPCC reports (the world's leading scientific body on climate change whose final reports are approved by governments) and ratified the Paris Agreement under the UN climate convention.
Under the Paris Agreement, countries agreed to hold temperature rise to well under 2°C, with the aim of limiting it to 1.5°C. To do so, they committed to reduce greenhouse gas emissions over the coming decades with the aim of reaching net zero emissions by the second half of the century. With those goals in mind, New Zealand's commitment is laughable – a reduction of only 11% by 2030 compared to 1990 levels.
This is irresponsible not only from an international perspective, but it is suicidal for New Zealand itself.
As Sarah's case points out, the IPCC has concluded that New Zealand will be hit with increasingly intense and frequent floods and wildfires if greenhouse gases continue to be emitted at current rates. And despite its relative isolation, the country can expect an influx of refugees from neighboring Pacific Island States as their islands ultimately disappear under the waves.
Indeed the first climate refugees have already arrived: in 2014, a family from Tuvalu was granted residence in New Zealand on humanitarian grounds, taking into account the impacts of climate change.
More requests are starting to come in, suggesting that this is only the tip of a melting iceberg.
If Sarah is successful, New Zealand's Minister for Climate Change Issues will have to revise the government's policy to bring it in line with the global consensus regarding the actions that developed countries must take to prevent dangerous climate change.
In the meantime, regardless of the outcome, Sarah has joined a powerful and growing global movement of citizens taking their governments to court for climate change.
Lawsuits are costly, and are generally seen as a strategy of last resort. But with only a few short years remaining to bend the curve on emissions to stave off a full-blown climate catastrophe, we can expect many more to come.
Desperate times clearly call for desperate measures.

Links