Scientists zero in on only solution to climate crisis

Scientists zero in on only solution to climate crisis

Panel of international climate scientists says the world has only until 2050 to become a zero-carbon society − but the rewards for doing so would be immense.

LONDON, 22 April, 2015 – If you want to know what we have to do to avoid catastrophic climate change, 17 of the world’s leading climate scientists have worked out a simple but challenging solution: the world, they say, must turn by mid-century into a zero-carbon society.

The signatories to today’s “Earth Statement” say: “This trajectory is not one of economic pain, but of economic opportunity, progress and inclusiveness. It is a chance too good to be missed.

“The latest science indicates that there are critical thresholds in the Earth system. Transgressing them may lead to dramatic and irreversible environmental changes.

“We are probably edging very close to such thresholds, and may already have crossed one with regard to melting of parts of Antarctica. Sea-level rise of more than one metre due to this event alone may be inevitable.”

Window of opportunity

They are convinced that time is short. “The window of opportunity is closing fast,” says Johan Rockström, chair of the Earth League, an international group of scientists from leading research institutions working on issues caused by climate change, natural resource depletion, land degradation and water scarcity.

“We are on a trajectory that will leave our world irrevocably changed, far exceeding the 2°C mark. This gamble risks disaster for humanity, with unmanageable sea-level rise, heat waves, droughts and floods.

“We would never consider this level of risk in any other walk of life, yet we seem prepared to take this risk with our planet. Conversely, the scientific evidence shows that we can create a positive future, but only with bold action now.”

The 2°C threshold is the limit beyond which world leaders have agreed to prevent global temperatures rising as climate change intensifies.

“For the sake of fairness, rich countries and progressive industries can and should take the lead and decarbonise well before mid-century”

The Earth League’s first Earth Statement is issued as a warning ahead of the UN climate conference in Paris in December − referred to by the UN Framework Convention on Climate Change as COP21, the 21st conference of the parties to the original climate treaty.

The League is supported in its statement − published today to mark Earth Day, an annual reinvigoration of the global environmental movement − by the Global Challenges Foundation.

Professor Jeffrey Sachs, director of the Earth Institute at Columbia University, US, and one of the authors of the statement, says: “COP21 is the moment of truth − the last chance to stay within the 2°C upper limit.

Quality of life

“The key to success is deep decarbonisation by mid-century. Our studies show that this can be accomplished, at modest cost, and with a significant improvement in the quality of life.”

The Earth Statement lists what it calls “eight essential elements of climate action”, which it says any agreement achieved in Paris in December should achieve in order to provide the world with a good chance of avoiding dangerous climate change.

They include the need for the process of deep decarbonisation to start immediately. One of the eight points, which may prove contentious, reads: “Equity is critical. Every country must formulate an emissions pathway consistent with deep decarbonisation.

“For the sake of fairness, rich countries and progressive industries can and should take the lead and decarbonise well before mid-century.”

Prof Rockström and Prof John Schellnhuber, a fellow Earth League member and director of the Potsdam Institute for Climate Impact Research, will present the Earth Statement tomorrow at the fourth Nobel Laureates Symposium on Global Sustainability in Hong Kong. – Climate News Network

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Antarctica blows hot and cold – for now

Antarctica blows hot and cold – for now

Natural variability may at the moment be affecting Antarctica’s temperature more than human activity, but climate change will still be a major influence.

LONDON, 19 April, 2015 – German scientists have identified a pattern of natural change in Antarctica. The discovery appears to suggest that human influence may not be a cause of apparent warming in the seas around the great, frozen continent. Instead, natural variability might have a role.

The finding doesn’t undermine the thesis that human burning of fossil fuels is enriching the atmosphere with greenhouse gases and triggering climate change: it might however account for the so-called pause in the rate of warming this century.

The verdict remains inconclusive. But new evidence published in the journal Climate Dynamics introduces a new layer of complexity in the understanding of the planetary climate system.

In brief, the rate of warming in the northern hemisphere is considerable, and highest in the Arctic Circle. Overall, the southern hemisphere remains colder, and evidence from the Antarctic has been ambiguous, although there have been widely reported fears of potentially dramatic change in West Antarctica. Rapid melting in the region would constitute a “climate tipping point” which would have consequences across the entire planet.

Too simple

But Josef Ludescher of the Institute for Theoretical Physics at the Justus Liebig University of Giessen and colleagues made an analysis of the full range of air temperature records from the southern continent and decided that the simple picture of a consistently cold and hostile world possibly modified by human activity was too simple: instead they found a propensity for “large and enduring natural excursions from the mean.”

Put simply, sometimes the winds blow colder, sometimes not quite so cold, but the coldest spells last for decades, followed by extended periods that might be measurably warmer overall.

The finding – it is based on sophisticated mathematical analysis and like all such hypotheses invites both confirmation and demolition by other climate science researchers – has a consequence: it means that the warming now observed in Antarctica may not be because of human influence. Or it may be that any human influence is so far swamped by a larger cyclic shift between two natural states.

“So far it seemed that there were hardly any major natural temperature fluctuations in Antarctica, so almost every rise in temperature was attributed to human influence,” said Armin Bunde of the Justus Liebig University, another member of the team.

“Global warming as a result of our greenhouse emissions from burning fossil fuel is a fact. However the human influence on the warming of West Antarctica is much smaller than previously thought. The warming of East Antarctica up to now can even be explained by natural variability alone.”

“At the end of this natural cold spell temperatures will rise even more fiercely – globally, but also in Antarctica”

But the study – if backed by other findings – could explain another climate puzzle. Although global warming increased rapidly during the last three decades of the last century, the rate of warming has slowed. All but one of the hottest years ever recorded have been in this century, and 2014 broke all records, but the rate at which the temperatures have risen has slowed.

There have been many potential explanations for this apparent slowdown. And perhaps the proposed Antarctic cycle has a role in that too.

“Our estimates show that we are currently facing a natural cooling period – while temperatures rise slowly but inexorably, due to our heating up the atmosphere by emitting greenhouse gases,” said another of the authors, Hans Joachim Schellnhuber, of the Potsdam Institute for Climate Impact Research.

“At the end of this natural cold spell temperatures will rise even more fiercely – globally, but also in Antarctica, which therefore is in danger of tipping.” – Climate News Network

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Polar bears weakened by pollution as well as warmth

Polar bears weakened by pollution as well as warmth

Climate change causing habitat loss and reduced food is the main problem for polar bears, but plastic waste and other pollutants are growing risks.

LONDON, 17 April, 2015 − Greenland’s polar bears have a thyroid problem. Their endocrine systems, too, are being disrupted. In both cases the culprit agency is environmental pollution by a range of long-lived industrial chemicals and pesticides.

Kristin Møller Gabrielsen of the Norwegian University of Science and Technology in Trondheim and colleagues report in the journal Environmental Research that they examined the liver, muscle and kidney tissues taken from seven polar bears killed by Inuit hunters in East Greenland in 2011 and analysed the effect of more than 50 contaminants in plasma samples from Ursus maritimus, to see what effect organohalogen compounds could have on the bears’ thyroid systems.

All mammals have thyroid systems, and these are physiologically essential for growth, development, reproduction, stress response, tissue repair, metabolism and thermoregulation (an animal’s ability to keep its body temperature within limits): disruption at any stage of life can be damaging, but thyroid regulation is vital in the earlier stages of life.

But the researchers found high concentrations of plastic pollution and pesticide contamination in the creatures’ tissues, many of which could affect the hormonal systems.

Retreating ice

Polar bears face an uncertain future: the Arctic’s most iconic predator depends on sea ice for access to the most nourishing prey – seals − but thanks to global warming driven by greenhouse gases discharged by humankind since the start of the Industrial Revolution, the ice is in retreat. The bears can and do forage on land for small prey, eggs, berries and so on, but new research suggests that this is unlikely to help them much.

“The health of the Arctic polar bear is being attacked from all fronts, but among many other factors is the exposure to environmental contaminants,” said Maria Jesus Obregon, of the Biomedical Research Institute in Madrid, one of the authors.

“A wide variety of organochlorine compounds and pesticides have an effect on the thyroid hormones in plasma, tissues and deiodinase enzymes, which are in charge of stabilising the thyroid hormones in tissues.”

The biggest problem that confronts Ursus maritimus is still climate change, loss of habitat and a more precarious food supply. But as a marine mammal, the bear is exposed to a huge range of pollutants delivered by modern industry, transport and commerce.

Conservation guidelines

Researchers in February calculated that in 2010, around eight million tons of plastic waste
ended up in the world’s oceans.

A second team of researchers has framed guidelines for the conservation of the polar bear, and proposed 15 measures that could determine the factors important in saving the creature from ultimate extinction.

They report in the journal Science of the Total Environment that they questioned 13 specialists from four nations to propose ways of measuring polar bear health. Not surprisingly, climate change topped the list of threats, but the list also included nutritional stress, chronic physiological stress, diseases and parasites, and increasing exposure to competitors. Exposure to contaminants was the third largest threat.

“We still don’t know to what extent environmental changes will affect polar bear health and therefore its conservation,” say the authors. − Climate News Network

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Permafrost holds key to release of trapped carbon

Permafrost holds key to release of trapped carbon

The frozen soil of the northern polar regions holds billions of tonnes of organic carbon – and global warming could speed its escape into the atmosphere.

LONDON, 14 April, 2015 − Three sets of scientists in the same week have helped narrow the uncertainties about how the natural world will respond to extra carbon dioxide in the atmosphere caused by the burning of fossil fuels.

Carbon locked in the frozen earth will escape gradually as the Arctic permafrost melts – but the scientists say the process could accelerate.

As greenhouse gas levels soar, and soils warm, and plant roots tap down into the carbon stored there by centuries of ancient growth, they will release potent chemicals that will accelerate microbial attack – and speed up the release of carbon dioxide into the atmosphere.

The soil carbon cycle is one of the great headaches of climate science. And the Arctic is the first place to look for answers about it, and about how the Earth and oceans that store atmospheric carbon will respond to global warming.

Locked away

Around half of the world’s buried organic carbon is locked away in the soils of the northern circumpolar permafrost, and this huge vault of deep-frozen peat and leaf litter – more than 1,000 billion metric tonnes in the top three metres, at the latest estimate − contains twice as much carbon as is held in the atmosphere.

But the Arctic is the fastest-warming region on the planet, so what will happen as the permafrost thaws and plants begin to move north? Would it all be surrendered to the atmosphere in one devastating exhalation, triggering an explosion in global warming and causing trillions of dollars in economic damage?

An international team within the Permafrost Carbon Network thinks not. Their verdict, published in Nature journal, is that the current evidence suggests “a gradual and prolonged release of greenhouse gas emissions in a warming climate”. That is, humankind would have time to adapt.

“The data from our team’s syntheses don’t support the permafrost carbon bomb view,” says one of the team members, David McGuire, professor of landscape ecology at the University of Alaska Fairbanks.

“What our syntheses do show is that permafrost carbon is likely to be released in a gradual and prolonged manner, and that the rate of release through 2100 is likely to be of the same order as the current rate of tropical deforestation in terms of its effects on the carbon cycle.”

Since the tropical forests are already under pressure, this is hardly good news. And the picture is not a simple one.

“Even small changes will have serious effects on carbon concentrations in the atmosphere, and by extension on climate”

As the permafrost thaws, the soil microbes will get to work on the buried carbon, which will inevitably add to the soil warming, and provide an instance of what engineers call positive feedback, according to a team led by Jøgen Hollesen, senior researcher at the University of Copenhagen’s Centre for Permafrost.

He and colleagues report in Nature Climate Change that when they measured heat production in 21 contrasting organic permafrost soils, they found it to be between 10 and 130 times higher than in mineral soils measured in Greenland − and this would have “crucial implications for the amounts of carbon being decomposed”.

And in the same issue of Nature Climate Change, a team led by researchers from Oregon State University have confirmed that any kind of warming or plant growth is likely to get the soil microbes working as hard as they can – partly because the plants use chemistry to free the soil carbon so the bacteria can start to turn it back into carbon dioxide.

Neither of the two Nature Climate Change studies was directly concerned with climate change. The Danish scientists’ findings sprang from concern about what warming might do to the ancient middens that hold as-yet-unexamined evidence of early human settlement in the Arctic. The Oregon team were more concerned about the interactions that go on in the soil, and how they could be measured.

Chemical bonds

They found that plant roots released an exudate that acted to release the chemical bonds that keep a carbon bound to non-organic minerals in the soil. Warming could only speed the process, so more carbon dioxide will get into the atmosphere from the soil because of global warming.

This, again, is positive feedback at work. And it suggests climate scientists might be underestimating carbon loss from the soil by as much as 1% a year.

“Our main concern is that this is an important mechanism, and we are not presently considering it in global models of carbon cycling,” says soil and environmental geochemist Markus Kleber, one of the authors of the Oregon report.

“There is more carbon stored in the soil, on a global scale, than in vegetation, or even in the atmosphere. Since this reservoir is so large, even small changes will have serious effects on carbon concentrations in the atmosphere, and by extension on climate.” – Climate News Network

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Canada will lose many glaciers as climate warms

Canada will lose many glaciers as climate warms

Climate change could cause many glaciers in western Canada to start to disappear by 2040, affecting people and places that depend on their water.

LONDON, 10 April, 2015 − As the world warms, many of the great frozen rivers of Canada will not just retreat, but could vanish altogether.

New research suggests that maritime glaciers in the far northwest might survive, but more than two-thirds of Canada’s existing glaciers in British Columbia and Alberta could be lost altogether by 2100.

Garry Clarke, a glaciologist at the University of British Columbia in Vancouver, says: “Soon our mountains could look like those in Colorado or California, and you don’t see much ice in those landscapes.”

The consequences for the forests, grasslands, animals and communities that depend on glacial meltwater could be serious. The disappearance of the glaciers will also create problems for Canada’s hydroelectric industry, for agriculture and grazing, for the mining industry, for the salmon fishery, and for tourism.

Professor Clarke and his colleagues report in Nature Geoscience that they devised a model – a high-resolution computer simulation – of the glaciers of western Canada that explicitly mimicked glacial flow. Then they tested it with a range of scenarios for climate change, driven by human combustion of fossil fuels and rising atmospheric carbon dioxide levels in the last two centuries.

“Once the glaciers are gone, the streams will be a lot warmer and this will hugely change freshwater habitat”

There are more than 17,000 glaciers in British Columbia and Alberta, covering more than 26,000 square kilometres of the two provinces, and holding an estimated 2,980 cubic kilometres of ice. This puts western Canada as more glaciated than the Himalayas (which have less than 23,000 sq kms of glacier): the entire continent of South America has only 31,000 sq kms of glacier.

The researchers found that maritime glaciers in the northwest would endure, in a diminished state. But overall, the volume of the glaciers in western Canada would shrink by 70%, give or take 10%.

Right now glaciers, most of them between 100 and 200 metres thick, are thinning at a rate of about a metre a year. The peak flow of meltwater would most likely occur between 2020 and 2040. Thereafter, the rivers would be in decline.

Potential sea level rise as a consequence of this, the scientists say, would be “modest” at around 6mm, but the consequences for that part of Canada would be substantial.

The Columbia River, which flows from the interior to the Pacific coast of Washington and Oregon, yields the largest hydroelectric production of any river in North America. And the impact on freshwater ecosystems could be considerable.

“These glaciers act as a thermostat for freshwater systems,” said Professor Clarke. “Once the glaciers are gone, the streams will be a lot warmer and this will hugely change freshwater habitat. We could see some unpleasant surprises in terms of salmon productivity.” – Climate News Network

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Cut carbon now to avoid climate tipping points

Cut carbon now to avoid climate tipping points

The price to be paid for not cutting greenhouse gas emissions could push the planetary climate system closer to irreversible “tipping points”.

LONDON, 3 April, 2015 – An international team of scientists has tried a new approach to addressing the complex argument about the costs of climate change – and, once again, the prediction is that the costs of inaction will be so much greater than paying the bills now.

The researchers − from the UK, Switzerland and the US − conclude that policy-makers must apply the brakes and put a high price on carbon emissions “before it is too late”.

Much of the argument on this issue revolves around the perceived cost of carbon emissions and any tax that should be imposed on fossil fuel use. Social scientists and economists and climate modellers have tried a number of approaches.

One group tried to work out the interval between the burning of fossil fuels and the consequent greenhouse warming, and concluded it could be as little as 10 years.

Other groups have separately tried to calculate the true cost of emitted carbon dioxide. The US government works on the basis of $37 in social costs per tonne emitted, but two US scientists proposed that the true cost in future health and habitat losses was probably six times higher.

“The additional carbon tax that our model recommends can be thought of as an insurance premium levied on society”

And yet another researcher began to examine the costs of petrol, or coal, or methane gas if the long-term economic damage and health costs were factored in, and concluded that these made “expensive” renewables cheap by comparison.

Now researchers from the universities of Exeter in the UK, Zurich in Switzerland and Chicago and Stanford in the US report in Nature Climate Change that they considered the risk that emitted greenhouse gases from fossil fuels would push the planetary climate system closer to what climate scientists call “tipping points.”

These are outcomes that would irreversibly change regional climate patterns, disrupt agriculture, precipitate greater flooding in some places, more sustained droughts in others, and accelerate sea level rise.

And, once again, they find that governments have underestimated the price to be paid by society for carbon dioxide emissions from fossil fuels.

“We are calling on policy-makers to respond to the prospect of triggering future climate tipping points by applying the brakes now and putting a high price on carbon emissions before it is too late,” says one of the authors, Tim Lenton, professor of climate change and earth system science at the University of Exeter.

“The additional carbon tax that our model recommends can be thought of as an insurance premium levied on society to delay irreversible changes in the future.”

The researchers selected five potential tipping points − all of which have separately been in the news recently. They relate to:

The researchers say their act-now, save-future-costs model not only demonstrates the dangers of underestimating the cost of future climate change, but is the first one to emerge from a purely market-based approach. The considerations do not have to be based on moral judgements about sustainability and the wellbeing of future generations. – Climate News Network

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Climate-driven loss of habitat endangers marine mammals

Climate-driven loss of habitat endangers marine mammals

Global survey of threatened Arctic species warns that conservation won’t work without regulation of greenhouse gas emissions to halt climate change.

LONDON, 2 April, 2015 − Three kinds of whale, six varieties of seal, the walrus and the polar bear all have things in common: they are marine mammals, they depend on the Arctic for survival as species, they are vulnerable, and biologists know surprisingly little about them.

And since the Arctic is warming twice as fast as the rest of the planet, their future could become even more threatened as climate change increases habitat loss.

The stress, so far, is on the word “could”, as the first challenge is to establish the facts.

A global study team led by Kristin Laidre, principal scientist at the University of Washington Polar Science Centre in Seattle, reports in the journal Conservation Biology that marine mammals are “disproportionately threatened and data poor compared with their terrestrial counterparts”.

The narwhal, beluga and bowhead whales, the ringed, bearded, spotted, ribbon, harp and hooded seals, the walrus, and the polar bear are “particularly vulnerable due to their dependence on sea ice”.

Important predators

All these animals make their living on the ice and in waters north of the Arctic Circle, and all are important predators. They are also important to indigenous and settler peoples in the frozen North as many can be legally harvested, and others are iconic tourist attractions. Either way, they help communities survive.

“These species are not only icons of climate change, they are also indicators of ecosystem health, and key resources for humans,” Dr Laidre says. “Accurate scientific data – currently lacking for many species – will be key to making informed and efficient decisions about conservation challenges and trade-offs in the 21st century.”

So the researchers set out on what they believe is the first comprehensive global review of what is known about the populations of these animals, and about the way their local habitats may be changing.

“They need ice to find food, find mates, reproduce, and rear their young. It’s their platform of life.”

The study divided the Arctic into 12 regions and began to look at population numbers and trends, and the local pattern of seasonal change in the ice.

They identified 78 distinct populations of the 11 species, and began to assemble estimates of numbers. These range from millions for the ringed seals to a few hundred for the beluga whales of Ungava Bay in the Canadian Arctic.

In many cases, researchers had too little information even to make a guess about whether local populations of any species were stable, declining or increasing. In their table of the trends of the 11 species in the 78 populations, the word “unknown” occurs more than 60 times.

They also charted profound reductions in ice cover. The sea ice naturally advances each winter, and retreats each spring, but because of global warming driven by human emissions of greenhouse gases released by fossil fuel combustion, the pattern of advance and retreat has changed dramatically. By 2040, according to some projections, the Arctic could be more or less ice-free each summer.

Extended summer

But change is visible now. In most regions, the scientists found that the summer period was extended by between five and 10 weeks. In Russia’s Barents Sea, the summer ice period is now 20 weeks longer – five months – than it was 30 years ago.

This presents a threat to the polar bear, and to the seals on which they feed. “These animals require sea ice,” Dr Laidre says. “They need ice to find food, find mates, reproduce, and rear their young. It’s their platform of life. It is very clear those species are going to feel the effects the hardest.”

On the other hand, the whale species might benefit – at least for a while – from reduced ice cover. Open water could offer a wider feeding range and greater marine productivity, and therefore more food.

The scientists provide a set of general recommendations for biologists, local authorities, government agencies and international organisations concerned with conservation of Arctic marine mammals. They also have a message for the entire planet.

As Dr Laidre says: “We may introduce conservation measures or protected species legislation, but none of those things can really address the primary driver of Arctic climate change and habitat loss for these species. The only thing that can do that is regulation of greenhouse gases.” – Climate News Network

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Changing climate causes weather chaos in Chile

Changing climate causes weather chaos in Chile

What is being described as an environmental catastrophe is hitting Chile as torrential rains batter the north while the south suffers prolonged drought and wildfires.

LONDON, 30 March, 2015 − The Atacama desert region of northern Chile, one of the driest areas on Earth, has been hit in recent days by torrential rains and floods that have caused deaths, swept away homes and left much of the region without power.

Meanwhile, in the usually lush southern parts of the country, wildfires are raging across lands and forests parched by the longest period of drought in living memory, endangering some of the world’s richest flora and fauna.

“We are witnessing a massive environmental catastrophe,” Luis Mariano Rendon, head of the Accion Ecologica environmental group, told the AFP news agency.

Irreparable loss

“There have been whole species lost, such as the Araucaria araucana (monkey puzzle tree). They are trees that take hundreds of years to reach maturity, so this is a practically irreparable loss for current generations.”

The trees, a distant relative of the pine, are considered sacred by indigenous Mapuche people, and have been declared part of Chile’s unique natural heritage.

Scientists say the drought in the southern region – which is the powerhouse of Chile’s multi-billion dollar agricultural sector, and site of many of its famous vineyards – is a long-term trend, linked to climate change.

“There is no choice but to assume that the lack of water resources is a reality that is here to stay”

Chile’s president, Michelle Bachelet, says millions of dollars will have to be invested in desalination plants and new reservoirs to cope with the continuing drought. Canals and irrigation systems will also have to be upgraded.

“Faced with this critical situation,” he says, “there is no choice but to assume that the lack of water resources is a reality that is here to stay, and that puts at risk the development of important regions of the country.”

The Maipo river basin − which includes Santiago, Chile’s capital − contains nearly 40% of the country’s population and is an important area for agriculture, mining, and for power generation, much of which comes from hydroelectric sources.

Researchers, led by the Centre for Global Change at the Pontifical Catholic University of Chile, have been mapping the impact that climate change is likely to have on the Maipo basin.

Projections so far indicate that rainfall is likely to drop by 10% in the area over the period up to 2040, and by up to 30% by the end of the century. Meanwhile, temperatures will rise by 1˚C above the historical average over the next 25 years, and by between 2.5˚C and 3.5˚C by 2100.

Power source

The researchers have also been investigating glacier mass and melt in the Andes − the source of the bulk of the country’s water supply for millions of people in the region, and a crucial power source.

Scientists say that accelerated melting of Andean glaciers is being caused by atmospheric warming.

Water shortages are hitting not only the agricultural sector, but also mining – one of Chile’s major industries. The country is the world’s biggest producer of copper, and mining companies say they are having to invest in costly desalination plants in order to get water for processing copper concentrate from milled rock.

A drop in river levels feeding hydroelectric facilities is also leading to an increase in coal-fired power plants – a major source of climate-changing greenhouse gases.

Despite the recent rains in the north of the country, scientists are warning of the dangers of desertification in the region, with the northern desert advancing further south each year. – Climate News Network

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Shrinking of ice shelves raises sea level concerns

Shrinking of ice shelves raises sea level concerns

Evidence of rapid reduction of West Antarctica’s shelf ice could have serious implications for global sea levels in a warming world.

LONDON, 29 March, 2015 – Scientists in the US report that the volume of Antarctic shelf ice is diminishing, and that there has been an 18% shrinkage in the mass of some ice floating on coastal waters over the last 18 years.

And because much of the loss has been off West Antarctica, where shelf ice helps to keep the ice sheet stable, it could mean that global sea levels will rise even faster as a result of increased glacial flow into the ocean.

The findings once again raise concern about the link between man-made emissions of greenhouse gases and the dangerous new world of global warming, climate change and sea level rise.

Fernando Paolo, a researcher at the Scripps Institution of Oceanography at the University of California, San Diego, and colleagues report in the journal Science that they used continuous radar altimetry measurements − taken from three European Space Agency satellites between 1994 and 2012 − to compose a high-resolution record of shelf ice thickness.

Declined swiftly

They found that the total volume of shelf ice – the thickness multiplied by the shelf area – around Antarctica stayed more or less the same from 1994 to 2003, but then declined very swiftly.

The ice shelves of West Antarctica lost ice during the entire period, and although East Antarctica had been gaining shelf ice, these gains ceased after 2003. Some shelves had lost 18% of their volume.

“Eighteen per cent over the course of 18 years really is a substantial change,” Paolo says. “Overall, we show not only that the total ice shelf volume is decreasing, but we see an acceleration in the last decade.”

Shelf ice is frozen sea, so when it melts, it makes no difference to sea levels. But there could be an indirect effect.

“The ice shelves buttress the flow from grounded ice into the ocean, and that flow impacts sea levels rise, so that’s a key concern from our new study,” says co-author Helen Fricker, a glaciologist at the Scripps Institution.

In climate science, one such study is never enough: such conclusions need support from other studies. But the ice volume measurements are likely to add to growing concern about West Antarctica.

“The ice shelves buttress the flow from
grounded ice into the ocean, and that
flow impacts sea levels rise”

One earlier study looked at the potential loss of ice from West Antarctica by examining the “grounding lines” of the terrestrial glaciers, and found evidence of continuous and accelerating retreat. In effect, the West Antarctic ice sheet could be approaching a point of no return, scientists reported.

And a second group used other satellite measurements to calculate that ice was being lost from the southern continent at an increasing rate – around 150 cubic kilometres a year from West Antarctica.

So the Scripps study indirectly backs up earlier findings. It calculates that most mass has been lost from ice shelves in the Amundsen and Bellingshausen seas, off the coast of West Antarctica. These account for less than 20% of the total West Antarctic ice-shelf area, but contribute more than 85% of the total ice-shelf volume loss from West Antarctica.

Slow process

Were the West Antarctic ice sheet to melt completely – a long, slow process at almost any temperatures – sea levels would rise by more than three metres worldwide.

At current rates, a couple of the ice shelves off the western coast of the continent could disappear completely within 100 years, the Scripps team says.

Although the Arctic is one of the fastest-warming places on the planet, and although this warming has been directly linked to man-made climate change, the pattern of temperature shifts in the southern hemisphere has been more ambiguous.

The Scripps team have now begun to think about possible reasons for the loss of shelf ice in the far south, and one factor might be the cycle of El Niño events – natural and periodic bubbles of Pacific ocean warmth that have waxed and waned at intervals and changed the prevailing weather patterns worldwide through history.

“We’re looking into connections between El Niño events in the tropical Pacific and changes in the Antarctic ice sheet,” Paolo says. “It’s very far apart, but we know these teleconnections exist. That may ultimately allow us to improve our models for predicting future ice loss.” – Climate News Network

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Deep concerns as climate impacts on Gulf Stream flow

Deep concerns as climate impacts on Gulf Stream flow

Ocean scientists find evidence of an increasing slowdown in the Atlantic’s “invisible river” that could seriously affect weather and sea levels in the US and Europe.

LONDON, 25 March, 2015 − Climate scientists have once again confirmed an alarming slowdown in the circulation of the Atlantic Ocean − the process that drives the current that warms Europe, and powers the planetary climate.

And this time, they are prepared to say that the changes are recent − and may be linked to global warming.

The Atlantic Conveyor is a great invisible river that flows in two directions at the same time. The equatorial surface waters − warm, and therefore less dense − flow towards the north in the form of the Gulf Stream. Around Greenland, the denser and colder Arctic waters sink to the ocean bottom and begin their progress towards the south.

It is the difference in temperatures that maintains the turnover and keeps the climate engine going.

As a consequence, the two-way traffic of warm and cold water redistributes heat around the planet and keeps Britain and maritime Europe in relatively mild conditions.

But as global average temperatures rise, and the Greenland ice sheet melts, ocean scientists have warned that the speed of the ocean turnover could be put at risk.

Greater weakening

Stefan Rahmstorf, an ocean physicist at the Potsdam Institute for Climate Impact Research in Germany, is lead author of a report in Nature Climate Change that says they now have evidence of a slowdown during the 20th century, and greater weakening since the first alarms 40 years ago about the possible effects of greenhouse emissions.

“It is conspicuous that one specific area in the North Atlantic has been cooling in the past hundred years, while the rest of the world heats up,” Professor Rahmstorf says. “Now we have detected strong evidence that the global conveyor has indeed been weakening in the past hundred years, particularly since 1970.”

The paradox of the Atlantic current is that, in a warmer world, it could slow down or halt, which would deliver uncomfortable consequences for maritime Europe.

Fears of such an effect provided the scenario for the 2004 climate disaster movie, The Day After Tomorrow, which predicated a frozen Britain and a glaciated US.

“Now we have detected strong evidence that the global conveyor has indeed been weakening in the past hundred years, particularly since 1970”

No such extreme outcome was ever likely, but the Gulf Stream certainly makes a big difference to Britain. A former UK chief scientist once calculated that it delivered 27,000 times the warmth that Britain’s power stations could supply and, as a consequence, the UK is on average 5°C warmer than it might be, given its latitude.

Strength of current

At a number of points in the last two decades, researchers have wondered about the strength of the Atlantic current, but since systematic oceanographic record-keeping began only relatively recently, they had no way of distinguishing between a natural oceanic cycle and real change.

So the Potsdam team used all available data, and “proxy temperatures” derived from ice-cores, tree-rings, coral, and ocean and lake sediments, to reconstruct the story of the Atlantic current − and, in particular, the phenomenon called the Atlantic meridional overturning circulation (AMOC) − for the last 1,000 years.

The changes happening now have no precedent since 900 AD, they say. And the increasingly rapid melting of the Greenland icecap – bringing an increased flow of water that is less saline and also less dense, and therefore less likely to sink − could disturb the circulation.

The consequences of all this could, they say, “contribute to further weakening of the AMOC” in the coming decades.

Atlantic Conveyor: a graph of the Atlantic Meridional Overturning Circulation (AMOC). Image: Stefan Rahmstorf/PIK

Atlantic Conveyor: a graph of the Atlantic Meridional Overturning Circulation (AMOC).
Image: Stefan Rahmstorf/PIK

This is not the first such alarm. The same weakening was identified last year, but at the time researchers could not be sure they were not looking at a natural fluctuation.

Now they are sure, and they suspect that the cooling of the north Atlantic that they now observe is even stronger than most computer simulations have so far predicted.

“Common climate models are underestimating the change we’re facing, either because the Atlantic overturning is too stable in the models or because they don’t properly account for the Greenland ice sheet melt, or both,” says one of the co-authors, Michael Mann, professor of meteorology at Pennsylvania State University in the US.

Climate predictions

“That is another example where observations suggest that climate model predictions are in some respects still overly-conservative when it comes to the pace at which certain aspects of climate change are proceeding.”

Another of the authors, Jason Box, professor of glaciology at the Geological Survey of Denmark and Greenland, adds that “the human-caused mass loss of the Greenland ice sheet appears to be slowing down the Atlantic overturning − and this effect might increase if temperatures are allowed to rise further”.

The stakes are high. If the Atlantic conveyor system continues to weaken, ocean ecosystems will change, fishing communities will be affected, and some coastal cities – such as New York and Boston in the US − could be hit by additional regional sea level rises.

The 2004 Hollywood version – promoted with a huge poster of New York’s Statue of Liberty all but covered by ice – is not likely to happen. But if the ocean circulation weakens too much, there could be a relatively rapid and difficult-to-reverse change in the world’s climate system.

The Intergovernmental Panel on Climate Change estimates that there is a one-in-10 chance of this “tipping point” happening within the 21st century.

But the evidence from the Potsdam team is now likely to prompt other climate scientists to go back to their calculations and re-evaluate the risk. – Climate News Network

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