Antarctic ice is under attack from sea and air

Antarctic ice is under attack from sea and air

Satellite and radar studies show that twin forces causing the vast ice shelf to thin and become less stable could have a serious impact on global sea levels.

LONDON, 18 May, 2015 − Scientists have measured the rate of thinning of the great sea ice shelf of the Antarctic Peninsula and have identified the mechanisms at work above and below the shelf.

The collapse of floating sea ice makes no direct difference to global sea levels – but the effects could nevertheless lead to higher waters everywhere.

Paul Holland, of the British Antarctic Survey (BAS), and research colleagues from the US report in the journal The Cryosphere that they used satellite measurements and radar studies between 1998 and 2012 to confirm that the Larsen C ice shelf has lost four metres of ice, and is a metre lower at the surface.

Warmer waters

This is the largest of three shelves that have been under study for decades; the Larsen A and Larsen B shelves have already broken off and drifted north to warmer waters.

The Antarctic Peninsula is one of the fastest-warming regions of the world: 2.5°C in the last 50 years.

“What’s exciting about this study is we now know that two different processes are causing Larsen C to thin and become less stable,” says Dr Paul Holland, lead author of the BAS study.

“Air is being lost from the top layer of snow (called the firn), which is becoming more compacted, probably because of increased melting by a warmer atmosphere.

“We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present”

“We know also that Larsen C is losing ice, probably from warmer ocean currents or changing ice flow. If this vast ice shelf − which is over two and a half times the size of Wales, and 10 times bigger than Larsen B − was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise.”

A collapse of the shelf could occur within a century. When the two companion Larsen glaciers broke away, the glaciers that flowed from the ice-capped continent towards the sea began to accelerate.

Offshore ice, held fast to the shoreline, is a factor that helps keep glacier flow at its proverbially glacial pace. Once it has gone, the frozen rivers of ice onshore naturally begin to flow faster.

“We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present, and that will cause problems for coastal and low-lying cities,” says David Vaughan, director of science at the BAS.

“Understanding and counting up these small contributions from Larsen C and all the glaciers around the world is very important if we are to project, with confidence, the rate of sea-level rise into the future.”

The study is a confirmation of earlier research in which other groups, using different approaches, have already identified shelf ice loss and have warned that Antarctic melting could accelerate. Satellite-based measurements have also linked glacial melting with an acceleration in sea level rise.

Precision measurement of sea level rise is not easy. Oceans rise and fall with the tides, the water isn’t level anyway, and salinity and temperature differences in the oceans, and gravitational anomalies in the ocean basins, all mean that the ocean surfaces naturally undulate.

And the continents don’t keep still. Land surfaces from which researchers base their measurements also slowly rise or fall.

Accelerated rise

Christopher Watson, senior lecturer in the School of Land and Earth at the University of Tasmania, Australia, and colleagues report in Nature Climate Change that a different approach to the problem suggests that – contrary to previous estimates – sea level rise has accelerated in the last decade.

He and his colleagues searched not just global positioning satellite evidence from the surface waters but also from the land for signs of “bias” in the data. They also used evidence from hourly tide gauges from around the world and recalculated the rate of change.

What they found was that, overall, sea level rise in the last two decades has been at a rate just under, rather than just over, 3mm a year.

But the overestimate for the first six years of the survey had been much higher, which in turn suggested that the rate of rise had actually accelerated during this century, in a way that is consistent with the rate of glacial melting − at least from the Greenland and West Antarctic ice caps. – Climate News Network

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Permafrost thaw’s runaway effect on carbon release

Permafrost thaw’s runaway effect on carbon release

Arctic warming is causing organic carbon deep-frozen in the soil for millennia to be released rapidly into the air as CO2, with potentially catastrophic impacts on climate.

LONDON, 14 May, 2015 − An international team of scientists has settled one puzzle of the Arctic permafrost and confirmed one long-standing fear: the vast amounts of carbon now preserved in the frozen soils could one day all get back into the atmosphere.

Since the Arctic is the fastest-warming place on the planet, such a release of greenhouse gas could only accelerate global warming and precipitate catastrophic climate change.

That the circumpolar regions of the northern hemisphere hold vast amounts of deep-frozen carbon is not in question.

The latest estimate is 1,700 billion tonnes, which is twice the level of carbon dioxide in the atmosphere and perhaps 10 times the quantity put into the atmosphere by burning fossil fuels since the start of the Industrial Revolution.

Hazard underlined

In recent weeks, researchers have already underlined the potential hazard. But the big question has been that if some of the trapped carbon must be escaping now, where is it going?

Researchers have checked the mouths of the Arctic rivers for the telltale evidence of ancient dissolved organic carbon – partly-rotted vegetable matter deep-frozen more than 20,000 years ago − and found surprisingly little.

Now Robert Spencer, an oceanographer at Florida State University, and colleagues from the US, UK, Russia, Switzerland and Germany report in Geophysical Research Letters that the answer lies in the soil − and in the headwater streams of the terrestrial Arctic regions.

Instead of flowing down towards the sea, the thawing peat and ancient leaf litter of the warming permafrost is being metabolised by microbes and released swiftly into the atmosphere as carbon dioxide.

“We found that decomposition converted 60% of the carbon in the thawed permafrost to carbon dioxide in two weeks”

The scientists conclude that the microbes, once they get a chance to work at all, act so fast that half of all the soil carbon they can get at is turned into carbon dioxide within a week. It gets into the atmosphere before it has much chance to flow downstream with the soil meltwater.

The researchers centred their study on Duvanny Yar in Siberia, where the Kolyma River sluices through a bank of permafrost to expose the frozen organic carbon.

They worked at 19 different sites − including places where the permafrost was more than 30 metres deep − and they found tributary streams made entirely of thawed permafrost.

Measurement of the carbon concentration confirmed that it was indeed ancient. The researchers analysed its form in the meltwater, then they bottled it with a selection of local microbes, and waited.

Used by microbes

“We found that decomposition converted 60% of the carbon in the thawed permafrost to carbon dioxide in two weeks,” says Aron Stubbins, assistant professor at the University of Georgia’s Skidaway Institute of Oceanography. “This shows that permafrost carbon is definitely in a form that can be used by the microbes.”

The finding raises a new – and not yet considered – aspect of the carbon cycle jigsaw puzzle, because what happens to atmospheric and soil carbon is a huge element in all climate simulations.

At he moment, permafrost carbon is not a big factor in projections by the Intergovernmental Panel on Climate Change.

Dr Spencer says: “When you have a huge frozen store of carbon and it’s thawing, we have some big questions. The primary question is, when it thaws, what happens to it?

“Our research shows that this ancient carbon is rapidly utilised by microbes and transferred to the atmosphere, leading to further warming in the region, and therefore more thawing. So we get into a runaway effect.” – Climate News Network

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Plant growth may speed up Arctic warming

Plant growth may speed up Arctic warming

Arctic plants may absorb more greenhouse gases as the region warms – but scientists say this could intensify the warming rather than moderate it.

LONDON, 10 May, 2015 – Green may not automatically mean innocent or planet-friendly after all. Korean and German scientists have identified a mechanism that could encourage plants to take up more carbon dioxide – and at the same time amplify Arctic warming by 20%. This counter-intuitive finding is published in the Proceedings of the National Academy of Sciences.

Jong-Yeon Park of the Max Planck Institute for Meteorology and colleagues have been looking at the role of phytoplankton, those tiny marine plants that flourish around land masses, exploit the nutrients that flow from rivers and turn the blue ocean sea-green. Like any grass or shrub or tree, they exploit sunlight and employ photosynthesis to soak up atmospheric carbon dioxide.

So as the Arctic Ocean warms, because of increasing emissions of carbon dioxide from the burning of fossil fuels, the ice melts, the blue sea water absorbs more sunlight, and the green things get a chance to grow and soak up some of that greenhouse gas as organic carbon in plant tissues. This is what engineers call negative feedback.

But it may not work like that. The scientists matched up a model of the climate system with a model of the ecosystem and did all the sums again. And they found that instead of reducing warming, an explosion of phytoplankton growth could actually amplify it.

More warming

If the seas warmed and the ice melted, then the overall albedo – the reflectivity of the Arctic – would be changed. More high energy solar radiation would get into the sea, and the phytoplankton harvest would be greater and go on for longer.

But more phytoplankton would mean more biological activity, which would directly warm the surface layer of the ocean, “triggering additional positive feedbacks in the Arctic, and consequently warming the Arctic further,” the authors warn.

“We believe that, given the inseparable connection of the Arctic and global climate, the positive feedback in Arctic warming triggered by phytoplankton and their biological heating is a crucial factor that must be taken into consideration when projecting future climate changes,” said Jong-Seong Kug, a professor at Pohang University of Science and Technology in Korea.

Science like this is a reminder that the climate system is a subtle and complex machine driven by sunlight, atmosphere, water – and carbon. A British team has warned that rainforests could in fact be emitting much more carbon than climate modellers have accounted for. That’s because they haven’t allowed for all of the dead wood.

“A large proportion of forests worldwide are less of a sink and more of a source”

Marion Pfeifer of Imperial College and colleagues report in Environmental Research Letters  that they surveyed a large area of forest in Malaysian Borneo to make their calculations.

Pristine, untouched forest is rare. Most forests provide an income for someone, and increasingly parts of the great forests are exploited by loggers and planters. In untouched forests, dead wood makes up less than 20% of the biomass. Dr Pfeifer and her colleagues found that in partially-logged forests, the dead wood could account for 64% of the biomass.

Details such as this could send climate modellers back to the drawing board. That is because the great riddle of climate science is: where does all the carbon go? The assumption has been that forests are “sinks” that collect atmospheric carbon. But that depends on the forest.

“I was surprised by how much of the biomass dead wood accounted for in badly-logged forests. That such logged forests are not properly accounted for in carbon calculations is a significant factor. It means that a large proportion of forests worldwide are less of a sink and more of a source, especially immediately following logging, as carbon dioxide is released from dead wood during decomposition,” Dr Pfeifer said.

“Selectively-logged tropical forests now make up about 30% of rainforests worldwide. That means such global calculations are wrong at least 30% of the time.” – Climate News Network

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Scientists weigh up new evidence on Antarctic ice melt

Scientists weigh up new evidence on Antarctic ice melt

Southern continent’s mysteries start to unfold as satellite data is used to measure the extent and pattern of increased ice loss that threatens to be a “runaway problem”.

LONDON, 7 May, 2015 − Antarctica has been losing its ice cover at an average rate of 92 billion tons a year since at least 2003, according to new research.

And while the scientists can’t yet say for certain that human-made climate change is the main cause, they warn that the ice loss has the potential to have serious impacts on sea level rise.

The southern continent is the Earth’s largest store of fresh water, but is also its least studied area, having had no known human visitors until the late 18th century. So while scientists have a clear idea of processes at work in the Arctic, the big picture at the other end of the planet has been uncertain.

Heavier snowfalls

West Antarctica has been losing vast chunks of ice, but greater average warmth has meant there have been heavier snowfalls, and the icepack in east Antarctica has been on the increase.

Now Christopher Harig and Frederik Simons, geoscientists at Princeton University in the US, report in the journal Earth and Planetary Science Letters that gravitational satellite data has delivered a method of “weighing” the ice sheet, and identifying a pattern of change.

Most of the loss has been from the West Antarctic region, where the glaciers are increasingly unstable. In 2008, the region was shedding ice at the rate of 121 billion tons a year. By 2014, this rate of loss had doubled.

At the same time, the ice sheet in East Antarctica had thickened – but  the gain made up for only about half the ice lost from the west.

Most scientists would be hard-pressed to find mechanisms that do not include human-made climate change”

In the period since 2003, ice loss over the whole continent increased at the rate of six billion tons a year. West Antarctica’s melting rate, however, accelerated by 18 billion tons a year during the same timespan.

So the researchers did the sums and arrived at an annual average loss of 92 billion tons a year. This could be envisaged as an iceberg the size of Manhattan Island in New York, and more than 1,600 metres high.

What the researchers cannot be sure of is the cause: is a natural cycle of climate at play, or is it a consequence of global warming because  of greenhouse gas emissions from the burning of fossil fuels?

“We have a solution that is very solid, very detailed and unambiguous,” Dr Simons says. “A decade of gravity analysis alone cannot force you to take a position on this ice loss being due to anthropogenic global warming. All we have done is take the balance of the ice on Antarctica and found that it is melting – there is no doubt.

Rapidly accelerating

“But with the rapidly accelerating rates at which the ice is melting, and in the light of other, well-publicised lines of evidence, most scientists would be hard-pressed to find mechanisms that do not include human-made climate change.”

The two scientists used data from a US-German research satellite called GRACE − short for Gravity Recovery and Climate Experiment.

The agency linked to the ice loss is a measured warming of the southern ocean that is reducing the sea ice, which in turn holds back the flow of ice on land. So glaciers are melting, and flowing towards the sea at a faster rate.

“The fact that West Antarctic ice melt is still accelerating is a big deal because it’s increasing its contribution to sea level rise,” Dr Harig says. “It really has the potential to be a runaway problem.

“It has come to the point that if we continue losing mass in those areas, the loss can generate a self-reinforcing feedback, whereby we will be losing more and more ice, ultimately raising sea levels.” – Climate News Network

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No green light for whitening Arctic’s melting ice

No green light for whitening Arctic’s melting ice

Scientists pour cold water on the idea of preventing ice melt by using geo-technology to keep it white so that it reflects sunlight and stays frozen.

LONDON, 4 May, 2015 – Yet another geo-engineering solution to climate change has been proven potentially useless: even if you could paint the Arctic white, the world would still get warmer.

For the second time in months, scientists at the Carnegie Institution for Science in the US have shown that some technological solutions won’t work even in principle, let alone in practice.

Geo-engineering is, for some, the simple technological answer to climate change: if humans have inadvertently warmed the planet’s climate through technological change, then surely they can cool it again intentionally through technological ingenuity.

But Carnegie global ecologist Ken Caldeira and research colleagues − having already demonstrated that piping cold deep waters to the ocean surface would accelerate global warming, rather than reduce it − now report in Environmental Research Letters that changing the reflectivity of the northern hemisphere won’t have the intended consequences either.

Climate machinery

Caldeira, Ivana Cvijanovic, now at the Lawrence Livermore National Laboratory, and Douglas MacMartin, of the California Institute of Technology, decided to consider an aspect of the climate machinery known as albedo. This is a measure of the planet’s reflectivity.

It works like this: dark colours, such as blue oceans and green rainforests, absorb more sunlight, while white and pale surfaces – snow caps and ice sheets, for instance  – reflect most sunlight.

So the Arctic and Antarctic keep cold simply by staying frozen. But any consistent thawing pattern will make an icy region warmer, at an increasing rate.

This is happening at measurable speed, in the northern hemisphere. “By the middle of the century, the Arctic Ocean is predicted to be ice-free during part of the year,” Dr Cvijanovic says. “This could create substantial ecological problems in the Arctic, including habitat range and loss of biodiversity.

“However, the problem is not only local. A number of studies have indicated that Arctic sea ice loss can affect weather patterns across the northern mid-latitudes, including Europe, most of North America and much of Asia.”

“Even if you could do it, the direct negative consequences of reducing the amount of sunlight available to marine ecosystems could be huge”

So it would make sense to keep the Arctic cold and white − perhaps by filling the ocean with floating reflective grains, or the air above it with tiny bubbles to bounce back the incoming sunlight.

But the Carnegie team decided to work out, with help from computer models, what a whiter Arctic would achieve in a world in which humans went on burning fossil fuels in ever-increasing quantities, in which the atmosphere eventually held four times the carbon dioxide levels recorded at the start of the Industrial Revolution, and in which average planetary temperatures went up by a devastating 10°C.

Cooling effect

The whitening of the Arctic would restore a percentage of the ice – about three-quarters of a square kilometre for every whitened square kilometre. But the cooling effect would be much more modest.

And the return of the ice would not preserve the permafrost – home to colossal quantities of organic carbon that could, if released, become carbon dioxide – or prevent escapes of another potent greenhouse gas, methane.

While it might work to keep a bay or inlet frozen, it would not, in principle, save a frozen ocean, or save the world from catastrophic climate change.

“Simply put, our results indicate that whitening the surface of the Arctic Ocean would not be an effective tool for offsetting the effects of climate change caused by atmospheric greenhouse gases,” Professor Caldeira says.

“Furthermore, it is not clear to me that there is a technologically feasible way of actually doing this. And even if you could do it, the direct negative consequences of reducing the amount of sunlight available to marine ecosystems could be huge.” – Climate News Network

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High anxiety that mountain peaks are warming faster

High anxiety that mountain peaks are warming faster

Scientists call for international efforts to determine why temperatures on high-altitude mountains appear to be rising faster than in nearby lowlands.

LONDON, 28 April, 2015 − Temperatures could be climbing on mountains − with new research suggesting that the highest altitudes may be warming at a rate greater than expected.

Members of the Mountain Research Initiative collective report in Nature Climate Change that they found evidence that mountain peak regions were warming faster than the surrounding plateaus and lowlands.

The study − by Nick Pepin, leader of the Environmental Processes and Change Research Group at Portsmouth University in the UK, and colleagues from the US, Switzerland, Canada, Ecuador, Pakistan, China, Italy, Austria and Kazakhstan − comes with more than the usual set of health warnings.

The authors concede that the evidence is “extremely sparse”. But just as the Arctic region – the high latitudes of the northern hemisphere – is warming faster than anywhere else in the world, so the high altitude could also be at risk. The important thing is to find out.

No long-term data

There are few weather stations above 4,500 metres, and no long-term data for peaks higher than 5,000 metres anywhere in the world. The summit of Kilimanjaro, Africa’s highest mountain, has been monitored longest of all, but measurements have been recorded there on a systematic basis only for the last decade.

Other indications come from the Tibetan plateau, where temperatures recorded at 139 stations have risen steadily over the past 50 years, and the rate of change is accelerating.

“There is growing evidence that high mountain regions are warming faster than lower elevations,” Dr Pepin say. “Such warming can accelerate many other environmental changes, such as glacial melt and vegetation change, but scientists urgently need more and better data to confirm this.

“The social and economic consequences could be serious, and we could see much more dramatic changes sooner than previously thought”

“If we are right, and mountains are warming more rapidly than other environments, the social and economic consequences could be serious, and we could see much more dramatic changes sooner than previously thought.”

Kilimanjaro’s snow-covered peak in 1938. Image: Mary Meader/American Geographical Society Library via Wikimedia Commons

Kilimanjaro’s snow-covered peak in 1938.
Image: Mary Meader/American Geographical Society Library via Wikimedia Commons

There are two obvious causes for concern, the first being the simple problem of biodiversity. Plants and animals that occupy the highest elevations are at the optimum limits of their climatic tolerance, and if the climate gets warmer, they must move uphill to survive.

There is already evidence from alpine Switzerland that this is indeed happening. But those species already at the highest altitudes have nowhere else to go −  and so face extinction.

The second concern relates to an even more immediate impact. The highest mountain regions are glaciated, and this store of winter snow and ice becomes a source of spring and summer meltwater on which farmers, cities and even whole nations have grown to depend.

There is also good evidence that glaciers are in retreat, almost everywhere in the world. So the economic consequences could be considerable.

Endangered species

“This alone requires that close attention be paid to the issue,” the authors write. “In addition, mountains provide habitat for many of the world’s rare and endangered species, and the presence of many different ecosystems in close proximity enhances the ecological sensitivity of mountains to environmental change.”

In essence, the study incorporates a warning: more evidence is needed.

Raymond Bradley, who directs the Climate System Research Centre at the University of Massachusetts Amherst, spells it out: “We are calling for special efforts to be made to extend scientific observations upwards to the highest summits to capture what is happening across the world’s mountains.

“We also need a strong effort to find, collate and evaluate observational data that already exists wherever it is in the world. This requires international collaboration.” – Climate News Network

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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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