Global warming’s record-breaking trend continues

Global warming’s record-breaking trend continues

Detailed update by hundreds of scientists on climate indicators in 2014 reveals highest recorded rises in temperatures, sea levels and greenhouse gases.

LONDON, 22 July, 2015 – Forget talk of a slowdown in global warming. Scientists say the climate is heading smartly in the opposite direction, with 2014 proving to be a record-breaking year.

The US National Oceanic and Atmospheric Administration (NOAA), one of the most respected sources of climate science, says that last year “the most essential indicators of Earth’s changing climate continued to reflect trends of a warming planet”. Some − including rising land and ocean temperatures, sea levels and greenhouse gases − reached record highs.

The authoritative report by the NOAA’s Centre for Weather and Climate at the National Centres for Environmental Information (NCEI), published by the American Meterological Society, draws on contributions from 413 scientists in 58 countries to provide a detailed update on global climate indicators.

“The variety of indicators shows us how our climate is changing, not just in temperature but from the depths of the oceans to the outer atmosphere,” says Thomas R. Karl, director of the NCEI.

Rising concentrations

The authors report that concentrations of greenhouse gases continued to climb during the year. Atmospheric carbon dioxide concentrations rose by 1.9 parts per million (ppm), reaching a global average of 397.2 ppm for the year. This compares with a global average of 354ppm in 1990 when the first edition of this report was published. And levels of methane and nitrous oxide also went up.

“Variety of indicators shows how our climate is changing, not just in temperature but from the depths of the oceans to the outer atmosphere”

Four independent global datasets showed that 2014 was the warmest year on record, with the warmth widespread across land areas.

Europe experienced its warmest year; Africa had above-average temperatures across most of the continent throughout 2014; Australia recorded its third warmest year; and Mexico had its warmest. Eastern North America was the only major region to experience below-average annual temperatures.

Global average sea level rose to a record high, and the globally averaged sea surface temperature was also the highest recorded. The warmth was particularly notable in the North Pacific Ocean, where temperatures are in part probably driven by a transition of the Pacific decadal oscillation – a recurring pattern of ocean-atmosphere climate variability centred in the region.

Earlier snow melt

The Arctic continued to warm, and sea ice extent remained low. Arctic snow melt occurred 20–30 days earlier than the 1998–2010 average. On the North Slope of Alaska, record high temperatures at a 20-metre depth were measured at four of five permafrost observatories. The eight lowest minimum sea ice extents during this period have occurred in the last eight years.

But temperature patterns across the Antarctic showed strong seasonal and regional patterns of warmer-than-normal and cooler-than-normal conditions, resulting in near-average conditions for the year for the continent as a whole. Last year was the third consecutive year of record maximum sea ice extent in the Antarctic.

The El Niño-Southern Oscillation (ENSO), a periodic warming of the water in the central and eastern Pacific that disrupts weather over thousands of miles, was in a neutral state during 2014, although it was on the cool side of neutral at the beginning of the year and approached warm El Niño conditions by the end of the year. This pattern played a major role in several regional climate outcomes.

There were 91 tropical cyclones in 2014, well above the 1981-2010 average of 82 storms. But the North Atlantic season, as in 2013, was quieter than most years of the last two decades with respect to the number of storms. – Climate News Network

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Melting sea ice means shortage of bear necessities

Melting sea ice means shortage of bear necessities

Researchers explode theory that polar bears can use hibernation techniques to last without food as climate change reduces their summertime hunting habitat.

LONDON, 20 July, 2015 – Global warming is likely to leave the polar bear high and dry and very hungry as increasing loss of sea ice reduces the hunting grounds of the Arctic’s top predator.

Researchers have established that while Ursus maritimus can survive for months without eating during winter hibernation, in the summertime it is not much better at going without food than any other mammal.

The polar bear is capable of shutting its own metabolism down to astonishingly low levels during hibernation and, until now, zoologists have surmised that the bear could minimise energy losses by entering a hibernation-like state when deprived of food.

But John Whiteman, a doctoral student in ecology, zoology and physiology at the University of Wyoming, and colleagues report in Science journal that that theory is wrong. Once they are up and hunting, bears need food.

Energy expenditure

“We report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, non-hibernating mammals,” they write.

As carbon dioxide levels in the atmosphere creep up, as a consequence of the human combustion of fossil fuels, so Arctic temperatures have on average risen.

The loss of sea ice in the Arctic has, over the last decade, happened even faster than climate scientists predicted, which creates problems for bears that need to hunt and gorge on high-calorie diets in preparation for the winter.

The polar bear hunts on the ice, and its preferred diet is the blubber-rich flesh of seals and small whales. On shore, it must forage for scraps, berries and small mammals while waiting for the seas to freeze again.

“Polar bears appear unable to meaningfully prolong their reliance on stored energy”

But Arctic summers have stayed milder for longer, and the areas of summer sea ice have steadily dwindled. So the bears have spent increasing periods without their preferred diet.

The orthodoxy had been that bears, while waiting for the first freeze, had been able to enter a state called “walking hibernation”. Whiteman and his fellow researchers took a closer look.

With help from government agencies, a US coastguard icebreaker, helicopter pilots and a large number of other people, they captured two dozen polar bears, fitted satellite collars, and implanted little devices that recorded body temperature and tracked their movements on shore and on ice in the Beaufort Sea, north of Alaska and Canada, between 2008 and 2010.

Core temperature

They found that the bears could do something physiologically clever to keep warm while swimming – they could temporarily cool their outermost skin layers to insulate their inner selves and keep their core body temperatures at a healthy level, and one bear was reported to have survived a nine-day swim from shore to ice.

But they also found that the bears were not much better than other mammals at walking around on dry land, looking for food that wasn’t there.

“We found that polar bears appear unable to meaningfully prolong their reliance on stored energy, confirming their vulnerability to lost hunting opportunities on the sea ice − even as they surprised us by also exhibiting an unusual ability to minimise heat loss while swimming in Arctic waters,” Whiteman says.

The evidence, however, suggested that “walking hibernation” didn’t actually exist. The researchers conclude that the bears “are unlikely to avoid deleterious loss in body condition, and ultimately survival, that are expected with continuous ice loss and lengthening of the ice-melt period”. – Climate News Network

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Too few specialists to track loss of Himalayan glaciers

Too few specialists to track loss of Himalayan glaciers

Millions of people rely on meltwater from the Himalayas, but lack of expertise and manpower is hampering the study of climate change impacts.

DELHI, 11 July, 2015 − Studying ice loss in the vast, inhospitable region of the Himalayas can be a very tricky business as most glaciers are found above 12,000 feet.

While much of the data is derived from satellite surveys, reliable field data is also vital − but skill shortages mean that only four of the approximately 9,500 glaciers spread across the Indian section of the Himalayas are being studied in detail.

Gathering field data involves a combination of skills that include high-altitude mountaineering. Weather restricts such work to about four months of the year, and there is also the constant danger of avalanches.

The mighty Gangotri glacier, in the far northwest of the country, is one of the four glaciers monitored in detail by field researchers.

Rapidly disintegrating

Recent studies indicate that the Gangotri, one of the Himalayas’ largest glaciers and a primary source of the Ganges, is rapidly disintegrating. Nearly 30 kilometres long and between 0.5 and 2.5km wide, it is at present retreating by between 12 and 13 metres a year.

To analyse the impacts of climate change, and to predict what will happen in the future in glacial regions, it is necessary to carry out what glaciologists refer to as surveys of mass balance – analysing the relative difference between the accumulation and melting of ice and snow on a glacier over a given period.

Collecting and interpreting data – from satellite imagery and from field surveys – is highly specialised. And Indian institutions say a big knowledge gap has developed, with only limited field data being collected and a lack of trained personnel available to interpret the results of remote sensing and other data.

A determined effort is now being made by several institutions to produce more trained glaciologists.

“There is evidence of changing climatic patterns leading to changing water flow patterns that
could have serious impacts”

The Indian government’s Department of Science and Technology is undertaking a project with the Swiss Agency for Development and Co-operation to train young scientists in glaciology as part of a Himalayan climate change and adaptation programme.

The Indian Space Research Organisation, which has been collecting satellite data on glaciers for many years, has a fully-fledged climate change department that is becoming more involved in monitoring glacier size and mass balance data.

The Divecha Centre for Climate Change, part of the prestigious Indian Institute of Science, is also combining studies of glaciology and climate change.

The generally accepted view is that the majority of glaciers in the Himalayas – an area often referred to as “The Third Pole”, due to its vast ice mass – are in retreat.

Reliable conclusions

Yet in some areas, such as the Karakoram Range in the west of the Himalayas, satellite data indicates that glaciers are advancing.

The International Centre for Integrated Mountain Development (ICIMOD), a regional organisation based in Nepal and specialising in the Himalayas/Hindu Kush region, says much more field work is needed to draw reliable conclusions about the extent of glacial loss across the Himalayas.

It points to data collected in Nepal and to studies in China that clearly show a decrease in glacial area. At the same time, fragmentation means that more smaller glaciers are being created.

The world should be concerned about glacial melt in the Himalayas, ICIMOD says, because “there is evidence of changing climatic patterns leading to changing water flow patterns that could have serious impacts”. − Climate News Network

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Global warming threatens colder climate for Europe

Global warming threatens colder climate for Europe

New evidence that increased melting of sea ice as the Earth warms could weaken the Gulf Stream and reduce temperatures in western Europe.

LONDON, 3 July, 2015 – Scientists have yet again warned that weakening ocean circulation in the North Atlantic could deliver a climate paradox − a colder Europe as a consequence of global warming.

A study published in Nature Climate Change found that as sea ice off Iceland and Greenland retreats, the flow of cold, dense water to the bottom of the North Atlantic ocean could be reduced, and therefore weaken the warming effects of the Gulf Stream.

The great submarine current − sometimes called the Atlantic Conveyor − flows south to surface in the tropics as the Gulf Stream, which then flows north again to deliver tropic warmth to European coasts.

However, a slowdown in the natural overturning of the ocean could weaken the Gulf Stream, which in turn could cool the atmosphere over the British Isles and western Europe.

“A warm western Europe requires a cold North Atlantic, and the warming that the North Atlantic is now experiencing has the potential to result in a cooling over Western Europe,” says Kent Moore, a professor of physics at the University of Toronto Mississauga, Canada.

Calamitous change

Such a possible collapse of a natural oceanic system is predicated as one of the irreversible tipping points that could result in calamitous climate change.

Scientists have twice warned in the past six months that such change could be irreversible, unless governments jointly decide to dramatically reduce greenhouse gas emissions from the combustion of fossil fuels by switching to renewable sources of energy.

Another research group reported in March this year on how the changing salinity of the northern ocean waters − because of the increasing flow of meltwater from land-borne glaciers − threatened a weakening of the Atlantic Conveyor.

“The heat exchange is weaker – it’s like turning down the stove 20%”

In the latest study, Professor Moore and colleagues from Norway, the US and the UK looked not at changes in ocean salinity, but at the exchange of heat between sea and air.

Climate is driven by contrasts, and the flow of heat between water and wind in winter has weakened by around 20% since 1979. The Arctic is the fastest-warming region of the planet, and changes in the polar climate can have dramatic consequences for the temperate zones.

Prof Moore and his colleagues looked at wintertime data from the Iceland and Greenland Seas between 1958 and 2014, then used computer simulations to model potential changes to the Conveyor − more formally known to oceanographers and climate scientists as the Atlantic Meridional Ocean Circulation.

Cold and salty

The warm current loses its heat to the atmosphere as it moves north, and water that is both cold and salty is denser and more likely to descend.

The most effective place for such a process to happen is at the edge of the sea ice. If the sea ice retreats, then so does the region of maximum heat exchange. For the past 10,000 years or so, this heat exchange has happened at the ideal spot for surface waters to sink. Any change might not be for the better.

The Gulf Stream is the agency that makes Britain, for example, about 5°C warmer than Labrador in Canada, on the same latitude. A British government chief scientific adviser once calculated that the Gulf Stream delivered the warmth of 27,000 power stations. So if it weakens, Europe could start to feel the chill.

“The heat exchange is weaker – it’s like turning down the stove 20%,” Prof Moore says. “We believe the weakening will continue and eventually cause changes in the Atlantic Meridional Overturning Circulation and the Gulf Stream, which can impact the climate of Europe.” – Climate News Network

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Alaska’s glaciers melt faster as climate change speeds up

Alaska's glaciers melt faster as climate change speeds up

Climate change rather than natural causes is the main cause of Alaska’s glacier loss, which is set to speed up, US scientists say.

LONDON, 30 June, 2015 – The glaciers of Alaska are melting and retreating: the chief cause is climate change and the loss of ice is unlikely to slow, according to a new study by US scientists.

They calculate that the frozen rivers of the Pacific coast of America’s northernmost state are melting fast enough to cover the whole of Alaska with 30 cms of water every seven years.

Since Alaska is enormous – it covers 1.5 million square kilometres and is the size of California, Texas and Montana put together – this adds up to a significant contribution to sea level rise.

“The Alaska region has long been considered a primary player in the global sea level budget, but the exact details of the drivers and mechanisms of Alaska glacier change have been stubbornly elusive,” said Chris Larsen, a geophysicist at the University of Alaska Fairbanks, and lead author of a study in Geophysical Research Letters.

Taxonomy of change

Scientists from the University of Alaska and the US Geological Survey analysed studies of 116 glaciers in the Alaska region over a 19-year-period to estimate the rate at which ice melted and icebergs calved.

They used airborne lidar remote sensing technology and other techniques, historical data and a global glacier inventory to establish a kind of taxonomy of glacier change.

The Columbia Glacier in Prince William Sound had retreated more than 19 kilometres because of iceberg calving and had thinned by 450 meters in height since 1980. But, unexpectedly, tidewater glaciers – those that end in the ocean – seemed to make comparatively little contribution to sea level rise.

“Instead we show that glaciers ending on land are losing mass exceptionally fast, overshadowing mass changes due to iceberg calving, and making climate-related melting the primary control on mountain glacier mass loss,” Dr Larsen said.

Big contributor

He and his colleagues calculated that Alaska is losing ice at the rate of 75 billion metric tons a year. Such research is just one more piece of careful cross-checking in the great mosaic of climate research: another systematic confirmation that overall, glaciers are not losing ice in response to some natural cycle of change of the kind that occasionally confuses the picture for climate science.

The agency at work is largely global warming as a response to the steady rise in atmospheric carbon dioxide as a consequence of the burning of fossil fuels.

Mountain glaciers represent only 1% of the total ice on the planet: the other 99% is found in Greenland – which is melting fast – and in the great frozen continent of Antarctica, where ice mass is being lost at an increasing rate.

But although the mountains of the temperate and tropic zones bear only a tiny percentage of the planet’s ice, their melting accounts for almost a third of the sea level rise currently measured by oceanographers, and this melting will go on to become a big contributor to the sea levels later this century.

“Alaska will continue to be a major driver of sea level change in the upcoming decades”

Across the border in Canada, glaciologists have warned that the country will lose a huge volume of flowing ice, and while one team has confirmed that air pollution rather than global warming long ago began to strip Europe’s Alps of their glaciers, in general mountain peaks are warming faster than the valleys and plains below them.

Geophysicists and glaciologists have established that the glaciers of the tropical Andes are at risk, and in the Himalayan mountain chain glaciers seem to be in inexorable retreat with consequences that could be devastating for the many millions in the Indian subcontinent and in China who rely on seasonal meltwater for agriculture.

Glaciers are by definition hard to study – they are high, cold and in dangerous terrain – and such research is inevitably incomplete: the scientists for instance excluded glaciers smaller than three square kilometres. But together these small patches of flowing ice account for 16% of Alaska’s glaciated landscape. The 116 glaciers in the survey together added up to only 41% of the state’s glaciated area.

But the pattern established by the Fairbanks team suggests that melting will accelerate with climate change. “Rates of loss from Alaska are unlikely to decline, since surface melt is the predominant driver, and summer temperatures are expected to increase,” said Dr Larsen.

“There is a lot of momentum in the system, and Alaska will continue to be a major driver of sea level change in the upcoming decades.” – Climate News Network

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New flood alert as warming raises sea levels threat

New flood alert as warming raises sea levels threat

Scientists warn countries in northern Europe to plan for dramatic new worst-case scenarios as climate change increases the risk of seas sweeping inland.

LONDON, 22 June, 2015 − Europe could face a higher marine invasion than anybody anticipated. As polar ice melts, tides could be as much as 1.5 metres higher around the coasts of Scandinavia, Germany, the Netherlands and England, according to a new study.

This is considerably higher than the average sea level rise – driven by global warming as a consequence of burning fossil fuels – projected by the Intergovernmental Panel on Climate Change under a “business as usual” scenario and a global average temperature rise of 4°C.

But there is no contradiction. The discrepancy arises because the seas have never been level, and the land keeps moving too.

Aslak Grinsted, associate professor in the Centre for Ice and Climate at the Niels Bohr Institute of the University of Copenhagen, Denmark, and colleagues report in the journal Climate Research that they took a closer look at the dynamics of sea level change in the North Sea, the North Atlantic and the Baltic for the remainder of this century.

Land uplift

“Even though the oceans are rising, they do not rise evenly across the globe,” Dr Grinsted says. “This is partly due to changes in the gravitational field and land uplift.”

He and his colleagues started with the anomalies they knew best. These are in Greenland, which is covered by a sheet of ice so massive that it gathers up the sea around it. So, to reach Greenland, ships must sail uphill.

As the ice sheet melts – and there are studies that show it is melting at an accelerating rate that would heighten sea levels by 14 cms this century – the mass will be reduced and the sea levels will fall, even though more water has entered the oceans.

“In England . . . we cannot exclude a sea level rise of up to 1.75 metres this century”

But although waters are notionally lapping ever higher along coastlines, these too are changing. Northern Europe 12,000 years ago was covered by deep ice, and the bedrock below was depressed. Now the ice has gone, but the land once crushed by it is still rising.

Equipped with the latest research and measurements, the Copenhagen team began their reinterpretation of the local future. They found that what had once been considered “high” scenarios for the Netherlands and England will be surpassed.

Best estimate

Dr Grinsted says: “For London, the calculated best estimate is that sea level will rise by 0.8 metres. In England, a sea level rise of more than 0.9 meters in this century has been considered highly unlikely, but our new calculation shows that there is a 27% chance that this limit is surpassed, and we cannot exclude a sea level rise of up to 1.75 metres this century.”

For the Netherlands, the best estimate of sea level rise is 0.83 metres, but the calculations show that there is a 26% chance that it will exceed the existing high-end scenario of 1.05 metres, and could even reach 1.80 metres.

Dr Grinsted says: “Both countries have already established protections for the coasts with barriers, sluice gates and dikes, but is it enough? I hope that our calculations for worst-case scenarios will be taken into consideration as the countries prepare for climate change.”

The IPCC sea level projection is of 80 cms worldwide. Sea levels overall might change little in Scotland, Ireland and Norway. And in the Gulf of Bothnia, in Finland, where the land is rising even faster than the sea, tides could be as much as 10cms lower at the end of the century. − Climate News Network

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Glacier loss raises high concern over water supplies

Glacier loss raises high concern over water supplies

Massively increased ice melt in the high Himalayas because of climate change could seriously jeopardise the flow of water for billions of people in Asia.

LONDON, 2 June, 2015 − The glaciers of the Everest region of the Himalayan massif – home to the highest peak of all – could lose between 70% and 99% of their volume as a result of global warming.

Asia’s mountain ranges contain the greatest thickness of ice beyond the polar regions. But new research predicts that, by 2100, the world’s highest waters – on which billions of people depend for their water supply – could be at their lowest ebb because of the ice loss.

Many of the continent’s great rivers begin up in the snows, fed by melting ice in high-peak regions such as the Hindu Kush, the Pamir and the Himalayas.

Joseph Shea, a glacial hydrologist at the International Centre for Integrated Mountain Development in Kathmandu, Nepal, and French and Dutch colleagues report in The Cryosphere journal that they used more than 50 years of climate data and sophisticated computer models of predicted climate change to study the pattern of snowpack and seasonal melt in the Everest region.

Temperature increase

They found a decrease of 20% since 1961, and signs that most, if not quite all, of the stored ice could disappear in the next 85 years.

“The signal of future glacier change in the region is clear: continued and possibly accelerated mass loss from glaciers is likely, given the projected increase in temperatures,” Dr Shea says.

”Our results indicate that these glaciers may be highly sensitive to changes in temperature, and that increases in precipitation are not enough to offset the increased melt.”

That mountain glaciers in the temperate zones and the tropics are in retreat is not in doubt. In the last two years, researchers have established patterns of ice loss in Nepal, in the tropical Andes of South America, and in the Canadian highlands.

“The signal for future glacier change in the region is clear and compelling”

Other teams have stepped back to look at the big picture, and one calculation is that around 160,000 glaciers in Europe, Asia, and the Americas are shedding 260 billion tonnes of ice each year. This is roughly as much as is now being lost from the Greenland and Antarctic ice sheets.

The consequences for sea level rise are obvious, and ominous. But glaciers have local importance too: their spring and summer meltwater drives hydroelectric power, nourishes industrial growth in the cities, and irrigates the rice and wheat crops on which billions of people depend.

The rate and extent of glacial retreat, the scientists say, depends on the levels of greenhouse gases emitted from the burning of fossil fuels in future. And some of the loss depends on the changes in the altitude at which water freezes.

Freezing levels

Right now, in the Everest region, ice forms at 3,200 metres in January, but at 5,500 metres in August. But according to Walter Immerzeel, assistant professor of physical geography at the University of Utrecht in the Netherlands, these freezing levels could rise by between 800 and 1,200 metres by 2100.

“Such an increase would not only reduce snow accumulation over the glaciers, but would also expose 90% of the current glacier area to melt in the warmer months,” he says.

Research at high altitudes is difficult, dangerous, and subject to error. The scientists focused their study on four large glaciers in Nepal’s Dudh Kosi river basin, which holds 400 square kilometres of glacial ice. They then tested eight future climate scenarios to construct the pattern of the future.

In 2007, the Intergovernmental Panel on Climate Change reported that the Himalayan glaciers could vanish as early as 2035 − but three years later had to apologise for what was described as an “unfounded” claim.

The Cryosphere authors say their own results should also be treated cautiously. But, their paper concludes, “the signal for future glacier change in the region is clear and compelling”. – Climate News Network

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Science puzzles over recent rapid Antarctic thaw

Science puzzles over recent rapid Antarctic thaw

Part of Antarctica has begun thawing unusually fast, leaving scientists unsure whether a natural cycle or human-caused climate change is responsible.

LONDON, 31 May, 2015 − Antarctic glaciers once thought relatively stable are starting to melt. Evidence from a five-year satellite study of the frozen rivers on the southern Antarctic Peninsula now reveal that these are shedding ice at the rate of 60 cubic kilometres a year: altogether around 300 trillion litres of water has moved from the frozen continent to the oceans.

Bert Wouters of the University of Bristol, UK, and colleagues report in the journal Science  that they used data from two very different research satellites to confirm their findings.

The European Space Agency’s CryoSat-2 has been orbiting the polar world since April 2010, bouncing radar signals off the surface and measuring the return travel time. An examination of five years of results shows that the glacial surfaces are sinking, in some places by as much as four metres a year. There could be two reasons for that: either the snow is compacting or the ice is flowing faster.

“The glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings”

But results from the US space agency Nasa’s GRACE mission – the acronym stands for Gravity Recovery and Climate Experiment – settle the matter. The mass of ice lost in the region is so large that it changes the local gravity field, and the changes in the sheer weight of 750 kilometres of glaciers in the region can be measured from space.

“To date, the glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings combined,” Dr Wouters said.

“The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us. It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted.”

Melting maintained

That the southern continent is responding to climate change of some kind is not in doubt: another study has put the overall mass loss at 92 billion tons a year, and twin assaults of warmer air above, and warmer waters around the continent, continue the attrition.

What is not yet certain is whether scientists are looking at the consequences of human-made global warming or at the see-saw conditions inherent in some kind of as-yet-unidentified natural cycle.

But ice loss on that scale cannot be easily explained by changes in snowfall or air temperatures, so suspicion falls on the effect of warmer waters. The glaciers flow into seas that are surrounded by ice shelves. The ice shelves have lost one fifth of their thickness in recent decades, so they offer less resistance to the land-based ice, allowing the glaciers to accelerate.

There is a second factor: some of the glaciers are grounded on continental bedrock that is depressed below sea level, which means that warmer ocean waters can penetrate further inland and melt the glaciers from below.

Cautious response

There are questions that have yet to be resolved. As usual in science, the interpretations are open to debate. “Although these latest CryoSat measurements of Antarctic thinning agree with findings from two studies reported last year, I think the new estimates of ice loss computed from them are far too high, because the glaciers in this sector just haven’t speeded up that much,” said Andy Shepherd, professor of earth observation at the University of Leeds in the UK and principal scientific advisor to the CryoSat mission.

“It could be that a bigger chunk of the thinning is down to snowfall fluctuations than the authors have accounted for, and so I would be cautious about the new numbers until more information is to hand.”

Dr Wouters agrees that more research is necessary. “It appears that some time around 2009, the ice shelf thinning and the subsurface melting of the glaciers passed a critical threshold which triggered the sudden ice loss. However, compared to other regions in Antarctica, the Southern Peninsula is rather understudied, exactly because it did not show any changes in the past, ironically,” he said.

“To pinpoint the cause of the changes, more data need to be collected. A detailed knowledge of the geometry of the local ice shelves, the ocean floor topography, ice sheet thickness and glacier flow speeds are crucial to tell how much longer the thinning will continue.” − Climate News Network

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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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