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by Kieran Cooke

Royal goings-on freeze out climate

May 24, 2013 in Warming

 EMBARGOED till 2301 GMT on Thursday 23 May

Members of the British Royal Family make more news in the US than climate change Image: Carfax2

Members of the British royal family make more news in the US than climate change
Image: Carfax2

By Kieran Cooke

The major US news broadcasters are hot on stories about the British royal family, but media monitoring research shows that they are still left cold by climate change – despite Prince Charles’s dire warnings

LONDON, 23 May − Prince Charles, heir to the British throne, made one of his strongest speeches yet on the dangers of a warming planet when he warned this month that climate change is “the greatest risk we have ever faced”. Action must be taken now, the Prince said,  because the risk of doing nothing is “too great”.

It is therefore a little ironic to look at the latest results from a study by the monitoring organisation Media Matters for America and find that the goings-on of the British royal family – but not their comments on the dire state of the planet – feature far more prominently on the major US networks than any topic related to climate change.

“Even during the warmest year on record in the US, the nightly news programmes combined devoted only 12 full segments to climate change,” Media Matters reports. “By contrast, these programmes dedicated over seven times more coverage to the royals in 2012.”

One programme, ABC World News, devoted 43 segments to the British royal family in 2012 and only one to climate change, says Media Matters.

Earlier this month, as scientists announced the amount of CO² in the atmosphere had gone beyond 400 parts per million, two of the major US news programmes ignored the story, preferring instead to cover the visit to the country of Prince Harry, the younger son of Prince Charles.

“In 2012, the US experienced record-breaking heat, a historic drought, massive wildfires in the West, and Hurricane Sandy,” Media Matters says.  “Meanwhile, Arctic sea ice extent shattered the previous record low and the Greenland ice sheet saw the greatest melt in recorded history…

“Broadcast news outlets devoted very little time to climate change”

“Yet despite these illustrations of climate change, the broadcast news outlets devoted very little time to climate change in 2012, following a downward trend since 2009.”

Evidence suggests the paucity of reporting on climate change is not limited to the US alone. An ongoing study of various media outlets around the world by the Center for Science and Technology Policy Research at the University of Colorado-Boulder charts global climate change media coverage, noting a peak at the Copenhagen climate summit in late 2009.

A separate study  found that more than 3,200 climate-related stories appeared in the world’s mainstream newspapers concerning events at the ill-fated Copenhagen meeting. By the time of the climate summit in Durban two years later, the number of stories had shrunk to a quarter of that amount.

Meanwhile, the scientific consensus on the causes and impacts of climate change seems never to have been stronger.

Public perceptions changing

 

Despite the lack of media coverage, it seems that public perceptions about climate change are also changing − perhaps influenced by a rise in extreme weather events around the world.

The subject of climate change and its causes continues to be hotly debated in the US. However, an analysis carried out late last year by the Pew Research Center for the People and the Press found that nearly 70% of Americans now say there is solid evidence that the world has been getting warmer over recent decades, with more than 40% saying it is caused by human activity – up from 34% in 2010.

A petition, which already has more than 70,000 signatures, has been organised by Media Matters, the Sierra Club and the League of Conservation Voters. It urges the major broadcast networks to give more attention to climate change and allow scientists the opportunity to explain the connections between humanity activity, climate change and extreme weather events. − Climate News Network

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by Tim Radford

Glaciers are melting slowly – but surely

May 20, 2013 in Warming

EMBARGOED until 2301 GMT on Sunday 19 May

Glacier in the Tian Shan mountains of Central Asia, where ice loss is considerable Image: Andrzej Barabasz (Chepry)

Glacier in the Tian Shan mountains of Central Asia, where ice loss is considerable
Image: Andrzej Barabasz (Chepry)

By Tim Radford

Although hundreds of the world’s glaciers are shrinking fast, far more are losing ice much more slowly, new research has established. But it shows that, almost everywhere, the glaciers are in retreat.

LONDON, 20 May – Forget, for the moment, the Greenland and Antarctic ice sheets: what about all the other stuff? What kind of difference does the melting of glaciers in Scandinavia, or Alaska, or the Himalayas make to the ocean levels?

Alex Gardner of Clark University, Massachusetts, and 15 colleagues from the US, Canada and Europe decided to take a closer look: their answer is that shrinking glaciers lost 259 billion tonnes (259 gigatonnes) of mass in the form of meltwater every year between 2003 and 2009, give or take 28 gigatonnes, an amount equal to around 30% of observed sea level rise.

This equals the combined losses from the permanent ice sheets that blanket, in layers thousands of metres thick, the two vast land masses of Greenland and Antarctica.

The scientists report their findings in the journal Science. They used both measurements on the ground – necessarily selective – and measurements from orbiting satellites, which naturally give a bigger picture, but also a more imprecise one.

The satellites carried instruments specifically designed to study ice loss: one was called GRACE, short for gravity recovery and climate experiment, and the other was called ICEsat – an ice, cloud and land elevation satellite. The first measured tiny changes in gravity as the ice melts away. The second used lasers to measure changes in height, and therefore volume.

The scientists also consulted an authoritative store of geographical data, the Randolph Glacier Inventory, which defines 19 glacier regions with a total area under flowing ice of 729,400 square kilometres. They chose the dates under study because for those six years, ICEsat and GRACE were both in orbit, and sending back data, and thus providing a record of both seasonal and overall ice loss during that time.

Long-term concern

 

The conclusion was that although the 300 most closely-observed glaciers, the ones that have caused the most alarm, are indeed losing mass at a disturbing rate, this is not the whole picture. The other 160,000 glaciers distributed across the planet are losing ice overall at a slower rate.

This sounds like relatively good news, considering that global anxiety about retreating glaciers was based mostly on direct measurements of famous or easy-to-observe ice flows. But the research confirms the big picture: that glaciers are in retreat almost everywhere.

And this spells problems in the long run everywhere: glaciers store winter water for summer irrigation, city water supplies and hydroelectric power. They keep rivers navigable, and they maintain mountain ecosystems.

If they shrink, that’s not good news for mountain creatures or the people, forests, plains and settlements downstream. The largest losses were from Arctic Canada, Alaska, coastal Greenland, the southern Andes and the high peaks of Asia. There was little loss from Antarctica’s glaciers. – Climate News Network

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by Paul Brown

Arctic tundra ‘will turn to forest’

May 18, 2013 in Warming

EMBARGOED until 2301 GMT on Friday 17 May

Tundra will turn into fir forests at the current levels of carbon dioxide Photo by Jason Hollinger

Tundra will turn into fir forests at the current levels of carbon dioxide.             Image: Jason Hollinger

By Paul Brown

Two sets of scientists, working independently, come to the same conclusion: that the Arctic will soon become ice-free and forested.

LONDON, 18 May – An ice-free Arctic, the disappearance of tundra and forests up to the edge of the newly open ocean is how the north will look as the natural world reacts to the new climate caused by carbon dioxide reaching 400 parts per million (ppm) in the atmosphere, according to analysis of new lake sediments.

So far scientists have been guessing what a warmer world will look like, but lake bed cores from Russia provide evidence of the trees and plants that thrived north of the Arctic Circle last time CO2 was at 400 ppm – a barrier broken earlier this month.

There is a time lag of up to 30 years for the temperature to be forced up by the extra CO2 in the atmosphere, so the scientists’ findings give a clue to what to expect by the middle of the century.

Julie Brigham-Grette of the University of Massachusetts Amherst, who led a team of international scientists, says summer temperatures were about 8°C warmer in the Arctic than they are today, and the rainfall three times greater. At the same time the West Antarctic ice sheet did not exist, showing that both landscape and sea level were vastly different.

Underestimating the effects

 

She said the results showed that scientists might have badly underestimated the effect of existing carbon dioxide levels in altering the climate over time.

Another unconnected team of researchers has been studying how the temperature changes that are already occurring in the northern hemisphere are affecting plants. The two pieces of research appear to point to the same conclusions.

Hans Tømmervik at the Fram-High North Research Centre for Climate and the Environment and 21 scientists from 17 academic institutions have been looking at all the Arctic countries and how they are already reacting to increased temperatures.

He said: “Norwegian climate and vegetation as we know it today might be totally changed within some decades. The same process is happening in Siberia, in Alaska and in the northern parts of Canada. Mountain plateaus become forest land and the winter period is shorter and shorter every year”.

The growing season has increased by up to 40 days in some areas. The temperature difference between summer and winter is getting smaller because the winters are no longer so cold. Spring and autumn seasons are also shorter.

Tømmervik says the start and end period for vegetation growth are very dependent on threshold temperatures. When the trends of these temperatures change and thus change the start of photosynthesis, it will in time change the vegetation.

Pollen in the sediment

 

The result is that trees and bushes will be able to grow where only lichen and heather were living earlier. Species move slowly towards the north and up into the mountains. The increased vegetation in the north also gives an extra boost to global warming, because it reflects less sunlight back into space than the ice and snow it has replaced, and thus causes even more rapid changes.

The other team were looking at sediment layers and analysed cores collected in the winter of 2009 from under ice-covered Lake El’gygytgyn, the oldest deep lake in the northeast Russian Arctic. “Lake E” was formed 3.6 million years ago when a huge meteorite hit the Earth and blasted out an 11-mile (18 km) wide crater.

It has been collecting sediment layers ever since. Luckily for geoscientists, it lies in one of the few Arctic areas not eroded by continental glaciers, so a thick, continuous sediment record was left remarkably undisturbed. Cores from Lake E reach back in geological time nearly 30 times farther than Greenland ice cores that cover the past 140,000 years.

“One of our major findings is that the Arctic was very warm in the Pliocene [~ 5.3 to 2.6 million years ago] when others have suggested atmospheric CO2 was very much like levels we see today. This could tell us where we are going in the near future.

“In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier models”, say the co-authors from Russia, Germany and the United States.

Also important to the story are fossil pollens extracted from the lake sediments, which allow scientists to reconstruct life around the lake in the past using modern habitat tolerances to reconstruct past winter and summer temperatures and precipitation.

Another significant finding to emerge from this first continuous, high-resolution record of the Middle Pliocene is the documentation of sustained warmth, with summer temperatures of about 59 to 61° F [15 to 16°C], about 8°C warmer than today, and regional precipitation three times higher than today.

“We show that this warmth well north of the Arctic Circle occurred throughout both warm and cold orbital cycles and coincides, in part, with a long interval of 1.2 million years when the West Antarctic Ice sheet did not exist”, Brigham-Grette notes. Thus both poles share some common history, but the pace of change differed, she said  – Climate News Network

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by Tim Radford

Hare undone by unshed summer coat

May 4, 2013 in Science

FOR IMMEDIATE RELEASE

Camouflage does work: A snowshoe hare in Canada Image: Ansgar Walk

Camouflage does work: A snowshoe hare in Canada
Image: Ansgar Walk

By Tim Radford

Species which protect themselves by turning white to match the snow of the long northern winters may be caught out as a warming climate reduces the numbers of days of snow cover.

LONDON, 4 May – Milder winters mean bad news for the snowshoe hare of western North America. Lepus americanus is famous for two things: an evolutionary camouflage adaptation that keeps it white in the winter snow and turns it a reddish brown in spring and summer; and its intimate population polka with one of the continent’s most glamorous predators, the Canada lynx.

When hares are numerous, the lynx population increases. As the numbers of hares diminish, so its predators go hungry and the lynx population starts to drop, giving the snowshoe hares another chance.

But the hare may be losing the battle, thanks to climate change. Biologists report in the Proceedings of the National Academy of Sciences that they monitored 148 wild hares in western Montana and observed that the adaptation that gave the hares an advantage in stable climates is likely to work to their disadvantage as temperatures rise, snow cover shrinks and the winters get shorter. The three years of their study included both the shortest and the longest snow seasons since 1970.

The researchers found that the spring and autumn moults seemed to occur independently of the arrival of the snows: they conjecture that they may be triggered by changes in daylight length.

Since hares don’t get much chance to die of old age – predation comprises 85 to 100% of mortality in different regions and different years – camouflage would play an important role in keeping hares alive long enough to breed and rear their young.

Poster child

 

A white hare on brown soil or a brown hare in the snow would both be at a serious disadvantage. Over the three-year period, the researchers had plenty of chances to observe both.

They expect “increased coat colour mismatch as snow seasons shorten under future climate change” and without rapid adaptation, this mismatch will increase as much as fourfold by mid-century and eightfold by the late century if humans go on pumping greenhouse gases into the atmosphere at an increasing rate.

The average annual duration of snow cover is forecast to fall by 29 to 35 days by mid-century and by 40 to 69 days by the end of the century.

Hares, the researchers warn, won’t be the only coat-changing mammals left exposed by ever-shorter winters. They conclude that there is a lot to learn from the plight of the hare (and see our story of 18 January)..

“The compelling image of a white animal on a brown snowless background can be a poster child for both educational outreach and for profound scientific inquiry into fitness consequences, mechanisms of seasonal coat colour change, and the potential for rapid local adaptation”, they say. – Climate News Network

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by alex kirby

World went on warming in 2012 – WMO

May 2, 2013 in Warming

EMBARGOED until 0900 GMT on Thursday 2 May

Arctic sea ice underwent a record loss in 2012 - "a disturbing sign" Image: US Fish and Wildlife Service

Arctic sea ice underwent a record loss in 2012 – “a disturbing sign”
Image: US Fish and Wildlife Service

By Alex Kirby

The year just past confirmed the Earth’s warming trend, which will continue and is reason for concern, says the World Meteorological Organisation.

LONDON, 2 May – Last year was among the ten warmest years since records began more than 160 years ago, the World Meteorological Organisation says.

The WMO says 2012 was the ninth warmest year recorded since 1850, and the 27th consecutive year in which the global land and ocean temperatures were above the 1961-1990 average.

The WMO Secretary-General Michel Jarraud said the continuing warming was cause for worry, and that it was on track to continue.

The assessment comes in the WMO’s Statement on the status of the global climate in 2012, the latest in an annual series providing information about temperatures, precipitation, extreme events, tropical cyclones, and sea ice extent.

It estimates the 2012 global land and ocean surface temperature during January-December 2012 at 0.45°C (±0.11°C) above the 1961-1990 average of 14.0°C. The years 2001-2012 were all among the top 13 warmest years on record.

The warming in 2012 happened despite the cooling influence of La Niña, a periodic upswelling of cold water off the west coast of South America which with its twin El Niño can affect weather patterns thousands of miles away. One of the effects of a La Niña episode can be to keep global average temperatures down.

“Although the rate of warming varies from year to year due to natural variability caused by the El Niño cycle, volcanic eruptions and other phenomena, the sustained warming of the lower atmosphere is a worrisome sign”, Michel Jarraud said.

“The continued upward trend in atmospheric concentrations of greenhouse gases and the consequent increased radiative forcing of the Earth’s atmosphere confirm that the warming will continue.

Growing variability

 

“The record loss of Arctic sea ice in August-September – 18% less than the previous record low in 2007 of 4.17 million sq km – was also a disturbing sign of climate change.

“The year 2012 saw many other extremes as well, such as droughts and tropical cyclones. Natural climate variability has always resulted in such extremes, but the physical characteristics of extreme weather and climate events are being increasingly shaped by climate change.

“For example, because global sea levels are now about 20 cm higher than they were in 1880, storms such as Hurricane Sandy are bringing more coastal flooding than they would have otherwise”, said Mr Jarraud.

Above-average temperatures were recorded during 2012 across most of the globe’s land surface areas, most notably North America, southern Europe, western Russia, parts of northern Africa and southern South America. But cooler-than-average conditions affected Alaska, parts of northern and eastern Australia and central Asia

Precipitation across the globe was slightly above the 1961-1990 long-term average, although with drier-than-average conditions across much of the central US, northern Mexico, north-eastern Brazil, central Russia, and south-central Australia.

Wetter-than-average conditions affected northern Europe, western Africa, north-central Argentina, western Alaska and most of northern China.

In early July, Greenland’s surface ice cover melted dramatically, with an estimated 97% of the ice sheet surface having thawed by mid-July – the largest melt extent since satellite records began 34 years ago.

Polar extremes

 

Arctic sea ice extent reached its record lowest level in its annual cycle on 16 September at 3.41 million sq km – 49% or nearly 3.3 million sq km below the 1979–2000 average minimum.

The difference between the maximum Arctic sea-ice extent on 20 March and the lowest minimum extent on 16 September was 11.83 million sq km, the largest seasonal sea-ice extent loss in the 34-year satellite record.

Antarctic sea-ice extent in March was the fourth largest on record at 5.0 million sq km or 16.0% above the 1979–2000 average. During its growth season, the Antarctic sea-ice extent reached its maximum extent since records began in 1979 on 26 September, at 19.4 million sq km.

“It is vital that we continue to invest in the observations and research that will improve our knowledge about climate variability and climate change,” said Mr Jarraud.

“We need to understand how much of the extra heat captured by greenhouse gases is being stored in the oceans and the consequences this brings in terms of ocean acidification and other impacts.

“We need to know more about the temporary cooling effects of pollution and other aerosols emitted into the atmosphere.” – Climate News Network

Figure: WMO

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by Tim Radford

Fast-moving climate zones speed extinction

April 26, 2013 in Science

FOR IMMEDIATE RELEASE

Heading for extinction? Rising temperatures are heightening the risk Image: Dick Mudde

Heading for extinction? Rising temperatures are heightening the risk
Image: Dick Mudde

By Tim Radford

An increasingly warm climate will mean ever more rapid changes in the Earth’s climatic zones, researchers say, and the species that live there will face a heightened extinction risk.

LONDON, 26 April – As global temperatures rise, climate zones will shift at greater speed, according to new research in Nature Climate Change.

If greenhouse gas emissions carry on increasing, then about 20% of the land area of the planet will undergo change – and the creatures that have made their homes in what were once stable ecosystems will have to adapt swiftly, or face grim consequences.

“The warmer the climate gets, the faster the climate zones are shifting”, says Irina Mahlstein, of the US NOAA Earth System Research Laboratory in Boulder, Colorado. “This could make it harder for plants and animals to adjust.”

Such fears are not new: in the past two decades biologists and ecologists have repeatedly warned that vulnerable species were at risk from climate change.

But vulnerable species are at risk anyway, just from pollution, habitat destruction and the spread of humanity across the habitable globe. What Dr Mahlstein and her colleagues have done is to look at geography’s mosaic of climates and landscapes and measure the rates of change in these.

Late in the 19th century, European geographers began to map and define – and create labels for – climatic regions: the hot arid regions, the tundra, the tropical rainforests, the steppes, monsoon climates, Mediterranean climates and so on.

“…species will have increasingly less time to adapt to zone changes, which is expected to increase the risk of extinction”

The idea was to be able to predict the life that might make its home in such places, according to temperature, precipitation and seasonal cycles. This Köppen-Geiger climate classification became a handy base for considering what might happen as the world gets hotter.

Mahlstein and her colleagues considered what might happen over a two century stretch: from 1900 to 2098, under climate model simulations based on scenarios for warming.

They found that with a warming of 2°C, about 5% of land would shift into a new climate zone. As the temperatures rise another 2°C, 10% of the land area shifts to a new zone.

Temperate regions and the high latitudes will experience the most dramatic change, and in the tropics, the mountain regions will experience greater change than the lowlands.

Frost climates will begin to shrink; arid zones will increase, and regions that once experienced cool summers will find that things get hotter.

“About 20% of all land area undergoes a change in its original climate,” say the researchers. “This implies that species will have increasingly less time to adapt to Köppen zone changes in the future, which is expected to increase the risk of extinction.” – Climate News Network

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by alex kirby

Climate alters global vegetation

April 17, 2013 in Science

EMBARGOED until 2301 GMT on Tuesday 16 April

Clearing forests for plantations reduces vegetation Image: Irvin calicut

Clearing forests for plantations reduces vegetation
Image: Irvin calicut

By Alex Kirby

Climate change is responsible for more than half the changes detected in the world’s vegetation, researchers say, and human activities for only about a third.

LONDON, 17 April – The amount of vegetation in the world, and the way it is spread across the planet, has changed significantly in the last three decades, researchers say.

They attribute more than half the changes they detected to the effects of the warming climate, with people responsible for only around a third. Surprisingly, perhaps, they are at a loss to attribute about 10% of the changes unequivocally to either the climate or us.

They say their work marks a scientific advance, because it has only recently become possible to quantify how far climate variability, human activity or a combination of the two are responsible for what is happening.

While the researchers, geographers from the University of Zurich, Switzerland, and colleagues from the Netherlands, say the last 30 years have seen substantial changes, satellites have during that time been recording how vegetation has altered.

In a striking and perhaps unexpected development, the team found that while vegetation has declined south of the Equator, it has increased in the northern hemisphere.

The climate is what governs the seasonal activity of vegetation. In the humid mid-latitudes, temperature is the largest factor influencing plant growth.

In mainly dry areas, though, it is the availability of water and in high latitudes the amount of solar radiation that is key. And everywhere humans influence vegetation in myriad ways – and are influenced by it.

There is evidence that the arid expanses of the Sahara desert were once wet enough to support lush vegetation, so much so that the Sahara was known as the breadbasket of North Africa.

A reverse process is under way in Greenland, where the rapid warming of the Arctic means that in some southern parts of the formerly ice-bound island vegetables will now grow happily.

Vanishing forests

 

A pervasive human influence in many parts of the world is the pressure from growing human populations and their demand for wood for fuel and building and for plant matter for food and fodder.

The researchers have developed a model that can show the influences on vegetation of human activity and climate variability separately. Using satellite data on the increase or decline over the last thirty years, climate measurements and models, and data on the kind of land cover, they conclude that around 54% of the changes in global vegetation can be attributed to climate variability.

One of their reports, Spatial relationship between climatologies and changes in global vegetation activity, is published in the journal Global Change Biology. The other, Shifts in Global Vegetation Activity Trends, appears in Remote Sensing.

The main decline they detected has happened south of the Sahel, in countries such as Tanzania, Zimbabwe and other parts of central Africa.

“We assume that this was caused by clear cutting, the transformation of rain forest into plantations, or changes in agriculture in general”, said Rogier de Jong, a postdoctoral student at the University of Zurich’s Remote Sensing Laboratories (RSL).

But even after identifying the difference between the hemispheres and the probable reasons for it, that still leaves the tantalising 10% of change which the team cannot explain fully by either climatology or human activity.

“We suspect that this is due to unexplained effects of the interactions between humans and the climate”‘, says the head of the RSL, Michael Schaepman.

He and his team will continue to work on trying to find an explanation for what is happening under a newly created research priority programme, Global Change and Biodiversity, at Zurich. – Climate News Network

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by Paul Brown

Antarctic Peninsula’s thaw speeds up

April 14, 2013 in Warming

EMBARGOED until 1700 GMT on Sunday 14 April

The ice core camp on James Ross Island: Scientists worked in shifts to drill to the base of the ice sheet. Image: Nerilie Abram

James Ross Island: Scientists worked in shifts to drill to the base of the ice sheet.
Image: Nerilie Abram

By Paul Brown

Ice in parts of the Antarctic Peninsula is now melting during the summer faster than at any time in the last thousand years, and the most marked speed-up in the thaw has occurred since 1960, scientists say.

LONDON, 14 April – Summer ice melt in the Antarctic Peninsula has increased almost 10-fold in the last 600 years,  weakening the area’s large ice shelves and reducing glacier size, scientists have discovered.

The findings explain a series of sudden collapses of ice shelves in the last 20 years, which scientists studying them had not expected. The researchers say the melting that is now occurring could lead to further dramatic events, making the loss of large quantities of ice on the Peninsula more likely, and adding to sea level rise.

The results are significant because in the last two decades scientists have been divided on whether the Antarctic would gain mass through extra snow falling and so reduce sea level rise, or would lose ice because of higher sea and air temperatures and so multiply the effect. The new data come from a 1,000-year Antarctic Peninsula climate reconstruction published in the journal Nature Geoscience.

In 2008 a UK-French team drilled a 364-metre ice core from James Ross Island, near the northern tip of the Peninsula, with the idea of measuring past temperatures in the area. What surprised them was that the core also gave an unexpected insight into ice melt in the region over that period.

Layers in the ice core showed periods when summer snow on the ice cap thawed and then refroze.  By measuring the thickness of these melt layers the scientists were able to examine how the history of melting compared with changes in temperature at the ice core site over the last thousand years.

In the last 600 years the temperature has increased by 1.6C, but only in the last 50 years has it reached a level at which summer melting has increased dramatically.

Lead author Dr Nerilie Abram of the Australian National University and the British Antarctic Survey (BAS) said: “We found that the coolest conditions on the Antarctic Peninsula and the lowest amount of summer melt occurred around 600 years ago.

“At that time temperatures were around 1.6°C lower than those recorded in the late 20th century and the amount of annual snowfall that melted and refroze was about 0.5%. Today, we see almost ten times as much (5%) of the annual snowfall melting each year.

“…even small changes in temperature can result in large increases in the amount of melting…”

“Summer melting at the ice core site today is now at a level that is higher than at any other time over the last 1,000 years.  And whilst temperatures at this site increased gradually in phases over many hundreds of years, most of the intensification of melting has happened since the mid-20th century.”

Dr Robert Mulvaney from the BAS led the ice core drilling expedition and co-authored the paper.  He said: “Having a record of previous melt intensity for the Peninsula is particularly important because of the glacier retreat and ice shelf loss we are now seeing in the area.

“Summer ice melt is a key process that is thought to have weakened ice shelves along the Antarctic Peninsula leading to a succession of dramatic collapses, as well as speeding up glacier ice loss across the region over the last 50 years.”

The changes in the Peninsula do not necessarily apply to other parts of Antarctica, for example the West Antarctic Ice sheet, where melting is occurring and there is potentially an even greater risk of large-scale sea level rise.

It is not yet clear that the levels of recent ice melt and glacier loss in West Antarctica are exceptional or are caused by human-driven climate changes.

However, Dr Abram said: “This new ice core record shows that even small changes in temperature can result in large increases in the amount of melting in places where summer temperatures are near to 0°C, such as along the Antarctic Peninsula, and this has important implications for ice instability and sea level rise in a warming climate.” – Climate News Network

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by Tim Radford

Missing heat ‘is in the oceans’

April 12, 2013 in Warming

FOR IMMEDIATE RELEASE

Calm - and warming? The Atlantic appears to be absorbing more heat Image: Tiago Fioreze

Calm – and warming? The Atlantic appears to be absorbing more heat
Image: Tiago Fioreze

By Tim Radford

The recent slow-down in the rate at which the atmosphere is warming may be at least partly explained by European research, which suggests that the heat is going, not into the air, but into the seas.

LONDON, 12 April – Here is the puzzle: humans continue to pump increasing quantities of greenhouse gases into the atmosphere, and the world has warmed accordingly. Eleven of the 12 warmest years ever recorded have fallen in this century – but the rate of warming seems to have slowed rather than increased. So what has been taking the heat?

Climate scientists from Barcelona in Spain and Toulouse in France think they have the answer. They report in Nature Climate Change that instead of going into the near-surface atmosphere where meteorologists could easily measure it, much of the extra heat has been absorbed by the oceans.

This may not be the only explanation. There have also been arguments that volcanic eruptions might have put enough aerosols into the upper atmosphere to dim the sunlight and counter global warming a little. Stratospheric water vapour might also have damped things down, and some say the solar minimum – the spell of least activity in the Sun’s 11-year cycle – has been prolonged.

But Virginie Guemas of the Catalan Institute of Climate Science in Barcelona and colleagues propose more than speculation. They used a technique sometimes called “hindcasting” and in their case labeled “retrospective prediction” to argue what ought to have happened – and then checked the evidence.

This is the basis of science: frame a hypothesis, make a prediction from it and then check the evidence to see if the hypothesis is wrong. The advantage of doing it retrospectively is that it doesn’t take so long to find out whether you are right or wrong.

Trouble ahead

Guemas and her colleagues believe they were right. They argue that they successfully (and retrospectively) predicted the warming slowdown five years before it started around 2000.

And their conclusion is that the extra heat has been absorbed in the top 700 metres of the planet’s oceans below the surface layer, and more than half of this has been concentrated in the tropical Pacific and Atlantic oceans: enough to explain at least a three-year pause in the apparent rate of global warming.

Water in circulating oceans eventually delivers its heat back to the atmosphere, so the logic is that there is more and faster warming to come.

“Our results hence point at the key role of the ocean heat uptake in the recent warming slowdown”, the scientists claim.

“The ability to predict retrospectively this slowdown not only strengthens our confidence in the robustness of our climate models, but also enhances the socio-economic relevance of operational decadal climate predictions.” – Climate News Network

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by Tim Radford

Flight paths are set to get bumpier

April 9, 2013 in Science

FOR IMMEDIATE RELEASE

Happy landings - but it may be a little more unpredictable before touchdown Image: NASA

Happy landings – but it may be a little more unpredictable before touchdown
Image: NASA

By Tim Radford

As growing carbon dioxide emissions continue to warm the climate, more aircraft are likely to encounter turbulence in flight, meaning bumpier and perhaps longer journeys for passengers, scientists say.

LONDON, 9 April – Airline passengers – and airlines too – could be in for a rough ride as the decades pass and the world warms. Two British scientists have asked the question literally uppermost in the minds of transatlantic flight planners: what difference will global warming make to atmospheric turbulence?

Clear air turbulence is an enduring problem for commercial aircraft: pilots cannot see it coming, it doesn’t reflect signals to onboard radar, and satellite monitors cannot detect it.

Pilots however encounter moderate or uncomfortable clear air turbulence at least one per cent of cruise time. This adds up to tens of thousands of bumpy episodes each year, and hundreds of passengers who didn’t fasten their seatbelts in time may be injured.

Clear air turbulence is calculated to cost airlines £100 million ($150 million) a year in delays and damage, and although air crew and passengers have been facing such discomforts almost since the invention of flight 110 years ago, the mechanisms of turbulence are still, in that famously enigmatic scientific phrase, “not fully understood.”

But Paul Williams of the University of Reading and Manoj Joshi of the University of East Anglia report in Nature Climate Change that they decided to look at computer models to see whether climate change would make a difference. Turbulence is linked to atmospheric jet streams and these are likely to be strengthened by man-made global warming.

Since, right now, climate scientists cannot predict episodes of turbulence in particular latitudes at identifiable altitudes, the researchers could reach only very general conclusions.

“Aviation is partly responsible for changing the climate in the first place”

And since the factors involved in churning up flows of air are the subject of serious academic debate, they had a lot of possibilities to consider and at least 20 different units of measurement to factor into their models – technicalities like the magnitude of vertical shear of horizontal wind, flow deformation and simple wind speed, and highly specialised meteorological considerations such as the negative Richardson number, and the Brown energy dissipation rate.

They also had to consider the air traffic lanes between Europe and the Americas, the changes according to season, and the projected rates of increase in carbon dioxide emissions into the atmosphere. They decided to focus on the case for winter flights, because that is when turbulence is at its peak.

They found that at typical cruise altitudes in the northern half of the North Atlantic corridor in winter, most of their diagnostics showed between 10% and 40% increase in median strength of turbulence, and a 40% to 170% increase in the frequency of episodes of moderate or greater turbulence. So the airplanes that significantly increase the potential for global warming will also be affected by global warming.

“We conclude that climate change will lead to bumpier transatlantic flights by the middle of this century, assuming the same flight tracks are used”, they report. “Observational evidence suggests that this increase in bumpiness has already begun.

“Flight paths may need to become more convoluted to avoid patches of turbulence that are stronger and more frequent, in which case journey times will lengthen and fuel consumption and emissions will increase, in the same season and location that contrails have their largest climatic impact.”

Finally, they say, any increase in clear air turbulence would have important implications for large-scale atmospheric circulation, because clear air turbulence contributes significantly to exchanges between the stratosphere and the lower atmosphere.

“Aviation is partly responsible for changing the climate in the first place”, said Dr Williams. “It is ironic that the climate looks set to exact its revenge by creating a more turbulent atmosphere for flying.” – Climate News Network

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