IPCC’s urgent warning to tackle climate change

IPCC’s urgent warning to tackle climate change

The UN panel of climate scientists says some consequences of global warming will become irreversible unless greenhouse gas emissions fall to zero by the end of the century − but latest research suggests the reality may be even more urgent than that.

LONDON, 3 November, 2014 − Climate change threatens to become “severe, pervasive and irreversible”, according to the latest report from the Intergovernmental Panel on Climate Change (IPCC).

Without drastic cuts in greenhouse gas emissions, the report says, global average temperatures will probably increase by another 2°C by mid-century on their 1986-2005 levels. This implies temperatures nearly 4°C higher by 2100.

The warnings come in the Summary for Policymakers of the IPCC’s Climate Change 2014 Synthesis Report, itself a distillation of the three distinct volumes of the Panel’s Fifth Assessment Report (on climate science, impacts and mitigation) published since September 2013.

Will to change

The IPCC chair, Dr R K Pachauri, said at the Summary’s launch in Copenhagen: “We have the means to limit climate change. The solutions are many, and allow for continued economic and human development. All we need is the will to change. . .”

The Panel insists that adapting to climate change will not be enough, and that the world must make “substantial and sustained reductions of greenhouse gas emissions”.

Dr Pachauri said: “To keep a good chance of staying below 2ºC [the international threshold for temperature rise], and at manageable costs, our emissions should drop by 40% to 70% globally between 2010 and 2050, falling to zero or below by 2100.”

“A large fraction of anthropogenic climate change resulting from CO2 emissions is irreversible . . .”

The Summary, spelling out in careful terms what this means, says: “A large fraction of anthropogenic climate change resulting from CO2 emissions is irreversible on a multi-century to millennial timescale, except in the case of a large net removal of CO2 from the atmosphere over a sustained period.”

Put more simply, this means that without an effective way to clean up the main greenhouse gas, the world will face permanent changes. Unfortunately, the method proposed for cleaning the atmosphere − carbon capture and storage − has not yet proved itself at scale.

So Dr Pachauri’s plea that the world finds “the will to change“ is fine, so far as it goes. The problem is that there are also several technological hurdles still to surmount.

And that’s not the only problem with this report. As with previous major IPCC reports, it unavoidably trails some way behind the facts. The authors of the three volumes on which the Summary is based, published in the last 14 months, were able to consider only climate science published up till 15 March, 2013.

Serious consequences

But among research published since then − and too late to be considered by the IPCC teams − was a NASA report suggesting that the melting glaciers of West Antarctica may have passed the point of no return, with serious consequences for global sea levels.

Yet the IPCC Summary says simply: “Abrupt and irreversible ice loss from the Antarctic ice sheet is possible, but current evidence and understanding is insufficient to make a quantitative assessment.”

Other recent advances in climate science that were published too late for the Panel to consider relate to the Greenland ice sheet and to the Amazon.

This is not to blame the IPCC for producing a report that has serious gaps. Its assessment reports appear only once every six or seven years, and are written by unpaid volunteers, supported by a permanent staff of around 12 people.

But if you hear the IPCC being accused − as it often is − of alarmism, consider how truly alarming the Summary would have been if the authors had been able to digest all we now know about the effects of climate change. − Climate News Network

Share This:

Arctic melting sends winter warning to Europe and Asia

Arctic melting sends winter warning to Europe and Asia

Patterns of winds and pressure systems traced by researchers to the decline in Arctic sea ice can transport cold air further south and create harsher winters in Eurasia.

LONDON, October 30, 2014 − A less-icy Arctic could mean that parts of Europe and Asia are twice as likely to experience severe winters, according to new research from Japan.

Masato Mori and fellow climate system researchers at the University of Tokyo report in Nature Geoscience that they see a connection between the loss of ice in the Barents and Kara Seas and the increased probability of colder winters in Eurasia.

Notoriously, the Arctic is one of the fastest warming regions of the planet, and scientists have repeatedly warned that the whole Northern seas could be free of ice by the summer of 2050.

Big freeze

The Japanese team performed 200 different simulations of global atmospheric circulation to disentangle the Eurasian winter effect. As sea ice declined in the two Arctic waters, so there arose persistent patterns of winds and pressure systems that, since 2004, have enabled the transport of cold air further south, and made a big freeze more likely.

There have already been suggestions that changes in Arctic sea ice could be linked to the ferocious recent winter in the north-eastern United States, and there is consistent evidence that the great Arctic melt will continue.

“We can expect these weather extremes to continue
to occur, and maybe worsen”

But the researchers also ran their models forward well into the 21st century, and they don’t think things will get frostier in the long run for southern Russia, Mongolia and other such tracts of the interior.

“We conclude that the sea-ice-driven cold winters are unlikely to dominate in a warming future climate, although uncertainty remains,” they warn

Such calculations are provisional, and the Japanese scientists know their findings are tentative. But earlier research has suggested similar conclusions.

Highly damaging

Peter Wadhams, who heads the Polar Ocean Physics Group at the University of Cambridge in the UK, said the study supported other, earlier analyses.

He warned: “Annual average global temperatures continue to rise, but the distribution of temperature through the year is giving us more extremes, which is highly damaging to food production. As ice continues to retreat, we can expect these weather extremes to continue to occur, and maybe worsen.”

Colin Summerhayes, a marine geologist and oceanographer with the Scott Polar Research Institute at the University of Cambridge, also said that more research was needed. But he added: “The counter-intuitive effect of the global warming that led to sea ice decline in the first place makes some people think that global warming has stopped. It has not.

“Although average surface warming has been slower since 2000, the Arctic has gone on warming rapidly throughout this time.” – Climate News Network

Share This:

Sea rise may still pose a man-sized threat

Sea rise may still pose a man-sized threat

Although new research discounts the likelihood of a two-metre sea rise this century, the predicted impacts of global warming are still bad news for the many millions of people living at or near sea level.

LONDON, 21 October, 2014 − For those who think climate change means deep trouble, some comfort: there is a limit to how deep. Danish-led researchers have looked at all the projections and satisfied themselves that, at the very worst, sea levels this century will rise by a maximum 1.8 metres − roughly the height of an average man.

They report in Environmental Research Letters that they contemplated rates of melting in Greenland and Antarctica, the retreat of mountain glaciers worldwide, and the impact of groundwater extraction for agriculture and industry.

They also looked at all the projections for thermal expansion of the oceans, because warmer water is less dense than colder water and therefore occupies a greater volume. Then they began to calculate the band of possibilities.

“We have created a picture of probable limits for how much global sea levels will rise this century,” said Aslak Grinsted, assistant professor in the Niels Bohr Institute’s Centre for Ice and Climate at the University of Copenhagen. “Our calculations show that seas will likely rise by around 80cm. An increase of more than 180 cm has a likelihood of less than 5%. We find that a rise in sea levels of more than 2 metres is improbable.”

Critical infrastructure

The worst-case scenario, he says, is something that it would be wise to consider for critical infrastructure, such as the Delta Works, a series of construction projects that protect a large area of land in the south-west of the Netherlands, or the Thames Barrier, which aims to prevent London from being inundated by exceptionally high tides and storm surges from the North Sea.

The finding comes with two important provisos: one is that any significant rise remains extremely bad news for people in those regions of the planet that are already more or less at sea level − among them the coral atolls of the tropical oceans, the Netherlands, the Nile Delta, Bangladesh, Venice in Italy, and some of the world’s great maritime cities.

The other is that the man-high limit extends only to 2100, and researchers have repeatedly warned that, once begun, sea level rise will continue for centuries.

The Danish calculations fall into the category of things that could happen: melting in polar waters inevitably means even warmer equatorial waters, and another ominous projection for the near future is that commercially valuable fish could desert the tropics by 2050.

William Cheung, head of the Changing Ocean Research Unit at the University of British Columbia, Canada, and Miranda Jones, an environmental scientist at the same university, considered what would happen if the world warmed by 3°C by 2100.

“The tropics will be the overall losers. This area has
a high dependence on fish for food, diet and nutrition”

They report in ICES Journal of Marine Science that, under such a scenario, tropical fish could move away from their present habitats at a rate of 26 kilometres a decade. Even with a 1°C warming, they would desert their home waters at 15 km a decade.

Altogether, the two scientists considered the possibilities for 802 commercially important species, concluding that such a set of migrations might introduce new potential catches in Arctic waters, but could be very bad news for tropical fishermen, and for the hundreds of millions who depend on fish as a source of protein.

“The tropics will be the overall losers,” Dr Cheung said. “This area has a high dependence on fish for food, diet and nutrition. We’ll see a loss of fish populations that are important to the fisheries and communities in these regions.”

Accelerated rates

Paradoxically, as researchers consistently forecast accelerated rates of melting in polar waters, the Antarctic sea ice in September occupied a greater area than ever before, with the five-day average on September 19 reaching 20 million sq km, according to the US National Snow and Ice Data Centre.

That means that while most of the planet continued to warm, the Antarctic continent and the seas around it were icier, for one season at least.

Such measurements ultimately depend on satellite and aerial surveillance, and according to Claire Parkinson, climate change senior scientist at  the NASA Goddard Space Flight Centre, the anomaly simply reflects the complexity of climate dynamics and the diversity of the Earth’s environments.

“The planet as a whole is doing what was expected in terms of warming,” she says. “Sea ice as a whole is decreasing as expected, but just like with global warming, not every location with sea ice will have a downward trend in ice extent.”

But, overall, the planet is still saying goodbye to ice. The Antarctic’s gain is roughly a third in area of the loss of ice in the Arctic. – Climate News Network

Share This:

Ice loss sends Alaskan temperatures soaring

Ice loss sends Alaskan temperatures soaring

Scientists analysing more than three decades of weather data for the northern Alaska outpost of Barrow have linked an astonishing 7°C temperature rise to the decline in Arctic sea ice.

LONDON, 17 October, 2014 − If you doubt that parts of the planet really are warming, talk to residents of Barrow, the Alaskan town that is the most northerly settlement in the US.

In the last 34 years, the average October temperature in Barrow has risen by more than 7°C − an increase that, on its own, makes a mockery of international efforts to prevent global temperatures from rising more than 2°C above their pre-industrial level.

A study by scientists at the University of Alaska Fairbanks analysed several decades of weather information. These show that temperature trends are closely linked to sea ice concentrations, which have been recorded since 1979, when accurate satellite measurements began.

The study, published in the Open Atmospheric Science Journal, traces what has happened to average annual and monthly temperatures in Barrow from 1979 to 2012.

Most striking

In that period, the average annual temperature rose by 2.7°C. But the November increase was far higher − more than six degrees. And October was the most striking of all, with the month’s average temperature 7.2°C higher in 2012 than in 1979.

Gerd Wendler, the lead author of the study and a professor emeritus at the university’s International Arctic Research Center, said he was “astonished”. He told the Alaska Dispatch News: “I think I have never, anywhere, seen such a large increase in temperature over such a short period.”

The study shows that October is the month when sea ice loss in the Beaufort and Chukchi Seas, which border northern Alaska, has been highest. The authors say these falling ice levels over the Arctic Ocean after the maximum annual melt are the reason for the temperature rise. “You cannot explain it by anything else,” Wendler said.

They have ruled out the effects of sunlight because, by October, the sun is low in the sky over Barrow and, by late November, does not appear above the horizon.

Instead, they say, the north wind picks up stored heat from water that is no longer ice-covered in late autumn and releases it into the atmosphere.

At first sight, the team’s findings are remarkable, as Barrow’s 7.2°C rise in 34 years compares with a global average temperature increase over the past century of up to about 0.8°C. But what’s happening may be a little more complex.

Warming faster

The fact that temperatures in and around Barrow are rising fast is no surprise, as the Arctic itself is known to be warming faster than most of the rest of the world.

The Intergovernmental Panel on Climate Change says observed warming in parts of northern Alaska was up to 3°C from the early 1980s to the mid-2000s. It also concludes that about two-thirds of the last century’s global temperature increase has occurred since 1980.

But Barrow’s long-term temperature rise has not been uniform, the Fairbanks study says. Its analysis of weather records between 1921 and 2012 shows a much more modest average annual rise, of 1.51°C. In 2014, the city experienced the coolest summer day recorded − 14.5°C.

So one conclusion is to remember just how complex a system the climate is − and how even 34 years may be too short a time to allow for any certainty. − Climate News Network

Share This:

Why Greenland is likely to melt more quickly

Why Greenland is likely to melt more quickly

Scientists who have examined the role of the bedrock on which the Greenland ice sheet rests think it shows the huge island is more vulnerable than realised to global warming.

LONDON, 1 October – Climate scientists have thought a little more deeply about the state of the Greenland ice sheet and their conclusions are ominous.

They think that the northern hemisphere’s largest assembly of ice and compacted snow is more vulnerable to climate change than anybody had previously thought.

Marion Bougamont of the Scott Polar Research Institute in Cambridge, UK, and colleagues report in Nature Communications that they factored in not just a mathematical model of the melting ice from Greenland, but also the role of the soft, yielding and absorbent mud and rock beneath.

The Greenland ice sheet is the planet’s second largest body of terrestrial ice. It covers 1.7 million square kilometres and if it were all to melt, the world’s sea levels would rise by more than seven metres.

Right now, about 200 gigatonnes of Greenland ice a year turn to water and run into the sea. This alone raises sea levels at the rate of 0.6 millimetres a year. In fact the increase in sea levels from all causes – glacier retreat worldwide, ice cap melting and ocean thermal expansion –  is now 3 mm a year.

Researchers have repeatedly found evidence of an acceleration of melting, in some cases by looking at what is happening within the ice or on the surface, or by taking a new look at satellite data.

Less stable

But the latest calculation goes even deeper: into the mud below the ice. According to the new model, and to evidence from surveys, melting will be complicated by the conditions deep under the ice.

The ice sheets are moving, naturally and at different speeds, causing the ice to shear or flow, and the assumption has always been that the ice is flowing over hard and impermeable rock. A closer look suggests a different process.

Lakes of summer meltwater tend to form on the ice sheet surface: if the ice below fractures, these lakes can drain in a matter of hours. The meltwater flows down within the ice, and into the sediment below it.

“The soft sediment gets weaker as it tries to soak up more water, making it less resistant, so that the ice above moves faster. The Greenland ice sheet is not nearly as stable as we think,” said Poul Christofferson, a co-author.

And Dr Bougamont said: “There are two sources of net ice loss: melting on the surface and increased flow of the ice itself, and there is a connection between these mechanisms that isn’t taken into account by standard ice sheet models.”

Rapid change

At present, the annual flow of ice meltwater is more or less stable. In warmer years, the ice sheet becomes more vulnerable because more meltwater gets to the muddy absorbent bedrock. Because there is a limit to how much the sediment below can hold, the ice sheet becomes more vulnerable during extreme events such as heat waves.

And, of course, if under such a scenario it is vulnerable, it continues to become more vulnerable as average temperatures rise and extreme events become more frequent, and more extreme. And a closer look at recent geological history shows just how fast change can happen.

In a separate study in Nature Communications, Katharine Grant of the Australian National University and colleagues report that they examined evidence of the melting process at the close of each of the last five ice ages.

They looked at data from wind-blown dust in sediment cores from the Red Sea, and matched these with records from Chinese stalagmites to confirm a picture of pronounced climate change at the end of each ice age, and calculated that sea levels rose at the rate of 5.5 metres per century.

These however were exceptional events, and there were more than 100 smaller sea level events in between the big five.

“Time periods with less than twice the modern global ice volume show almost no indications of sea level rise faster than about 2 metres per century,” said Dr Grant. “Those with close to the modern amount of ice on Earth show rates of up to one to 1.5 metres per century.” – Climate News Network

Share This:

Ice melt dilutes Arctic sea’s CO2 clean-up role

Ice melt dilutes Arctic sea’s CO2 clean-up role

New scientific research confirms that global warming is melting increasingly larger areas of Arctic sea ice − and reducing its vital function of removing CO2 from the atmosphere.

LONDON, 26 September, 2014 − The Arctic ice cap has just passed its summer minimum – and it’s the sixth lowest measure of sea ice recorded since 1978, according to scientists at the US space agency NASA.

For three decades, the shrinking Arctic ice – and the growing area of clear blue water exposed each summer – has been a cause of increasing alarm to climate scientists.

Polar seasonal changes are measured annually by NASA, but reliable satellite data goes back only to 1978, For much of the 20th century, the Arctic was part of the Cold War zone, so only Soviet naval icebreakers and US nuclear submarines took consistent measurements − and neither side published the data.

But studies of 17th and 18th century whaling ships’ logbooks and other records make it clear that the ice once stretched much further south each summer than it does today.

Steady decline

In the last 30 years, the thickness and the area of the ice have both been in steady decline, with predictions that in a few decades the Arctic Ocean could be virtually ice free by September, opening up new sea routes between Asia and Europe.

This year could have been worse, although the area of ice fell to little more than 5 million square kilometres − significantly below the 1981-2010 average of 6.22 million sq km.

“The summer started off relatively cool, and lacked the big storms or persistent winds that can break up ice and increase melting,” said Walter Meier, a research scientists at NASA’s Goddard Space Flight Centre. “Even with a relatively cool year, the ice is so much thinner than it used to be. It is more susceptible to melting.”

Warming in the Arctic is likely to affect climate patterns in the temperate zones, and the state of the polar ice has become of such concern that researchers are using ground-based and sea-based monitors to explore the physics of the phenomenon.

But there is another reason for the attention: as polar ice diminishes, so does the planet’s albedo − its ability to reflect sunlight back into space.

So, as the ice shrinks, the seas warm, making it more difficult for new ice to form. And greater exposure to sunlight increases the probability that permafrost will thaw, releasing even more greenhouse gases locked in the frozen soils.

Now researchers have found another and unexpected example of climate feedback that could affect the cycle of warming. Climate scientist Dorte Haubjerg Søgaard, of the Greenland Institute of Natural Resources and the University of Southern Denmark, and research colleagues have discovered that sea ice itself is an agency that removes carbon dioxide from the atmosphere.

That the oceans absorb the stuff, and tuck it away as calcium carbonate or other marine minerals, is old news.

“But we also thought that this did not apply to ocean areas covered by ice, because the ice was considered impenetrable,” Søgaard said. “However, new research shows that sea ice in the Arctic draws large amounts of CO2 from the atmosphere into the ocean.”

The research is published in four journals, Polar Biology, The Cryosphere, The Journal of Geophysical Research: Atmospheres and Marine Ecology Progress Series.

Two-stage pattern

The Danish research team observed a complex, two-stage pattern of gas exchange as ice floes formed off southern Greenland. They measured the role of atmospheric carbon dioxide in the formation and release of calcium carbonate crystals form in the sea ice, and kept a tally during a 71-day cycle of the carbon dioxide budget.

In the course of this complicated bit of natural cryo-chemistry, they found that some CO2 was carried deep into the ocean with dense, heavy brines, as the ice froze and some was captured by algae in the thawing ice.

They also identified a third factor: the “frost flowers” that formed on the new ice had an unexpectedly high concentration of calcium carbonate.

The profit-and-loss accounting meant that every square metre of ice effectively removed 56 milligrams of carbon from the atmosphere during the 71-day cycle. Over an area of 5 million sq km, this would represent a significant uptake.

But the real importance of the discovery is that scientists have identified yet another way in which the ice – while it is there – helps keep the Arctic cold, and yet another way in which carbon dioxide is absorbed by the oceans.

“If our results are representative, then the sea ice plays a greater role than expected, and we should take account of this in future global CO2 budgets,” Søgaard said. – Climate News Network

Share This:

Bluefin tuna follow prey to warming high Arctic

Bluefin tuna follow prey to warming high Arctic

A research ship’s surprise catch of bluefin tuna further north than ever recorded indicates that climate change is restructuring the food web as the waters of east Greenland get warmer.

LONDON, 8 September, 2014 − Biologists and fishermen aboard a scientific cruise in the Arctic while they investigated mackerel stocks caught more than they bargained for − three large bluefin tuna, each weighing about 100 kilograms.

The research ship was sailing through the Denmark Strait, which separates Greenland from Iceland. Bluefin tuna are very seldom found near Greenland, and there are no other scientific reports of them venturing that far north. The most recent report of a tuna anywhere near was a stranding in 1900, a long way south at Qaqortoq, on the south-western tip of Greenland.

Details of the find, during a cruise in August 2012 organised by the Center for Macroecology, Evolution and Climate at the University of Copenhagen, have now been published in the journal Global Change Biology.

Expanded range

The lead author, Professor Brian MacKenzie, said bluefin tuna usually search for prey in areas where surface temperatures are warmer than 11°C.

At the time of the catch, the Denmark Strait was unusually warm, and one of tuna’s preferred prey species, mackerel, had already expanded their range into the region.

Professor MacKenzie and his colleagues write: “Regional temperatures in August 2012 were historically high and contributed to a warming trend since 1985, when temperatures began to rise.

“The presence of bluefin tuna in this region is likely due to a combination of warm temperatures . . . and immigration of an important prey species to the region. We conclude that a cascade of climate change impacts is restructuring the food web in east Greenland waters.”

They say their data was too limited to estimate how many tuna came so far north, but because bluefins are a schooling species − with schools having from 10 to 100 individuals − and because the three tuna were caught in the same haul, it is likely there were many more present.

The report says: “Satellite imagery showing the spread of warm water from the south-east towards east Greenland suggests that recent warming and climate change may have opened a migration pathway from the European shelf towards Greenland for migratory species.”

It acknowledges that the fish may have swum to the Denmark Strait from the north-west Atlantic, and concludes: “Our results show that rising temperatures have been progressively leading a . . . trophic [high in the food chain] cascade into east Greenland waters via improved thermal conditions for migratory prey and predator species.”

New fishing quotas

Nobody knows why bluefin tuna disappeared from the waters near Denmark and in the Norwegian Sea during the 1960s, nor when they might return. But Iceland and Norway have been allocated new fishing quotas of 30 tonnes each for the species in 2014.

An adult bluefin tuna is typically 1.5m-2m long, but some have been as big as 4.5m and weighed 650 kg. The fish are highly prized for sushi, especially in Japan.

Further climate-related changes in distributions of commercial fish such as mackerel and herring will mean new fishery and ecosystem management plans are going to be needed, says the report’s co-author, Helle Siegstad, head of the Department for Fish and Shellfish at the Greenland Institute of Natural Resources.

The Denmark Strait tuna will be discussed at the annual science conference of the International Council for the Exploration of the Sea (ICES), which starts on 15 September in the Spanish coastal city of A Coruña. – Climate News Network

Share This:

Sun sheds light on Arctic carbon puzzle

Sun sheds light on Arctic carbon puzzle

Scientists discover that, as the Arctic continues to warm, sunlight will be the major cause of CO2 escaping into the atmosphere from vegetation preserved in frozen soil.

LONDON, 4 September, 2014 − One of the puzzles of the permafrost has been solved by scientists in the US. The key to the carbon cycle in the Arctic north is not the microbe population − it’s the sunlight.

Such a discovery is not, strictly speaking, concerned with climate change, but with the more detailed question of how the world works – specifically, how the carbon that was once plant material gets back into the atmosphere.

However, since the Arctic permafrost is home to half of all the organic carbon trapped in the soils of the entire Earth, the finding is ominous.

The Arctic is one of the fastest warming regions on the planet. As it warms, more and more carbon dioxide is likely to escape from the half-decayed tundra vegetation preserved in the frozen soil and will find its way into the atmosphere, to accelerate still further warming.

For the moment, the study is another piece fitted into place in a wider understanding of the carbon cycle.

Organic carbon

Rose Cory, of the University of Michigan, US, reports with colleagues, in the journal Science, that they measured the speeds at which bacteria and sunlight converted dissolved organic carbon in the lakes and rivers of Alaska.

In the standard domestic garden compost heap, the hard work of turning such things as decaying cabbage stalks, potato peelings and grass cuttings back into carbon dioxide and methane is performed by microbes.

But visible and ultraviolet light beams also pack a punch. They too can oxidise organic carbon and turn it back into gas molecules.

In 2013, Dr Cory and colleagues established that levels of dissolved organic carbon in a region that was once permanently frozen were rising, giving microbes and other conversion processes a chance to get to work.

The researchers took samples of flowing and still water from 135 lakes and 73 rivers on Alaska’s North Slope over a three-year period, and then incubated them under differing conditions of light.

More efficient

They found that sunlight was 19 times more efficient than microbes at processing the carbon, and could account for between 70% and 95% of all the carbon released from Alaskan water.

“We’re likely to see more carbon dioxide released from thawing permafrost than people had previously believed,” Dr Cory said. “We are able to say that because we now know that sunlight plays a key role and that carbon released from thawing permafrost is readily converted to carbon dioxide once it is exposed to sunlight.”

Microbes are less efficient in low temperatures. And the sunlight works more efficiently because it can directly degrade the dissolved organic carbon, and can also convert it into a condition that makes it more accessible for the microbes.

“This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river – and most lakes – so that no dissolved organic carbon is kept in the dark,” said Byron Crump, a microbial ecologist at Oregon State University, and a co-author of the report. “Also there is little shading of rivers and lakes in the Arctic because there are no trees.” – Climate News Network

Share This:

Satellite mapping shows ice caps’ faster melt rate

Satellite mapping shows ice caps’ faster melt rate

Scientists have been able to measure more accurately than ever the thickness of the world’s major ice caps – revealing that melting is causing the loss of 500 cubic kms of ice annually.

LONDON, 1 September, 2014 − German researchers have established the height of the Greenland and Antarctic ice caps with greater precision than ever before. And the new maps they have produced show that the ice is melting at an unprecedented rate.

The maps, produced with a satellite-mounted instrument, have elevation accuracies to within a few metres. Since Greenland’s ice cap is more than 2,000 metres thick on average, and the Antarctic bedrock supports 61% of the planet’s fresh water, this means that scientists can make more accurate assessments of annual melting.

Dr Veit Helm and other glaciologists at the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, report in the journal The Cryosphere that, between them, the two ice sheets are now losing ice at the unprecedented rate of 500 cubic kilometres a year.

Big picture

The measurements used to make the maps were taken by an instrument aboard the European Space Agency’s orbiting satellite CryoSat-2. The satellite gets closer to the poles − to 88° latitude − than any previous mission and traverses almost 16 million sq km of ice, adding an area of ice the size of Spain to the big picture of change and loss in the frozen world.

CryoSat-2’s radar altimeter transmitted 7.5 million measurements of Greenland and 61 million of Antarctica during 2012, enabling glaciologists to work with a set of consistent measurements from a single instrument.

Over a three-year period, the researchers collected 200 million measurements in Antarctica and more than 14 million in Greenland. They were able to study how the ice sheets changed by comparing the data with measurements made by NASA’s ICESat mission.

More complex

Greenland’s volume of ice is being reduced at the rate of 375 cubic km a year. In Antarctica, the picture is more complex as the West Antarctic ice sheet is losing ice rapidly, but is growing in volume in East Antarctica.

Overall, the southern continent − 98% of which is covered with ice and snow − is losing 125 cubic km a year. These are the highest rates observed since researchers started making satellite observations 20 years ago.

“Since 2009, the volume loss in Greenland has increased by a factor of about two, and the West Antarctic ice sheet by a factor of three,” said Angelika Humbert, one of the report’s authors. − Climate News Network

Share This:

Pre-history proof of climate’s see-saw sensitivity

Pre-history proof of climate’s see-saw sensitivity

Computer simulations reaching back deep into the last Ice Age have enabled scientists to put a historic perspective on how even small variations in the climate system can lead to dramatic temperature change.

LONDON, 24 August, 2014 − It doesn’t take much to change a planet’s climate – just a little shift in the Northern hemisphere glacial ice sheet and a bit more carbon dioxide in the atmosphere. After that, the response is rapid. The tropical rain belt moves north and the southern hemisphere cools a bit, in some sort of bipolar see-saw response.

Sound familiar? It does, and it doesn’t. It all happened long before the internal combustion engine, or even the new Stone Age.

Researchers from the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research, Bremerhaven, the University of Bremen, Germany, and the University of Cardiff in the UK, report in Nature journal that they have made climate simulations that agree with observations of historical climate change that date back 800,000 years.

Long before the present alarms about global warming through the emission of carbon dioxide from fossil fuels, climate researchers were puzzled by the phenomenon of the Ice Ages and the “interglacials” that punctuated those long periods when the Arctic ice extended from the North Pole to the Atlantic coast of France, and over huge tracts of North America.

Vanished species

Mysteriously, and at great speed, the temperatures would rise by up to 10°C and the vast walls of ice would retreat. Lion, hyena and rhinoceros would invade the wild plains of what is now southern England, and now-vanished species of humans would hunt big game and gather fruit and seeds in the valleys and forests of Europe and America.

Since the end 10,000 years ago of the last ice age – itself a very rapid event – was the springboard for agriculture and civilisation, and eventually an Industrial Revolution based on fossil fuels, the story of climate change plays a powerful role in human history.

So any analysis of the tiny shifts in ice cover that seemed to trigger these dramatic, bygone events can be helpful in understanding the long story of the making of the modern world.

The researchers found a tentative scenario involving weak ocean currents, and prevailing winds that shifted the sea ice and allowed the oceans and atmosphere to exchange heat, pushing warmer water into the north-east Atlantic.

These changes precipitated a dramatic warming of the northern hemisphere in just a few decades, and the retreat of the glaciers for an extended period before the ice returned to claim much of the landmass again. But, overall, such changes tended to occur when sea levels reached a certain height.

“The rapid climate changes known in the scientific world as Dansgaard-Oeschger events were limited to a period of time from 110,000 to 23,000 years before the present,” said Xu Zhang, the report’s lead author.

“The abrupt climate changes did not take place at the extreme low sea levels, corresponding to the time of maximum glaciations 20,000 years ago, or at high sea levels such as those prevailing today. They occurred during periods of intermediate ice volume and intermediate sea levels”

Climate swings

Co-author Gerrit Lohmann, who leads the Wegener Institute’s palaeoclimate dynamics group, said: “Using the simulations performed with our climate model, we were able to demonstrate that the climate system can respond to small changes with abrupt climate swings.

“At medium sea levels, powerful forces − such as the dramatic acceleration of polar ice cap melting − are not necessary to result in abrupt climate shifts and associated drastic temperature changes.”

How much this tells anybody about modern climate change is open to debate. Right now, according to this line of evidence, the planet’s climate could be in one of its more stable phases of the Earth’s history.

But while the conditions for the kind of rapid change recorded in pre-history do not exist today, Prof Lohmann warns that “sudden climate changes cannot be excluded in the future”. – Climate News Network

Share This: