Tag Archives: Glaciers

‘Upside-down rivers’ speed polar ice loss

polar ice

Researchers move closer to understanding the invisible dynamics that drive the loss of polar ice shelves – but what it means for global warming is still uncertain.

LONDON, October 16, 2019 – Scientists in the US believe they have now identified the machinery that drives the break-up of great chunks of polar ice shelves. What they call “upside down rivers” of warm, less dense, less saline water, tens of miles long and miles wide, find weaknesses in the massive ice shelves.

And because global temperature rise is causing polar currents to get warmer, the effect could be to accelerate the collapse of great tracts of ice shelf, and allow glacial flow to speed up – resulting in rising sea levels.

Call it subversion: these unexpected channels of water rise from underneath to concentrate their effect on fracture zones that form as land-bound glaciers flow slowly onto the marine surface.

“Warm water circulation is attacking the undersides of these ice shelves at their weakest points,” says Earth scientist Karen Alley, who did her research at the University of Colorado in Boulder, but is now at the College of Wooster in Ohio, US. “These effects matter. Exactly how much, we don’t yet know. But we need to.”

Frozen sheets

The research could explain the persistent appearance, at roughly the same place every year, of polynyas. These are great pools of open sea water in the ice shelves, and scientists have been puzzling for decades about the mechanisms that make them possible.

About 80% of Antarctica is bounded by frozen sheets of sea ice, many of them anchored by bumps and chasms on the sea floor, and this is what slows the flow of ice from high ground to ocean.

But satellite studies have long exposed crevasses in this ice, formed at what scientists call “shear margins” – weak points in flowing ice.

Once part of the floating shelf, these fracture zones are more vulnerable to plumes of more buoyant – that is, less saline and warmer – water that flow as “basal channels” to create long wrinkles or sags in the shelf.

Dr Alley and her colleagues report in Science Advances journal that they pieced together this picture of polar dynamism far below the surface by combing satellite data to expose patterns of surface change made possible only by some consistent erosion by warmer current.

Climate – winds, rainfall, heat and drought patterns – is driven by the temperature gradient. Large-scale weather systems happen because the poles are cold and the tropics are hot, and this difference powers the stratospheric jet stream and the most profound ocean flow.

So climate scientists are intensely interested in change in both Greenland and the Antarctic.

“Now we’re seeing a new process, where warm water cuts into the ice shelf from below”

Other teams have already established that ice shelves are melting ever faster in the coldest places on the planet, that this melting is happening ever faster, that the ice is being attacked from below, and that this can only accelerate sea-level rise in a world subject to global heating driven by human use of fossil fuels that deposit huge volumes of greenhouse gases in the atmosphere.

The latest study focused on Antarctica, but the findings could also be applied to Greenland, which has the greatest reserve of Arctic ice, and where ice loss is accelerating even faster.

Report co-author Ted Scambos, senior research scientist in the Earth Science and Observation Centre at the University of Colorado at Boulder, says: “Now we’re seeing a new process, where warm water cuts into the ice shelf from below.

“Like scoring a plate of glass, the trough renders the shelf weak and, in a few decades, it’s gone, freeing the ice sheet to ride out faster into the ocean.” – Climate News Network

Researchers move closer to understanding the invisible dynamics that drive the loss of polar ice shelves – but what it means for global warming is still uncertain.

LONDON, October 16, 2019 – Scientists in the US believe they have now identified the machinery that drives the break-up of great chunks of polar ice shelves. What they call “upside down rivers” of warm, less dense, less saline water, tens of miles long and miles wide, find weaknesses in the massive ice shelves.

And because global temperature rise is causing polar currents to get warmer, the effect could be to accelerate the collapse of great tracts of ice shelf, and allow glacial flow to speed up – resulting in rising sea levels.

Call it subversion: these unexpected channels of water rise from underneath to concentrate their effect on fracture zones that form as land-bound glaciers flow slowly onto the marine surface.

“Warm water circulation is attacking the undersides of these ice shelves at their weakest points,” says Earth scientist Karen Alley, who did her research at the University of Colorado in Boulder, but is now at the College of Wooster in Ohio, US. “These effects matter. Exactly how much, we don’t yet know. But we need to.”

Frozen sheets

The research could explain the persistent appearance, at roughly the same place every year, of polynyas. These are great pools of open sea water in the ice shelves, and scientists have been puzzling for decades about the mechanisms that make them possible.

About 80% of Antarctica is bounded by frozen sheets of sea ice, many of them anchored by bumps and chasms on the sea floor, and this is what slows the flow of ice from high ground to ocean.

But satellite studies have long exposed crevasses in this ice, formed at what scientists call “shear margins” – weak points in flowing ice.

Once part of the floating shelf, these fracture zones are more vulnerable to plumes of more buoyant – that is, less saline and warmer – water that flow as “basal channels” to create long wrinkles or sags in the shelf.

Dr Alley and her colleagues report in Science Advances journal that they pieced together this picture of polar dynamism far below the surface by combing satellite data to expose patterns of surface change made possible only by some consistent erosion by warmer current.

Climate – winds, rainfall, heat and drought patterns – is driven by the temperature gradient. Large-scale weather systems happen because the poles are cold and the tropics are hot, and this difference powers the stratospheric jet stream and the most profound ocean flow.

So climate scientists are intensely interested in change in both Greenland and the Antarctic.

“Now we’re seeing a new process, where warm water cuts into the ice shelf from below”

Other teams have already established that ice shelves are melting ever faster in the coldest places on the planet, that this melting is happening ever faster, that the ice is being attacked from below, and that this can only accelerate sea-level rise in a world subject to global heating driven by human use of fossil fuels that deposit huge volumes of greenhouse gases in the atmosphere.

The latest study focused on Antarctica, but the findings could also be applied to Greenland, which has the greatest reserve of Arctic ice, and where ice loss is accelerating even faster.

Report co-author Ted Scambos, senior research scientist in the Earth Science and Observation Centre at the University of Colorado at Boulder, says: “Now we’re seeing a new process, where warm water cuts into the ice shelf from below.

“Like scoring a plate of glass, the trough renders the shelf weak and, in a few decades, it’s gone, freeing the ice sheet to ride out faster into the ocean.” – Climate News Network

Extreme sea level events ‘will hit once a year by 2050’

This story originally appeared in The Guardian. It is republished here as part of the Climate News Network’s partnership with Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.

Extreme sea level events that used to occur once a century will strike every year on many coasts by 2050, no matter whether climate heating emissions are curbed or not, according to a landmark report by the world’s scientists.

25 September, 2019 − The stark assessment of the climate crisis in the world’s oceans and ice caps concludes that many serious impacts are already inevitable, from more intense storms to melting permafrost and dwindling marine life.

But far worse impacts will hit without urgent action to cut fossil fuel emissions, including eventual sea level rise of more than 4 metres in the worst case, an outcome that would redraw the map of the world and harm billions of people.

The report from the Intergovernmental Panel on Climate Change (IPCC), and approved by its 193 member nations, says that “all people on Earth depend directly or indirectly on the ocean” and ice caps and glaciers to regulate the climate and provide water and oxygen. But it finds unprecedented and dangerous changes being driven by global heating.

Sea level rise is accelerating as losses from Greenland and Antarctica increase, and the ocean is getting hotter, more acidic and less oxygenated. All these trends will continue to the end of the century, the IPCC report said.

Half the world’s megacities, and almost 2 billion people, live on coasts. Even if heating is restricted to just 2C, scientists expect the impact of sea level rise to cause several trillion dollars of damage a year, and result in many millions of migrants.

“The future for low-lying coastal communities looks extremely bleak,” said Prof Jonathan Bamber at Bristol University in the UK, who is not one of the report’s authors. “But the consequences will be felt by all of us. There is plenty to be concerned about for the future of humanity and social order from the headlines in this report.”

The new IPCC projections of likely sea level rise by 2100 are higher than those it made in 2014, due to unexpectedly fast melting in Antarctica. Without cuts in carbon emissions, the ocean is expected to rise between 61cm and 110cm, about 10cm more than the earlier estimate. A 10cm rise means 10 million additional people exposed to flooding, research shows.

The IPCC considers the likely range of sea level rise but not the worst-case scenario. Recent expert analysis led by Bamber concluded that up to 238cm of sea level rise remains possible by 2100, drowning many megacities around the world. “This cannot be ruled out,” said Zita Sebesvari at the United Nations University, a lead author of the IPCC report.

Even if huge cuts in emissions begin immediately, between 29cm and 59cm of sea level rise is already inevitable because the ice caps and glaciers melt slowly. Sea level will rise for centuries without action, Sebesvari warned. “The dramatic thing about sea level rise is if we accept 1 metre happening by 2100, we accept we will get about 4 metres by 2300. That is simply not an option we can risk.”

Extreme sea level impacts will be felt in many places very soon and well before 2050, Sebesvari said. The IPCC report states: “Extreme sea level events that [occur] once per century in the recent past are projected to occur at least once per year at many locations by 2050 in all scenarios.”

The heating oceans are causing more intense tropical storms to batter coasts, the IPCC report found, with stronger winds and greater deluges of rain. For example, Hurricane Harvey’s unprecedented deluge, which caused catastrophic flooding, was made three times more likely by climate change.

Ocean heating also harms kelp forests and other important ecosystems, with the marine heatwaves that sear through them like underwater wildfires having doubled in frequency in the last 40 years. They are projected to increase by at least 20 times by 2100, the IPCC reported.

Extreme El Niño events, which see heatwaves in some regions and floods in others, are projected to occur twice as often this century whether emissions are cut or not, the report said. Coral reefs, vital nurseries for marine life, will suffer major losses and local extinctions. Across the ocean, heat, acidification and lower oxygen is set to cut fisheries by a quarter and all marine life by 15% if emissions are not slashed.

The IPCC report also records the large reduction in Arctic ice. This loss exacerbates global heating, because the exposed darker ocean absorbs more heat from the sun than highly reflective ice. On Monday, scientists announced that the Arctic sea ice in 2019 shrank to its second lowest extent in the 41-year satellite record.

The world’s high mountain glaciers, upon which almost 2 billion people rely for water, are also melting fast, the IPCC found, while landslides are expected to increase. A third of the great Himalayan range is already doomed, with two-thirds projected to vanish if emissions are not cut.

One of the most worrying alarms sounded by the IPCC report is about melting tundra and increasing wildfires in northern latitudes: “Widespread permafrost thaw is projected for this century and beyond.” A quarter is already near certain to melt, it said, and 70% or more would go if emissions are not curbed. In the latter case, hundreds of billions of tonnes of carbon dioxide and methane could be released, supercharging the climate emergency.

“That risks taking us beyond the point where climate change could be easily constrained,” said Richard Black, at the UK’s Energy and Climate Intelligence Unit. “Nevertheless, the IPCC’s 2018 report concluded that governments can shrink emissions quickly enough to keep global warming to 1.5C if they choose. None can claim to be unaware of both the dangers of untrammelled climate change nor the feasibility of preventing it.”

Anne Hidalgo, the mayor of Paris and chair of the C40 Cities climate coalition, said the IPCC report was shocking. “Around 1.9 billion people and over half of the world’s megacities are all in grave danger if we don’t act immediately. Several cities, home to hundreds of thousands of people, are already disappearing underwater. This is what the climate crisis looks like now.”

Taehyun Park, of Greenpeace East Asia, said: “The science is both chilling and compelling. The impacts on our oceans are on a much larger scale and happening way faster than predicted. It will require unprecedented political action to prevent the most severe consequences to our planet.”

As well as cutting fossil fuel emissions, preparing for the inevitable impacts is also vital, said Sebesvari, especially in poorer nations that lack the funds to build sea walls, move settlements or restore protective coastal marshes.

“Action is needed now to secure the coast for our children and coming generations,” she said. The pressure now being exerted by the global school strikes for climate was important, she said. “I have very strong motivation. I have two kids and we are really being tested by our kids on our actions.”

* * * * * * *

Damian Carrington is The Guardian’s environment editor.

This story originally appeared in The Guardian. It is republished here as part of the Climate News Network’s partnership with Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.

Extreme sea level events that used to occur once a century will strike every year on many coasts by 2050, no matter whether climate heating emissions are curbed or not, according to a landmark report by the world’s scientists.

25 September, 2019 − The stark assessment of the climate crisis in the world’s oceans and ice caps concludes that many serious impacts are already inevitable, from more intense storms to melting permafrost and dwindling marine life.

But far worse impacts will hit without urgent action to cut fossil fuel emissions, including eventual sea level rise of more than 4 metres in the worst case, an outcome that would redraw the map of the world and harm billions of people.

The report from the Intergovernmental Panel on Climate Change (IPCC), and approved by its 193 member nations, says that “all people on Earth depend directly or indirectly on the ocean” and ice caps and glaciers to regulate the climate and provide water and oxygen. But it finds unprecedented and dangerous changes being driven by global heating.

Sea level rise is accelerating as losses from Greenland and Antarctica increase, and the ocean is getting hotter, more acidic and less oxygenated. All these trends will continue to the end of the century, the IPCC report said.

Half the world’s megacities, and almost 2 billion people, live on coasts. Even if heating is restricted to just 2C, scientists expect the impact of sea level rise to cause several trillion dollars of damage a year, and result in many millions of migrants.

“The future for low-lying coastal communities looks extremely bleak,” said Prof Jonathan Bamber at Bristol University in the UK, who is not one of the report’s authors. “But the consequences will be felt by all of us. There is plenty to be concerned about for the future of humanity and social order from the headlines in this report.”

The new IPCC projections of likely sea level rise by 2100 are higher than those it made in 2014, due to unexpectedly fast melting in Antarctica. Without cuts in carbon emissions, the ocean is expected to rise between 61cm and 110cm, about 10cm more than the earlier estimate. A 10cm rise means 10 million additional people exposed to flooding, research shows.

The IPCC considers the likely range of sea level rise but not the worst-case scenario. Recent expert analysis led by Bamber concluded that up to 238cm of sea level rise remains possible by 2100, drowning many megacities around the world. “This cannot be ruled out,” said Zita Sebesvari at the United Nations University, a lead author of the IPCC report.

Even if huge cuts in emissions begin immediately, between 29cm and 59cm of sea level rise is already inevitable because the ice caps and glaciers melt slowly. Sea level will rise for centuries without action, Sebesvari warned. “The dramatic thing about sea level rise is if we accept 1 metre happening by 2100, we accept we will get about 4 metres by 2300. That is simply not an option we can risk.”

Extreme sea level impacts will be felt in many places very soon and well before 2050, Sebesvari said. The IPCC report states: “Extreme sea level events that [occur] once per century in the recent past are projected to occur at least once per year at many locations by 2050 in all scenarios.”

The heating oceans are causing more intense tropical storms to batter coasts, the IPCC report found, with stronger winds and greater deluges of rain. For example, Hurricane Harvey’s unprecedented deluge, which caused catastrophic flooding, was made three times more likely by climate change.

Ocean heating also harms kelp forests and other important ecosystems, with the marine heatwaves that sear through them like underwater wildfires having doubled in frequency in the last 40 years. They are projected to increase by at least 20 times by 2100, the IPCC reported.

Extreme El Niño events, which see heatwaves in some regions and floods in others, are projected to occur twice as often this century whether emissions are cut or not, the report said. Coral reefs, vital nurseries for marine life, will suffer major losses and local extinctions. Across the ocean, heat, acidification and lower oxygen is set to cut fisheries by a quarter and all marine life by 15% if emissions are not slashed.

The IPCC report also records the large reduction in Arctic ice. This loss exacerbates global heating, because the exposed darker ocean absorbs more heat from the sun than highly reflective ice. On Monday, scientists announced that the Arctic sea ice in 2019 shrank to its second lowest extent in the 41-year satellite record.

The world’s high mountain glaciers, upon which almost 2 billion people rely for water, are also melting fast, the IPCC found, while landslides are expected to increase. A third of the great Himalayan range is already doomed, with two-thirds projected to vanish if emissions are not cut.

One of the most worrying alarms sounded by the IPCC report is about melting tundra and increasing wildfires in northern latitudes: “Widespread permafrost thaw is projected for this century and beyond.” A quarter is already near certain to melt, it said, and 70% or more would go if emissions are not curbed. In the latter case, hundreds of billions of tonnes of carbon dioxide and methane could be released, supercharging the climate emergency.

“That risks taking us beyond the point where climate change could be easily constrained,” said Richard Black, at the UK’s Energy and Climate Intelligence Unit. “Nevertheless, the IPCC’s 2018 report concluded that governments can shrink emissions quickly enough to keep global warming to 1.5C if they choose. None can claim to be unaware of both the dangers of untrammelled climate change nor the feasibility of preventing it.”

Anne Hidalgo, the mayor of Paris and chair of the C40 Cities climate coalition, said the IPCC report was shocking. “Around 1.9 billion people and over half of the world’s megacities are all in grave danger if we don’t act immediately. Several cities, home to hundreds of thousands of people, are already disappearing underwater. This is what the climate crisis looks like now.”

Taehyun Park, of Greenpeace East Asia, said: “The science is both chilling and compelling. The impacts on our oceans are on a much larger scale and happening way faster than predicted. It will require unprecedented political action to prevent the most severe consequences to our planet.”

As well as cutting fossil fuel emissions, preparing for the inevitable impacts is also vital, said Sebesvari, especially in poorer nations that lack the funds to build sea walls, move settlements or restore protective coastal marshes.

“Action is needed now to secure the coast for our children and coming generations,” she said. The pressure now being exerted by the global school strikes for climate was important, she said. “I have very strong motivation. I have two kids and we are really being tested by our kids on our actions.”

* * * * * * *

Damian Carrington is The Guardian’s environment editor.

Unique climate change has no natural cause

The planet is warming faster than ever, worldwide. Scientists know this unique climate change is not caused by nature. But they checked again, to be certain.

LONDON, 19 August, 2019 – European and US scientists have cleared up a point that has been nagging away at climate science for decades: not only is the planet warming faster than at any time in the last 2,000 years, but this unique climate change really does have neither a historic precedent nor a natural cause.

Other historic changes – the so-called Medieval Warm Period and then the “Little Ice Age” that marked the 17th to the 19th centuries – were not global. The only period in which the world’s climate has changed, everywhere and at the same time, is right now.

And other shifts in the past, marked by advancing Alpine glaciers and sustained droughts in Africa, could be pinned down to a flurry of violent volcanic activity.

The present sustained, ubiquitous warming is unique in that it can be coupled directly with the Industrial Revolution, the clearing of the forests, population growth and profligate use of fossil fuels.

The finding is part of a sustained examination of global climate history, based not just on written and pictorial records but also studies of ancient lake sediments, ice cores, tree rings and other proxy evidence assembled by an international partnership called the Past Global Changes Consortium. It is reported in the journal Nature.

“This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle”

Research like this is a tidying-up operation. Climate scientists, conservationists, glaciologists, marine biologists, geologists and economists all know that climate change is happening, and that it is happening as a consequence of accelerated human activity over the last two centuries.

But from the start, there have always been gnawing questions: hasn’t the climate always changed? If global temperatures rose between 700 AD and 1400 AD, and then fell again, is what is happening now not part of some similar long-term cycle? And until now, that has remained without a confident, categorical answer.

So the latest study surprises nobody. But it matters, because the Nature study clarifies a point of possible confusion. There have been changes in modern human history, but none of them global and synchronous (happening at the same time). They were random fluctuations within the climate system, and even changes in solar activity or volcanic surges could not affect all of the planet at any one time.

“It’s true that during the Little Ice Age it was generally colder across the whole world,” says Raphel Neukom of the University of Bern in Switzerland, and first author, “but not everywhere at the same time. The peak periods of pre-industrial warm and cold periods occurred at different times in different places.”

And his Bern colleague Stefan Brönnimann clears up another point in a related study in the pages of Nature Geoscience.

Volcanic influence

The Little Ice Age began in Europe with no obvious trigger, but it was certainly reinforced and extended by more violent than usual volcanic activity in the tropics between 1808 and 1835. Mt Tambora in what is now Indonesia put so much ash into the stratosphere to screen sunlight and drop temperatures that 1816 became known as the Year without a Summer.

But there were also four other eruptions. Between 1820 and 1850, Alpine glaciers – now in alarming retreat – actually advanced. African and Indian monsoon systems weakened, and rain that should have fallen on hot soils dropped as more snow over Europe.

“Given the large climatic changes seen in the early 19th century, it is difficult to define a pre-industrial climate, a notion to which all our climate targets refer,” said Professor Brönnimann. “Frequent volcanic eruptions caused an actual gear shift in the global climate system.”

Commenting on the Nature finding, Mark Maslin, a climatologist at University College London, said: “Over the last 2000 years the only time the global climate has changed synchronically has been in the last 150 years when over 98% of the surface of the planet has warmed. This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle.

“This paper shows the truly stark difference between regional and localised changes in climates of the past and the truly global effect of anthropogenic greenhouse emissions.” – Climate News Network

The planet is warming faster than ever, worldwide. Scientists know this unique climate change is not caused by nature. But they checked again, to be certain.

LONDON, 19 August, 2019 – European and US scientists have cleared up a point that has been nagging away at climate science for decades: not only is the planet warming faster than at any time in the last 2,000 years, but this unique climate change really does have neither a historic precedent nor a natural cause.

Other historic changes – the so-called Medieval Warm Period and then the “Little Ice Age” that marked the 17th to the 19th centuries – were not global. The only period in which the world’s climate has changed, everywhere and at the same time, is right now.

And other shifts in the past, marked by advancing Alpine glaciers and sustained droughts in Africa, could be pinned down to a flurry of violent volcanic activity.

The present sustained, ubiquitous warming is unique in that it can be coupled directly with the Industrial Revolution, the clearing of the forests, population growth and profligate use of fossil fuels.

The finding is part of a sustained examination of global climate history, based not just on written and pictorial records but also studies of ancient lake sediments, ice cores, tree rings and other proxy evidence assembled by an international partnership called the Past Global Changes Consortium. It is reported in the journal Nature.

“This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle”

Research like this is a tidying-up operation. Climate scientists, conservationists, glaciologists, marine biologists, geologists and economists all know that climate change is happening, and that it is happening as a consequence of accelerated human activity over the last two centuries.

But from the start, there have always been gnawing questions: hasn’t the climate always changed? If global temperatures rose between 700 AD and 1400 AD, and then fell again, is what is happening now not part of some similar long-term cycle? And until now, that has remained without a confident, categorical answer.

So the latest study surprises nobody. But it matters, because the Nature study clarifies a point of possible confusion. There have been changes in modern human history, but none of them global and synchronous (happening at the same time). They were random fluctuations within the climate system, and even changes in solar activity or volcanic surges could not affect all of the planet at any one time.

“It’s true that during the Little Ice Age it was generally colder across the whole world,” says Raphel Neukom of the University of Bern in Switzerland, and first author, “but not everywhere at the same time. The peak periods of pre-industrial warm and cold periods occurred at different times in different places.”

And his Bern colleague Stefan Brönnimann clears up another point in a related study in the pages of Nature Geoscience.

Volcanic influence

The Little Ice Age began in Europe with no obvious trigger, but it was certainly reinforced and extended by more violent than usual volcanic activity in the tropics between 1808 and 1835. Mt Tambora in what is now Indonesia put so much ash into the stratosphere to screen sunlight and drop temperatures that 1816 became known as the Year without a Summer.

But there were also four other eruptions. Between 1820 and 1850, Alpine glaciers – now in alarming retreat – actually advanced. African and Indian monsoon systems weakened, and rain that should have fallen on hot soils dropped as more snow over Europe.

“Given the large climatic changes seen in the early 19th century, it is difficult to define a pre-industrial climate, a notion to which all our climate targets refer,” said Professor Brönnimann. “Frequent volcanic eruptions caused an actual gear shift in the global climate system.”

Commenting on the Nature finding, Mark Maslin, a climatologist at University College London, said: “Over the last 2000 years the only time the global climate has changed synchronically has been in the last 150 years when over 98% of the surface of the planet has warmed. This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle.

“This paper shows the truly stark difference between regional and localised changes in climates of the past and the truly global effect of anthropogenic greenhouse emissions.” – Climate News Network

Humans cause Antarctic ice melt, study finds

Yes, it’s us. Human activities are to blame for at least part of what’s melting the West Antarctic Ice Sheet, scientists say.

LONDON, 13 August, 2019 − A team of British and American scientists has found what it says is unequivocal evidence that humans are responsible for significant Antarctic ice melt.

They say their study provides the first evidence of a direct link between global warming from human activities and the melting of the West Antarctic Ice Sheet (WAIS).

The discovery is fundamentally important to international efforts to limit climate change, as a small number of scientists still argue that global warming results from natural rather than human causes. That argument should from now on be harder to sustain.

Ice loss in West Antarctica has increased substantially in the last few decades, and is continuing. Scientists have known for some time that the loss is caused by melting driven from the ocean, and that varying winds in the region cause transitions between relatively warm and cool ocean conditions around key glaciers. But until now it was unclear how these naturally-occurring wind variations could cause the ice loss.

“We knew this region was affected by natural climate cycles. Now we have evidence that a century-long change underlies these cycles, and that it is caused by human activities”

The UK-US team report in the journal Nature Geoscience that, as well as the natural wind variations, which last about a decade, there has been a much longer-term change in the winds that can be linked with human activities.

This result is important for another reason as well: continued ice loss from the WAIS could cause tens of centimetres of sea level rise by the year 2100.

The researchers combined satellite observations and climate model simulations to understand how winds over the ocean near West Antarctica have changed since the 1920s in response to rising greenhouse gas concentrations.

Their investigation shows that human-induced climate change has caused the longer-term change in the winds, and that warm ocean conditions have gradually become more prevalent as a result.

The team’s members are from the British Antarctic Survey (BAS), Columbia University’s Lamont-Doherty Earth Observatory in New York, and the University of Washington.

Galloping speed-up

BAS is one of the organisations researching a huge West Antarctic ice mass in the International Thwaites Glacier Collaboration, aimed at finding out how soon it and its neighbour, the Pine Island glacier, may collapse, with implications for sea levels worldwide.

The fact that melting at both poles has been accelerating fast has been known for some time, though not the reason. Since 1979 Antarctica’s ice loss has grown six times faster, and Greenland’s four times since the turn of the century.

One British scientist, Professor Martin Siegert, has said what is happening in the Antarctic means the world “will be locked into substantial global changes” unless it alters course radically by 2030.

The lead author of the new study, Paul Holland from BAS, said the impact of human-induced climate change on the WAIS was not simple: “Our results imply that a combination of human activity and natural climate variations have caused ice loss in this region, accounting for around 4.5 cm of sea level rise per century.”

Act now

The team also looked at model simulations of future winds. Professor Holland added: “An important finding is that if high greenhouse gas emissions continue in future, the winds keep changing and there could be a further increase in ice melting.

“However, if emissions of greenhouse gases are curtailed, there is little change in the winds from present-day conditions. This shows that curbing greenhouse gas emissions now could reduce the future sea level contribution from this region.”

One co-author, Professor Pierre Dutrieux from Lamont-Doherty Earth Observatory, said: “We knew this region was affected by natural climate cycles lasting about a decade, but these didn’t necessarily explain the ice loss. Now we have evidence that a century-long change underlies these cycles, and that it is caused by human activities.”

Another co-author, Professor Eric Steig from the University of Washington, said: “These results solve a long-standing puzzle.  We have known for some time that varying winds near the West Antarctic Ice Sheet have contributed to the ice loss, but it has not been clear why the ice sheet is changing now.

“Our work with ice cores drilled in the Antarctic Ice Sheet have shown, for example, that wind conditions have been similar in the past. But the ice core data also suggest a subtle long-term trend in the winds. This new work corroborates that evidence and, furthermore, explains why that trend has occurred.” − Climate News Network

Yes, it’s us. Human activities are to blame for at least part of what’s melting the West Antarctic Ice Sheet, scientists say.

LONDON, 13 August, 2019 − A team of British and American scientists has found what it says is unequivocal evidence that humans are responsible for significant Antarctic ice melt.

They say their study provides the first evidence of a direct link between global warming from human activities and the melting of the West Antarctic Ice Sheet (WAIS).

The discovery is fundamentally important to international efforts to limit climate change, as a small number of scientists still argue that global warming results from natural rather than human causes. That argument should from now on be harder to sustain.

Ice loss in West Antarctica has increased substantially in the last few decades, and is continuing. Scientists have known for some time that the loss is caused by melting driven from the ocean, and that varying winds in the region cause transitions between relatively warm and cool ocean conditions around key glaciers. But until now it was unclear how these naturally-occurring wind variations could cause the ice loss.

“We knew this region was affected by natural climate cycles. Now we have evidence that a century-long change underlies these cycles, and that it is caused by human activities”

The UK-US team report in the journal Nature Geoscience that, as well as the natural wind variations, which last about a decade, there has been a much longer-term change in the winds that can be linked with human activities.

This result is important for another reason as well: continued ice loss from the WAIS could cause tens of centimetres of sea level rise by the year 2100.

The researchers combined satellite observations and climate model simulations to understand how winds over the ocean near West Antarctica have changed since the 1920s in response to rising greenhouse gas concentrations.

Their investigation shows that human-induced climate change has caused the longer-term change in the winds, and that warm ocean conditions have gradually become more prevalent as a result.

The team’s members are from the British Antarctic Survey (BAS), Columbia University’s Lamont-Doherty Earth Observatory in New York, and the University of Washington.

Galloping speed-up

BAS is one of the organisations researching a huge West Antarctic ice mass in the International Thwaites Glacier Collaboration, aimed at finding out how soon it and its neighbour, the Pine Island glacier, may collapse, with implications for sea levels worldwide.

The fact that melting at both poles has been accelerating fast has been known for some time, though not the reason. Since 1979 Antarctica’s ice loss has grown six times faster, and Greenland’s four times since the turn of the century.

One British scientist, Professor Martin Siegert, has said what is happening in the Antarctic means the world “will be locked into substantial global changes” unless it alters course radically by 2030.

The lead author of the new study, Paul Holland from BAS, said the impact of human-induced climate change on the WAIS was not simple: “Our results imply that a combination of human activity and natural climate variations have caused ice loss in this region, accounting for around 4.5 cm of sea level rise per century.”

Act now

The team also looked at model simulations of future winds. Professor Holland added: “An important finding is that if high greenhouse gas emissions continue in future, the winds keep changing and there could be a further increase in ice melting.

“However, if emissions of greenhouse gases are curtailed, there is little change in the winds from present-day conditions. This shows that curbing greenhouse gas emissions now could reduce the future sea level contribution from this region.”

One co-author, Professor Pierre Dutrieux from Lamont-Doherty Earth Observatory, said: “We knew this region was affected by natural climate cycles lasting about a decade, but these didn’t necessarily explain the ice loss. Now we have evidence that a century-long change underlies these cycles, and that it is caused by human activities.”

Another co-author, Professor Eric Steig from the University of Washington, said: “These results solve a long-standing puzzle.  We have known for some time that varying winds near the West Antarctic Ice Sheet have contributed to the ice loss, but it has not been clear why the ice sheet is changing now.

“Our work with ice cores drilled in the Antarctic Ice Sheet have shown, for example, that wind conditions have been similar in the past. But the ice core data also suggest a subtle long-term trend in the winds. This new work corroborates that evidence and, furthermore, explains why that trend has occurred.” − Climate News Network

Ancient water-saving can help modern Peru

Ancient water-saving methods may help Lima, Peru’s capital, through its water crisis, caused by climate change and population growth.

LONDON, 2 July, 2019 − There’s plenty to learn in modern Peru from the designers of ancient water-saving methods, scientists are finding. Our forebears could even keep the capital’s taps running through the summer heat.

Lima, Peru’s desert capital, a city of 12 million people, expects to run out of water by 2025. It already faces a crisis each summer as the supply from the mountains dwindles to a trickle. Yet the quantity of rain in the wet season can be overwhelming.

Between the Andes and the Pacific ocean, Lima sits on a coastal plain where the average rainfall is a tiny 9 mm a year, and it has to rely on the snow melt from the mountains and glaciers to provide summer drinking water and the needs of industry and farming.

But with the glaciers disappearing because of climate change, and the population increasing, the city will soon become untenable for many of the poor in summer, unless water supplies can be improved.

A group of scientists has found that reviving systems developed 1,400 years ago by local people before the Inca empire existed could harvest water from the winter rainy season in the mountains to ensure Lima’s summer supplies.

“You’d be forgiven for wondering how ancient methods could apply to modern-day problems. However we have lots to learn from our ancestors’ creative problem-solving skills”

Researchers from Imperial College London and their colleagues at the Regional Initiative for Hydrological Monitoring of Andean Ecosystems studied a water system in Huamantanga, in the central Andes, one of the last of its kind.

The local people still use a method developed in 600 AD by Peruvian civilisations that created systems in the mountains to divert excess rainwater from source streams through ponds and canals onto mountain slopes and down through fissures in the rocks.

The water would take weeks or even months to trickle through the system and resurface downstream – just in time for the dry season.

The researchers used dye tracers and hydrological monitoring to study the system from the wet to dry seasons of 2014–2015 and 2015–2016. Social scientists involved also worked with Huamantanga’s local people to understand the practice and help map the landscape.

Big increase

They found the water took between two weeks and eight months to re-emerge, with an average time of 45 days. From these timescales, they calculated that, if governments upscale the systems to cater for today’s population size, they could reroute and delay 35% of wet season water, equivalent to 99 million cubic metres per year of water flowing through Lima’s natural terrain.

This could increase the water available in the dry season by up to 33% in the early months, and an average of 7.5% for the rest of the summer.

The method could essentially extend the wet season, providing more drinking water and longer crop-growing periods for local farmers.

The study, published in the journal Nature Sustainability, is the first to examine the pre-Inca system in this much detail to find answers to modern problems. The authors say their research shows how indigenous systems could complement modern engineering solutions for water security in coastal Peru.

Lead author Dr Boris Ochoa-Tocachi, from Imperial’s Department of Civil and Environmental Engineering, said: “With the advent of modern science, you’d be forgiven for wondering how ancient methods could apply to modern-day problems. However, it turns out that we have lots to learn from our ancestors’ creative problem-solving skills.”

Growing too fast

Senior author Dr Wouter Buytaert, from the same department, said: “Like many tropical cities, Lima’s population is growing fast – too fast for water reserves to keep up during dry seasons. Upscaling existing pre-Inca systems could help relieve Peru’s wet months of water and quench its dry ones.”

The seasonal variability typical of coastal Peru is worsened by human impacts. Apart from glacier melting caused by global warming, humans also contribute to erosion, which renders soil too weak to support dams big enough to hold all the water needed in the summer.

Climate change also makes wet seasons wetter, and dry seasons drier − making the need for effective water storage in Peru even more urgent.

The authors say combining pre-Inca systems with classic structures, such as smaller dams, could also help to improve adaptability and water supply in an unpredictable climate. − Climate News Network

Ancient water-saving methods may help Lima, Peru’s capital, through its water crisis, caused by climate change and population growth.

LONDON, 2 July, 2019 − There’s plenty to learn in modern Peru from the designers of ancient water-saving methods, scientists are finding. Our forebears could even keep the capital’s taps running through the summer heat.

Lima, Peru’s desert capital, a city of 12 million people, expects to run out of water by 2025. It already faces a crisis each summer as the supply from the mountains dwindles to a trickle. Yet the quantity of rain in the wet season can be overwhelming.

Between the Andes and the Pacific ocean, Lima sits on a coastal plain where the average rainfall is a tiny 9 mm a year, and it has to rely on the snow melt from the mountains and glaciers to provide summer drinking water and the needs of industry and farming.

But with the glaciers disappearing because of climate change, and the population increasing, the city will soon become untenable for many of the poor in summer, unless water supplies can be improved.

A group of scientists has found that reviving systems developed 1,400 years ago by local people before the Inca empire existed could harvest water from the winter rainy season in the mountains to ensure Lima’s summer supplies.

“You’d be forgiven for wondering how ancient methods could apply to modern-day problems. However we have lots to learn from our ancestors’ creative problem-solving skills”

Researchers from Imperial College London and their colleagues at the Regional Initiative for Hydrological Monitoring of Andean Ecosystems studied a water system in Huamantanga, in the central Andes, one of the last of its kind.

The local people still use a method developed in 600 AD by Peruvian civilisations that created systems in the mountains to divert excess rainwater from source streams through ponds and canals onto mountain slopes and down through fissures in the rocks.

The water would take weeks or even months to trickle through the system and resurface downstream – just in time for the dry season.

The researchers used dye tracers and hydrological monitoring to study the system from the wet to dry seasons of 2014–2015 and 2015–2016. Social scientists involved also worked with Huamantanga’s local people to understand the practice and help map the landscape.

Big increase

They found the water took between two weeks and eight months to re-emerge, with an average time of 45 days. From these timescales, they calculated that, if governments upscale the systems to cater for today’s population size, they could reroute and delay 35% of wet season water, equivalent to 99 million cubic metres per year of water flowing through Lima’s natural terrain.

This could increase the water available in the dry season by up to 33% in the early months, and an average of 7.5% for the rest of the summer.

The method could essentially extend the wet season, providing more drinking water and longer crop-growing periods for local farmers.

The study, published in the journal Nature Sustainability, is the first to examine the pre-Inca system in this much detail to find answers to modern problems. The authors say their research shows how indigenous systems could complement modern engineering solutions for water security in coastal Peru.

Lead author Dr Boris Ochoa-Tocachi, from Imperial’s Department of Civil and Environmental Engineering, said: “With the advent of modern science, you’d be forgiven for wondering how ancient methods could apply to modern-day problems. However, it turns out that we have lots to learn from our ancestors’ creative problem-solving skills.”

Growing too fast

Senior author Dr Wouter Buytaert, from the same department, said: “Like many tropical cities, Lima’s population is growing fast – too fast for water reserves to keep up during dry seasons. Upscaling existing pre-Inca systems could help relieve Peru’s wet months of water and quench its dry ones.”

The seasonal variability typical of coastal Peru is worsened by human impacts. Apart from glacier melting caused by global warming, humans also contribute to erosion, which renders soil too weak to support dams big enough to hold all the water needed in the summer.

Climate change also makes wet seasons wetter, and dry seasons drier − making the need for effective water storage in Peru even more urgent.

The authors say combining pre-Inca systems with classic structures, such as smaller dams, could also help to improve adaptability and water supply in an unpredictable climate. − Climate News Network

Ice-free Greenland possible in 1,000 years

Look far enough ahead and in a millennium an ice-free Greenland is a possibility, scientists say. Sea levels too will be a lot higher by then.

LONDON, 25 June, 2019 − US scientists have just established that the long-term future may bring an ice-free Greenland, if melting continues at the current rate. By the year 3,000 it could simply be green, with rocky outcrops. Greenland’s icy mountains will have vanished.

By the end of this century, the island – the largest body of ice in the northern hemisphere, and home to 8% of the world’s fresh water in frozen form – will have lost 4.5% of its ice cover, and sea levels will have risen by up to 33cm.

And if melting continues, and the world goes on burning fossil fuels under climate science’s notorious “business as usual scenario”, then within another thousand years the entire cover will have run into the sea, which by then will have risen – just because of melting in Greenland – by more than seven metres, to wash away cities such as Miami, Los Angeles, Copenhagen, Shanghai and New Orleans.

“How Greenland will look in the future – in a couple of hundred years or in 1,000 years – whether there will be Greenland, or at least a Greenland similar to today, it’s up to us”, said Andy Aschwanden, of the University of Fairbanks, Alaska geophysical institute.

He and colleagues from the US and Denmark report in the journal Science Advances that they used new radar data that gave a picture of the thickness of the ice and the bedrock beneath it to estimate the total mass of ice.

“We project that Greenland will very likely become ice-free within a millennium without substantial reduction in greenhouse gas emissions”

They then selected three possible climate outcomes, depending on national and political responses to the climate emergency, considered the rates at which glaciers had begun to flow, the levels of summer and even winter ice melt, and the warming of the oceans, and ran 500 computer simulations to form a picture of the future.

Researchers have been warning for years that the rate of ice loss in Greenland is accelerating. Ice is being lost from the ice sheet surface, in some places at such speed that the bedrock beneath, once crushed by the weight of ice, is beginning to rise.

The great frozen rivers that carry ice to the sea to form summer icebergs are themselves gathering pace: one of these in 2014 was recorded as having quadrupled in speed, to move at almost 50 metres a day.

Research in polar regions is always difficult, and conclusions are necessarily tentative. On-the-ground studies are limited in summer and all but impossible in winter. The dynamic of ice loss changes, depending on conditions both in the atmosphere and the surrounding ocean.

Greenhouse gas increase

But the Fairbanks study is consistent with a huge body of other research. And the same computer simulations confirm that what happens depends ultimately on whether the world continues to heat up as a consequence of the profligate consumption of fossil fuels that increase the ratio of greenhouse gases in the atmosphere.

If carbon dioxide emissions are sharply reduced, the scientists say, the picture changes. Instead, the island could lose only up to a quarter of its ice cover by the end of this millennium, with a corresponding sea level rise of up to 1.88 metres.

Another, less hopeful scenario foresees a loss of up to 57% and sea level rise of up to 4.17 metres. In the worst case, the range of possible ice loss is from 72% to the lot, with the oceans higher by up to 7.28 metres, all of it from the existing ice mass of Greenland.

“We project that Greenland will very likely become ice-free within a millennium without substantial reduction in greenhouse gas emissions”, the researchers conclude. − Climate News Network

Look far enough ahead and in a millennium an ice-free Greenland is a possibility, scientists say. Sea levels too will be a lot higher by then.

LONDON, 25 June, 2019 − US scientists have just established that the long-term future may bring an ice-free Greenland, if melting continues at the current rate. By the year 3,000 it could simply be green, with rocky outcrops. Greenland’s icy mountains will have vanished.

By the end of this century, the island – the largest body of ice in the northern hemisphere, and home to 8% of the world’s fresh water in frozen form – will have lost 4.5% of its ice cover, and sea levels will have risen by up to 33cm.

And if melting continues, and the world goes on burning fossil fuels under climate science’s notorious “business as usual scenario”, then within another thousand years the entire cover will have run into the sea, which by then will have risen – just because of melting in Greenland – by more than seven metres, to wash away cities such as Miami, Los Angeles, Copenhagen, Shanghai and New Orleans.

“How Greenland will look in the future – in a couple of hundred years or in 1,000 years – whether there will be Greenland, or at least a Greenland similar to today, it’s up to us”, said Andy Aschwanden, of the University of Fairbanks, Alaska geophysical institute.

He and colleagues from the US and Denmark report in the journal Science Advances that they used new radar data that gave a picture of the thickness of the ice and the bedrock beneath it to estimate the total mass of ice.

“We project that Greenland will very likely become ice-free within a millennium without substantial reduction in greenhouse gas emissions”

They then selected three possible climate outcomes, depending on national and political responses to the climate emergency, considered the rates at which glaciers had begun to flow, the levels of summer and even winter ice melt, and the warming of the oceans, and ran 500 computer simulations to form a picture of the future.

Researchers have been warning for years that the rate of ice loss in Greenland is accelerating. Ice is being lost from the ice sheet surface, in some places at such speed that the bedrock beneath, once crushed by the weight of ice, is beginning to rise.

The great frozen rivers that carry ice to the sea to form summer icebergs are themselves gathering pace: one of these in 2014 was recorded as having quadrupled in speed, to move at almost 50 metres a day.

Research in polar regions is always difficult, and conclusions are necessarily tentative. On-the-ground studies are limited in summer and all but impossible in winter. The dynamic of ice loss changes, depending on conditions both in the atmosphere and the surrounding ocean.

Greenhouse gas increase

But the Fairbanks study is consistent with a huge body of other research. And the same computer simulations confirm that what happens depends ultimately on whether the world continues to heat up as a consequence of the profligate consumption of fossil fuels that increase the ratio of greenhouse gases in the atmosphere.

If carbon dioxide emissions are sharply reduced, the scientists say, the picture changes. Instead, the island could lose only up to a quarter of its ice cover by the end of this millennium, with a corresponding sea level rise of up to 1.88 metres.

Another, less hopeful scenario foresees a loss of up to 57% and sea level rise of up to 4.17 metres. In the worst case, the range of possible ice loss is from 72% to the lot, with the oceans higher by up to 7.28 metres, all of it from the existing ice mass of Greenland.

“We project that Greenland will very likely become ice-free within a millennium without substantial reduction in greenhouse gas emissions”, the researchers conclude. − Climate News Network

Himalayan melt rate doubles in 40 years

The pace of glacier thawing on the roof of the world has doubled in 40 years, scientists say, with the Himalayan melt rate affected by climate heating.

LONDON, 20 June, 2019 − The Himalayan melt rate is now thawing glaciers on whose water many millions of lives depend twice as fast as just four decades ago, researchers say. One scientist thinks the glaciers may have lost a quarter of their mass in the last 40 years.

A new, comprehensive study shows the glaciers’ melting, caused by rising temperatures, has accelerated significantly since the turn of the century. The study, which draws on 40 years of satellite observations across India, China, Nepal and Bhutan, shows the glaciers have been losing the equivalent of more than 20 inches (about half a metre) of ice each year since 2000, twice the amount of melting recorded from 1975 to 2000.

The study, published in the journal Science Advances, is the latest to show the threat that climate change represents to the water supplies of hundreds of millions of people living downstream across much of Asia.

“This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why,” said the lead author, Joshua Maurer, a Ph D candidate at Columbia University’s Lamont-Doherty Earth Observatory. While not specifically calculated in the study, the glaciers may have lost as much as a quarter of their mass over the last four decades, he said.

With around 600 billion tons of ice today, the Himalayas are sometimes called the Earth’s third pole. Many recent studies have suggested that the glaciers are dwindling, including one in February this year projecting that up to two-thirds of the current ice cover could be gone by 2100.

Wider picture

Until now, though, observations have usually focused on individual glaciers or specific regions, or on shorter lengths of time, and have sometimes produced contradictory results, on both the degree of ice loss and its causes. The new study incorporates data from across the region, stretching from early satellite observations to the present.

This shows the melting is consistent over time and in different areas, and that rising temperatures are to blame: they vary from place to place, but from 2000 to 2016 they have averaged 1°C (1.8°F) higher than those from 1975 to 2000.

Maurer and his co-authors analysed repeat satellite images of about 650 glaciers spanning 2,000 kilometres. Many of the 20th-century observations came from recently declassified photographic images taken by US spy satellites.

The researchers created an automated system to turn these into three-dimensional models that could show the changing elevations of glaciers over time. They then compared these images with post-2000 optical data from more sophisticated satellites, which show elevation changes more directly.

“This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why”

They found that from 1975 to 2000, glaciers across the region lost an average of about 0.25 metres (10 inches) of ice each year in the face of slight warming. Following a more pronounced warming trend which started in the 1990s, from 2000 the loss accelerated to about half a metre annually.

Recent yearly losses have averaged about 8 billion tons of water, Maurer says. On most glaciers the melting has been concentrated mainly at lower elevations, where some ice surfaces are losing as much as 5 metres (16 feet) a year.

Despite suggestions that changes in precipitation, or increasing deposits of soot from growing fossil fuel burning in Asia, might be affecting the glaciers rather than climate heating, Maurer believes rising temperature is the main cause of the melting.

“It looks just like what we would expect if warming were the dominant driver of ice loss,” he said. At least one recent study has found a similar process at work in Alaska.

Alpine parallel

Ice loss in the Himalayas resembles the much more closely studied European Alps, where temperatures started going up a little earlier, in the 1980s. Glaciers there began melting soon after that, and rapid ice loss has continued since. The Himalayas are generally not melting as fast as the Alps, but their changes are similar, the researchers say.

Their study does not include the huge adjoining ranges of high-mountain Asia such as the Pamir, Hindu Kush or Tian Shan, but other studies suggest similar melting is under way there as well.

About 800 million people depend in part on seasonal runoff from Himalayan glaciers for irrigation, hydropower and drinking water. The faster melting appears so far to be increasing runoff during warm seasons, but scientists think this will slow within decades as the glaciers lose mass, eventually leading to water shortages.

In many high mountain areas meltwater lakes are building up rapidly behind natural dams of rocky debris, threatening downstream communities with outburst floods. On Everest, the long-lost bodies of climbers who failed to return from the summits are emerging from the melting ice. − Climate News Network

The pace of glacier thawing on the roof of the world has doubled in 40 years, scientists say, with the Himalayan melt rate affected by climate heating.

LONDON, 20 June, 2019 − The Himalayan melt rate is now thawing glaciers on whose water many millions of lives depend twice as fast as just four decades ago, researchers say. One scientist thinks the glaciers may have lost a quarter of their mass in the last 40 years.

A new, comprehensive study shows the glaciers’ melting, caused by rising temperatures, has accelerated significantly since the turn of the century. The study, which draws on 40 years of satellite observations across India, China, Nepal and Bhutan, shows the glaciers have been losing the equivalent of more than 20 inches (about half a metre) of ice each year since 2000, twice the amount of melting recorded from 1975 to 2000.

The study, published in the journal Science Advances, is the latest to show the threat that climate change represents to the water supplies of hundreds of millions of people living downstream across much of Asia.

“This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why,” said the lead author, Joshua Maurer, a Ph D candidate at Columbia University’s Lamont-Doherty Earth Observatory. While not specifically calculated in the study, the glaciers may have lost as much as a quarter of their mass over the last four decades, he said.

With around 600 billion tons of ice today, the Himalayas are sometimes called the Earth’s third pole. Many recent studies have suggested that the glaciers are dwindling, including one in February this year projecting that up to two-thirds of the current ice cover could be gone by 2100.

Wider picture

Until now, though, observations have usually focused on individual glaciers or specific regions, or on shorter lengths of time, and have sometimes produced contradictory results, on both the degree of ice loss and its causes. The new study incorporates data from across the region, stretching from early satellite observations to the present.

This shows the melting is consistent over time and in different areas, and that rising temperatures are to blame: they vary from place to place, but from 2000 to 2016 they have averaged 1°C (1.8°F) higher than those from 1975 to 2000.

Maurer and his co-authors analysed repeat satellite images of about 650 glaciers spanning 2,000 kilometres. Many of the 20th-century observations came from recently declassified photographic images taken by US spy satellites.

The researchers created an automated system to turn these into three-dimensional models that could show the changing elevations of glaciers over time. They then compared these images with post-2000 optical data from more sophisticated satellites, which show elevation changes more directly.

“This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why”

They found that from 1975 to 2000, glaciers across the region lost an average of about 0.25 metres (10 inches) of ice each year in the face of slight warming. Following a more pronounced warming trend which started in the 1990s, from 2000 the loss accelerated to about half a metre annually.

Recent yearly losses have averaged about 8 billion tons of water, Maurer says. On most glaciers the melting has been concentrated mainly at lower elevations, where some ice surfaces are losing as much as 5 metres (16 feet) a year.

Despite suggestions that changes in precipitation, or increasing deposits of soot from growing fossil fuel burning in Asia, might be affecting the glaciers rather than climate heating, Maurer believes rising temperature is the main cause of the melting.

“It looks just like what we would expect if warming were the dominant driver of ice loss,” he said. At least one recent study has found a similar process at work in Alaska.

Alpine parallel

Ice loss in the Himalayas resembles the much more closely studied European Alps, where temperatures started going up a little earlier, in the 1980s. Glaciers there began melting soon after that, and rapid ice loss has continued since. The Himalayas are generally not melting as fast as the Alps, but their changes are similar, the researchers say.

Their study does not include the huge adjoining ranges of high-mountain Asia such as the Pamir, Hindu Kush or Tian Shan, but other studies suggest similar melting is under way there as well.

About 800 million people depend in part on seasonal runoff from Himalayan glaciers for irrigation, hydropower and drinking water. The faster melting appears so far to be increasing runoff during warm seasons, but scientists think this will slow within decades as the glaciers lose mass, eventually leading to water shortages.

In many high mountain areas meltwater lakes are building up rapidly behind natural dams of rocky debris, threatening downstream communities with outburst floods. On Everest, the long-lost bodies of climbers who failed to return from the summits are emerging from the melting ice. − Climate News Network

Unstable polar glaciers lose ice ever faster

As oceans warm, Antarctica’s ice sheets are at growing risk, with polar glaciers losing ice at rates to match the height of global monuments.

LONDON, 31 May, 2019 – Almost a quarter of all the glaciers in West Antarctica have been pronounced “unstable”. This means, in the simplest terms, that they are losing ice to the ocean faster than they can gain it from falling snow.

In the last 25 years most of the largest flows have accelerated the loss of ice fivefold.

And in places some glaciers, including those known as Pine Island and Thwaites, have “thinned” by 122 metres. That means that the thickness of the ice between the surface and the bedrock over which glaciers flow has fallen by almost the height of the Great Pyramid of Cheops in Egypt, and far more than the Statue of Liberty in New York or the tower of Big Ben in London.

The conclusions are based on climate simulation matched against 800 million measurements of the Antarctic ice sheet recorded by the altimeters aboard four orbiting satellites put up by the European Space Agency between 1992 and 2017. The conclusion is published in the journal Geophysical Research Letters.

“A wave of thinning has spread rapidly across some of Antarctica’s most vulnerable glaciers, and their losses are driving up sea levels around the planet”

Antarctic research is challenging. The continent is enormous – nearly twice the size of Australia – and frozen: 99.4% of it is covered by ice, to huge depths. It is also defined as a desert.

Snowfalls are low, but over millions of years these have built up to a reservoir of about nine-tenths of the planet’s fresh water, in the form of snow and ice.

It is also the coldest place on Earth and – even more of a problem for climate scientists – no observations or measurements of anything in Antarctica date back much further than the beginning of the 19th century. Most of the on-the-ground science is possible only in the Antarctic summer.

The latest study confirms a succession of alarming finds. The West Antarctic ice sheet is not just losing ice, it is doing so at ever-faster speeds. Scientists have already suggested that the rate of loss for the Pine Island and Thwaites glaciers could be irreversible. So much has already been lost that the bedrock, crushed by its burden of ice for aeons, is actually beginning to bounce up in response.

Huge ice losses

“In parts of Antarctica the ice sheet has thinned by extraordinary amounts, and we set out to show how much was due to changes in climate and how much was due to weather,” said Andrew Shepherd of the University of Leeds, UK, who led the research.

Changes in snowfall tended, they found, to be reflected over changes in height over large areas for a few years. But the most pronounced changes have persisted for decades: it’s the climate that is changing things, not the weather.

“Knowing how much snow has fallen has really helped us to detect the underlying change in glacier ice within the satellite record. We can see clearly now that a wave of thinning has spread rapidly across some of Antarctica’s most vulnerable glaciers, and their losses are driving up sea levels around the planet”, Professor Shepherd says.

“Altogether, ice losses from East and West Antarctica have contributed 4.6mm to global sea level rise since 1992.” – Climate News Network

As oceans warm, Antarctica’s ice sheets are at growing risk, with polar glaciers losing ice at rates to match the height of global monuments.

LONDON, 31 May, 2019 – Almost a quarter of all the glaciers in West Antarctica have been pronounced “unstable”. This means, in the simplest terms, that they are losing ice to the ocean faster than they can gain it from falling snow.

In the last 25 years most of the largest flows have accelerated the loss of ice fivefold.

And in places some glaciers, including those known as Pine Island and Thwaites, have “thinned” by 122 metres. That means that the thickness of the ice between the surface and the bedrock over which glaciers flow has fallen by almost the height of the Great Pyramid of Cheops in Egypt, and far more than the Statue of Liberty in New York or the tower of Big Ben in London.

The conclusions are based on climate simulation matched against 800 million measurements of the Antarctic ice sheet recorded by the altimeters aboard four orbiting satellites put up by the European Space Agency between 1992 and 2017. The conclusion is published in the journal Geophysical Research Letters.

“A wave of thinning has spread rapidly across some of Antarctica’s most vulnerable glaciers, and their losses are driving up sea levels around the planet”

Antarctic research is challenging. The continent is enormous – nearly twice the size of Australia – and frozen: 99.4% of it is covered by ice, to huge depths. It is also defined as a desert.

Snowfalls are low, but over millions of years these have built up to a reservoir of about nine-tenths of the planet’s fresh water, in the form of snow and ice.

It is also the coldest place on Earth and – even more of a problem for climate scientists – no observations or measurements of anything in Antarctica date back much further than the beginning of the 19th century. Most of the on-the-ground science is possible only in the Antarctic summer.

The latest study confirms a succession of alarming finds. The West Antarctic ice sheet is not just losing ice, it is doing so at ever-faster speeds. Scientists have already suggested that the rate of loss for the Pine Island and Thwaites glaciers could be irreversible. So much has already been lost that the bedrock, crushed by its burden of ice for aeons, is actually beginning to bounce up in response.

Huge ice losses

“In parts of Antarctica the ice sheet has thinned by extraordinary amounts, and we set out to show how much was due to changes in climate and how much was due to weather,” said Andrew Shepherd of the University of Leeds, UK, who led the research.

Changes in snowfall tended, they found, to be reflected over changes in height over large areas for a few years. But the most pronounced changes have persisted for decades: it’s the climate that is changing things, not the weather.

“Knowing how much snow has fallen has really helped us to detect the underlying change in glacier ice within the satellite record. We can see clearly now that a wave of thinning has spread rapidly across some of Antarctica’s most vulnerable glaciers, and their losses are driving up sea levels around the planet”, Professor Shepherd says.

“Altogether, ice losses from East and West Antarctica have contributed 4.6mm to global sea level rise since 1992.” – Climate News Network

Half of melting glaciers could go by 2100

Melting glaciers worldwide – all treasured for their beauty and as sources of summer water – could be half gone by 2100.

LONDON, 13 May, 2019 – Around half of some of the world’s most beautiful mountain ranges are about to lose their melting glaciers, the force that shapes and highlights their beauty.

Swiss-based scientists investigated 46 world heritage sites nominated by UNESCO, the UN Educational, Scientific and Cultural Organisation, and compiled an inventory of 19,000 glaciers. And then, they report in the journal Earth’s Future, they calculated recent changes and the glaciers’ present condition and projected the rate of mass loss into the future.

They warn that, if the world goes on burning fossil fuels at ever-increasing rates, almost half of all these glaciers will have vanished by 2100.

In somewhere between eight and 21 such world heritage sites – national parks that have a profound role in water management and often a powerful economic role as tourist attractions – there may be no glaciers at all by the century’s end.

Strengthened commitment

“Losing these iconic glaciers would be a tragedy and have major consequences for the availability of water resources, sea level rise and weather patterns,” warned Peter Shadie, who directs the world heritage programme of the International Union for the Conservation of Nature (IUCN).

“This unprecedented decline could also jeopardise the listing of the sites in question on the World Heritage list. States must reinforce their commitments to combat climate change and step up efforts to preserve these glaciers for future generations.”

And Jean-Baptiste Bosson, of the IUCN’s headquarters in Gland, Switzerland, who led the study, said: “We urgently need to see significant cuts in greenhouse gas emissions. This is the only way of avoiding long-lasting and irreversible glacier decline and the major natural, social, economic and migratory cascading consequences.”

Essentially, the study was based on a review of research so far: for more than a decade scientists have been alarmed at the increasing rates of loss in the great frozen rivers at high altitude and on the polar ice caps, in ways that will harm wealthy communities as well as poor farmers in both Asia and South America.

“Losing these iconic glaciers would be a tragedy and have major consequences for the availability of water resources, sea level rise and weather patterns”

But the researchers also looked at North America’s burden of mountain ice to forecast up to 70% of loss by 2100, and in the Pyrenees between France and Spain they warned of losses as early as 2040. Te Wahipounamu in the south-west of New Zealand could say farewell to between 25% and 80% of its ice this century.

The researchers looked at a series of projections for global warming. In some cases, the loss is inexorable. Even if the 195 nations that in Paris in 2015 vowed to keep global average temperatures “well below” a rise of 2°C by the end of the century actually take the drastic steps needed to keep that promise, at least a third of all the ice will disappear, and entirely in eight sites.

If the Paris signatories carry on with business as usual, the rate of loss could reach 60% in the 46 sites, and 21 of those would have lost all traces of ice altogether.

“The study of glacier decline further emphasises the need for individual and collective actions to achieve the mitigation and adaptation aspirations of the Paris Agreement on climate change,” Dr Bosson said. – Climate News Network

Melting glaciers worldwide – all treasured for their beauty and as sources of summer water – could be half gone by 2100.

LONDON, 13 May, 2019 – Around half of some of the world’s most beautiful mountain ranges are about to lose their melting glaciers, the force that shapes and highlights their beauty.

Swiss-based scientists investigated 46 world heritage sites nominated by UNESCO, the UN Educational, Scientific and Cultural Organisation, and compiled an inventory of 19,000 glaciers. And then, they report in the journal Earth’s Future, they calculated recent changes and the glaciers’ present condition and projected the rate of mass loss into the future.

They warn that, if the world goes on burning fossil fuels at ever-increasing rates, almost half of all these glaciers will have vanished by 2100.

In somewhere between eight and 21 such world heritage sites – national parks that have a profound role in water management and often a powerful economic role as tourist attractions – there may be no glaciers at all by the century’s end.

Strengthened commitment

“Losing these iconic glaciers would be a tragedy and have major consequences for the availability of water resources, sea level rise and weather patterns,” warned Peter Shadie, who directs the world heritage programme of the International Union for the Conservation of Nature (IUCN).

“This unprecedented decline could also jeopardise the listing of the sites in question on the World Heritage list. States must reinforce their commitments to combat climate change and step up efforts to preserve these glaciers for future generations.”

And Jean-Baptiste Bosson, of the IUCN’s headquarters in Gland, Switzerland, who led the study, said: “We urgently need to see significant cuts in greenhouse gas emissions. This is the only way of avoiding long-lasting and irreversible glacier decline and the major natural, social, economic and migratory cascading consequences.”

Essentially, the study was based on a review of research so far: for more than a decade scientists have been alarmed at the increasing rates of loss in the great frozen rivers at high altitude and on the polar ice caps, in ways that will harm wealthy communities as well as poor farmers in both Asia and South America.

“Losing these iconic glaciers would be a tragedy and have major consequences for the availability of water resources, sea level rise and weather patterns”

But the researchers also looked at North America’s burden of mountain ice to forecast up to 70% of loss by 2100, and in the Pyrenees between France and Spain they warned of losses as early as 2040. Te Wahipounamu in the south-west of New Zealand could say farewell to between 25% and 80% of its ice this century.

The researchers looked at a series of projections for global warming. In some cases, the loss is inexorable. Even if the 195 nations that in Paris in 2015 vowed to keep global average temperatures “well below” a rise of 2°C by the end of the century actually take the drastic steps needed to keep that promise, at least a third of all the ice will disappear, and entirely in eight sites.

If the Paris signatories carry on with business as usual, the rate of loss could reach 60% in the 46 sites, and 21 of those would have lost all traces of ice altogether.

“The study of glacier decline further emphasises the need for individual and collective actions to achieve the mitigation and adaptation aspirations of the Paris Agreement on climate change,” Dr Bosson said. – Climate News Network

Heat makes ocean winds and waves fiercer

The seas are rising. Ocean winds and waves are growing in speed and force. The oceans could be feeling the heat.

LONDON, 1 May, 2019 − The great swells of the Pacific are beginning to swell even more as fiercer ocean winds and waves leave their mark. The breakers that crash on the storm beaches now do so with greater force. The white horses are gathering pace.

A 33-year-study of data from 31 satellites and 80 ocean buoys has confirmed suspicions. The extreme ocean winds are now fiercer, and the waves are getting measurably higher.

It is a given of global warming that as average planetary temperatures rise, then more energy is available for storm, rainfall and drought.

In the past century, because of ever-increasing combustion of fossil fuels that release growing quantities of greenhouse gases, average global temperatures have crept higher by 1°C and in three decades the speed of extreme winds in the Southern Ocean has increased by 8%, or 1.5 metres per second. Extreme waves have increased by 30cms, or 5%, over the same period.

“These changes have impacts that are felt all over the world. Storm waves can increase coastal erosion, putting coastal settlements and infrastructures at risk”

“Although increases of 5 and 8% might not seem like much, if sustained into the future such changes to our climate will have major impacts,” said Ian Young, an engineer at the University of Melbourne in Australia

He and a colleague report in the journal Science that they reached their conclusion on the basis of 4 billion observations made between 1985 and 2018.

“Flooding events are caused by storm surge and associated breaking waves. The increased sea level makes these events more serious and more frequent,” said Professor Young. “Increases in wave height, and changes in other properties such as wave direction, will further increase the probability of coastal flooding.”

Sea levels have been creeping ever higher, in large part because of the retreat of most of the planet’s great glaciers and the ever-increasing meltwater from Greenland and West Antarctica, and also as a simple matter of physics: as the oceans warm, the waters become less dense and sea levels rise.

Difficult measurements

Surfers and pleasure-seekers began to worry about the impact of global warming and climate change on wave patterns years ago. But seemingly simple phenomena such as the effects wave height and wind speed have in the open oceans on a world-wide basis are harder to measure.

Spanish oceanographers reported earlier this year that they were sure that ocean waves were gathering in force and strength, and European engineers have warned of the impact of more intense storms backed up by rising seas on the Atlantic ports and coastlines of the continent.

But there are problems: precision measurements have been made only recently. Oceanographers cannot be sure that they are not witnessing a natural cycle of ocean change, in which storm intensities slowly vary over a pattern of decades.

Since 1985 earth observation satellites have been equipped with altimeters to measure wave height and wind speed, radiometers to measure wind speed, and scatterometers to record wind speed and direction. The next problem has been calibrating data from a range of different satellites, and indeed the slightly different stories told by instruments on the same satellite.

Worse to come

But the Australian engineers report that they are now 90% confident that they can measure ocean change: violent storms now arrive with higher wave crests and more dangerous winds than they did in 1985, and although this is true worldwide, the effect is most pronounced in the great ocean that swirls around Antarctica.

The next challenge is to make estimates of how much more violent the worst sea storms are likely to become later in the century, as planetary average temperatures – and sea levels – continue to rise.

“These changes have impacts that are felt all over the world. Storm waves can increase coastal erosion, putting coastal settlements and infrastructures at risk,” Professor Young said.

“We need a better understanding of how much this change is due to long-term climate change, and how much is due to multi-decadal fluctuations or cycles.” − Climate News Network

The seas are rising. Ocean winds and waves are growing in speed and force. The oceans could be feeling the heat.

LONDON, 1 May, 2019 − The great swells of the Pacific are beginning to swell even more as fiercer ocean winds and waves leave their mark. The breakers that crash on the storm beaches now do so with greater force. The white horses are gathering pace.

A 33-year-study of data from 31 satellites and 80 ocean buoys has confirmed suspicions. The extreme ocean winds are now fiercer, and the waves are getting measurably higher.

It is a given of global warming that as average planetary temperatures rise, then more energy is available for storm, rainfall and drought.

In the past century, because of ever-increasing combustion of fossil fuels that release growing quantities of greenhouse gases, average global temperatures have crept higher by 1°C and in three decades the speed of extreme winds in the Southern Ocean has increased by 8%, or 1.5 metres per second. Extreme waves have increased by 30cms, or 5%, over the same period.

“These changes have impacts that are felt all over the world. Storm waves can increase coastal erosion, putting coastal settlements and infrastructures at risk”

“Although increases of 5 and 8% might not seem like much, if sustained into the future such changes to our climate will have major impacts,” said Ian Young, an engineer at the University of Melbourne in Australia

He and a colleague report in the journal Science that they reached their conclusion on the basis of 4 billion observations made between 1985 and 2018.

“Flooding events are caused by storm surge and associated breaking waves. The increased sea level makes these events more serious and more frequent,” said Professor Young. “Increases in wave height, and changes in other properties such as wave direction, will further increase the probability of coastal flooding.”

Sea levels have been creeping ever higher, in large part because of the retreat of most of the planet’s great glaciers and the ever-increasing meltwater from Greenland and West Antarctica, and also as a simple matter of physics: as the oceans warm, the waters become less dense and sea levels rise.

Difficult measurements

Surfers and pleasure-seekers began to worry about the impact of global warming and climate change on wave patterns years ago. But seemingly simple phenomena such as the effects wave height and wind speed have in the open oceans on a world-wide basis are harder to measure.

Spanish oceanographers reported earlier this year that they were sure that ocean waves were gathering in force and strength, and European engineers have warned of the impact of more intense storms backed up by rising seas on the Atlantic ports and coastlines of the continent.

But there are problems: precision measurements have been made only recently. Oceanographers cannot be sure that they are not witnessing a natural cycle of ocean change, in which storm intensities slowly vary over a pattern of decades.

Since 1985 earth observation satellites have been equipped with altimeters to measure wave height and wind speed, radiometers to measure wind speed, and scatterometers to record wind speed and direction. The next problem has been calibrating data from a range of different satellites, and indeed the slightly different stories told by instruments on the same satellite.

Worse to come

But the Australian engineers report that they are now 90% confident that they can measure ocean change: violent storms now arrive with higher wave crests and more dangerous winds than they did in 1985, and although this is true worldwide, the effect is most pronounced in the great ocean that swirls around Antarctica.

The next challenge is to make estimates of how much more violent the worst sea storms are likely to become later in the century, as planetary average temperatures – and sea levels – continue to rise.

“These changes have impacts that are felt all over the world. Storm waves can increase coastal erosion, putting coastal settlements and infrastructures at risk,” Professor Young said.

“We need a better understanding of how much this change is due to long-term climate change, and how much is due to multi-decadal fluctuations or cycles.” − Climate News Network