Tag Archives: Temperature Increase

No way back for West Antarctic glaciers

Satellite data analysis reveals the ominous news that the melting glaciers of West Antarctica have passed the ‘point of no return’ as the southern hemisphere gets warmer LONDON, 22 May – The glaciers of the West Antarctic may be in irreversible retreat, according to the evidence of satellite data analysed by scientists at the US space agency Nasa. The study of 19 years of data, due to be reported in the journal Geophysical Research Letters, confirms the ominous news that the southern hemisphere is not just warming − it is that it is warming in a way that speeds up the melting of the West Antarctic glaciers. Long ago, glaciologists began to wonder whether the West Antarctic ice sheet was inherently unstable. The water locked in the ice sheet in the Amundsen Sea region – the area the Nasa researchers examined − is enough to raise global sea levels by more than a metre. If the whole West Antarctic ice sheet turned to water, sea levels would rise by at least five metres.

Steady change

What the latest research has revealed is a steady change in the glacial grounding line, which is the point in a glacier’s progress towards the sea where its bottom no longer scrapes on rock but starts to float on water. It is in the nature of a glacier to flow towards the sea, and at intervals to calve an iceberg that will then float away and melt. The puzzle for scientists has been to work out whether this process has begun to accelerate. Eric Rignot, a glaciologist at the Nasa Jet Propulsion Laboratory and the University of California, Irvine, thinks it has. He and his research partners believe that European Space Agency satellite data has recorded the points at which the grounding lines can be identified in a series of West Antarctic glaciers monitored between 1992 and 2011, as the glaciers flexed in response to the movement of tides. All the grounding lines had retreated upstream, away from the sea − some by more than 30 kilometres. The grounding lines are all buried under hundreds of metres of ice, and are difficult to identify. The shift of ice in response to tidal ebb and flow provides an important clue. It also signals an acceleration of melting, because it is the glacier’s slowness that keeps the sea levels static. As it inches towards the sea, there is time for more snow and ice to pile up behind it.

Speeds up

But if the water gets under the ice sheet, it reduces friction and accelerates the passage of frozen water downstream. So the whole glacier speeds up, and the grounding line moves yet further upstream. Something similar has been reported from the glaciers of Greenland. And once the process starts, there is no obvious reason why it would stop. The melting will still be slow, but the latest evidence indicates that it seems to be inexorable. “We’ve passed the point of no return,” Prof Rignot says. “At current melt rates, these glaciers will be history within a few hundred years. “The collapse of this sector of West Antarctica appears to be unstoppable. The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.” – Climate News Network

Satellite data analysis reveals the ominous news that the melting glaciers of West Antarctica have passed the ‘point of no return’ as the southern hemisphere gets warmer LONDON, 22 May – The glaciers of the West Antarctic may be in irreversible retreat, according to the evidence of satellite data analysed by scientists at the US space agency Nasa. The study of 19 years of data, due to be reported in the journal Geophysical Research Letters, confirms the ominous news that the southern hemisphere is not just warming − it is that it is warming in a way that speeds up the melting of the West Antarctic glaciers. Long ago, glaciologists began to wonder whether the West Antarctic ice sheet was inherently unstable. The water locked in the ice sheet in the Amundsen Sea region – the area the Nasa researchers examined − is enough to raise global sea levels by more than a metre. If the whole West Antarctic ice sheet turned to water, sea levels would rise by at least five metres.

Steady change

What the latest research has revealed is a steady change in the glacial grounding line, which is the point in a glacier’s progress towards the sea where its bottom no longer scrapes on rock but starts to float on water. It is in the nature of a glacier to flow towards the sea, and at intervals to calve an iceberg that will then float away and melt. The puzzle for scientists has been to work out whether this process has begun to accelerate. Eric Rignot, a glaciologist at the Nasa Jet Propulsion Laboratory and the University of California, Irvine, thinks it has. He and his research partners believe that European Space Agency satellite data has recorded the points at which the grounding lines can be identified in a series of West Antarctic glaciers monitored between 1992 and 2011, as the glaciers flexed in response to the movement of tides. All the grounding lines had retreated upstream, away from the sea − some by more than 30 kilometres. The grounding lines are all buried under hundreds of metres of ice, and are difficult to identify. The shift of ice in response to tidal ebb and flow provides an important clue. It also signals an acceleration of melting, because it is the glacier’s slowness that keeps the sea levels static. As it inches towards the sea, there is time for more snow and ice to pile up behind it.

Speeds up

But if the water gets under the ice sheet, it reduces friction and accelerates the passage of frozen water downstream. So the whole glacier speeds up, and the grounding line moves yet further upstream. Something similar has been reported from the glaciers of Greenland. And once the process starts, there is no obvious reason why it would stop. The melting will still be slow, but the latest evidence indicates that it seems to be inexorable. “We’ve passed the point of no return,” Prof Rignot says. “At current melt rates, these glaciers will be history within a few hundred years. “The collapse of this sector of West Antarctica appears to be unstoppable. The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.” – Climate News Network

Mild climate spurs Genghis Khan's cavalry

FOR IMMEDIATE RELEASE
Scientists have unearthed possible evidence that climate change played a role in the expansion of the Mongol empire of Genghis Khan. They say an exceptionally warm period promoted grass growth, vital for the Mongols’ legendary horses.

LONDON, 12 March – Climate change – already implicated in the fall of Bronze Age civilisations in the Mediterranean and in the Indus Valley  – may also account for the rise of one of the most fearsome empires in history.

US researchers mapping the pattern of rainfall in medieval Mongolia think they may have identified a season of plenty that put Genghis Khan on the road towards world domination.

Archaeologists and climate scientists have identified sustained drought as a reason for the fall of the Minoan civilisation in Crete, and the decay of the Harappan culture in 1,000 years earlier. But a team from Columbia University report in the Proceedings of the National Academy of Sciences that annual growth rings in a trove of stunted larches and Siberian pines in the Khangai mountains of Mongolia tell a different story.

Rings record

The seasonal growth rings record a chronicle of harsh dry centuries dating back to 658AD. But between the years 1211 to 1230, something unusual happened.

Rain fell, and central Mongolia had one of the wettest periods in its history. The same period was unusually warm. Since those years coincide with the rise of the Mongol empire the connection suggested itself immediately: the Mongols were herdsmen and nomads.

Wet and warm weather means plenty of grass. Suddenly, tribesmen who wandered far to find grazing space had a surplus of feed, and soon of animals, including a glut of war horses and cattle.

The Mongol cavalry were famous for their horsemanship. “The weather may literally have supplied the Mongols with the horsepower they needed to do what they did,” says Neil Pederson of Columbia’s Lamont Doherty Observatory.

All conquering

For a brief period, the Mongols, led by a commander of remarkable military and political genius, and then by his descendants, conquered and ruled most of modern Russia, Korea, China, Persia, India, the Middle East and eastern Europe.

There is never just one reason for a civilisation’s rise or fall, and historians have also argued that the Mongol invasions might have been driven instead by hunger and poverty in the Mongol heartland.

So the researchers would like to back up their tree ring evidence with studies of lake sediments, analyses of historical documents and so on, to establish that the steppes really could have provided for the great khan and his horde. The jury is still out.

The tree rings also show that after the first growth of the Mongol empire, the climate returned to its normal cold dry state. In the last 40 years, temperatures have risen. And since 1990, the country has experienced a series of devastating summer droughts often followed by a more than usually long cold winter.

Modern day drought

After the last such, an estimated eight million animals died, herdsmen became impoverished, and the poorest have moved to the capital of Ulaanbaatar, which is now home to half of the nation’s 3 million people.

“That last big drought is an example of what may happen in the future, not just in Mongolia but in a lot of inner Asia,” says Pederson. “The heat is a double whammy – even if the rainfall doesn’t change, the landscape is going to get drier.”

The potential consequences for modern Mongolia, the authors warn, could be severe.- Climate News Network

 

FOR IMMEDIATE RELEASE
Scientists have unearthed possible evidence that climate change played a role in the expansion of the Mongol empire of Genghis Khan. They say an exceptionally warm period promoted grass growth, vital for the Mongols’ legendary horses.

LONDON, 12 March – Climate change – already implicated in the fall of Bronze Age civilisations in the Mediterranean and in the Indus Valley  – may also account for the rise of one of the most fearsome empires in history.

US researchers mapping the pattern of rainfall in medieval Mongolia think they may have identified a season of plenty that put Genghis Khan on the road towards world domination.

Archaeologists and climate scientists have identified sustained drought as a reason for the fall of the Minoan civilisation in Crete, and the decay of the Harappan culture in 1,000 years earlier. But a team from Columbia University report in the Proceedings of the National Academy of Sciences that annual growth rings in a trove of stunted larches and Siberian pines in the Khangai mountains of Mongolia tell a different story.

Rings record

The seasonal growth rings record a chronicle of harsh dry centuries dating back to 658AD. But between the years 1211 to 1230, something unusual happened.

Rain fell, and central Mongolia had one of the wettest periods in its history. The same period was unusually warm. Since those years coincide with the rise of the Mongol empire the connection suggested itself immediately: the Mongols were herdsmen and nomads.

Wet and warm weather means plenty of grass. Suddenly, tribesmen who wandered far to find grazing space had a surplus of feed, and soon of animals, including a glut of war horses and cattle.

The Mongol cavalry were famous for their horsemanship. “The weather may literally have supplied the Mongols with the horsepower they needed to do what they did,” says Neil Pederson of Columbia’s Lamont Doherty Observatory.

All conquering

For a brief period, the Mongols, led by a commander of remarkable military and political genius, and then by his descendants, conquered and ruled most of modern Russia, Korea, China, Persia, India, the Middle East and eastern Europe.

There is never just one reason for a civilisation’s rise or fall, and historians have also argued that the Mongol invasions might have been driven instead by hunger and poverty in the Mongol heartland.

So the researchers would like to back up their tree ring evidence with studies of lake sediments, analyses of historical documents and so on, to establish that the steppes really could have provided for the great khan and his horde. The jury is still out.

The tree rings also show that after the first growth of the Mongol empire, the climate returned to its normal cold dry state. In the last 40 years, temperatures have risen. And since 1990, the country has experienced a series of devastating summer droughts often followed by a more than usually long cold winter.

Modern day drought

After the last such, an estimated eight million animals died, herdsmen became impoverished, and the poorest have moved to the capital of Ulaanbaatar, which is now home to half of the nation’s 3 million people.

“That last big drought is an example of what may happen in the future, not just in Mongolia but in a lot of inner Asia,” says Pederson. “The heat is a double whammy – even if the rainfall doesn’t change, the landscape is going to get drier.”

The potential consequences for modern Mongolia, the authors warn, could be severe.- Climate News Network

 

Mild climate spurs Genghis Khan’s cavalry

FOR IMMEDIATE RELEASE Scientists have unearthed possible evidence that climate change played a role in the expansion of the Mongol empire of Genghis Khan. They say an exceptionally warm period promoted grass growth, vital for the Mongols’ legendary horses. LONDON, 12 March – Climate change – already implicated in the fall of Bronze Age civilisations in the Mediterranean and in the Indus Valley  – may also account for the rise of one of the most fearsome empires in history. US researchers mapping the pattern of rainfall in medieval Mongolia think they may have identified a season of plenty that put Genghis Khan on the road towards world domination. Archaeologists and climate scientists have identified sustained drought as a reason for the fall of the Minoan civilisation in Crete, and the decay of the Harappan culture in 1,000 years earlier. But a team from Columbia University report in the Proceedings of the National Academy of Sciences that annual growth rings in a trove of stunted larches and Siberian pines in the Khangai mountains of Mongolia tell a different story.

Rings record

The seasonal growth rings record a chronicle of harsh dry centuries dating back to 658AD. But between the years 1211 to 1230, something unusual happened. Rain fell, and central Mongolia had one of the wettest periods in its history. The same period was unusually warm. Since those years coincide with the rise of the Mongol empire the connection suggested itself immediately: the Mongols were herdsmen and nomads. Wet and warm weather means plenty of grass. Suddenly, tribesmen who wandered far to find grazing space had a surplus of feed, and soon of animals, including a glut of war horses and cattle. The Mongol cavalry were famous for their horsemanship. “The weather may literally have supplied the Mongols with the horsepower they needed to do what they did,” says Neil Pederson of Columbia’s Lamont Doherty Observatory.

All conquering

For a brief period, the Mongols, led by a commander of remarkable military and political genius, and then by his descendants, conquered and ruled most of modern Russia, Korea, China, Persia, India, the Middle East and eastern Europe. There is never just one reason for a civilisation’s rise or fall, and historians have also argued that the Mongol invasions might have been driven instead by hunger and poverty in the Mongol heartland. So the researchers would like to back up their tree ring evidence with studies of lake sediments, analyses of historical documents and so on, to establish that the steppes really could have provided for the great khan and his horde. The jury is still out. The tree rings also show that after the first growth of the Mongol empire, the climate returned to its normal cold dry state. In the last 40 years, temperatures have risen. And since 1990, the country has experienced a series of devastating summer droughts often followed by a more than usually long cold winter.

Modern day drought

After the last such, an estimated eight million animals died, herdsmen became impoverished, and the poorest have moved to the capital of Ulaanbaatar, which is now home to half of the nation’s 3 million people. “That last big drought is an example of what may happen in the future, not just in Mongolia but in a lot of inner Asia,” says Pederson. “The heat is a double whammy – even if the rainfall doesn’t change, the landscape is going to get drier.” The potential consequences for modern Mongolia, the authors warn, could be severe.- Climate News Network  

FOR IMMEDIATE RELEASE Scientists have unearthed possible evidence that climate change played a role in the expansion of the Mongol empire of Genghis Khan. They say an exceptionally warm period promoted grass growth, vital for the Mongols’ legendary horses. LONDON, 12 March – Climate change – already implicated in the fall of Bronze Age civilisations in the Mediterranean and in the Indus Valley  – may also account for the rise of one of the most fearsome empires in history. US researchers mapping the pattern of rainfall in medieval Mongolia think they may have identified a season of plenty that put Genghis Khan on the road towards world domination. Archaeologists and climate scientists have identified sustained drought as a reason for the fall of the Minoan civilisation in Crete, and the decay of the Harappan culture in 1,000 years earlier. But a team from Columbia University report in the Proceedings of the National Academy of Sciences that annual growth rings in a trove of stunted larches and Siberian pines in the Khangai mountains of Mongolia tell a different story.

Rings record

The seasonal growth rings record a chronicle of harsh dry centuries dating back to 658AD. But between the years 1211 to 1230, something unusual happened. Rain fell, and central Mongolia had one of the wettest periods in its history. The same period was unusually warm. Since those years coincide with the rise of the Mongol empire the connection suggested itself immediately: the Mongols were herdsmen and nomads. Wet and warm weather means plenty of grass. Suddenly, tribesmen who wandered far to find grazing space had a surplus of feed, and soon of animals, including a glut of war horses and cattle. The Mongol cavalry were famous for their horsemanship. “The weather may literally have supplied the Mongols with the horsepower they needed to do what they did,” says Neil Pederson of Columbia’s Lamont Doherty Observatory.

All conquering

For a brief period, the Mongols, led by a commander of remarkable military and political genius, and then by his descendants, conquered and ruled most of modern Russia, Korea, China, Persia, India, the Middle East and eastern Europe. There is never just one reason for a civilisation’s rise or fall, and historians have also argued that the Mongol invasions might have been driven instead by hunger and poverty in the Mongol heartland. So the researchers would like to back up their tree ring evidence with studies of lake sediments, analyses of historical documents and so on, to establish that the steppes really could have provided for the great khan and his horde. The jury is still out. The tree rings also show that after the first growth of the Mongol empire, the climate returned to its normal cold dry state. In the last 40 years, temperatures have risen. And since 1990, the country has experienced a series of devastating summer droughts often followed by a more than usually long cold winter.

Modern day drought

After the last such, an estimated eight million animals died, herdsmen became impoverished, and the poorest have moved to the capital of Ulaanbaatar, which is now home to half of the nation’s 3 million people. “That last big drought is an example of what may happen in the future, not just in Mongolia but in a lot of inner Asia,” says Pederson. “The heat is a double whammy – even if the rainfall doesn’t change, the landscape is going to get drier.” The potential consequences for modern Mongolia, the authors warn, could be severe.- Climate News Network