Tag Archives: Ocean Warming

Arctic warming gives US and Europe the chills

The effects of Arctic climate change on the jet stream could mean harsher winters for some of the most highly populated regions of the world.

LONDON, 2 November, 2016 Warming in the Arctic – one of the fastest-warming regions on the planet – could be heightening the chances of extreme winters in Europe and the US.

As the Arctic warms, the stratospheric jet stream that brings occasionally catastrophic ice storms and record snow falls to the eastern United States could also be on the move, according to new research in the journal Nature Climate Change.

The phenomenon is a natural one. Some years the track of the jet stream is wavy, and delivers severe cold weather to the mid-latitudes of the northern hemisphere. Some years the pattern alters, and Europe in particular experiences mild winters. The temperate zones have always experienced occasional extremes. But climate change could be tilting the balance.

Extreme spells

“We’ve always had years with wavy and not so wavy jet-stream winds, but in the last one or two decades the warming Arctic could well have been amplifying the effects of the wavy patterns.

“This may have contributed to some recent extreme cold winter spells along the eastern seaboard of the United States, in western Asia and at times over the UK,” says Edward Hanna, a geographer at the University of Sheffield, UK, and one of a team of British, European and US scientists behind the study.

“Improving our ability to predict how climate change
is affecting the jet stream will help improve
our long-term prediction of winter weather”

The study doesn’t claim to settle the question: notoriously, climate is what you expect but weather is what you get, and it may be impossible to prove that this or that unexpected event happened because the global average temperatures are now at least 1°C higher than they used to be, before the human combustion of fossil fuels began to increase the concentration of the greenhouse gas carbon dioxide in the atmosphere from 280 parts per million to 400 ppm.

But there are changes in the Arctic that are happening because of global warming, and meteorologists have been watching the knock-on effect on the stratospheric winds, especially the jet stream.

In the same issue of the journal one group identified a persistent shift and a weakening in the Arctic winter polar vortex, a meteorological monster that plays a role in temperate zone weather patterns.

Others identified a link between Arctic changes and the speed of the jet stream, and its effect on transatlantic airline timetables.

Yet others have linked Arctic warming to dangerous extremes of heat further south, and yet another group has linked polar climate change to both ice storms and heatwaves.

Arctic signals

The debate continues. The important thing is to monitor the melting sea ice, the rising sea-surface temperatures and the emerging pattern of severe winter weather. If meteorologists can learn to read the signals from the Arctic, then communities could plan more effectively for the consequences.

“Improving our ability to predict how climate change is affecting the jet stream will help improve our long-term prediction of winter weather in some of the most highly populated regions of the world,” Professor Hanna says. “This would be highly beneficial for communities, businesses and entire economies in the northern hemisphere.

“The public could better prepare for severe winter weather and have access to extra crucial information that could help make life-saving and cost-saving decisions.” Climate News Network

The effects of Arctic climate change on the jet stream could mean harsher winters for some of the most highly populated regions of the world.

LONDON, 2 November, 2016 Warming in the Arctic – one of the fastest-warming regions on the planet – could be heightening the chances of extreme winters in Europe and the US.

As the Arctic warms, the stratospheric jet stream that brings occasionally catastrophic ice storms and record snow falls to the eastern United States could also be on the move, according to new research in the journal Nature Climate Change.

The phenomenon is a natural one. Some years the track of the jet stream is wavy, and delivers severe cold weather to the mid-latitudes of the northern hemisphere. Some years the pattern alters, and Europe in particular experiences mild winters. The temperate zones have always experienced occasional extremes. But climate change could be tilting the balance.

Extreme spells

“We’ve always had years with wavy and not so wavy jet-stream winds, but in the last one or two decades the warming Arctic could well have been amplifying the effects of the wavy patterns.

“This may have contributed to some recent extreme cold winter spells along the eastern seaboard of the United States, in western Asia and at times over the UK,” says Edward Hanna, a geographer at the University of Sheffield, UK, and one of a team of British, European and US scientists behind the study.

“Improving our ability to predict how climate change
is affecting the jet stream will help improve
our long-term prediction of winter weather”

The study doesn’t claim to settle the question: notoriously, climate is what you expect but weather is what you get, and it may be impossible to prove that this or that unexpected event happened because the global average temperatures are now at least 1°C higher than they used to be, before the human combustion of fossil fuels began to increase the concentration of the greenhouse gas carbon dioxide in the atmosphere from 280 parts per million to 400 ppm.

But there are changes in the Arctic that are happening because of global warming, and meteorologists have been watching the knock-on effect on the stratospheric winds, especially the jet stream.

In the same issue of the journal one group identified a persistent shift and a weakening in the Arctic winter polar vortex, a meteorological monster that plays a role in temperate zone weather patterns.

Others identified a link between Arctic changes and the speed of the jet stream, and its effect on transatlantic airline timetables.

Yet others have linked Arctic warming to dangerous extremes of heat further south, and yet another group has linked polar climate change to both ice storms and heatwaves.

Arctic signals

The debate continues. The important thing is to monitor the melting sea ice, the rising sea-surface temperatures and the emerging pattern of severe winter weather. If meteorologists can learn to read the signals from the Arctic, then communities could plan more effectively for the consequences.

“Improving our ability to predict how climate change is affecting the jet stream will help improve our long-term prediction of winter weather in some of the most highly populated regions of the world,” Professor Hanna says. “This would be highly beneficial for communities, businesses and entire economies in the northern hemisphere.

“The public could better prepare for severe winter weather and have access to extra crucial information that could help make life-saving and cost-saving decisions.” Climate News Network

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

E. Antarctic ice basin ‘may be at risk’

The East Antarctic ice sheet is thought by most scientists to be stable. But a German team says it has found how part of it could in time melt unstoppably. LONDON, 4 May – Part of the East Antarctic ice sheet may be less stable than anyone had realised, researchers based in Germany have found. Writing in Nature Climate Change, two scientists from the Potsdam Institute for Climate Impact Research (PIK) say the melting of quite a small volume of ice on the East Antarctic shore could ultimately trigger a discharge of ice into the ocean which would result in unstoppable sea-level rise for thousands of years ahead. Their findings, which they say amount to the discovery of a hitherto overlooked source of sea level rise, appear unlikely to happen any time soon. They are based on computer simulations of the Antarctic ice flow using improved data of the ground profile beneath the ice sheet. “East Antarctica’s Wilkes Basin is like a bottle on a slant,” said Matthias Mengel, the lead author of the study. “Once uncorked, it empties out.” The basin is the largest region of marine ice on rocky ground in East Antarctica. At the moment a rim of ice at the coast holds the ice behind it in place, like a cork holding back the contents of a bottle. The air over Antarctica remains cold, but oceanic warming can cause the ice on the coast to melt. This could make the relatively small “cork” disappear. Once it had gone, the result would be a long-term sea level rise of three to four metres. “The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork,” says the study’s co-author, Anders Levermann. “Until recently, only West Antarctica was considered unstable, but now we know that its ten times bigger counterpart in the East might also be at risk.”

Stability ‘over-estimated’

Levermann is a lead author of the sea-level change chapter of the most recent scientific assessment report by the Intergovernmental Panel on Climate Change, the IPCC. Its report, published in September 2013, says Antarctica’s total sea level contribution could be up to 16 centimetres during this century. “If half of that ice loss occurred in the ice-cork region, then the discharge would begin. We have probably overestimated the stability of East Antarctica so far,” says Levermann. Melting would cause the retreat of the grounding line, where the ice on the solid continental landmass meets the sea and starts to float. The rocky ground beneath the ice in the Wilkes Basin forms a huge valley below sea-level which slopes downwards as it heads inland. When the grounding line retreats from its current position on a ridge into the valley, the rim of the ice facing the ocean becomes higher than before. More ice is then pushed into the sea, eventually breaking off and melting. And the warmer it gets, the faster this happens. For all the ice in the Wilkes Basin to be lost in this way would take 5,000-10,000 years, the simulations showed. But once it had started, the discharge of ice would slowly but relentlessly continue until the whole basin was empty, even if the climate ceased to warm.

Unavoidable consequences

“This is the underlying issue here”, said Matthias Mengel. “By emitting more and more greenhouse gases we might trigger responses now that we may not be able to stop in the future.” He told the Climate News Network: “While the sparse existing observations do not indicate warmer water inflow towards the Wilkes ice sheet margin at present, there is no reason why changes similar to those in West Antarctica could not also occur here.” The possibility remains a distant prospect. Mengel said some simulations produced the warm ocean conditions needed to remove the ice cork within the next 200 years, but It would take around 2,000 years to raise global sea levels by one metre. He added: “The issue is that this would then be unstoppable…We have detected a new and previously overlooked source of sea level rise, therefore these numbers have to be added to the present sea level rise projections of the IPCC. “Sea level as projected for the forthcoming centuries is already potentially devastating for many coastal areas around the globe. Every centimetre of sea level rise on top of these projections is even more significant.” – Climate News Network

The East Antarctic ice sheet is thought by most scientists to be stable. But a German team says it has found how part of it could in time melt unstoppably. LONDON, 4 May – Part of the East Antarctic ice sheet may be less stable than anyone had realised, researchers based in Germany have found. Writing in Nature Climate Change, two scientists from the Potsdam Institute for Climate Impact Research (PIK) say the melting of quite a small volume of ice on the East Antarctic shore could ultimately trigger a discharge of ice into the ocean which would result in unstoppable sea-level rise for thousands of years ahead. Their findings, which they say amount to the discovery of a hitherto overlooked source of sea level rise, appear unlikely to happen any time soon. They are based on computer simulations of the Antarctic ice flow using improved data of the ground profile beneath the ice sheet. “East Antarctica’s Wilkes Basin is like a bottle on a slant,” said Matthias Mengel, the lead author of the study. “Once uncorked, it empties out.” The basin is the largest region of marine ice on rocky ground in East Antarctica. At the moment a rim of ice at the coast holds the ice behind it in place, like a cork holding back the contents of a bottle. The air over Antarctica remains cold, but oceanic warming can cause the ice on the coast to melt. This could make the relatively small “cork” disappear. Once it had gone, the result would be a long-term sea level rise of three to four metres. “The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork,” says the study’s co-author, Anders Levermann. “Until recently, only West Antarctica was considered unstable, but now we know that its ten times bigger counterpart in the East might also be at risk.”

Stability ‘over-estimated’

Levermann is a lead author of the sea-level change chapter of the most recent scientific assessment report by the Intergovernmental Panel on Climate Change, the IPCC. Its report, published in September 2013, says Antarctica’s total sea level contribution could be up to 16 centimetres during this century. “If half of that ice loss occurred in the ice-cork region, then the discharge would begin. We have probably overestimated the stability of East Antarctica so far,” says Levermann. Melting would cause the retreat of the grounding line, where the ice on the solid continental landmass meets the sea and starts to float. The rocky ground beneath the ice in the Wilkes Basin forms a huge valley below sea-level which slopes downwards as it heads inland. When the grounding line retreats from its current position on a ridge into the valley, the rim of the ice facing the ocean becomes higher than before. More ice is then pushed into the sea, eventually breaking off and melting. And the warmer it gets, the faster this happens. For all the ice in the Wilkes Basin to be lost in this way would take 5,000-10,000 years, the simulations showed. But once it had started, the discharge of ice would slowly but relentlessly continue until the whole basin was empty, even if the climate ceased to warm.

Unavoidable consequences

“This is the underlying issue here”, said Matthias Mengel. “By emitting more and more greenhouse gases we might trigger responses now that we may not be able to stop in the future.” He told the Climate News Network: “While the sparse existing observations do not indicate warmer water inflow towards the Wilkes ice sheet margin at present, there is no reason why changes similar to those in West Antarctica could not also occur here.” The possibility remains a distant prospect. Mengel said some simulations produced the warm ocean conditions needed to remove the ice cork within the next 200 years, but It would take around 2,000 years to raise global sea levels by one metre. He added: “The issue is that this would then be unstoppable…We have detected a new and previously overlooked source of sea level rise, therefore these numbers have to be added to the present sea level rise projections of the IPCC. “Sea level as projected for the forthcoming centuries is already potentially devastating for many coastal areas around the globe. Every centimetre of sea level rise on top of these projections is even more significant.” – Climate News Network

Acid seas make corals feeble but they survive

FOR IMMEDIATE RELEASE Two important habitats for marine life, coral reefs and eelgrass meadows, will survive climate change but it will make them vulnerable. LONDON 17 June – Ocean acidification will make coral skeletons more feeble and coral reefs more vulnerable to battering by the seas – but it may not kill the corals, according to new research from the University of California, Santa Cruz. The Californian scientists report in the Proceedings of the National Academy of Sciences (PNAS) that they tested coral’s response to changes in future ocean chemistry not by experiments in a tank in a laboratory, but under real conditions – off Mexico’s Yucatan Peninsula where submarine springs naturally alter the chemistry of the surrounding sea water. “People have seen similar effects in laboratory experiments,” said Adina Paytan, of the university’s Institute of Marine Sciences. “We looked in places where corals are exposed to lower pH for their entire lifespan. The good news is that they don’t just die. They are able to grow and calcify, but they are not producing robust structures.” As carbon dioxide levels rise, falling rain becomes even more weakly acidic, and all rain eventually makes its way into the oceans, changing the water chemistry subtly. Storm waves By monitoring seawater chemistry near natural submarine springs, and by examining cores from colonies of an important Caribbean reef-building coral called Porites astreoides, the scientists were able to show that predicted future changes in water chemistry did have consequences for creatures that exploit that chemistry: it became more demanding for the coral animals to build up the blocks of calcium carbonate skeletons. As the skeletons become less dense, so they become more vulnerable to storm waves, and to coral predators. Corals are also vulnerable to temperature rise, and recent research has shown that corals can recover slowly from devastating spells of heat. Now it seems they can survive changes in ocean acidity. The question of course is whether reefs can survive both at the same time – and other stresses such as pollution and overfishing. Eelgrass meadows Meanwhile, far away to the north and across the Atlantic, Swedish researchers at the University of Gothenburg have been testing the effect of both rising temperatures and changes in sea chemistry on another important marine ecosystem: the eelgrass meadows. Christian Alsterberg reports in the PNAS that they raised the temperature in laboratory tanks containing eelgrass, while at the same time bubbling extra carbon dioxide through the water, to simulate the real changes predicted in the decades to come. The aim was to see how the plants, and the animals for which the plants form a natural habitat, responded. As water temperatures increased, for instance, so did the metabolism of many of the crustaceans that live in the eelgrass meadows. As a consequence, the animals consumed more algae, and grazed the meadows more efficiently. Benthic microalgae on the sediment of the meadows responded more vigorously. Overall, there seemed to be no great effect on the meadows. But that depended on the presence of crustaceans: without these small, algae-eating animals, the outcome could have been much worse. The research is just another piece in the vast jigsaw puzzle of climate science, in which small changes can have complex outcomes. “The experiment also taught us the importance of investigating climate change using several different approaches, in order to fully understand its effects and to predict future impacts,” said Alsterberg. – Climate News Network

FOR IMMEDIATE RELEASE Two important habitats for marine life, coral reefs and eelgrass meadows, will survive climate change but it will make them vulnerable. LONDON 17 June – Ocean acidification will make coral skeletons more feeble and coral reefs more vulnerable to battering by the seas – but it may not kill the corals, according to new research from the University of California, Santa Cruz. The Californian scientists report in the Proceedings of the National Academy of Sciences (PNAS) that they tested coral’s response to changes in future ocean chemistry not by experiments in a tank in a laboratory, but under real conditions – off Mexico’s Yucatan Peninsula where submarine springs naturally alter the chemistry of the surrounding sea water. “People have seen similar effects in laboratory experiments,” said Adina Paytan, of the university’s Institute of Marine Sciences. “We looked in places where corals are exposed to lower pH for their entire lifespan. The good news is that they don’t just die. They are able to grow and calcify, but they are not producing robust structures.” As carbon dioxide levels rise, falling rain becomes even more weakly acidic, and all rain eventually makes its way into the oceans, changing the water chemistry subtly. Storm waves By monitoring seawater chemistry near natural submarine springs, and by examining cores from colonies of an important Caribbean reef-building coral called Porites astreoides, the scientists were able to show that predicted future changes in water chemistry did have consequences for creatures that exploit that chemistry: it became more demanding for the coral animals to build up the blocks of calcium carbonate skeletons. As the skeletons become less dense, so they become more vulnerable to storm waves, and to coral predators. Corals are also vulnerable to temperature rise, and recent research has shown that corals can recover slowly from devastating spells of heat. Now it seems they can survive changes in ocean acidity. The question of course is whether reefs can survive both at the same time – and other stresses such as pollution and overfishing. Eelgrass meadows Meanwhile, far away to the north and across the Atlantic, Swedish researchers at the University of Gothenburg have been testing the effect of both rising temperatures and changes in sea chemistry on another important marine ecosystem: the eelgrass meadows. Christian Alsterberg reports in the PNAS that they raised the temperature in laboratory tanks containing eelgrass, while at the same time bubbling extra carbon dioxide through the water, to simulate the real changes predicted in the decades to come. The aim was to see how the plants, and the animals for which the plants form a natural habitat, responded. As water temperatures increased, for instance, so did the metabolism of many of the crustaceans that live in the eelgrass meadows. As a consequence, the animals consumed more algae, and grazed the meadows more efficiently. Benthic microalgae on the sediment of the meadows responded more vigorously. Overall, there seemed to be no great effect on the meadows. But that depended on the presence of crustaceans: without these small, algae-eating animals, the outcome could have been much worse. The research is just another piece in the vast jigsaw puzzle of climate science, in which small changes can have complex outcomes. “The experiment also taught us the importance of investigating climate change using several different approaches, in order to fully understand its effects and to predict future impacts,” said Alsterberg. – Climate News Network

Old Data Reveals Warming Oceans

FOR IMMEDIATE RELEASE Indications the rate of warming in oceans is greater than previously thought. LONDON, 31 MAY – In 1872 the H.M.S. Challenger, converted from a British fighting vessel to a floating laboratory, set off on what was to be the first scientific survey of life in the world’s oceans. Now scientists are using data collected during the Challenger’s four year expedition to try to understand the heat content of the oceans and the relative level of warming taking place. A main finding is that the impact of global warming on the oceans might have been significantly underestimated: the oceans are absorbing far more heat than previously realised. The study, carried out by Australian and US scientists and appearing in the journal Geophysical Research Letters, is further proof of human-produced global warming over the past century, say the researchers. “Our research revealed warming of the planet can be clearly detected since 1873 and that our oceans continue to absorb the great majority of this heat” says Will Hobbs of the University of Tasmania’s Institute for Marine and Antarctic Studies and lead author of the report. “Currently, scientists estimate the oceans absorb more than 90% of the heat trapped by greenhouse gases, and we attribute the global warming to anthropogenic causes.”

Changes to ocean temperature

  The Challenger expedition, though concentrating on life forms of the oceans, dropped thermometers suspended on ropes of Italian hemp hundreds of metres deep.Those readings can now serve as baseline for understanding global warming in the oceans and the rate of heat build up. Prior to this study, say the researchers, climate models were the only way to estimate changes in oceans temperatures before the 1950s. “The key to this research was to determine the range of uncertainty for the measurements taken by the crew of the Challenger” says Josh Willis of NASA’s Jet Propulsion Laboratory and a key researcher in the study. “After we had taken all these uncertainties into account, it became apparent that the rate of warming we saw across the oceans far exceeded the degree of uncertainty around the measurements. So, while the uncertainty was large, the warming signal detected was far greater.” Those uncertainties relating to the Challenger temperature data include a lack of knowledge about how deep measurements were taken, variations in temperature readings in various regions and the relatively limited range of ocean covered in the voyage. By comparing data sets, the new study found that thermal expansion of sea water caused by global warming contributed about 40% of total sea level rise from 1873 to 1955 while about 60% of that rise is likely to have come from the melting of ice sheets and glaciers. – Climate News Network  

FOR IMMEDIATE RELEASE Indications the rate of warming in oceans is greater than previously thought. LONDON, 31 MAY – In 1872 the H.M.S. Challenger, converted from a British fighting vessel to a floating laboratory, set off on what was to be the first scientific survey of life in the world’s oceans. Now scientists are using data collected during the Challenger’s four year expedition to try to understand the heat content of the oceans and the relative level of warming taking place. A main finding is that the impact of global warming on the oceans might have been significantly underestimated: the oceans are absorbing far more heat than previously realised. The study, carried out by Australian and US scientists and appearing in the journal Geophysical Research Letters, is further proof of human-produced global warming over the past century, say the researchers. “Our research revealed warming of the planet can be clearly detected since 1873 and that our oceans continue to absorb the great majority of this heat” says Will Hobbs of the University of Tasmania’s Institute for Marine and Antarctic Studies and lead author of the report. “Currently, scientists estimate the oceans absorb more than 90% of the heat trapped by greenhouse gases, and we attribute the global warming to anthropogenic causes.”

Changes to ocean temperature

  The Challenger expedition, though concentrating on life forms of the oceans, dropped thermometers suspended on ropes of Italian hemp hundreds of metres deep.Those readings can now serve as baseline for understanding global warming in the oceans and the rate of heat build up. Prior to this study, say the researchers, climate models were the only way to estimate changes in oceans temperatures before the 1950s. “The key to this research was to determine the range of uncertainty for the measurements taken by the crew of the Challenger” says Josh Willis of NASA’s Jet Propulsion Laboratory and a key researcher in the study. “After we had taken all these uncertainties into account, it became apparent that the rate of warming we saw across the oceans far exceeded the degree of uncertainty around the measurements. So, while the uncertainty was large, the warming signal detected was far greater.” Those uncertainties relating to the Challenger temperature data include a lack of knowledge about how deep measurements were taken, variations in temperature readings in various regions and the relatively limited range of ocean covered in the voyage. By comparing data sets, the new study found that thermal expansion of sea water caused by global warming contributed about 40% of total sea level rise from 1873 to 1955 while about 60% of that rise is likely to have come from the melting of ice sheets and glaciers. – Climate News Network