Tag Archives: Natural variability

Polar sea ice reaches record low

Arctic sea ice polar

NASA scientists say that in the last six months the world has lost an area of polar sea ice that is bigger than Mexico.

LONDON, 30 March, 2017 Arctic sea ice in March reached a new record low: the area of frozen ocean at the height of winter on 7 March reached a new maximum low for the third year running, according to NASA scientists. Only a few days earlier, on 3 March, Antarctic sea ice reached its own new record summer low since satellite observations began in 1979.

And on 13 February the total area of frozen ocean in the two hemispheres was at its lowest: 16.21 million square kilometres, which is about 2m sq km less than the average global minimum for 1981 to 2010.

In effect, the NASA scientists report, the world had lost a chunk of sea ice of an area bigger than Mexico.

Extraordinary conditions

It has been quite extraordinary for several months in the Arctic,” says Julienne Stroeve, professor of polar observation at University College London. “Pretty much all through October, November, December, January, February and now March, we have been tracking record low conditions. I don’t think there has ever been a time in the Arctic when we have seen so many months of just record consecutive low conditions.”

The most dramatic losses of sea ice have over the decades been observed in summer – where the decline has been measured at 14% per decade. Winter shrinkage has been at a much lower rate: about 3% per decade. But the ice has been thinning as well as dwindling in area, and temperatures earlier in the winter were unusually high: 20°C above the average for the time of the year.

Nobody can be sure what will happen once the spring thaw has begun, but polar scientists are expecting the worst. “We are pretty much poised to have really low summer ice conditions,” Professor Stroeve says.

We have been at record low levels. There is a lot
of year-to-year variability, and it was only
a couple of years ago we saw a maximum”

The frozen ocean around the Antarctic continent, too, has scientists worried. Sea ice fell to 2.11m sq km on 3 March. This is below the previous lowest minimum on record, exactly 20 years ago.

The two poles are very different. The Arctic is an ocean surrounded by land, while the Antarctic is a vast continent ringed by ocean, therefore the dynamics of ice formation and loss are not the same. And in recent years, the extent of sea ice in Antarctica had been growing. But this March, at the close of the Antarctic summer, there was a dramatic change.

It is tempting to say that the record low we are seeing is global warming finally catching up with Antarctica,” says Walt Meier of NASA’s Goddard Space Flight Centre in Maryland.

However, this might just be an extreme case of pushing the envelope of year-to-year variability. We’ll need to have several more years of data to be able to say there has been a significant change in the trend.”

Both polar regions are affected by natural variation. But the suspicion is that the long-term trend in global warming driven by human combustion of fossil fuels that dump vast quantities of greenhouse gases into the atmosphere must be playing a part. One research group recently proposed that human action might be responsible for at least half and perhaps 70% of Arctic warming.

Polar variability

Southern polar sea ice reached its peak at the end of August, and November, December, January and February all saw rapid declines.

We have been at record low levels,” says Emily Shuckburgh, deputy head of polar oceans at the British Antarctic Survey. “There is a lot of year-to-year variability, and it was only a couple of years ago we saw a maximum.

This is just one year where there is a lot of variability, and really understanding what the implications are is the research challenge.” Climate News Network

NASA scientists say that in the last six months the world has lost an area of polar sea ice that is bigger than Mexico.

LONDON, 30 March, 2017 Arctic sea ice in March reached a new record low: the area of frozen ocean at the height of winter on 7 March reached a new maximum low for the third year running, according to NASA scientists. Only a few days earlier, on 3 March, Antarctic sea ice reached its own new record summer low since satellite observations began in 1979.

And on 13 February the total area of frozen ocean in the two hemispheres was at its lowest: 16.21 million square kilometres, which is about 2m sq km less than the average global minimum for 1981 to 2010.

In effect, the NASA scientists report, the world had lost a chunk of sea ice of an area bigger than Mexico.

Extraordinary conditions

It has been quite extraordinary for several months in the Arctic,” says Julienne Stroeve, professor of polar observation at University College London. “Pretty much all through October, November, December, January, February and now March, we have been tracking record low conditions. I don’t think there has ever been a time in the Arctic when we have seen so many months of just record consecutive low conditions.”

The most dramatic losses of sea ice have over the decades been observed in summer – where the decline has been measured at 14% per decade. Winter shrinkage has been at a much lower rate: about 3% per decade. But the ice has been thinning as well as dwindling in area, and temperatures earlier in the winter were unusually high: 20°C above the average for the time of the year.

Nobody can be sure what will happen once the spring thaw has begun, but polar scientists are expecting the worst. “We are pretty much poised to have really low summer ice conditions,” Professor Stroeve says.

We have been at record low levels. There is a lot
of year-to-year variability, and it was only
a couple of years ago we saw a maximum”

The frozen ocean around the Antarctic continent, too, has scientists worried. Sea ice fell to 2.11m sq km on 3 March. This is below the previous lowest minimum on record, exactly 20 years ago.

The two poles are very different. The Arctic is an ocean surrounded by land, while the Antarctic is a vast continent ringed by ocean, therefore the dynamics of ice formation and loss are not the same. And in recent years, the extent of sea ice in Antarctica had been growing. But this March, at the close of the Antarctic summer, there was a dramatic change.

It is tempting to say that the record low we are seeing is global warming finally catching up with Antarctica,” says Walt Meier of NASA’s Goddard Space Flight Centre in Maryland.

However, this might just be an extreme case of pushing the envelope of year-to-year variability. We’ll need to have several more years of data to be able to say there has been a significant change in the trend.”

Both polar regions are affected by natural variation. But the suspicion is that the long-term trend in global warming driven by human combustion of fossil fuels that dump vast quantities of greenhouse gases into the atmosphere must be playing a part. One research group recently proposed that human action might be responsible for at least half and perhaps 70% of Arctic warming.

Polar variability

Southern polar sea ice reached its peak at the end of August, and November, December, January and February all saw rapid declines.

We have been at record low levels,” says Emily Shuckburgh, deputy head of polar oceans at the British Antarctic Survey. “There is a lot of year-to-year variability, and it was only a couple of years ago we saw a maximum.

This is just one year where there is a lot of variability, and really understanding what the implications are is the research challenge.” Climate News Network

Warming’s mixed effects on migratory animals

Global warming brent geese

New studies on beluga whales and Brent geese reveal that they respond to global warming in conflicting ways, making species survival hard to predict.

LONDON, 13 January, 2017 Beluga whales are responding to climate change in a rapidly warming Arctic – but only some of them. And migratory geese ought to be flourishing with milder conditions at nesting grounds in the far north – but the mother geese are at greater risk.

Both studies leave biologists guessing a bit at the response of their animal subjects to climate change. But the evidence shows that even the animals themselves may have to take a guess.

Warming Arctic

US scientists report in Global Change Biology that one population of beluga whales is taking advantage of the longer summers in the far north, while another is keeping to a calendar that pre-dates climate change.

Beluga whales, those ghostly white hunters of the northern seas, tend to winter in the Bering Sea between two continents, and then swim north as the ice melts and the Arctic seas open up.

The two populations of whales are genetically distinct – they have different ancestries – and travel as family groups, the young learning from their mothers.

Those that feed on fish and molluscs in the Beaufort Sea north of Alaska and Canada tend to leave the summer feeding grounds in autumn with the first risk of freezing. Those that hunt in the Chukchi Sea to the north and east of Alaska are delaying their response to take advantage of the longer spells of open water.

Summer sea ice has been in retreat for the last 30 years, and last autumn was an astonishing 20°C above average.

So biologists are confronted with a big question: is one population guarding against being caught by a sudden build-up of Arctic ice, while the other is consciously taking a risk but benefiting from a longer spell in richer feeding grounds?

The biggest take-home message is that belugas can respond relatively quickly to their changing environment, yet we can’t expect a uniform response across all beluga populations,” says Donna Hauser, of the University of Washington’s polar science centre in the US, who led the research.

If were trying to understand how these species are going to respond to climate change, we should expect to see variability in the response across populations and across time. That may complicate our predictions for the future.”

The polar puzzle is nothing new for biologists: creatures that migrate to the Arctic have always experienced a mix of good and bad summers.

Research like this is important because
we have to understand how animal populations
will respond to the changing climate if we want
to make decisions about protecting biodiversity”

Some Arctic predators, such as the polar bear, which depends on sea ice for a living, are imperilled by the early thaw and the late freeze. Other predators and herbivores can shift to new territories, or gain from changing climate one year and lose the next.

But as ecosystems shift dramatically in response to global warming, the tally of winners and losers becomes harder to predict.

The light-bellied Brent geese that breed each summer in northeast Canada could become a textbook example, according to a new study in the Journal of Animal Ecology.

Climate change means that nesting mothers breed more successfully in longer, warmer summers. But the latest study suggests that the same high productivity is accompanied by a higher death rate among mothers. That could be because the birds nest on the ground, stay longer in better conditions and become more vulnerable to predators.

In a bad breeding season, mothers abandon nests or do not breed – but they do survive to try again another year.

Climate change

We tend to think of climate change as being all one way, but here we’ve got a population being affected in conflicting ways,” says Ian Cleasby, of the Centre for Ecology and Conservation at the University of Exeter in the UK.

This population is sensitive to changes in adult survival, so the increased breeding may not be enough to offset the loss of more adult females.

Research like this is important because we have to understand how animal populations will respond to the changing climate if we want to make decisions about protecting biodiversity.” Climate News Network

New studies on beluga whales and Brent geese reveal that they respond to global warming in conflicting ways, making species survival hard to predict.

LONDON, 13 January, 2017 Beluga whales are responding to climate change in a rapidly warming Arctic – but only some of them. And migratory geese ought to be flourishing with milder conditions at nesting grounds in the far north – but the mother geese are at greater risk.

Both studies leave biologists guessing a bit at the response of their animal subjects to climate change. But the evidence shows that even the animals themselves may have to take a guess.

Warming Arctic

US scientists report in Global Change Biology that one population of beluga whales is taking advantage of the longer summers in the far north, while another is keeping to a calendar that pre-dates climate change.

Beluga whales, those ghostly white hunters of the northern seas, tend to winter in the Bering Sea between two continents, and then swim north as the ice melts and the Arctic seas open up.

The two populations of whales are genetically distinct – they have different ancestries – and travel as family groups, the young learning from their mothers.

Those that feed on fish and molluscs in the Beaufort Sea north of Alaska and Canada tend to leave the summer feeding grounds in autumn with the first risk of freezing. Those that hunt in the Chukchi Sea to the north and east of Alaska are delaying their response to take advantage of the longer spells of open water.

Summer sea ice has been in retreat for the last 30 years, and last autumn was an astonishing 20°C above average.

So biologists are confronted with a big question: is one population guarding against being caught by a sudden build-up of Arctic ice, while the other is consciously taking a risk but benefiting from a longer spell in richer feeding grounds?

The biggest take-home message is that belugas can respond relatively quickly to their changing environment, yet we can’t expect a uniform response across all beluga populations,” says Donna Hauser, of the University of Washington’s polar science centre in the US, who led the research.

If were trying to understand how these species are going to respond to climate change, we should expect to see variability in the response across populations and across time. That may complicate our predictions for the future.”

The polar puzzle is nothing new for biologists: creatures that migrate to the Arctic have always experienced a mix of good and bad summers.

Research like this is important because
we have to understand how animal populations
will respond to the changing climate if we want
to make decisions about protecting biodiversity”

Some Arctic predators, such as the polar bear, which depends on sea ice for a living, are imperilled by the early thaw and the late freeze. Other predators and herbivores can shift to new territories, or gain from changing climate one year and lose the next.

But as ecosystems shift dramatically in response to global warming, the tally of winners and losers becomes harder to predict.

The light-bellied Brent geese that breed each summer in northeast Canada could become a textbook example, according to a new study in the Journal of Animal Ecology.

Climate change means that nesting mothers breed more successfully in longer, warmer summers. But the latest study suggests that the same high productivity is accompanied by a higher death rate among mothers. That could be because the birds nest on the ground, stay longer in better conditions and become more vulnerable to predators.

In a bad breeding season, mothers abandon nests or do not breed – but they do survive to try again another year.

Climate change

We tend to think of climate change as being all one way, but here we’ve got a population being affected in conflicting ways,” says Ian Cleasby, of the Centre for Ecology and Conservation at the University of Exeter in the UK.

This population is sensitive to changes in adult survival, so the increased breeding may not be enough to offset the loss of more adult females.

Research like this is important because we have to understand how animal populations will respond to the changing climate if we want to make decisions about protecting biodiversity.” Climate News Network

Africa’s dust is a priceless export

dust storm

Scientists show how different the world would be without a sprinkling of the wind-borne African dust that fertilises oceans and forests.

LONDON, 3 December, 2016 − Climate scientists have identified Africa’s single biggest export – the wind-borne dust that fertilises the Amazon forests, nourishes life in the Atlantic ocean and softens the noonday blaze of the sun. And they have calculated its vital role in climate change over the last 23,000 years.

In the words of US oceanographers and Earth scientists, “North Africa exports teragrams of wind-blown mineral aerosol over the tropical North Atlantic each year, with significant climate and biogeochemical impacts.”

A teragram is a million tonnes, and the quantities airlifted into the sky from the Sahara and the Sahel each year by the trade winds and blown abroad would be enough to fill 10 million heavy trucks.

About 11,000 years ago, the continent’s total exports of fine dust began to fall dramatically, the researchers report in Science Advances journal.

Fine particles

The lower levels of fine particles in the sky may have allowed more sunlight to hit the ocean waters, may have warmed surface temperatures by 0.15°C, and may have helped whip up monsoons over North Africa to make the conditions far more temperate than they are today.

“In the tropical ocean, fractions of a degree can cause big differences in precipitation patterns and winds,” says one of the report’s authors, David McGee, assistant professor of paleoclimate and geochronology at the Massachusetts Institute of Technology.

“It does seem like dust variations may have large enough effects that it’s important to know how big those impacts are on past and future climates.”

Researchers have already established the importance of windblown dust, both as a source of mineral nutrient for marine life and for the rainforests of Brazil. Scientists have even identified dust kicked into the air by heavy rain.

“We need to figure out how big those dust impacts are, to understand both past and future climates”

But the latest study focused on the changing pattern of dust delivery from the peak of the last Ice Age to the present, the role it may have played in bygone climate change, and its importance in the human story.

North Africa was once a more temperate and hospitable place. Dr McGee says: “There was also extensive human settlement throughout the Sahara, with lifestyles that would never be possible today.

“Researchers at archaeological sites have found fish hooks and spears in the middle of the Sahara, in places that would be completely uninhabitable today. So there was clearly much more water and precipitation over the Sahara.”

Some of this may be explained by subtle cyclic shifts in the planetary axis, exposing the northern hemisphere to more sunlight, more evaporation and more rainfall over land.

Dust sediments

But climate models suggest that this might not be enough, so the researchers examined dust sediments deposited in the Bahamas over the last 23,000 years to identify the role of dust.

Towards the end of the last Ice Age, 16,000 years ago, African dust exports were twice what they are today. But between 11,000 and 5,000 years ago, Africa exported only about half the dust it airlifts now.

The implication is that wind-blown dust is an important factor in climate science, and even small changes in sea surface temperatures – of the sort that could be attributed to dusty skies – can have big effects on Atlantic winds and African rainfall.

“We’re not saying, the expansion of monsoon rains into the Sahara was caused solely by dust impacts,” Dr McGee says. “We’re saying we need to figure out how big those dust impacts are, to understand both past and future climates.” – Climate News Network

Scientists show how different the world would be without a sprinkling of the wind-borne African dust that fertilises oceans and forests.

LONDON, 3 December, 2016 − Climate scientists have identified Africa’s single biggest export – the wind-borne dust that fertilises the Amazon forests, nourishes life in the Atlantic ocean and softens the noonday blaze of the sun. And they have calculated its vital role in climate change over the last 23,000 years.

In the words of US oceanographers and Earth scientists, “North Africa exports teragrams of wind-blown mineral aerosol over the tropical North Atlantic each year, with significant climate and biogeochemical impacts.”

A teragram is a million tonnes, and the quantities airlifted into the sky from the Sahara and the Sahel each year by the trade winds and blown abroad would be enough to fill 10 million heavy trucks.

About 11,000 years ago, the continent’s total exports of fine dust began to fall dramatically, the researchers report in Science Advances journal.

Fine particles

The lower levels of fine particles in the sky may have allowed more sunlight to hit the ocean waters, may have warmed surface temperatures by 0.15°C, and may have helped whip up monsoons over North Africa to make the conditions far more temperate than they are today.

“In the tropical ocean, fractions of a degree can cause big differences in precipitation patterns and winds,” says one of the report’s authors, David McGee, assistant professor of paleoclimate and geochronology at the Massachusetts Institute of Technology.

“It does seem like dust variations may have large enough effects that it’s important to know how big those impacts are on past and future climates.”

Researchers have already established the importance of windblown dust, both as a source of mineral nutrient for marine life and for the rainforests of Brazil. Scientists have even identified dust kicked into the air by heavy rain.

“We need to figure out how big those dust impacts are, to understand both past and future climates”

But the latest study focused on the changing pattern of dust delivery from the peak of the last Ice Age to the present, the role it may have played in bygone climate change, and its importance in the human story.

North Africa was once a more temperate and hospitable place. Dr McGee says: “There was also extensive human settlement throughout the Sahara, with lifestyles that would never be possible today.

“Researchers at archaeological sites have found fish hooks and spears in the middle of the Sahara, in places that would be completely uninhabitable today. So there was clearly much more water and precipitation over the Sahara.”

Some of this may be explained by subtle cyclic shifts in the planetary axis, exposing the northern hemisphere to more sunlight, more evaporation and more rainfall over land.

Dust sediments

But climate models suggest that this might not be enough, so the researchers examined dust sediments deposited in the Bahamas over the last 23,000 years to identify the role of dust.

Towards the end of the last Ice Age, 16,000 years ago, African dust exports were twice what they are today. But between 11,000 and 5,000 years ago, Africa exported only about half the dust it airlifts now.

The implication is that wind-blown dust is an important factor in climate science, and even small changes in sea surface temperatures – of the sort that could be attributed to dusty skies – can have big effects on Atlantic winds and African rainfall.

“We’re not saying, the expansion of monsoon rains into the Sahara was caused solely by dust impacts,” Dr McGee says. “We’re saying we need to figure out how big those dust impacts are, to understand both past and future climates.” – Climate News Network

Speed of Arctic changes defies scientists

The Arctic climate is changing so quickly that science can barely keep track of what is happening and predict the global consequences, the UN says.

LONDON, 29 September, 2016 In an unusually stark warning a leading international scientific body says the Arctic climate is changing so fast that researchers are struggling to keep up. The changes happening there, it says, are affecting the weather worldwide.

The World Meteorological Organisation (WMO) says: Dramatic and unprecedented warming in the Arctic is driving sea level rise, affecting weather patterns around the world and may trigger even more changes in the climate system.

The rate of change is challenging the current scientific capacity to monitor and predict what is becoming a journey into uncharted territory. 

The WMO is the United Nations’ main agency responsible for weather, climate and water.    

Its president, David Grimes, said: The Arctic is a principal, global driver of the climate system and is undergoing an unprecedented rate of change with consequences far beyond its boundaries.

Arctic collaboration

The changes in the Arctic are serving as a global indicator – like a canary in the coal mine – and are happening at a much faster rate than we would have expected.

He was speaking before addressing the first White House Science Ministerial meeting in Washington DC, held to develop international collaboration on Arctic science.

Climate change is causing global average temperatures to rise: 2014, 2015 and the first eight months of 2016 have all been record-breakers. The Arctic is warming at least twice as fast as the global average, in places even faster: the Canadian town of Inuvik has warmed by almost 4°C since 1948, about four times more than the global figure.

The increasing loss of Arctic sea ice is threatening polar bears across their range; melting sea ice is affecting the Arctic climate in a feedback loop; and scientists expect melting permafrost will release more carbon dioxide and methane

The WMO secretary-general, Petteri Taalas, said the Arctic changes had also been a factor in unusual winter weather patterns in North America and Europe. He said the thawing of the permafrost could release vast quantities of greenhouse gases into the atmosphere.

These are part of the vicious circles of climate change which are the subject of intense scientific research, he said.

The Arctic is a principal, global driver of the climate system and is undergoing an unprecedented rate of change with consequences far beyond its boundaries

Despite its certainty that the Arctic is in trouble, the WMO says it is hard to establish the implications of what is happening there. The Arctic makes up about 4% of the Earth’s surface, but the WMO says it is one of the most data-sparse regions in the world because of its remoteness and previous inaccessibility.

Lack of data and forecasts in the Arctic does impact on the quality of weather forecasts in other parts of the world. 

That’s a worry which is echoed at the other end of the planet. A study led by Dr Julie Jones, from the department of geography at the University of Sheffield, UK, says limited data on Antarctica’s climate is making it difficult for researchers to disentangle changes caused by human activity from natural climate fluctuations.

It was only when regular satellite observations began in 1979 that measurement of surface climate over the Antarctic and the Southern Ocean became possible, says the study, published in the journal Nature Climate Change

To gain a longer view, Dr Jones and her colleagues used a compilation of records from natural archives such as ice cores from the Antarctic ice sheet, which show how the region’s climate has changed over the last 200 years.

Separating signals

They confirmed that human-induced changes have caused the belt of prevailing westerly winds over the Southern Ocean to shift towards Antarctica.

But they conclude that for other changes, including regional warming and sea ice changes, the observations since 1979 are not yet long enough for the signal of human activity to be clearly separated from the strong natural variability.

The shift in the westerly winds has moved rainfall away from southern Australia. This year is set to be the country’s hottest on record.

Dr Jones said: “The Antarctic climate is like a giant jigsaw puzzle with most of the pieces still missing.

“There are some parts of the picture which are clear, particularly the way that climate change is causing westerly winds to shift southwards, but there are still huge gaps that we need to fill in order to fully understand how much human activity is changing weather in the region.” – Climate News Network

The Arctic climate is changing so quickly that science can barely keep track of what is happening and predict the global consequences, the UN says.

LONDON, 29 September, 2016 In an unusually stark warning a leading international scientific body says the Arctic climate is changing so fast that researchers are struggling to keep up. The changes happening there, it says, are affecting the weather worldwide.

The World Meteorological Organisation (WMO) says: Dramatic and unprecedented warming in the Arctic is driving sea level rise, affecting weather patterns around the world and may trigger even more changes in the climate system.

The rate of change is challenging the current scientific capacity to monitor and predict what is becoming a journey into uncharted territory. 

The WMO is the United Nations’ main agency responsible for weather, climate and water.    

Its president, David Grimes, said: The Arctic is a principal, global driver of the climate system and is undergoing an unprecedented rate of change with consequences far beyond its boundaries.

Arctic collaboration

The changes in the Arctic are serving as a global indicator – like a canary in the coal mine – and are happening at a much faster rate than we would have expected.

He was speaking before addressing the first White House Science Ministerial meeting in Washington DC, held to develop international collaboration on Arctic science.

Climate change is causing global average temperatures to rise: 2014, 2015 and the first eight months of 2016 have all been record-breakers. The Arctic is warming at least twice as fast as the global average, in places even faster: the Canadian town of Inuvik has warmed by almost 4°C since 1948, about four times more than the global figure.

The increasing loss of Arctic sea ice is threatening polar bears across their range; melting sea ice is affecting the Arctic climate in a feedback loop; and scientists expect melting permafrost will release more carbon dioxide and methane

The WMO secretary-general, Petteri Taalas, said the Arctic changes had also been a factor in unusual winter weather patterns in North America and Europe. He said the thawing of the permafrost could release vast quantities of greenhouse gases into the atmosphere.

These are part of the vicious circles of climate change which are the subject of intense scientific research, he said.

The Arctic is a principal, global driver of the climate system and is undergoing an unprecedented rate of change with consequences far beyond its boundaries

Despite its certainty that the Arctic is in trouble, the WMO says it is hard to establish the implications of what is happening there. The Arctic makes up about 4% of the Earth’s surface, but the WMO says it is one of the most data-sparse regions in the world because of its remoteness and previous inaccessibility.

Lack of data and forecasts in the Arctic does impact on the quality of weather forecasts in other parts of the world. 

That’s a worry which is echoed at the other end of the planet. A study led by Dr Julie Jones, from the department of geography at the University of Sheffield, UK, says limited data on Antarctica’s climate is making it difficult for researchers to disentangle changes caused by human activity from natural climate fluctuations.

It was only when regular satellite observations began in 1979 that measurement of surface climate over the Antarctic and the Southern Ocean became possible, says the study, published in the journal Nature Climate Change

To gain a longer view, Dr Jones and her colleagues used a compilation of records from natural archives such as ice cores from the Antarctic ice sheet, which show how the region’s climate has changed over the last 200 years.

Separating signals

They confirmed that human-induced changes have caused the belt of prevailing westerly winds over the Southern Ocean to shift towards Antarctica.

But they conclude that for other changes, including regional warming and sea ice changes, the observations since 1979 are not yet long enough for the signal of human activity to be clearly separated from the strong natural variability.

The shift in the westerly winds has moved rainfall away from southern Australia. This year is set to be the country’s hottest on record.

Dr Jones said: “The Antarctic climate is like a giant jigsaw puzzle with most of the pieces still missing.

“There are some parts of the picture which are clear, particularly the way that climate change is causing westerly winds to shift southwards, but there are still huge gaps that we need to fill in order to fully understand how much human activity is changing weather in the region.” – Climate News Network

Antarctic peninsula cools – for now

After warming for nearly 50 years the Antarctic peninsula has begun cooling, though probably not for long, UK scientists say.

LONDON, 21 July, 2016  Life is full of surprises, not least the climate. The Antarctic Peninsula, part of which reported spectacularly high temperatures as recently as last year, is now in a cooling phase.

Scientists from the British Antarctic Survey (BAS), based in Cambridge, UK, www.bas.ac.uk say the warming which occurred on the peninsula from the early 1950s to the late 1990s has paused.

But they say they know at least some of the reasons for the change, and that if greenhouse gas concentrations continue to rise at their current rate, temperatures will increase across the peninsula by several degrees Celsius by the end of this century.

It is the slowing rate of ozone loss and the climate’s natural variability, the researchers say, that were “significant in bringing about the change” to a temporary cooling phase. But temperatures remain higher than measured during the middle of the last century, and glaciers are still retreating. 

“The Antarctic peninsula is one of the most challenging places on Earth on which to identify the causes of decade-to-decade temperature changes“ 

Writing in the journal Nature, researchers from BAS describe how the stabilisation of the ozone hole and changing wind patterns have driven a regional cooling phase that is temporarily masking the warming influence of greenhouse gases.

In the last month, atmospheric levels of carbon dioxide above Antarctica rose past the 400 parts per million (ppm) milestone, contrasting with the pre-industrial level of 280 ppm recorded in Antarctic ice cores.

Average temperatures on the peninsula rose by about 0.5⁰C each decade from the early 1950s until the late 1990s, when the researchers found they began falling at the same rate..  

The lead author, Professor John Turner of BAS, says: “The Antarctic peninsula is one of the most challenging places on Earth on which to identify the causes of decade-to-decade temperature changes.

“The Antarctic peninsula climate system shows large natural variations, which can overwhelm the signals of human-induced global warming . . . Even in a generally warming world, over the next couple of decades, temperatures in this region may go up or down, but our models predict that in the longer term greenhouse gases will lead to an increase in temperatures by the end of the 21st century.”

Warming century

During the last century the temperature rise of up to 0.5⁰C each decade on the peninsula helped to trigger the collapse of ice shelves and caused many glaciers to retreat.  

While sea ice extent around the peninsula fell towards the end of the last century it has been increasing in recent years, particularly in the north-east of the region. The cold easterly winds observed this century have had a greater impact on the region because the sea ice has prevented ocean heat from entering the atmosphere.    

The researchers also looked at a 2,000-year climate reconstruction using the chemical signals in ice cores. This suggested that peninsula warming over the whole twentieth century was unusual, but not unprecedented in the context of two millennia.  

Climate model simulations predict that if greenhouse gas concentrations continue to increase at currently projected rates their warming effect will predominate over natural variability and the cooling effect associated with recovering ozone levels, producing several degrees of warming across the region by the end of this century.

Not surprising

The researchers’ study needs to be seen in context. The area they examined is about 1% of the entire Antarctic continent and is an area roughly the size of England.

Eric J. Steig, of the University of Washington, US, wrote: “Even before Turner and colleagues’ analysis, there was little evidence that the rapid warming in Antarctica falls outside the range of natural variability. . . In short, Turner and co-workers’ findings should not be surprising.”

But the work by the BAS team, if not an outright surprise, is still a valuable reminder that natural limits can vary widely, and that well-intentioned adjustments to the climate in one area (limiting ozone loss, for example, or efforts to reduce air pollution) can have unpredictable consequences elsewhere.

It is a reminder as well that, so far as science can see, the inexorable trend of present fossil fuel use is towards more warming and greater disruption. – Climate News Network

After warming for nearly 50 years the Antarctic peninsula has begun cooling, though probably not for long, UK scientists say.

LONDON, 21 July, 2016  Life is full of surprises, not least the climate. The Antarctic Peninsula, part of which reported spectacularly high temperatures as recently as last year, is now in a cooling phase.

Scientists from the British Antarctic Survey (BAS), based in Cambridge, UK, www.bas.ac.uk say the warming which occurred on the peninsula from the early 1950s to the late 1990s has paused.

But they say they know at least some of the reasons for the change, and that if greenhouse gas concentrations continue to rise at their current rate, temperatures will increase across the peninsula by several degrees Celsius by the end of this century.

It is the slowing rate of ozone loss and the climate’s natural variability, the researchers say, that were “significant in bringing about the change” to a temporary cooling phase. But temperatures remain higher than measured during the middle of the last century, and glaciers are still retreating. 

“The Antarctic peninsula is one of the most challenging places on Earth on which to identify the causes of decade-to-decade temperature changes“ 

Writing in the journal Nature, researchers from BAS describe how the stabilisation of the ozone hole and changing wind patterns have driven a regional cooling phase that is temporarily masking the warming influence of greenhouse gases.

In the last month, atmospheric levels of carbon dioxide above Antarctica rose past the 400 parts per million (ppm) milestone, contrasting with the pre-industrial level of 280 ppm recorded in Antarctic ice cores.

Average temperatures on the peninsula rose by about 0.5⁰C each decade from the early 1950s until the late 1990s, when the researchers found they began falling at the same rate..  

The lead author, Professor John Turner of BAS, says: “The Antarctic peninsula is one of the most challenging places on Earth on which to identify the causes of decade-to-decade temperature changes.

“The Antarctic peninsula climate system shows large natural variations, which can overwhelm the signals of human-induced global warming . . . Even in a generally warming world, over the next couple of decades, temperatures in this region may go up or down, but our models predict that in the longer term greenhouse gases will lead to an increase in temperatures by the end of the 21st century.”

Warming century

During the last century the temperature rise of up to 0.5⁰C each decade on the peninsula helped to trigger the collapse of ice shelves and caused many glaciers to retreat.  

While sea ice extent around the peninsula fell towards the end of the last century it has been increasing in recent years, particularly in the north-east of the region. The cold easterly winds observed this century have had a greater impact on the region because the sea ice has prevented ocean heat from entering the atmosphere.    

The researchers also looked at a 2,000-year climate reconstruction using the chemical signals in ice cores. This suggested that peninsula warming over the whole twentieth century was unusual, but not unprecedented in the context of two millennia.  

Climate model simulations predict that if greenhouse gas concentrations continue to increase at currently projected rates their warming effect will predominate over natural variability and the cooling effect associated with recovering ozone levels, producing several degrees of warming across the region by the end of this century.

Not surprising

The researchers’ study needs to be seen in context. The area they examined is about 1% of the entire Antarctic continent and is an area roughly the size of England.

Eric J. Steig, of the University of Washington, US, wrote: “Even before Turner and colleagues’ analysis, there was little evidence that the rapid warming in Antarctica falls outside the range of natural variability. . . In short, Turner and co-workers’ findings should not be surprising.”

But the work by the BAS team, if not an outright surprise, is still a valuable reminder that natural limits can vary widely, and that well-intentioned adjustments to the climate in one area (limiting ozone loss, for example, or efforts to reduce air pollution) can have unpredictable consequences elsewhere.

It is a reminder as well that, so far as science can see, the inexorable trend of present fossil fuel use is towards more warming and greater disruption. – Climate News Network

Europe’s floods come as no surprise

Scientists have warned that the extra moisture in warmer air will mean more intense rainfall, but floods still leave governments unprepared.

LONDON, 5 June, 2016 – At least 18 people have lost their lives in central Europe as severe floods engulf the continent from France to Ukraine. In Paris the River Seine reached 6.1 metres (20 feet) above normal, and tens of thousands of people have fled their homes.

If the downpours and swollen rivers came as a surprise, they shouldn’t have done. Not only are there historical precedents for disastrous floods. There have been graphic recent warnings too, spelling out the growing likelihood that the warming climate will make bouts of flooding and other extreme weather more frequent. 

Last March a study reported in the journal Nature said climate change was already driving an increase in extremes of rainfall and snowfall across most of the globe, even in arid regions. The study said the trend would continue as the world warmed.

The role of global warming in unusually large rainfall events in countries from the United Kingdom to China has been hotly debated. But this latest study showed that climate change is driving an overall increase in rainfall extremes.

Its lead author, Markus Donat, a climate scientist at the University of New South Wales in Australia, said: “In both wet and dry regions, we see these significant and robust increases in heavy precipitation.”

“It is probably a good idea to invest in infrastructure that helps in dealing with heavier precipitation”

Warm air holds more moisture, and global warming is already increasing the odds of extreme rainfall. “The paper is convincing and provides some useful insights,” said Sonia Seneviratne, a climate scientist at the Swiss Federal Institute of Technology. “What is particularly new in this article is the demonstration of such a signal for observed changes in dry regions.”

The results obtained by Donat and his team suggest that both annual precipitation and extreme precipitation increased by 1–2% per decade in dry regions, with wet areas showing similar increases in the extent of extreme precipitation and smaller increases for annual totals.

Their results are in line with a 2015 study by researchers at the Potsdam Institute for Climate Impact Research (PIK) in Germany, which found that global warming has increased the number of record-breaking rainfall events.

Both studies strengthen predictions by models that more extreme weather is in prospect. Donat said their findings were an alert to governments. In a comment which could have been directed at several European countries, he said: “It is probably a good idea to invest in infrastructure that helps in dealing with heavier precipitation, in particular if you are not yet used to those events.”

Breaking records 

The PIK researchers found that heavy rainfall events setting ever new records had been “increasing strikingly” in the past thirty years. Before 1980 natural variability was enough to explain rainfall fluctuations, they said, but they had detected a clear upward trend in the past few decades towards more unprecedented daily rainfall events.

The researchers said this worldwide increase was consistent with rising global temperatures caused by greenhouse gas emissions from burning fossil fuels. The year 2010 had seen extreme rainfall cause devastating flooding in Pakistan, killing hundreds of people and prompting an outbreak of cholera. There had also been rainstorms in Texas, causing dozens of flash floods.

No fewer than than three supposedly “once-in-a-century” floods occurred in Germany in the space of a couple of years, starting in 1997. “In all of these places, the amount of rain pouring down in one day broke local records – and while each of these individual events has been caused by a number of different factors, we find a clear overall upward trend for these unprecedented hazards”, said the PIK study’s lead author, Jascha Lehmann.

The team found that from 1980 to 2010 there were 12% more of these extreme events than would be expected in what they called “a stationary climate”, one without global warming. In the last year they studied, that increase rose to 26%. – Climate News Network

Scientists have warned that the extra moisture in warmer air will mean more intense rainfall, but floods still leave governments unprepared.

LONDON, 5 June, 2016 – At least 18 people have lost their lives in central Europe as severe floods engulf the continent from France to Ukraine. In Paris the River Seine reached 6.1 metres (20 feet) above normal, and tens of thousands of people have fled their homes.

If the downpours and swollen rivers came as a surprise, they shouldn’t have done. Not only are there historical precedents for disastrous floods. There have been graphic recent warnings too, spelling out the growing likelihood that the warming climate will make bouts of flooding and other extreme weather more frequent. 

Last March a study reported in the journal Nature said climate change was already driving an increase in extremes of rainfall and snowfall across most of the globe, even in arid regions. The study said the trend would continue as the world warmed.

The role of global warming in unusually large rainfall events in countries from the United Kingdom to China has been hotly debated. But this latest study showed that climate change is driving an overall increase in rainfall extremes.

Its lead author, Markus Donat, a climate scientist at the University of New South Wales in Australia, said: “In both wet and dry regions, we see these significant and robust increases in heavy precipitation.”

“It is probably a good idea to invest in infrastructure that helps in dealing with heavier precipitation”

Warm air holds more moisture, and global warming is already increasing the odds of extreme rainfall. “The paper is convincing and provides some useful insights,” said Sonia Seneviratne, a climate scientist at the Swiss Federal Institute of Technology. “What is particularly new in this article is the demonstration of such a signal for observed changes in dry regions.”

The results obtained by Donat and his team suggest that both annual precipitation and extreme precipitation increased by 1–2% per decade in dry regions, with wet areas showing similar increases in the extent of extreme precipitation and smaller increases for annual totals.

Their results are in line with a 2015 study by researchers at the Potsdam Institute for Climate Impact Research (PIK) in Germany, which found that global warming has increased the number of record-breaking rainfall events.

Both studies strengthen predictions by models that more extreme weather is in prospect. Donat said their findings were an alert to governments. In a comment which could have been directed at several European countries, he said: “It is probably a good idea to invest in infrastructure that helps in dealing with heavier precipitation, in particular if you are not yet used to those events.”

Breaking records 

The PIK researchers found that heavy rainfall events setting ever new records had been “increasing strikingly” in the past thirty years. Before 1980 natural variability was enough to explain rainfall fluctuations, they said, but they had detected a clear upward trend in the past few decades towards more unprecedented daily rainfall events.

The researchers said this worldwide increase was consistent with rising global temperatures caused by greenhouse gas emissions from burning fossil fuels. The year 2010 had seen extreme rainfall cause devastating flooding in Pakistan, killing hundreds of people and prompting an outbreak of cholera. There had also been rainstorms in Texas, causing dozens of flash floods.

No fewer than than three supposedly “once-in-a-century” floods occurred in Germany in the space of a couple of years, starting in 1997. “In all of these places, the amount of rain pouring down in one day broke local records – and while each of these individual events has been caused by a number of different factors, we find a clear overall upward trend for these unprecedented hazards”, said the PIK study’s lead author, Jascha Lehmann.

The team found that from 1980 to 2010 there were 12% more of these extreme events than would be expected in what they called “a stationary climate”, one without global warming. In the last year they studied, that increase rose to 26%. – Climate News Network

Climate may have defeated Mongol invaders

Historical research suggests 13th-century climatic change left the grasslands of Hungary unable to provide for the Mongols’ vast invading army and forced their retreat from Europe.

LONDON, 31 May, 2016 – Climate fluctuation not only may have paved the way for Genghis Khan’s conquests of Asia in the 13th century, sudden climatic change may also have halted the Mongol invasion of Europe, according to new research.

Two scholars − one skilled in historical documents and another in interpreting tree rings to deliver weather reports through history − say that cold and heavy snowfalls may have blighted the pastureland of the Great Hungarian Plain in 1242.

This would have produced marshy conditions that would have made it difficult or impossible for 130,000 horsemen to campaign or even survive so far from home.

Genghis Khan’s vast but fleeting empire began in 1206, when the leader united the Mongol tribes, and by 1279 one hitherto impoverished group of nomads had swept across China, Russia, central Asia and Iran. Genghis died in 1227, but by 1242 an army of 130,000 Mongol cavalry had entered Hungary.

On the march

In 2014, a team of US scientists looked at tree ring and other data and found that the explosion of Mongol power from a harsh, dry homeland coincided with a mild climate spell that must have produced good pasture that was ideal for nomads on the march. So conditions made military adventure possible, they hypothesised.

Now Ulf Büntgen, a dendrochronologist at the Swiss Federal Institute for Forest, Snow and Landscape Research, and Nicola Di Cosmo, a historian at the Institute for Advanced Study at Princeton in the US, think that another change in the weather may have saved Europe from the Mongols.

They suggest in the Scientific Reports journal that local climate change may have been behind the sudden and unexplained decision of the Mongol army to withdraw to Russia.

Their study is just the latest in a long list of papers that link social turmoil and collapse of imperial power with changes in climate. Dr Büntgen himself was one of a team that recently linked the turmoil of Europe’s so-called Dark Ages with a Little Ice Age between 556 and 660 AD.

“Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility”

Such arguments are necessarily tentative: history is complex and records unreliable. But the tree ring chronologies from the period tell a story of cold, wet conditions in early 1242, when the seemingly-invincible Mongols crossed the Danube into western Hungary.

But after two months they withdrew, through Serbia and Bulgaria. And although historians have been conjecturing reasons for the retreat for the last 700 years, the Mongol generals left no record or explanation of the decision to leave Hungary alone.

So climate scientists took up the challenge. “Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility, as well as the military effectiveness of the Mongol cavalry, while despoliation and depopulation ostensibly contributed to widespread famine,” the researchers write.

“These circumstances arguably contributed to the determination of the Mongols to abandon Hungary and return to Russia.”

Initial victories

Geography certainly played a part in the Mongol advance. A great stretch of open grassland or steppe links the Mongolian homeland with the Hungarian plain, and the invaders entered Europe through the Carpathians to win convincing initial victories.

Hungary’s King Bela IV fled to Austria and the Mongol cavalry pursued him to the Dalmatian coast, and seemed to prepare for a long campaign. And then, abruptly, the Mongols departed. Some believe it may have been because of the death of the Great Khan’s successor in 1241; others believe that the Mongols were really pursuing another set of nomads, the Cumans.

But medieval armies provided for themselves only by forage and pillage, and there is also evidence that, given the climate conditions, the grasslands of Hungary could not have provided for so vast an army.

This is not the kind of debate that could ever be satisfactorily concluded, but authors of the Scientific Reports study are content that climate aspects may have played a part and contributed to withdrawal.

“Our ‘environmental hypothesis’ demonstrates the importance of minor climatic fluctuations on major historical events,” they write. – Climate News Network

Historical research suggests 13th-century climatic change left the grasslands of Hungary unable to provide for the Mongols’ vast invading army and forced their retreat from Europe.

LONDON, 31 May, 2016 – Climate fluctuation not only may have paved the way for Genghis Khan’s conquests of Asia in the 13th century, sudden climatic change may also have halted the Mongol invasion of Europe, according to new research.

Two scholars − one skilled in historical documents and another in interpreting tree rings to deliver weather reports through history − say that cold and heavy snowfalls may have blighted the pastureland of the Great Hungarian Plain in 1242.

This would have produced marshy conditions that would have made it difficult or impossible for 130,000 horsemen to campaign or even survive so far from home.

Genghis Khan’s vast but fleeting empire began in 1206, when the leader united the Mongol tribes, and by 1279 one hitherto impoverished group of nomads had swept across China, Russia, central Asia and Iran. Genghis died in 1227, but by 1242 an army of 130,000 Mongol cavalry had entered Hungary.

On the march

In 2014, a team of US scientists looked at tree ring and other data and found that the explosion of Mongol power from a harsh, dry homeland coincided with a mild climate spell that must have produced good pasture that was ideal for nomads on the march. So conditions made military adventure possible, they hypothesised.

Now Ulf Büntgen, a dendrochronologist at the Swiss Federal Institute for Forest, Snow and Landscape Research, and Nicola Di Cosmo, a historian at the Institute for Advanced Study at Princeton in the US, think that another change in the weather may have saved Europe from the Mongols.

They suggest in the Scientific Reports journal that local climate change may have been behind the sudden and unexplained decision of the Mongol army to withdraw to Russia.

Their study is just the latest in a long list of papers that link social turmoil and collapse of imperial power with changes in climate. Dr Büntgen himself was one of a team that recently linked the turmoil of Europe’s so-called Dark Ages with a Little Ice Age between 556 and 660 AD.

“Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility”

Such arguments are necessarily tentative: history is complex and records unreliable. But the tree ring chronologies from the period tell a story of cold, wet conditions in early 1242, when the seemingly-invincible Mongols crossed the Danube into western Hungary.

But after two months they withdrew, through Serbia and Bulgaria. And although historians have been conjecturing reasons for the retreat for the last 700 years, the Mongol generals left no record or explanation of the decision to leave Hungary alone.

So climate scientists took up the challenge. “Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility, as well as the military effectiveness of the Mongol cavalry, while despoliation and depopulation ostensibly contributed to widespread famine,” the researchers write.

“These circumstances arguably contributed to the determination of the Mongols to abandon Hungary and return to Russia.”

Initial victories

Geography certainly played a part in the Mongol advance. A great stretch of open grassland or steppe links the Mongolian homeland with the Hungarian plain, and the invaders entered Europe through the Carpathians to win convincing initial victories.

Hungary’s King Bela IV fled to Austria and the Mongol cavalry pursued him to the Dalmatian coast, and seemed to prepare for a long campaign. And then, abruptly, the Mongols departed. Some believe it may have been because of the death of the Great Khan’s successor in 1241; others believe that the Mongols were really pursuing another set of nomads, the Cumans.

But medieval armies provided for themselves only by forage and pillage, and there is also evidence that, given the climate conditions, the grasslands of Hungary could not have provided for so vast an army.

This is not the kind of debate that could ever be satisfactorily concluded, but authors of the Scientific Reports study are content that climate aspects may have played a part and contributed to withdrawal.

“Our ‘environmental hypothesis’ demonstrates the importance of minor climatic fluctuations on major historical events,” they write. – Climate News Network

Dead zones devour oceans’ oxygen

Marine life faces increased threats as researchers warn that warmer waters caused by climate change could seriously reduce the levels of oxygen in the world’s seas.

LONDON, 4 May, 2016 – Scientists in the US have identified a new hazard in a world in which the climates change and the oceans warm: measurable stretches of the seas could become sapped of oxygen.

They say that parts of the southern Indian Ocean, the eastern tropical Pacific and the Atlantic are already less oxygen-rich because of global warming. And oxygen deprivation could become increasingly widespread across large regions of ocean between 2030 and 2040.

Anyone who has ever kept a home aquarium knows that, in the summer, the fish in the tank are more likely to be seen gasping nearer the surface. That is because the colder the water, the greater its capacity for dissolved oxygen.

Chemistry change

Growing concentrations in the atmosphere of the greenhouse gas carbon dioxide have begun to change the ocean chemistry, making sea water gradually and alarmingly more acidic and less hospitable to many of the species adapted to ocean life.

Now Matthew Long, an oceanographer at the US National Centre for Atmospheric Research in Boulder, Colorado and colleagues report in Global Biogeochemical Cycles journal that they repeatedly modelled changes in the ocean’s oxygen content over the years 1920 to 2100.

“This new study tells us when we can expect
the impact from climate change to overwhelm
the natural variability”

Oxygen from the atmosphere gets into the sea only when it dissolves directly, or is released by photosynthesising marine plants and phytoplankton. The warmer the water, the harder life is for the creatures nearer the surface.

To make things more difficult, warmer waters are less dense, making them less likely to sink and bring the colder, more oxygen-rich waters to the surface. In unusually hot weather, “dead zones” appear in the seas, where fish and shellfish cannot survive.

The researchers warn that there will be more of these as global temperatures continue to rise. “Loss of oxygen in the ocean is one of the serious side-effects of a warming atmosphere, and a major threat to marine life,” Dr Long says.

Swiftly detectable

“Since oxygen concentrations in the ocean naturally vary, depending on variations in winds and temperature at the surface, it’s been challenging to attribute any deoxygenation to climate change. This new study tells us when we can expect the impact from climate change to overwhelm the natural variability.”

The new map suggests that even by 2100, some waters – off the east coasts of Africa and Australia and Southeast Asia, and parts of the South Atlantic, for instance – will remain oxygen-rich. But oxygen loss due to climate change will become detectable much more swiftly in northern waters in the Pacific, and parts of the Atlantic.

There are uncertainties. Oxygen measurements in the world’s oceans − and 70% of the planet is covered by blue water – are relatively sparse.

“We need comprehensive and sustained observations of what’s going on in the oceans to compare with what we’re learning from our models, and to understand the full impact of a changing climate,” Dr Long says. – Climate News Network

Marine life faces increased threats as researchers warn that warmer waters caused by climate change could seriously reduce the levels of oxygen in the world’s seas.

LONDON, 4 May, 2016 – Scientists in the US have identified a new hazard in a world in which the climates change and the oceans warm: measurable stretches of the seas could become sapped of oxygen.

They say that parts of the southern Indian Ocean, the eastern tropical Pacific and the Atlantic are already less oxygen-rich because of global warming. And oxygen deprivation could become increasingly widespread across large regions of ocean between 2030 and 2040.

Anyone who has ever kept a home aquarium knows that, in the summer, the fish in the tank are more likely to be seen gasping nearer the surface. That is because the colder the water, the greater its capacity for dissolved oxygen.

Chemistry change

Growing concentrations in the atmosphere of the greenhouse gas carbon dioxide have begun to change the ocean chemistry, making sea water gradually and alarmingly more acidic and less hospitable to many of the species adapted to ocean life.

Now Matthew Long, an oceanographer at the US National Centre for Atmospheric Research in Boulder, Colorado and colleagues report in Global Biogeochemical Cycles journal that they repeatedly modelled changes in the ocean’s oxygen content over the years 1920 to 2100.

“This new study tells us when we can expect
the impact from climate change to overwhelm
the natural variability”

Oxygen from the atmosphere gets into the sea only when it dissolves directly, or is released by photosynthesising marine plants and phytoplankton. The warmer the water, the harder life is for the creatures nearer the surface.

To make things more difficult, warmer waters are less dense, making them less likely to sink and bring the colder, more oxygen-rich waters to the surface. In unusually hot weather, “dead zones” appear in the seas, where fish and shellfish cannot survive.

The researchers warn that there will be more of these as global temperatures continue to rise. “Loss of oxygen in the ocean is one of the serious side-effects of a warming atmosphere, and a major threat to marine life,” Dr Long says.

Swiftly detectable

“Since oxygen concentrations in the ocean naturally vary, depending on variations in winds and temperature at the surface, it’s been challenging to attribute any deoxygenation to climate change. This new study tells us when we can expect the impact from climate change to overwhelm the natural variability.”

The new map suggests that even by 2100, some waters – off the east coasts of Africa and Australia and Southeast Asia, and parts of the South Atlantic, for instance – will remain oxygen-rich. But oxygen loss due to climate change will become detectable much more swiftly in northern waters in the Pacific, and parts of the Atlantic.

There are uncertainties. Oxygen measurements in the world’s oceans − and 70% of the planet is covered by blue water – are relatively sparse.

“We need comprehensive and sustained observations of what’s going on in the oceans to compare with what we’re learning from our models, and to understand the full impact of a changing climate,” Dr Long says. – Climate News Network

Plants’ heat response means fiercer heatwaves

Asia faces more extreme heat by mid-century as some plant species react unexpectedly to rising average temperatures, new research shows.

LONDON, 28 March, 2016 – Tomorrow’s heat waves could be even hotter than climate scientists have so far predicted. Maximum temperatures across the Asian continent from Europe to China could be 3°C to 5°C higher than previous estimates – because the forests and grasslands will respond in a different way.

Australian scientists report in the journal Scientific Reports that they looked at the forecasts made by the Intergovernmental Panel on Climate Change under the notorious “business-as-usual” scenario, in which the world’s nations go on burning ever more fossil fuels, to release ever more greenhouse gases.

The average global temperatures will rise steadily – but this rise will be accompanied by ever greater and more frequent extremes of heat.

But then Jatin Kala of Murdoch University in Perth, Western Australia, and colleagues factored in the responses of the plants to rising temperatures.

They looked at data from 314 species of plant from 54 research field sites. In particular, they investigated stomatas, tiny pores on the leaves through which plants absorb carbon dioxide and shed water to the atmosphere.

Response crucial

What matters is how vegetation responds to extremes of heat. Researchers have already established that plants respond, not always helpfully: extremes can alter the atmospheric chemistry unfavourably for plants, and certainly reduce crop yields

But other scientists have confirmed the so-called carbon dioxide fertilisation effect: as more carbon becomes available, plants use water more economically and so even though drylands may get drier the landscape can also get greener, and growth tends to begin ever earlier as winters get warmer, and spring arrives earlier.

Dr Kala and his fellow researchers used their field observation data to model the response of species, and types of plants, to higher temperatures, and to make some estimates of the balance of carbon taken up by the stomata, and the water released.

There has been an assumption that plants respond to temperature in roughly the same way. But there can be considerable variation.

The scientists found, overall, that the response of the plants became increasingly important: over Eurasia – they decided not to model the pattern in North America because cloudiness introduced extra uncertainties – needleleaf forests, tundra and farmland would actually release lower levels of water into the atmosphere.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures”

And since water in the atmosphere helps lower the daytime temperatures, this means that the temperatures would rise even higher than the models suggest.

“We often underestimate the role of vegetation in extreme temperature events as it has not been included in enough detail in climate models up to this point,” Dr Kala said.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures when compared to observations.”

Unexpected results invite challenge. The test will be in the replication of the findings by other groups of scientists. And the Australian scientists intend to pursue the questions too. But they see their work as one of the rewards of the interdisciplinary approach: the marriage of ecology and climate simulation.

Surprise findings

Belinda Medlyn, a theoretical biologist at Western Sydney University, and a co-author, said: “Our study of stomata was originally intended just to learn more about how plants work. We were not really expecting to find these important implications for heat waves.”

The part played by the vegetation would not affect either the frequency or the duration of the heat waves. But the traffic between stomata and atmosphere could certainly affect their intensity.

The bottom line is, the scientists conclude, that there could be increases of 5°C by 2040 to 2059, and these increases would be “additive to those likely caused by increasing greenhouse gases over the same period.” – Climate News Network

Asia faces more extreme heat by mid-century as some plant species react unexpectedly to rising average temperatures, new research shows.

LONDON, 28 March, 2016 – Tomorrow’s heat waves could be even hotter than climate scientists have so far predicted. Maximum temperatures across the Asian continent from Europe to China could be 3°C to 5°C higher than previous estimates – because the forests and grasslands will respond in a different way.

Australian scientists report in the journal Scientific Reports that they looked at the forecasts made by the Intergovernmental Panel on Climate Change under the notorious “business-as-usual” scenario, in which the world’s nations go on burning ever more fossil fuels, to release ever more greenhouse gases.

The average global temperatures will rise steadily – but this rise will be accompanied by ever greater and more frequent extremes of heat.

But then Jatin Kala of Murdoch University in Perth, Western Australia, and colleagues factored in the responses of the plants to rising temperatures.

They looked at data from 314 species of plant from 54 research field sites. In particular, they investigated stomatas, tiny pores on the leaves through which plants absorb carbon dioxide and shed water to the atmosphere.

Response crucial

What matters is how vegetation responds to extremes of heat. Researchers have already established that plants respond, not always helpfully: extremes can alter the atmospheric chemistry unfavourably for plants, and certainly reduce crop yields

But other scientists have confirmed the so-called carbon dioxide fertilisation effect: as more carbon becomes available, plants use water more economically and so even though drylands may get drier the landscape can also get greener, and growth tends to begin ever earlier as winters get warmer, and spring arrives earlier.

Dr Kala and his fellow researchers used their field observation data to model the response of species, and types of plants, to higher temperatures, and to make some estimates of the balance of carbon taken up by the stomata, and the water released.

There has been an assumption that plants respond to temperature in roughly the same way. But there can be considerable variation.

The scientists found, overall, that the response of the plants became increasingly important: over Eurasia – they decided not to model the pattern in North America because cloudiness introduced extra uncertainties – needleleaf forests, tundra and farmland would actually release lower levels of water into the atmosphere.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures”

And since water in the atmosphere helps lower the daytime temperatures, this means that the temperatures would rise even higher than the models suggest.

“We often underestimate the role of vegetation in extreme temperature events as it has not been included in enough detail in climate models up to this point,” Dr Kala said.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures when compared to observations.”

Unexpected results invite challenge. The test will be in the replication of the findings by other groups of scientists. And the Australian scientists intend to pursue the questions too. But they see their work as one of the rewards of the interdisciplinary approach: the marriage of ecology and climate simulation.

Surprise findings

Belinda Medlyn, a theoretical biologist at Western Sydney University, and a co-author, said: “Our study of stomata was originally intended just to learn more about how plants work. We were not really expecting to find these important implications for heat waves.”

The part played by the vegetation would not affect either the frequency or the duration of the heat waves. But the traffic between stomata and atmosphere could certainly affect their intensity.

The bottom line is, the scientists conclude, that there could be increases of 5°C by 2040 to 2059, and these increases would be “additive to those likely caused by increasing greenhouse gases over the same period.” – Climate News Network

Rising seas slow the planet’s yearly journey

US scientists say climate change affects the speed at which the Earth circles the Sun and even the length of a terrestrial day.

LONDON, 17 December, 2015 – Scientists may be about to resolve one of the trickiest – and least obvious – questions of climate change: its effect on the rotation of the planet, and therefore on the length of the day.

That doesn’t mean scientists have an answer, and if they get one, it is likely to  be measured in units of time that are vanishingly small. But even if the answer is insignificant, the attempt to resolve the question is a measure of the intricacy, impact and reach of global warming as a consequence of the human combustion of fossil fuels: it even affects the axis of the planet, and it changes our days.

Jerry Mitrovica, a planetary scientist at Harvard University, and colleagues report in the journal Science Advances that they have managed to make a connection between global sea level rises of the past and the rotation of the Earth on its year-long journey around the Sun.

More precisely, they have addressed a 13-year-old puzzle known as Munk’s enigma. This study raised a simple question that cannot be answered simply: if changes on the Earth’s surface slow its rotation, surely it should be possible to detect the contribution of sea level rise?

Almost anything can affect the rotation of the planet: the 2011 Tohoku earthquake and tsunami shortened the day by 1.8 millionths of a second, but the advance and retreat of the ice ages would also have altered the clocks, had there been any clocks at the time, and the daily ocean tides have for billions of years been making the day drag on.

Fossil corals reveal that a year in the Devonian period 400 million years ago lasted more than 400 days. Now there are only 365 and a bit. 

Slowing down

Astronomers have checked ancient Babylonian, Chinese, Greek and Arab records of solar eclipses and used them to make a relatively precise calculation of the rate at which the Earth’s rotation has slowed.

They have arrived at an answer: since 500 BC, Earth time and universal time have diverged by 16,000 seconds, or 4.5 hours.

The measurement of time is one of mankind’s oldest headaches, and remains one, because the second is by its first definition a division of the minute and the hour, and a day is defined as 24 hours, and this means that if the Earth slows, the day gets longer, and so does the second.

That is why astronomers agreed to fix the second at a precise division of the year 1820, and call that universal time. And then when that wasn’t precise enough, they fixed it to the number of vibrations in a caesium-133 atom at a precise temperature.

But that then divorced the second from the 24 hours of the day. Which is why, every so often – the latest was in July 2015 – the time lords of the international scientific bureaucracy had to insert a leap second to keep universal and terrestrial time in step.

Since 1972 there have been a total of 26 leap seconds to keep the two ways of measuring time in synchronicity.

Then in 2002 Walter Munk of the Scripps Institution of Oceanography in San Diego put the question: if 40,000 billion tons of ice turned into  rising sea levels, and were changing the axis and rotation of the planet, could the effect be measured? And since it could not be measured accurately, why not?

Re-examination required

The Harvard authors now think they have an answer: the estimates on which Munk’s paper was based need to be re-examined. This re-examination involves geophysics, archaeo-astronomy and micro-measurement.

It involves dynamic processes far below the Earth’s crust, as well as a new and closer look at the message from the ancient observations of eclipse, and more detailed scrutiny of the data of sea level rise.

That doesn’t mean they have an answer to the effect of climate change upon the rotation of the Earth but, when they do, it is likely to be measured in millionths of a second per year.

So people need not adjust their watches. But the study is an indicator of the sheer range of questions raised in pursuit of the wider understanding of the science of global climate. And there may even be a pay-off in terms of more accurate climate prediction.

The Harvard team conclude: “Confronting Munk’s elegant statement of the enigma has thus improved our understanding of Earth’s rotation spanning the last three millennia and the individual sources of sea-level rise in the century before the early 1990s.

“The reconciliation also adds confidence to ongoing efforts to project this rise to the end of the current century and beyond.” – Climate News Network

US scientists say climate change affects the speed at which the Earth circles the Sun and even the length of a terrestrial day.

LONDON, 17 December, 2015 – Scientists may be about to resolve one of the trickiest – and least obvious – questions of climate change: its effect on the rotation of the planet, and therefore on the length of the day.

That doesn’t mean scientists have an answer, and if they get one, it is likely to  be measured in units of time that are vanishingly small. But even if the answer is insignificant, the attempt to resolve the question is a measure of the intricacy, impact and reach of global warming as a consequence of the human combustion of fossil fuels: it even affects the axis of the planet, and it changes our days.

Jerry Mitrovica, a planetary scientist at Harvard University, and colleagues report in the journal Science Advances that they have managed to make a connection between global sea level rises of the past and the rotation of the Earth on its year-long journey around the Sun.

More precisely, they have addressed a 13-year-old puzzle known as Munk’s enigma. This study raised a simple question that cannot be answered simply: if changes on the Earth’s surface slow its rotation, surely it should be possible to detect the contribution of sea level rise?

Almost anything can affect the rotation of the planet: the 2011 Tohoku earthquake and tsunami shortened the day by 1.8 millionths of a second, but the advance and retreat of the ice ages would also have altered the clocks, had there been any clocks at the time, and the daily ocean tides have for billions of years been making the day drag on.

Fossil corals reveal that a year in the Devonian period 400 million years ago lasted more than 400 days. Now there are only 365 and a bit. 

Slowing down

Astronomers have checked ancient Babylonian, Chinese, Greek and Arab records of solar eclipses and used them to make a relatively precise calculation of the rate at which the Earth’s rotation has slowed.

They have arrived at an answer: since 500 BC, Earth time and universal time have diverged by 16,000 seconds, or 4.5 hours.

The measurement of time is one of mankind’s oldest headaches, and remains one, because the second is by its first definition a division of the minute and the hour, and a day is defined as 24 hours, and this means that if the Earth slows, the day gets longer, and so does the second.

That is why astronomers agreed to fix the second at a precise division of the year 1820, and call that universal time. And then when that wasn’t precise enough, they fixed it to the number of vibrations in a caesium-133 atom at a precise temperature.

But that then divorced the second from the 24 hours of the day. Which is why, every so often – the latest was in July 2015 – the time lords of the international scientific bureaucracy had to insert a leap second to keep universal and terrestrial time in step.

Since 1972 there have been a total of 26 leap seconds to keep the two ways of measuring time in synchronicity.

Then in 2002 Walter Munk of the Scripps Institution of Oceanography in San Diego put the question: if 40,000 billion tons of ice turned into  rising sea levels, and were changing the axis and rotation of the planet, could the effect be measured? And since it could not be measured accurately, why not?

Re-examination required

The Harvard authors now think they have an answer: the estimates on which Munk’s paper was based need to be re-examined. This re-examination involves geophysics, archaeo-astronomy and micro-measurement.

It involves dynamic processes far below the Earth’s crust, as well as a new and closer look at the message from the ancient observations of eclipse, and more detailed scrutiny of the data of sea level rise.

That doesn’t mean they have an answer to the effect of climate change upon the rotation of the Earth but, when they do, it is likely to be measured in millionths of a second per year.

So people need not adjust their watches. But the study is an indicator of the sheer range of questions raised in pursuit of the wider understanding of the science of global climate. And there may even be a pay-off in terms of more accurate climate prediction.

The Harvard team conclude: “Confronting Munk’s elegant statement of the enigma has thus improved our understanding of Earth’s rotation spanning the last three millennia and the individual sources of sea-level rise in the century before the early 1990s.

“The reconciliation also adds confidence to ongoing efforts to project this rise to the end of the current century and beyond.” – Climate News Network