Tag Archives: Warming

Heat

Climate heating just makes things hotter still

August 13th, 2021, by Tim Radford

The past has an uncomfortable lesson for a warming world: climate heating begets even more of the same.

LONDON, 13 August, 2021 − Climate heating has a way of making the globe even hotter. As higher temperatures kick in, there is a pronounced planetary tendency to send the mercury rising even further.

And − on the evidence of the last 66 million years − this is a process that doesn’t even need human help. Some kind of warming bias seems to have been baked into the climate machinery, according to a new study.

And if the warming process gets a bit of help from humankind in the form of greenhouse gases from fossil fuel combustion, natural planetary ecosystems and global geochemistry could augment the process and take it a lot further.

“The northern hemisphere’s ice sheets are shrinking, and could potentially disappear as a long-term consequence of human actions,” said Constantin Arnscheidt of the Massachusetts Institute of Technology, who led the research outlined in the journal Science Advances.

“Our research suggests that this may make the Earth’s climate fundamentally more susceptible to extreme, long-term global warming events such as those seen in the geologic past.”

Continuous cycle

It’s not a new idea. Researchers have been saying for decades that as the polar ice retreats, more open sea and rock is exposed. Ice and snow reflect radiation, dark rock and blue sea absorb it, to amplify warming and accelerate climate change.

As the permafrost thaws, long-buried plant remains begin to surrender methane and carbon dioxide into the atmosphere, to speed up the thaw even more. As forests − vast stores of atmospheric carbon − become hotter and more drought-stricken, they are at risk of fire, which puts even more greenhouse gas  back into the atmosphere to warm the world even more intensely.

But these have all been warnings: what two researchers at MIT did was to look at the tell-tale patterns of climate change deep in prehistory. Because fossil evidence tells a reliable story of past climates, they could study changes in the composition of the shells of foraminifera preserved in ocean sediments.

These identified a continuous cycle of temperature rise and fall and, in particular, the way temperature rose during the aeons that followed the extinction of the dinosaurs at the close of the Cretaceous.

The researchers found the curve of warming and cooling was more skewed to warm events than cool ones: warm events tended to be of a more extreme temperature than the most extreme cool spells. Sometimes the planetary climate changed dramatically, to bring crocodiles to Arctic waters, and forests to Antarctica.

“This may make the Earth’s climate fundamentally more susceptible to extreme, long-term global warming events such as those seen in the geologic past”

The researchers call this a multiplier effect: increases in temperature bias the climate system towards even more increases.

The study may throw additional light on an enduring climate puzzle: the pattern of temperature for much of the Earth’s history can be matched to the pattern of cyclic shifts in the planetary orbit around the sun, over hundreds of thousands of years.

But these changes are themselves tiny. The multiplier effect could explain why they jolt the planet’s climate into a new regime.

“Climate warms and cools in synchrony with orbital changes, but the orbital cycles themselves would predict only modest changes in climate. But if we consider a multiplicative model, then modest warming, paired with this multiplier effect, can result in extreme events that tend to occur at the same times as these orbital changes,” said Daniel Rothman, a geophysicist at MIT, and a co-author.

And Constantin Arnscheidt said: “Humans are forcing the system in a new way. And this study is showing that, when we increase extreme temperature, we’re likely going to interact with these natural, amplifying effects.” − Climate News Network

The past has an uncomfortable lesson for a warming world: climate heating begets even more of the same.

LONDON, 13 August, 2021 − Climate heating has a way of making the globe even hotter. As higher temperatures kick in, there is a pronounced planetary tendency to send the mercury rising even further.

And − on the evidence of the last 66 million years − this is a process that doesn’t even need human help. Some kind of warming bias seems to have been baked into the climate machinery, according to a new study.

And if the warming process gets a bit of help from humankind in the form of greenhouse gases from fossil fuel combustion, natural planetary ecosystems and global geochemistry could augment the process and take it a lot further.

“The northern hemisphere’s ice sheets are shrinking, and could potentially disappear as a long-term consequence of human actions,” said Constantin Arnscheidt of the Massachusetts Institute of Technology, who led the research outlined in the journal Science Advances.

“Our research suggests that this may make the Earth’s climate fundamentally more susceptible to extreme, long-term global warming events such as those seen in the geologic past.”

Continuous cycle

It’s not a new idea. Researchers have been saying for decades that as the polar ice retreats, more open sea and rock is exposed. Ice and snow reflect radiation, dark rock and blue sea absorb it, to amplify warming and accelerate climate change.

As the permafrost thaws, long-buried plant remains begin to surrender methane and carbon dioxide into the atmosphere, to speed up the thaw even more. As forests − vast stores of atmospheric carbon − become hotter and more drought-stricken, they are at risk of fire, which puts even more greenhouse gas  back into the atmosphere to warm the world even more intensely.

But these have all been warnings: what two researchers at MIT did was to look at the tell-tale patterns of climate change deep in prehistory. Because fossil evidence tells a reliable story of past climates, they could study changes in the composition of the shells of foraminifera preserved in ocean sediments.

These identified a continuous cycle of temperature rise and fall and, in particular, the way temperature rose during the aeons that followed the extinction of the dinosaurs at the close of the Cretaceous.

The researchers found the curve of warming and cooling was more skewed to warm events than cool ones: warm events tended to be of a more extreme temperature than the most extreme cool spells. Sometimes the planetary climate changed dramatically, to bring crocodiles to Arctic waters, and forests to Antarctica.

“This may make the Earth’s climate fundamentally more susceptible to extreme, long-term global warming events such as those seen in the geologic past”

The researchers call this a multiplier effect: increases in temperature bias the climate system towards even more increases.

The study may throw additional light on an enduring climate puzzle: the pattern of temperature for much of the Earth’s history can be matched to the pattern of cyclic shifts in the planetary orbit around the sun, over hundreds of thousands of years.

But these changes are themselves tiny. The multiplier effect could explain why they jolt the planet’s climate into a new regime.

“Climate warms and cools in synchrony with orbital changes, but the orbital cycles themselves would predict only modest changes in climate. But if we consider a multiplicative model, then modest warming, paired with this multiplier effect, can result in extreme events that tend to occur at the same times as these orbital changes,” said Daniel Rothman, a geophysicist at MIT, and a co-author.

And Constantin Arnscheidt said: “Humans are forcing the system in a new way. And this study is showing that, when we increase extreme temperature, we’re likely going to interact with these natural, amplifying effects.” − Climate News Network

Emissions, Oceans

Ancient sea level rises may have been fairly minimal

August 12th, 2021, by Tim Radford

Maybe ancient sea level rises were not so dramatic. But they’d still have been pretty frightening.

LONDON, 12 August, 2021 − Earth scientists have measured the rising tides of a warmer world more than 100 millennia ago and found a glimmer of good news: ancient sea level rises during a warm spell in the last Ice Age were quite possibly only about 1.2 metres higher than they are today.

Since, between 128,000 and 117,000 years ago, the world was perhaps as much as 2°C warmer than it would become for most of human history, this really is encouraging. Right now, climate scientists project a rise of somewhere between 60cm and 1.5m later this century, as global temperature levels rise 2°C or more above those normal before the Industrial Revolution.

But until now, geological orthodoxy has proposed that during the last “interglacial” or sudden warming, sea levels rose by six metres or possibly even nine metres. This could only happen if the Antarctic or Greenland ice sheets had collapsed.

And although these are indeed already losing ice at an accelerating rate, it doesn’t seem possible for such a colossal quantity of ice to melt in only a handful of decades.

Missing factor

So there was a mismatch between the predictions of the world’s scientists and the apparent evidence from the past.

Now a new study in the Proceedings of the National Academy of Sciences offers a solution: calculations about past sea level heights may have been perhaps too gloomy because they did not fully factor in sea level’s other great uncertainty — the movement of the continents lapped by the sea.

This bedevils all predictions about sea level rise. Seas rise and fall with global temperatures, but so do landmasses. Right now, although sea level is creeping up at a rate measured in millimetres per year, the land under a number of great coastal cities is sinking dramatically, as humans build  ever more massive cities and abstract ever more groundwater. So predictions warn that millions could be at risk of coastal flooding.

But there is another, deeper reason for the uncertainty: as rising temperatures remove the massive burden of ice from glaciated land, and wind and rain erode mountains, so the subterranean rocks in the Earth’s mantle, far below the crust, respond by inching upwards. Even the seemingly solid rocks are elastic, subsiding under pressure and rising when the mass is removed.

“Models of ice sheets are still in their toddlerhood”

All this means that, unless researchers can make an accurate estimate of land movement as well, sea level estimates are riven with uncertainties.

So a team from Columbia University in the US has looked at evidence of sea level rise and fall preserved in fossilised reefs and dunes in just one 1200km chain of islands − the Bahamas in the Atlantic − to come up with a new set of projections.

In the next 100 years, sea levels will rise by about 1.2 metres. This could be too modest: sea levels could just possibly rise by perhaps 5.3 metres, but this doesn’t seem likely. And a nine-metre rise is highly improbable.

“To get to nine metres of sea level rise, you’d have to melt large parts of Greenland and Antarctica,” said Blake Dyer, of the university’s Lamont-Doherty Earth Observatory.

Tricky calculation

“This suggests that didn’t happen. So maybe we should feel not so bad about the future. On the other hand, our lower estimate is bad, and our upper one is really bad.”

At the heart of the puzzle is a phenomenon known to geophysicists as isostasy: vast tracts of continental landmass have been heaving up and down, imperceptibly, over periods of tens of thousands of years, in response to ice and erosion.

So calculating sea level rise and fall when the thing on which sea level measurements are recorded − the land − is itself always shifting becomes tricky. That has always been why climate projections of sea levels contain a range of forecasts, rather than a hard number.

The argument is that changes recorded along the north-south lie of the Bahamas would provide a new and more sophisticated way of reconstructing sea heights in the relatively recent past.

Melting not guaranteed

The study doesn’t settle the question: estimates of past sea level change on a dramatic scale come from many parts of the planet, and glaciologists still have to reconstruct the rate at which the northern ice, for instance, may have retreated while the southern ice cap continued to advance during the last interglacial: that too would have limited sea level rise.

“This is still a question. Models of ice sheets are still in their toddlerhood,” said Maureen Raymo, director of the Earth Observatory and a co-author.

Human carbon emissions are now heating the globe far more rapidly and evenly than during the last interglacial, so there is no guarantee of any melting at different rates in two hemispheres

“That makes it more difficult to apply the results to today. The easy thing to say would be, ‘Oh we showed that sea levels were not so bad, and that’s terrific.’  The harder answer, the more honest answer, is that maybe things were different then, and we’re not in the clear.” − Climate News Network

Maybe ancient sea level rises were not so dramatic. But they’d still have been pretty frightening.

LONDON, 12 August, 2021 − Earth scientists have measured the rising tides of a warmer world more than 100 millennia ago and found a glimmer of good news: ancient sea level rises during a warm spell in the last Ice Age were quite possibly only about 1.2 metres higher than they are today.

Since, between 128,000 and 117,000 years ago, the world was perhaps as much as 2°C warmer than it would become for most of human history, this really is encouraging. Right now, climate scientists project a rise of somewhere between 60cm and 1.5m later this century, as global temperature levels rise 2°C or more above those normal before the Industrial Revolution.

But until now, geological orthodoxy has proposed that during the last “interglacial” or sudden warming, sea levels rose by six metres or possibly even nine metres. This could only happen if the Antarctic or Greenland ice sheets had collapsed.

And although these are indeed already losing ice at an accelerating rate, it doesn’t seem possible for such a colossal quantity of ice to melt in only a handful of decades.

Missing factor

So there was a mismatch between the predictions of the world’s scientists and the apparent evidence from the past.

Now a new study in the Proceedings of the National Academy of Sciences offers a solution: calculations about past sea level heights may have been perhaps too gloomy because they did not fully factor in sea level’s other great uncertainty — the movement of the continents lapped by the sea.

This bedevils all predictions about sea level rise. Seas rise and fall with global temperatures, but so do landmasses. Right now, although sea level is creeping up at a rate measured in millimetres per year, the land under a number of great coastal cities is sinking dramatically, as humans build  ever more massive cities and abstract ever more groundwater. So predictions warn that millions could be at risk of coastal flooding.

But there is another, deeper reason for the uncertainty: as rising temperatures remove the massive burden of ice from glaciated land, and wind and rain erode mountains, so the subterranean rocks in the Earth’s mantle, far below the crust, respond by inching upwards. Even the seemingly solid rocks are elastic, subsiding under pressure and rising when the mass is removed.

“Models of ice sheets are still in their toddlerhood”

All this means that, unless researchers can make an accurate estimate of land movement as well, sea level estimates are riven with uncertainties.

So a team from Columbia University in the US has looked at evidence of sea level rise and fall preserved in fossilised reefs and dunes in just one 1200km chain of islands − the Bahamas in the Atlantic − to come up with a new set of projections.

In the next 100 years, sea levels will rise by about 1.2 metres. This could be too modest: sea levels could just possibly rise by perhaps 5.3 metres, but this doesn’t seem likely. And a nine-metre rise is highly improbable.

“To get to nine metres of sea level rise, you’d have to melt large parts of Greenland and Antarctica,” said Blake Dyer, of the university’s Lamont-Doherty Earth Observatory.

Tricky calculation

“This suggests that didn’t happen. So maybe we should feel not so bad about the future. On the other hand, our lower estimate is bad, and our upper one is really bad.”

At the heart of the puzzle is a phenomenon known to geophysicists as isostasy: vast tracts of continental landmass have been heaving up and down, imperceptibly, over periods of tens of thousands of years, in response to ice and erosion.

So calculating sea level rise and fall when the thing on which sea level measurements are recorded − the land − is itself always shifting becomes tricky. That has always been why climate projections of sea levels contain a range of forecasts, rather than a hard number.

The argument is that changes recorded along the north-south lie of the Bahamas would provide a new and more sophisticated way of reconstructing sea heights in the relatively recent past.

Melting not guaranteed

The study doesn’t settle the question: estimates of past sea level change on a dramatic scale come from many parts of the planet, and glaciologists still have to reconstruct the rate at which the northern ice, for instance, may have retreated while the southern ice cap continued to advance during the last interglacial: that too would have limited sea level rise.

“This is still a question. Models of ice sheets are still in their toddlerhood,” said Maureen Raymo, director of the Earth Observatory and a co-author.

Human carbon emissions are now heating the globe far more rapidly and evenly than during the last interglacial, so there is no guarantee of any melting at different rates in two hemispheres

“That makes it more difficult to apply the results to today. The easy thing to say would be, ‘Oh we showed that sea levels were not so bad, and that’s terrific.’  The harder answer, the more honest answer, is that maybe things were different then, and we’re not in the clear.” − Climate News Network

Emissions

Flood risk will rise as climate heat intensifies

August 5th, 2021, by Tim Radford

A warmer world will be a wetter one. Ever more people will face a higher flood risk as rivers rise and city streets fill up.

LONDON, 5 August, 2021 − In a world of climate change, the flood risk will be more intense and more frequent, presenting higher danger to ever more people in a greater number of countries.

In this century alone, the global population has increased by 18%. But the number of people exposed to damage and death by rising waters has increased by more than 34%.

This finding is not based on mathematical simulations powered by weather data. It is based on direct and detailed observation. Researchers report in the journal Nature that they looked at more than 12,700 satellite images, at a resolution of 250 metres, of 913 large flood events between the years 2000 and 2015.

During those years, and those floods, water spilled from the rivers to inundate a total of 2.23 million square kilometres. This, considered as one event, would cover a total area larger than Saudi Arabia. And during those first 15 years of the century, the number of people directly affected by the floods was at least 255m, and possibly 290m.

“Governments across the world have been too slow in reducing greenhouse gas emissions . . . This, alongside the current floods in Europe, is the wake-up call we need”

In those 15 years, the numbers of people in the way of the ever more devastating floods rose by at least 58m, and possibly as many as 86m. That’s a rise of as much as 24%.

It will get worse. According to the researchers, climate change and the multiplication of human numbers will extend the reach of flood risk: 32 nations already experience ever more flooding. By 2030, another 25 countries will have joined them.

The humans caught up in the sickening flow of mud, sewage and silt spilling from the rising rivers will mostly be in south and south-east Asia − think of the Indus, Ganges-Brahmaputra and Mekong Rivers − and many of them will have migrated to the danger zones: poverty and population pressure will leave them no choice.

None of this should come as a surprise. In the past 50 years, according to a new compilation by the World Meteorological Organisation, weather, climate and water were implicated in 50% of all disasters of any kind; in 45% of all reported deaths and 74% of all economic losses. Floods have claimed 58,700 lives in the last five decades. Between them, floods and storms − the two are often linked − cost Europe at least US$377bn in economic losses.

Higher flooding frequency

And things will certainly get much worse for Europe as global average temperatures continue to rise in response to ever higher greenhouse gas emissions from ever greater use of fossil fuels. That is because what had once been relatively rare events will grow in force and frequency.

More heat means more evaporation, and a warmer atmosphere has a greater capacity to absorb water vapour. So it will rain harder. And the arrival, say researchers in the journal Geophysical Research Letters, of intense, slow-moving storms that precipitate devastating flash floods of the kind that swept Belgium and Germany this summer will by the close of the century become 14 times more frequent.

“Governments across the world have been too slow in reducing greenhouse gas emissions and global warming continues apace,” said Hayley Fowler, a climate scientist at Newcastle University in the UK, and one of the researchers.

“This study suggests that changes to extreme storms will be significant and cause an increase in the frequency of devastating flooding across Europe. This, alongside the current floods in Europe, is the wake-up call we need.” − Climate News Network

A warmer world will be a wetter one. Ever more people will face a higher flood risk as rivers rise and city streets fill up.

LONDON, 5 August, 2021 − In a world of climate change, the flood risk will be more intense and more frequent, presenting higher danger to ever more people in a greater number of countries.

In this century alone, the global population has increased by 18%. But the number of people exposed to damage and death by rising waters has increased by more than 34%.

This finding is not based on mathematical simulations powered by weather data. It is based on direct and detailed observation. Researchers report in the journal Nature that they looked at more than 12,700 satellite images, at a resolution of 250 metres, of 913 large flood events between the years 2000 and 2015.

During those years, and those floods, water spilled from the rivers to inundate a total of 2.23 million square kilometres. This, considered as one event, would cover a total area larger than Saudi Arabia. And during those first 15 years of the century, the number of people directly affected by the floods was at least 255m, and possibly 290m.

“Governments across the world have been too slow in reducing greenhouse gas emissions . . . This, alongside the current floods in Europe, is the wake-up call we need”

In those 15 years, the numbers of people in the way of the ever more devastating floods rose by at least 58m, and possibly as many as 86m. That’s a rise of as much as 24%.

It will get worse. According to the researchers, climate change and the multiplication of human numbers will extend the reach of flood risk: 32 nations already experience ever more flooding. By 2030, another 25 countries will have joined them.

The humans caught up in the sickening flow of mud, sewage and silt spilling from the rising rivers will mostly be in south and south-east Asia − think of the Indus, Ganges-Brahmaputra and Mekong Rivers − and many of them will have migrated to the danger zones: poverty and population pressure will leave them no choice.

None of this should come as a surprise. In the past 50 years, according to a new compilation by the World Meteorological Organisation, weather, climate and water were implicated in 50% of all disasters of any kind; in 45% of all reported deaths and 74% of all economic losses. Floods have claimed 58,700 lives in the last five decades. Between them, floods and storms − the two are often linked − cost Europe at least US$377bn in economic losses.

Higher flooding frequency

And things will certainly get much worse for Europe as global average temperatures continue to rise in response to ever higher greenhouse gas emissions from ever greater use of fossil fuels. That is because what had once been relatively rare events will grow in force and frequency.

More heat means more evaporation, and a warmer atmosphere has a greater capacity to absorb water vapour. So it will rain harder. And the arrival, say researchers in the journal Geophysical Research Letters, of intense, slow-moving storms that precipitate devastating flash floods of the kind that swept Belgium and Germany this summer will by the close of the century become 14 times more frequent.

“Governments across the world have been too slow in reducing greenhouse gas emissions and global warming continues apace,” said Hayley Fowler, a climate scientist at Newcastle University in the UK, and one of the researchers.

“This study suggests that changes to extreme storms will be significant and cause an increase in the frequency of devastating flooding across Europe. This, alongside the current floods in Europe, is the wake-up call we need.” − Climate News Network

Emissions

Melting tropical glaciers sound an early warning

July 5th, 2021, by Tim Radford

Climate change means melting tropical glaciers are losing frozen landscapes of great beauty − and high value to millions.

LONDON, 5 July, 2021 − The world’s remotest water towers are in retreat. The snows of Kilimanjaro in Africa are diminishing: between 1986 and 2017 the area of ice that crowns the most famous mountain in Tanzania has decreased by 71%. A tropical glacier near Puncak Jaya in Papua in Indonesia has lost 93% of its ice in the 38 years from 1980 to 2018. Melting tropical glaciers are together sounding an ominous warning.

The frozen summit of Huascarán, the highest peak in the tropics, in Peru has decreased in area by 19% between 1970 and 2003. In 1976, US scientists first took cores from the ice cap of Quelccaya in the Peruvian Andes: by 2020, around 46% had gone.

The darkening summits of the highest tropical mountains have a message for the world about the rate of climate change. “These are in the most remote parts of our planet − they’re not next to big cities, so you don’t have a local pollution effect,” said Lonnie Thompson of Ohio University.

“These glaciers are sentinels, they’re early warning systems for the planet and they are all saying the same thing.”

Millennial climate records

He and colleagues report in the journal Global and Planetary Change that they analysed the impact of warming on what they call “rapidly retreating high-altitude, low-latitude glaciers” in four separate regions of the planet: Africa, the Andes in Peru and Bolivia, the Tibetan Plateau and Himalayas of Asia, and the mountains of Papua province in Indonesia on the island known as New Guinea in the southwestern Pacific.

Each of the sample glaciers has yielded cores of ice that preserve, in their snow chemistry and trapped pollen, a record of many thousands of years of subtle climate change. And, since 1972, Earth observation satellites such as Nasa’s Landsat mission have monitored their surfaces.

In a world now heating as a response to greenhouse gas emissions into the atmosphere, where once snow had fallen, there is now rain to wash away the high-altitude ice. Glaciers serve as sources of fresh water for farmers and villagers in the tropical mountain zones: they also provide the river melt for many millions downstream.

The latest research confirms something climate scientists already knew: that almost everywhere, mountain ice is in retreat, with potentially devastating consequences for local economies. And the culprit is climate change driven by profligate fossil fuel combustion.

“These glaciers are sentinels, they’re early warning systems for the planet and they are all saying the same thing”

The Ohio researchers say: “Since the beginning of the 21st century the rates of ice loss have been at historically unprecedented levels.”

Within two or three years, the high snows near Puncak Jaya − these have powerful religious and cultural significance for the local people − will have gone.

But, the scientists argue, it is not too late to slow or stop the rate of greenhouse gas emissions into the atmosphere, and to slow or stop the retreat of many tropical glaciers.

“The science doesn’t change the trajectory we’re on,” said Professor Thompson. “Regardless of how clear the science is, we need something to happen to change that trajectory.” − Climate News Network

Climate change means melting tropical glaciers are losing frozen landscapes of great beauty − and high value to millions.

LONDON, 5 July, 2021 − The world’s remotest water towers are in retreat. The snows of Kilimanjaro in Africa are diminishing: between 1986 and 2017 the area of ice that crowns the most famous mountain in Tanzania has decreased by 71%. A tropical glacier near Puncak Jaya in Papua in Indonesia has lost 93% of its ice in the 38 years from 1980 to 2018. Melting tropical glaciers are together sounding an ominous warning.

The frozen summit of Huascarán, the highest peak in the tropics, in Peru has decreased in area by 19% between 1970 and 2003. In 1976, US scientists first took cores from the ice cap of Quelccaya in the Peruvian Andes: by 2020, around 46% had gone.

The darkening summits of the highest tropical mountains have a message for the world about the rate of climate change. “These are in the most remote parts of our planet − they’re not next to big cities, so you don’t have a local pollution effect,” said Lonnie Thompson of Ohio University.

“These glaciers are sentinels, they’re early warning systems for the planet and they are all saying the same thing.”

Millennial climate records

He and colleagues report in the journal Global and Planetary Change that they analysed the impact of warming on what they call “rapidly retreating high-altitude, low-latitude glaciers” in four separate regions of the planet: Africa, the Andes in Peru and Bolivia, the Tibetan Plateau and Himalayas of Asia, and the mountains of Papua province in Indonesia on the island known as New Guinea in the southwestern Pacific.

Each of the sample glaciers has yielded cores of ice that preserve, in their snow chemistry and trapped pollen, a record of many thousands of years of subtle climate change. And, since 1972, Earth observation satellites such as Nasa’s Landsat mission have monitored their surfaces.

In a world now heating as a response to greenhouse gas emissions into the atmosphere, where once snow had fallen, there is now rain to wash away the high-altitude ice. Glaciers serve as sources of fresh water for farmers and villagers in the tropical mountain zones: they also provide the river melt for many millions downstream.

The latest research confirms something climate scientists already knew: that almost everywhere, mountain ice is in retreat, with potentially devastating consequences for local economies. And the culprit is climate change driven by profligate fossil fuel combustion.

“These glaciers are sentinels, they’re early warning systems for the planet and they are all saying the same thing”

The Ohio researchers say: “Since the beginning of the 21st century the rates of ice loss have been at historically unprecedented levels.”

Within two or three years, the high snows near Puncak Jaya − these have powerful religious and cultural significance for the local people − will have gone.

But, the scientists argue, it is not too late to slow or stop the rate of greenhouse gas emissions into the atmosphere, and to slow or stop the retreat of many tropical glaciers.

“The science doesn’t change the trajectory we’re on,” said Professor Thompson. “Regardless of how clear the science is, we need something to happen to change that trajectory.” − Climate News Network

Nature

Climate heat is changing Earth’s water cycle

June 29th, 2021, by Tim Radford

Humans have begun to alter Earth’s water cycle, and not in a good way: expect later monsoon rains and thirstier farmlands.

LONDON, 29 June, 2021 − Prepare for a hotter, drier world, even in monsoon country. As global temperatures rise, in response to greenhouse gas emissions, the northern hemisphere rainy seasons are likely to arrive ever later as Earth’s water cycle reacts.

And even though more carbon dioxide in the atmosphere means more fertility and more moisture in the atmosphere, in the last 30 years the world’s green canopy has become more and more water-stressed, according to an entirely separate study.

US scientists report in Nature Climate Change that humankind has, in effect, begun to alter the planetary hydrological cycle. Increasing levels of greenhouse gases in the atmosphere and falling emissions of aerosols from car exhausts and factory chimneys have together combined to affect the tropical rainy season.

The Asian monsoons are arriving four days later, along with the rains over the Sahel in sub-Saharan Africa. By the century’s end the monsoons could sweep over India five days, and over the Sahel eight days, later.

“For monsoon regions, a delayed onset of summer rainfall could devastate crop production and jeopardise the livelihoods of large populations”

A warmer world should be a wetter one: standing water evaporates more swiftly, and with every degree Celsius temperatures rise, the capacity of the air to hold moisture also rises significantly. But, paradoxically, this extra atmospheric moisture is also the problem: ever more energy is needed to warm up the atmosphere as spring becomes summer.

The problem is compounded by cleaner air; industrial pollution had the effect of reflecting sunlight and damping down the global warming trend. As nations enforce clean air legislation − and create conditions for healthier lives − more sunlight gets through, to escalate both warming and rainfall delays. Later rains will mean later crop harvests, more extreme heat waves, and more intense wildfires.

“For monsoon regions, like India, with an agrarian economy, a delayed onset of summer rainfall could devastate crop production and jeopardise the livelihoods of large populations, unless farmers recognise and adapt to the long-term changes amidst highly variable monsoon onset dates,” said Ruby Leung, of Pacific Northwest National Laboratory, one of the authors.

And in a second study, in the journal Nature Communications, another US research team warns that vegetation in the northern hemisphere has been becoming increasingly (as they put it) “water-limited” over the last 30 years.

Inflexible limits

In what they say is a first-of-its-kind large-scale study, scientists analysed satellite and weather data from 604,800 locations each year over the three decades from 1982 to 2015. They identified a kind of vegetable go-slow overall: those areas where water supplies for plant growth were constrained had expanded, while those places where there was plenty of water tended to shrink.

In recent decades, plants have responded to extra atmospheric carbon dioxide by growing more vigorously to “green” the planet a little more measurably and slow the rate of climate change. This, however, looks as though it cannot last, because ultimately growth is limited by water availability.

“Without water, living things struggle to survive. Changes in vegetation response to water availability can result in significant shifts of climate-carbon interaction,” said Lixin Wang, of the University of Indiana, one of the authors.

“The results emphasise the need for actions that could slow down CO2 emissions. Without that, water constraints impacting plant growth − and the weakening of vegetation’s ability to remove CO2 from the atmosphere − are unlikely to slow.” − Climate News Network

Humans have begun to alter Earth’s water cycle, and not in a good way: expect later monsoon rains and thirstier farmlands.

LONDON, 29 June, 2021 − Prepare for a hotter, drier world, even in monsoon country. As global temperatures rise, in response to greenhouse gas emissions, the northern hemisphere rainy seasons are likely to arrive ever later as Earth’s water cycle reacts.

And even though more carbon dioxide in the atmosphere means more fertility and more moisture in the atmosphere, in the last 30 years the world’s green canopy has become more and more water-stressed, according to an entirely separate study.

US scientists report in Nature Climate Change that humankind has, in effect, begun to alter the planetary hydrological cycle. Increasing levels of greenhouse gases in the atmosphere and falling emissions of aerosols from car exhausts and factory chimneys have together combined to affect the tropical rainy season.

The Asian monsoons are arriving four days later, along with the rains over the Sahel in sub-Saharan Africa. By the century’s end the monsoons could sweep over India five days, and over the Sahel eight days, later.

“For monsoon regions, a delayed onset of summer rainfall could devastate crop production and jeopardise the livelihoods of large populations”

A warmer world should be a wetter one: standing water evaporates more swiftly, and with every degree Celsius temperatures rise, the capacity of the air to hold moisture also rises significantly. But, paradoxically, this extra atmospheric moisture is also the problem: ever more energy is needed to warm up the atmosphere as spring becomes summer.

The problem is compounded by cleaner air; industrial pollution had the effect of reflecting sunlight and damping down the global warming trend. As nations enforce clean air legislation − and create conditions for healthier lives − more sunlight gets through, to escalate both warming and rainfall delays. Later rains will mean later crop harvests, more extreme heat waves, and more intense wildfires.

“For monsoon regions, like India, with an agrarian economy, a delayed onset of summer rainfall could devastate crop production and jeopardise the livelihoods of large populations, unless farmers recognise and adapt to the long-term changes amidst highly variable monsoon onset dates,” said Ruby Leung, of Pacific Northwest National Laboratory, one of the authors.

And in a second study, in the journal Nature Communications, another US research team warns that vegetation in the northern hemisphere has been becoming increasingly (as they put it) “water-limited” over the last 30 years.

Inflexible limits

In what they say is a first-of-its-kind large-scale study, scientists analysed satellite and weather data from 604,800 locations each year over the three decades from 1982 to 2015. They identified a kind of vegetable go-slow overall: those areas where water supplies for plant growth were constrained had expanded, while those places where there was plenty of water tended to shrink.

In recent decades, plants have responded to extra atmospheric carbon dioxide by growing more vigorously to “green” the planet a little more measurably and slow the rate of climate change. This, however, looks as though it cannot last, because ultimately growth is limited by water availability.

“Without water, living things struggle to survive. Changes in vegetation response to water availability can result in significant shifts of climate-carbon interaction,” said Lixin Wang, of the University of Indiana, one of the authors.

“The results emphasise the need for actions that could slow down CO2 emissions. Without that, water constraints impacting plant growth − and the weakening of vegetation’s ability to remove CO2 from the atmosphere − are unlikely to slow.” − Climate News Network

Emissions, Health

Drought and famine stalk desperate Madagascar

June 23rd, 2021, by Kieran Cooke

Erratic rainfall, locusts and cyclones are causing havoc in desperate Madagascar. Now the climate crisis adds to the misery.

LONDON, 23 June, 2021 – Dense swarms of locusts ravage croplands. Starved of food, local people are forced to eat the locusts and other insects. Changes in climate threaten famine across large areas of increasingly desperate Madagascar, an island nation of 27 million people off the east coast of Africa.

The outlook is stark. Amer Daoudi, a senior director of the UN’s World Food Programme, (WFP) says people are desperate, particularly in the semi-arid south of the country, where there’s been a prolonged drought.

“Famine looms in southern Madagascar as communities witness an almost total disappearance of food sources, which has created a full-blown nutrition emergency”, says Daoudi.

“People have had to resort to desperate survival measures, such as eating locusts, raw red cactus fruits and wild leaves.”

Single day’s rain

Daoudi, a veteran aid worker, says that on a fact-finding tour of villages across southern Madagascar, he came across horrific scenes. “They are on the periphery of famine; these are images I haven’t seen for quite some time across the globe.”

For years droughts have been a regular occurrence for the people of understandably desperate Madagascar, particularly in the south. The World Bank says climate change is exacerbating the area’s problems.

“Now climate change poses potential risks and has already increased average temperatures in the region, combined with erratic rainfall patterns which have compounded the effects of droughts, cyclones and the influence of plagues of locusts.”

The annual rains have failed to arrive in several recent years. In southern Madagascar the rainy season occurs in November and December. Last year it rained for only one day over those months.

“They are on the periphery of famine; these are images I haven’t seen for quite some time across the globe”

As a result the local crops – mainly maize, manioc and beans – failed. Cattle and goats died for lack of water. Farmers have no seeds to plant fresh crops.

WFP and other aid organisations estimate that more than 1.3 million people are in danger of running out of food. Many living in the south migrate around the country at various times of the year in search of work. The Covid pandemic has shut down this valuable source of cash. The drought, combined with Covid, has meant most services have halted.

“Children have abandoned schools”, says the WFP. “75% of children in this area are either begging or foraging for food.”

Apart from the drought, rising temperatures and locusts, farmers in southern Madagascar have had to cope with another climate phenomenon – an increase in both the number and ferocity of dust storms, locally called tiomena.

The next pandemic

These storms have blown in regularly over the last few months, covering farmlands with a thick layer of dust. Aid agencies, starved of cash, have struggled to cope, though some progress has been made.

UNICEF, the UN Children’s Fund, together with Madagascar’s central government, opened a new 180 km water pipeline to the south in 2019. Women do most of the water fetching and carrying duties in Madagascar, often having to go more than 15 km for supplies.

The new pipeline has brought relief to some, but many thousands of households in the area are still without readily accessible water supplies.

Drought is a growing problem worldwide as the climate undergoes often dramatic change. In a recent report the UN likened drought to the Covid pandemic. “Drought is on the verge of becoming the next pandemic and there is no vaccine to cure it”, it said. – Climate News Network

Erratic rainfall, locusts and cyclones are causing havoc in desperate Madagascar. Now the climate crisis adds to the misery.

LONDON, 23 June, 2021 – Dense swarms of locusts ravage croplands. Starved of food, local people are forced to eat the locusts and other insects. Changes in climate threaten famine across large areas of increasingly desperate Madagascar, an island nation of 27 million people off the east coast of Africa.

The outlook is stark. Amer Daoudi, a senior director of the UN’s World Food Programme, (WFP) says people are desperate, particularly in the semi-arid south of the country, where there’s been a prolonged drought.

“Famine looms in southern Madagascar as communities witness an almost total disappearance of food sources, which has created a full-blown nutrition emergency”, says Daoudi.

“People have had to resort to desperate survival measures, such as eating locusts, raw red cactus fruits and wild leaves.”

Single day’s rain

Daoudi, a veteran aid worker, says that on a fact-finding tour of villages across southern Madagascar, he came across horrific scenes. “They are on the periphery of famine; these are images I haven’t seen for quite some time across the globe.”

For years droughts have been a regular occurrence for the people of understandably desperate Madagascar, particularly in the south. The World Bank says climate change is exacerbating the area’s problems.

“Now climate change poses potential risks and has already increased average temperatures in the region, combined with erratic rainfall patterns which have compounded the effects of droughts, cyclones and the influence of plagues of locusts.”

The annual rains have failed to arrive in several recent years. In southern Madagascar the rainy season occurs in November and December. Last year it rained for only one day over those months.

“They are on the periphery of famine; these are images I haven’t seen for quite some time across the globe”

As a result the local crops – mainly maize, manioc and beans – failed. Cattle and goats died for lack of water. Farmers have no seeds to plant fresh crops.

WFP and other aid organisations estimate that more than 1.3 million people are in danger of running out of food. Many living in the south migrate around the country at various times of the year in search of work. The Covid pandemic has shut down this valuable source of cash. The drought, combined with Covid, has meant most services have halted.

“Children have abandoned schools”, says the WFP. “75% of children in this area are either begging or foraging for food.”

Apart from the drought, rising temperatures and locusts, farmers in southern Madagascar have had to cope with another climate phenomenon – an increase in both the number and ferocity of dust storms, locally called tiomena.

The next pandemic

These storms have blown in regularly over the last few months, covering farmlands with a thick layer of dust. Aid agencies, starved of cash, have struggled to cope, though some progress has been made.

UNICEF, the UN Children’s Fund, together with Madagascar’s central government, opened a new 180 km water pipeline to the south in 2019. Women do most of the water fetching and carrying duties in Madagascar, often having to go more than 15 km for supplies.

The new pipeline has brought relief to some, but many thousands of households in the area are still without readily accessible water supplies.

Drought is a growing problem worldwide as the climate undergoes often dramatic change. In a recent report the UN likened drought to the Covid pandemic. “Drought is on the verge of becoming the next pandemic and there is no vaccine to cure it”, it said. – Climate News Network

Oceans, Polar

Polar concerns rise as ice now melts ever faster

June 15th, 2021, by Tim Radford

An Antarctic glacier gathers pace. In the north, the Arctic ice thins faster. Racing climate heat is feeding polar concerns.

LONDON, 15 June, 2021 − An Antarctic glacier has begun to move more quickly towards the open ocean, as the shelf of sea ice that once held it back starts to collapse. The water in that one glacier is enough to raise global sea levels by half a metre. And that’s not all that’s raising polar concerns across the scientific world.

At the other end of the Earth global heating is accelerating the loss of Arctic ice. A new study reports that the thinning of sea ice in three separate coastal regions could now be happening twice as fast.

Both findings are linked to the inexorable rise in global average temperatures as the profligate use of fossil fuels heightens the ratio of greenhouse gases in the planet’s atmosphere.

Antarctic scientists have been worrying about warming in Antarctica for years. And they have been anxiously watching the Pine Island glacier in West Antarctica for decades.

Glaciers move at the proverbial glacial pace towards the sea, to be held in check, in the polar oceans, by vast shelves of sea ice. Between 2017 and 2020 the ice shelves have undergone a series of collapses and lost one fifth of their area, possibly because the glacier has been accelerating.

“The thickness of the sea ice is a sensitive indicator of the health of the Arctic”

“We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected,” said Ian Joughin, of the University of Washington in the US.

“The processes we’d been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf.”

He and his colleagues report in the journal Science Advances that the Pine Island glacier has already become Antarctica’s biggest contributor to sea level rise. The pace of flow remained fairly steady from 2009 to 2017, but they found that data from Europe’s Copernicus Sentinel satellite system showed an acceleration of 12% in the past three years.

The Pine Island glacier contains roughly 180 trillion tonnes of ice, enough to raise global sea levels by 0.5 metres. Researchers had calculated that it might take a century or more for slowly-warming polar waters to thin the ice shelves to the point where they could no longer stem the glacier flow. But it now seems that the big player in the shelf ice collapse is the glacier itself, as the flow rate increases.

“The loss of Pine Island’s ice shelf now looks possibly like it could occur in the next decade or two, as opposed to the melt-driven sub-surface change playing out over more than 100 or more years,” said Pierre Dutrieux of the British Antarctic Survey, a co-author. “So it’s a potentially much more rapid and abrupt change.”

Snow fall dwindles

Abrupt change, too, may be on the way in the Arctic Ocean. British researchers used a new computer simulation to explore measurements from Europe’s CryoSat-2 satellite. The scientists report in the journal The Cryosphere that the thinning of ice in the Laptev and Kara Seas north of Siberia, and the Chukchi Sea between Siberia and Alaska, has stepped up by 70%, 98% and 110% respectively.

Sea ice diminishes each summer and forms again each winter; each successive summer reveals an ever-greater loss, as the ice itself thins and the area covered by ice dwindles.

Calculations of ice thickness have always allowed for the falls of fresh winter snow. But since the formation of sea ice has been later every year, there has been less time for the snow to accumulate. Such things make a difference.

“The thickness of the sea ice is a sensitive indicator of the health of the Arctic,” said Robbie Mallett, of University College London.

“It is important as thicker ice acts as an insulating blanket, stopping the ocean from warming up the atmosphere in winter, and protecting the ocean from sunshine in summer. Thinner ice is also less likely to survive the summer melt.” − Climate News Network

An Antarctic glacier gathers pace. In the north, the Arctic ice thins faster. Racing climate heat is feeding polar concerns.

LONDON, 15 June, 2021 − An Antarctic glacier has begun to move more quickly towards the open ocean, as the shelf of sea ice that once held it back starts to collapse. The water in that one glacier is enough to raise global sea levels by half a metre. And that’s not all that’s raising polar concerns across the scientific world.

At the other end of the Earth global heating is accelerating the loss of Arctic ice. A new study reports that the thinning of sea ice in three separate coastal regions could now be happening twice as fast.

Both findings are linked to the inexorable rise in global average temperatures as the profligate use of fossil fuels heightens the ratio of greenhouse gases in the planet’s atmosphere.

Antarctic scientists have been worrying about warming in Antarctica for years. And they have been anxiously watching the Pine Island glacier in West Antarctica for decades.

Glaciers move at the proverbial glacial pace towards the sea, to be held in check, in the polar oceans, by vast shelves of sea ice. Between 2017 and 2020 the ice shelves have undergone a series of collapses and lost one fifth of their area, possibly because the glacier has been accelerating.

“The thickness of the sea ice is a sensitive indicator of the health of the Arctic”

“We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected,” said Ian Joughin, of the University of Washington in the US.

“The processes we’d been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf.”

He and his colleagues report in the journal Science Advances that the Pine Island glacier has already become Antarctica’s biggest contributor to sea level rise. The pace of flow remained fairly steady from 2009 to 2017, but they found that data from Europe’s Copernicus Sentinel satellite system showed an acceleration of 12% in the past three years.

The Pine Island glacier contains roughly 180 trillion tonnes of ice, enough to raise global sea levels by 0.5 metres. Researchers had calculated that it might take a century or more for slowly-warming polar waters to thin the ice shelves to the point where they could no longer stem the glacier flow. But it now seems that the big player in the shelf ice collapse is the glacier itself, as the flow rate increases.

“The loss of Pine Island’s ice shelf now looks possibly like it could occur in the next decade or two, as opposed to the melt-driven sub-surface change playing out over more than 100 or more years,” said Pierre Dutrieux of the British Antarctic Survey, a co-author. “So it’s a potentially much more rapid and abrupt change.”

Snow fall dwindles

Abrupt change, too, may be on the way in the Arctic Ocean. British researchers used a new computer simulation to explore measurements from Europe’s CryoSat-2 satellite. The scientists report in the journal The Cryosphere that the thinning of ice in the Laptev and Kara Seas north of Siberia, and the Chukchi Sea between Siberia and Alaska, has stepped up by 70%, 98% and 110% respectively.

Sea ice diminishes each summer and forms again each winter; each successive summer reveals an ever-greater loss, as the ice itself thins and the area covered by ice dwindles.

Calculations of ice thickness have always allowed for the falls of fresh winter snow. But since the formation of sea ice has been later every year, there has been less time for the snow to accumulate. Such things make a difference.

“The thickness of the sea ice is a sensitive indicator of the health of the Arctic,” said Robbie Mallett, of University College London.

“It is important as thicker ice acts as an insulating blanket, stopping the ocean from warming up the atmosphere in winter, and protecting the ocean from sunshine in summer. Thinner ice is also less likely to survive the summer melt.” − Climate News Network

Emissions, Oceans

Pathway to global climate catastrophe is clear

June 8th, 2021, by Tim Radford

Global climate catastrophe could be nearer than we think. New research suggests how it could happen.

LONDON, 8 June, 2021 − Here is a set of circumstances that could trigger global climate catastrophe. The Greenland ice sheet could begin a process of irreversible melting.

As it does, greater quantities of fresh water would flood into the Arctic Ocean, to further slow the already slowing Atlantic meridional overturning circulation, that great flow of water sometimes called the Gulf Stream that  distributes warmth from the tropics.

But as the Atlantic flow weakens, so rises the probability of increased and sustained drought and dieback in the Amazon rainforest: the entire region could begin to tip inexorably into savannah.

And the Southern Ocean would begin to warm: it could warm enough to hasten the disintegration of the West Antarctic ice sheet, to accelerate the rise of global sea levels and intensify the whole machinery of global heating.

Alarmingly, this process could begin to happen while global temperatures are still not much higher than they are now: 1.5°C has been repeatedly described as the limit beyond which global average temperatures should not rise, but the official global agreed target is a limit of 2°C.

In fact, the chance of a cascade of domino effects − of tipping points that trigger other climate tipping points − could begin somewhere between those two figures, and the probability rises thereafter.

No way back

And, researchers warn, when they say irreversible, they mean it. Once the Greenland ice sheet starts to slide into the sea, there will be no stopping it. The only question is how swiftly all these things could happen.

“Once triggered, the actual tipping process might take several years up to millennia, depending on the respective response times of the system,” the scientists write in the journal Earth System Dynamics.

It’s a scenario, not a prediction. It’s a calculation of possibilities and probabilities inherent in the process of global warming and climate change. It’s an identification of the way atmospheric warming driven by greenhouse gas emissions from human economies can and might change the climate system that drives planetary weather.

“We provide risk analysis, not a prediction, yet our findings still raise concern,” said Ricarda Winkelmann, of the Potsdam Institute for Climate Impact Research, one of the authors.

She and her colleagues base their study on computer simulations of planetary response to temperature rise. And one third of those simulations suggest that if the world reaches 2°C, then one of those elements could begin to tip towards irreversible change, and at the same time trigger other tipping points.

“We’re shifting the odds, and not to our favour − the risk is clearly increasing the more we heat our planet,” said her colleague and co-author Jonathan Donges. “It rises substantially between 1°C and 3°C.

“Rapidly reducing greenhouse gas emissions is indispensable to limit the risks of crossing tipping points in the climate system”

“If greenhouse gas emissions and the resulting climate change cannot be halted, the upper level of this warming range could most likely be crossed by the end of this century. With even higher temperatures, more tipping cascades are to be expected, with long-term devastating effects.”

Climate science has been concerned with the idea of tipping points − temperatures beyond which climate change might be irreversible − for decades. There have been repeated findings that some of these might be nearer than anybody had suspected.

Greenland is in effect the reservoir of most of the Northern hemisphere’s ice − enough to raise sea levels by seven metres − and it is melting at an ever-accelerating rate.

Researchers have again and again identified a possible faltering of the Atlantic current, to warn of a paradoxical consequence: if the Gulf Stream slows, then average temperatures in western Europe could actually fall in a globally-heating world.

The Amazon rainforest − a vital part of the planet’s climate machinery since the end of the last Ice Age − has been hit not just by human degradation but by drought and forest fire, and could be about to slide into permanent savannah.

Overshoot nears

And scientists in Antarctica have been warning for a decade of thinning ice sheets, and accelerating glaciers.

The planet has already warmed by more than a degree Celsius in the last century or so. There is a high chance that some time this decade the annual average planetary temperature could pass the 1.5°C threshold, if only temporarily.

Right now, although 195 nations in Paris in 2015 committed themselves to a target of “well below” 2°C by 2100, the world is heading for a temperature rise by the end of the century of more than 3°C.

The authors concede that their results contain a lot of uncertainties: there is more research to be done. But that doesn’t mean there is no urgency.

“Our analysis is conservative in the sense that several interactions and tipping elements are not yet considered”, said Professor Winkelmann. It would hence be a daring bet to hope that the uncertainties play out in a good way, given what is at stake.

“From a precautionary perspective, rapidly reducing greenhouse gas emissions is indispensable to limit the risks of crossing tipping points in the climate system, and potentially causing domino effects.” − Climate News Network

Global climate catastrophe could be nearer than we think. New research suggests how it could happen.

LONDON, 8 June, 2021 − Here is a set of circumstances that could trigger global climate catastrophe. The Greenland ice sheet could begin a process of irreversible melting.

As it does, greater quantities of fresh water would flood into the Arctic Ocean, to further slow the already slowing Atlantic meridional overturning circulation, that great flow of water sometimes called the Gulf Stream that  distributes warmth from the tropics.

But as the Atlantic flow weakens, so rises the probability of increased and sustained drought and dieback in the Amazon rainforest: the entire region could begin to tip inexorably into savannah.

And the Southern Ocean would begin to warm: it could warm enough to hasten the disintegration of the West Antarctic ice sheet, to accelerate the rise of global sea levels and intensify the whole machinery of global heating.

Alarmingly, this process could begin to happen while global temperatures are still not much higher than they are now: 1.5°C has been repeatedly described as the limit beyond which global average temperatures should not rise, but the official global agreed target is a limit of 2°C.

In fact, the chance of a cascade of domino effects − of tipping points that trigger other climate tipping points − could begin somewhere between those two figures, and the probability rises thereafter.

No way back

And, researchers warn, when they say irreversible, they mean it. Once the Greenland ice sheet starts to slide into the sea, there will be no stopping it. The only question is how swiftly all these things could happen.

“Once triggered, the actual tipping process might take several years up to millennia, depending on the respective response times of the system,” the scientists write in the journal Earth System Dynamics.

It’s a scenario, not a prediction. It’s a calculation of possibilities and probabilities inherent in the process of global warming and climate change. It’s an identification of the way atmospheric warming driven by greenhouse gas emissions from human economies can and might change the climate system that drives planetary weather.

“We provide risk analysis, not a prediction, yet our findings still raise concern,” said Ricarda Winkelmann, of the Potsdam Institute for Climate Impact Research, one of the authors.

She and her colleagues base their study on computer simulations of planetary response to temperature rise. And one third of those simulations suggest that if the world reaches 2°C, then one of those elements could begin to tip towards irreversible change, and at the same time trigger other tipping points.

“We’re shifting the odds, and not to our favour − the risk is clearly increasing the more we heat our planet,” said her colleague and co-author Jonathan Donges. “It rises substantially between 1°C and 3°C.

“Rapidly reducing greenhouse gas emissions is indispensable to limit the risks of crossing tipping points in the climate system”

“If greenhouse gas emissions and the resulting climate change cannot be halted, the upper level of this warming range could most likely be crossed by the end of this century. With even higher temperatures, more tipping cascades are to be expected, with long-term devastating effects.”

Climate science has been concerned with the idea of tipping points − temperatures beyond which climate change might be irreversible − for decades. There have been repeated findings that some of these might be nearer than anybody had suspected.

Greenland is in effect the reservoir of most of the Northern hemisphere’s ice − enough to raise sea levels by seven metres − and it is melting at an ever-accelerating rate.

Researchers have again and again identified a possible faltering of the Atlantic current, to warn of a paradoxical consequence: if the Gulf Stream slows, then average temperatures in western Europe could actually fall in a globally-heating world.

The Amazon rainforest − a vital part of the planet’s climate machinery since the end of the last Ice Age − has been hit not just by human degradation but by drought and forest fire, and could be about to slide into permanent savannah.

Overshoot nears

And scientists in Antarctica have been warning for a decade of thinning ice sheets, and accelerating glaciers.

The planet has already warmed by more than a degree Celsius in the last century or so. There is a high chance that some time this decade the annual average planetary temperature could pass the 1.5°C threshold, if only temporarily.

Right now, although 195 nations in Paris in 2015 committed themselves to a target of “well below” 2°C by 2100, the world is heading for a temperature rise by the end of the century of more than 3°C.

The authors concede that their results contain a lot of uncertainties: there is more research to be done. But that doesn’t mean there is no urgency.

“Our analysis is conservative in the sense that several interactions and tipping elements are not yet considered”, said Professor Winkelmann. It would hence be a daring bet to hope that the uncertainties play out in a good way, given what is at stake.

“From a precautionary perspective, rapidly reducing greenhouse gas emissions is indispensable to limit the risks of crossing tipping points in the climate system, and potentially causing domino effects.” − Climate News Network

Nature, Polar

Polar cod face new threat from Arctic oil pollution

June 2nd, 2021, by Kieran Cooke

Already struggling to survive in warming Arctic seas, the polar cod are now at risk from rising oil pollution.

LONDON, 2 June, 2021 – They are small – on average around 25cm long. But polar cod (Boreogadus saida) are a vital part of the Arctic food chain, a major ingredient in the diet of seals, narwhals and a wide variety of seabirds.

The Arctic is warming faster than any other area on the planet, and a study published in 2020 found that declines in winter sea ice cover in the Barents Sea region of the Arctic, plus warmer sea temperatures, were causing declines in polar cod reproduction rates.

The latest research indicates that the polar cod is now under threat not only from warming Arctic seas, but because of oil pollution as well, as the region’s rapidly diminishing ice cover allows more shipping traffic and commercial activity.

Morgan Lizabeth Bender is a researcher in the department of Arctic and Marine Biology at the University of Tromsø (UiT) in northern Norway. Her research has found that when the polar cod is exposed to a combination of warmer waters and only very slight levels of oil pollution, its development is interrupted, with abnormalities common.

“Polar cod is a somewhat difficult species that hasn’t been researched that much,” Dr Bender told the Science Norway website. “The fish are a difficult species to find and to take care of in the lab. However, this species has a very important ecological role.”

“Increased water temperature can increase the harmful effects of oil exposure”

The fish, monitored during the breeding process, were sorted into aquariums – some at a current Arctic water temperature of 0.5°C, others at a warmer 2.8°C to mimic an Arctic affected by climate change.

The aquariums contained either pure water or water contaminated by minuscule amounts of crude oil. “The pollution level would be the equivalent of about five drops of oil in an Olympic-size swimming pool,” says Dr Bender.

Though the study found that polar cod eggs in the warmer water hatched much faster than those in the colder water, at first there was little difference between survival rates in the various aquariums.

But then something strange started happening to the fry – the young fish – that were exposed to oil.

“When they first hatched, there wasn’t much difference,” says Dr Bender. “But as their jaw, face and eyes started to develop, we saw very clearly that they weren’t forming properly.”

Lower survival rates

The research found that the fry were very sensitive to even the slightest amount of oil pollution: death rates were highest among fry exposed to both warmer water and oil.

When the fry became large enough to start feeding, only 8% survived in the contaminated warmer water and 23% in the contaminated cold water.

Marine scientists say that polar cod numbers have shown a downward trend since 2010, despite the fact that they are not a fished species.

Sonnich Meier, of the Norwegian Institute of Marine Research, has been examining the impact of both global warming and oil pollution on Arctic fish species for a number of years.

“Polar cod is one of the fish species that is hardest hit by climate change in the Arctic,” he says. “The study shows that increased water temperature can increase the harmful effects of oil exposure.” – Climate News Network

Already struggling to survive in warming Arctic seas, the polar cod are now at risk from rising oil pollution.

LONDON, 2 June, 2021 – They are small – on average around 25cm long. But polar cod (Boreogadus saida) are a vital part of the Arctic food chain, a major ingredient in the diet of seals, narwhals and a wide variety of seabirds.

The Arctic is warming faster than any other area on the planet, and a study published in 2020 found that declines in winter sea ice cover in the Barents Sea region of the Arctic, plus warmer sea temperatures, were causing declines in polar cod reproduction rates.

The latest research indicates that the polar cod is now under threat not only from warming Arctic seas, but because of oil pollution as well, as the region’s rapidly diminishing ice cover allows more shipping traffic and commercial activity.

Morgan Lizabeth Bender is a researcher in the department of Arctic and Marine Biology at the University of Tromsø (UiT) in northern Norway. Her research has found that when the polar cod is exposed to a combination of warmer waters and only very slight levels of oil pollution, its development is interrupted, with abnormalities common.

“Polar cod is a somewhat difficult species that hasn’t been researched that much,” Dr Bender told the Science Norway website. “The fish are a difficult species to find and to take care of in the lab. However, this species has a very important ecological role.”

“Increased water temperature can increase the harmful effects of oil exposure”

The fish, monitored during the breeding process, were sorted into aquariums – some at a current Arctic water temperature of 0.5°C, others at a warmer 2.8°C to mimic an Arctic affected by climate change.

The aquariums contained either pure water or water contaminated by minuscule amounts of crude oil. “The pollution level would be the equivalent of about five drops of oil in an Olympic-size swimming pool,” says Dr Bender.

Though the study found that polar cod eggs in the warmer water hatched much faster than those in the colder water, at first there was little difference between survival rates in the various aquariums.

But then something strange started happening to the fry – the young fish – that were exposed to oil.

“When they first hatched, there wasn’t much difference,” says Dr Bender. “But as their jaw, face and eyes started to develop, we saw very clearly that they weren’t forming properly.”

Lower survival rates

The research found that the fry were very sensitive to even the slightest amount of oil pollution: death rates were highest among fry exposed to both warmer water and oil.

When the fry became large enough to start feeding, only 8% survived in the contaminated warmer water and 23% in the contaminated cold water.

Marine scientists say that polar cod numbers have shown a downward trend since 2010, despite the fact that they are not a fished species.

Sonnich Meier, of the Norwegian Institute of Marine Research, has been examining the impact of both global warming and oil pollution on Arctic fish species for a number of years.

“Polar cod is one of the fish species that is hardest hit by climate change in the Arctic,” he says. “The study shows that increased water temperature can increase the harmful effects of oil exposure.” – Climate News Network

Emissions, Polar

Faster Greenland ice melt could be unstoppable

May 24th, 2021, by Tim Radford

A rapid thaw could destroy a whole ice sheet if the faster Greenland ice melt scientists have found spreads across the island.

LONDON, 24 May, 2021 − Researchers say the faster Greenland ice melt affecting part of the island could mean a large area is on the verge of irreversible loss. Their new study shows that the central western region of the ice sheet is near what climate scientists call “a tipping point.”

That is, once the ice starts to slide away, most of it will tip into the sea, to raise global sea levels and potentially to trigger the collapse of the great Atlantic Ocean current that enhances the climate of north-west Europe.

“We have found evidence that the central western part of the Greenland ice sheet has been destabilising and is now close to a critical transition,” said Niklas Boers, of the Potsdam Institute for Climate Impact Research. “Our results suggest there will be substantially enhanced melting in the future − which is quite worrying.”

Dr Boers and his colleague Martin Rypdal of the Arctic University of Norway report in the Proceedings of the National Academy of Sciences that they looked at data since 1880 of melt rates and ice-sheet altitude shifts of a region called the Jakobshavn basin in the central western region of the northern hemisphere’s biggest single block of ice − a block big enough to raise global sea levels by seven metres, were it all to melt.

And what they saw was something alarming: evidence that surface melting is beginning to accelerate. The conclusion, for now, is tentative.

“It’s high time we dramatically and substantially reduce greenhouse gas emissions from burning fossil fuels”

“We might be seeing the beginning of a large scale destabilisation, but at the moment we cannot tell, unfortunately,” Dr Boers said. “So far the signals we see are only regional, but that might simply be due to the scarcity of accurate and long-term data for other parts of the ice sheet.”

The region is home to the Jakobshavn glacier, which began to accelerate its flow to the sea this century, but the alarm is consistent with other studies of the mass of ice piled up on Greenland.

For most of the last 10,000 years or so, the summer loss of ice through melt and glacial flow has been replaced by winter snow. But in recent years, other research teams have warned, repeatedly, that the rate of  melting of Greenland’s surface ice has increased, in ways that really could threaten the stability of the entire sheet. Last year, ice loss reached a new record.

Greenland’s ice sheet is high: colder, therefore, at altitude. As the surface melts, the elevation becomes lower, and therefore increasingly warmer. So once the high ground surface begins to melt away, it could reach a level below which there is no obvious reason why the process should stop.

Climate computer simulations predict a threshold of global average temperature change that could, in effect, start a process in which the loss of the entire ice sheet would become inevitable. The loss would happen over hundreds of years, or perhaps thousands, but once begun it would continue inexorably.

Extreme Arctic warming

Global sea levels would rise at ever faster rates, and the arrival of so much fresh water in the north Atlantic would be enough to interfere with the ocean circulation.

For years oceanographers have been warning that the existing current, which takes warm tropical water as far north as the Arctic, could weaken, or fail, with unpredictable and uncomfortable consequences for north European nations.

The only way to stop Greenland’s accelerated melt, once it reaches a critical point, would be to lower the temperature of the whole planet back to that which was normal more than 200 years ago. That is unlikely to happen. Instead, for the moment, the evidence is that average temperatures worldwide could rise by 3°C or more by 2100. The Arctic, however, is likely to become much, much warmer.

“So practically, the current and near-future mass loss will be irreversible,” said Dr Boers, “That’s why it’s high time we dramatically and substantially reduce greenhouse gas emissions from burning fossil fuels and restabilise the ice sheet and our climate.” − Climate News Network

A rapid thaw could destroy a whole ice sheet if the faster Greenland ice melt scientists have found spreads across the island.

LONDON, 24 May, 2021 − Researchers say the faster Greenland ice melt affecting part of the island could mean a large area is on the verge of irreversible loss. Their new study shows that the central western region of the ice sheet is near what climate scientists call “a tipping point.”

That is, once the ice starts to slide away, most of it will tip into the sea, to raise global sea levels and potentially to trigger the collapse of the great Atlantic Ocean current that enhances the climate of north-west Europe.

“We have found evidence that the central western part of the Greenland ice sheet has been destabilising and is now close to a critical transition,” said Niklas Boers, of the Potsdam Institute for Climate Impact Research. “Our results suggest there will be substantially enhanced melting in the future − which is quite worrying.”

Dr Boers and his colleague Martin Rypdal of the Arctic University of Norway report in the Proceedings of the National Academy of Sciences that they looked at data since 1880 of melt rates and ice-sheet altitude shifts of a region called the Jakobshavn basin in the central western region of the northern hemisphere’s biggest single block of ice − a block big enough to raise global sea levels by seven metres, were it all to melt.

And what they saw was something alarming: evidence that surface melting is beginning to accelerate. The conclusion, for now, is tentative.

“It’s high time we dramatically and substantially reduce greenhouse gas emissions from burning fossil fuels”

“We might be seeing the beginning of a large scale destabilisation, but at the moment we cannot tell, unfortunately,” Dr Boers said. “So far the signals we see are only regional, but that might simply be due to the scarcity of accurate and long-term data for other parts of the ice sheet.”

The region is home to the Jakobshavn glacier, which began to accelerate its flow to the sea this century, but the alarm is consistent with other studies of the mass of ice piled up on Greenland.

For most of the last 10,000 years or so, the summer loss of ice through melt and glacial flow has been replaced by winter snow. But in recent years, other research teams have warned, repeatedly, that the rate of  melting of Greenland’s surface ice has increased, in ways that really could threaten the stability of the entire sheet. Last year, ice loss reached a new record.

Greenland’s ice sheet is high: colder, therefore, at altitude. As the surface melts, the elevation becomes lower, and therefore increasingly warmer. So once the high ground surface begins to melt away, it could reach a level below which there is no obvious reason why the process should stop.

Climate computer simulations predict a threshold of global average temperature change that could, in effect, start a process in which the loss of the entire ice sheet would become inevitable. The loss would happen over hundreds of years, or perhaps thousands, but once begun it would continue inexorably.

Extreme Arctic warming

Global sea levels would rise at ever faster rates, and the arrival of so much fresh water in the north Atlantic would be enough to interfere with the ocean circulation.

For years oceanographers have been warning that the existing current, which takes warm tropical water as far north as the Arctic, could weaken, or fail, with unpredictable and uncomfortable consequences for north European nations.

The only way to stop Greenland’s accelerated melt, once it reaches a critical point, would be to lower the temperature of the whole planet back to that which was normal more than 200 years ago. That is unlikely to happen. Instead, for the moment, the evidence is that average temperatures worldwide could rise by 3°C or more by 2100. The Arctic, however, is likely to become much, much warmer.

“So practically, the current and near-future mass loss will be irreversible,” said Dr Boers, “That’s why it’s high time we dramatically and substantially reduce greenhouse gas emissions from burning fossil fuels and restabilise the ice sheet and our climate.” − Climate News Network