Tag Archives: Warming

Drought-hit forests may worsen climate change

Forests help to slow the challenge of climate change, don’t they? Only if climate change doesn’t fell the forests first.

LONDON, 7 July, 2020 − There could be big problems with national and international plans to plant forests to deal with climate change. One of them is uncertainty about how climate change is going to deal with the forests.

In six new studies of what might be called the plantation carbon conundrum, independent groups of researchers warn that:

That the loss of natural forests worldwide is a driver of global heating and climate change has never been in doubt. And climate scientists continue to count tomorrow’s forests as part of the answer to the threat of catastrophic climate change.

But researchers have already warned that a vow to plant one trillion trees is not of itself a readymade answer, and that national plans to conserve existing forest are less than effective.

So the challenge for foresters and ecologists is to decide what works best – and what would not. Researchers in the US argue in the journal Science that governments and policymakers need a masterplan to confront the risks forests face from the consequences of rising temperatures: drought, fire and insect disturbance.

Flying blind

Forests and other natural ecosystems absorb about one-third of all the greenhouse gas emissions that human actions release each year. New forests must be part of the answer, but only if the new timber goes on and on absorbing carbon.

“There’s a very real chance that many of those forest projects could go up in flames or to bugs or drought stress or hurricanes in the coming decades,” said William Anderegg of the University of Utah, who led the study. “Without good science to tell us what the risks are, we’re flying blind and not making the best policy decisions.”

The other papers look at aspects of the hazard, and of well-intentioned policies to combat climate change. The Bonn Challenge aims to restore an area of forest eight times the size of California, but 80% of the commitments so far involve plantations of single species or of exploitable species: fruit, for instance, and rubber on what might have been natural forest land, grassland or savannahs that support biodiversity.

Californian and Chilean researchers report in the journal Nature Sustainability that they looked at the role of long-running Chilean government subsidies in afforestation and found an uncomfortable result: exotic species flourished at the expense of native wilderness.

“Chile’s forest subsidies probably decreased biodiversity without increasing total carbon stored in aboveground biomass,” they conclude, bluntly. And one of the paper’s authors, Eric Lambin of Stanford University, spelled it out: “That’s the exact opposite of what these policies are aiming for.”

“Up until now, forests have stabilised the climate, but as they become more drought-stressed, they could become a destabilising carbon source”

German scientists report in the journal Basic and Applied Ecology that a warmer world has already delivered dramatic consequences for the forests of Germany, Austria and Switzerland.

The past five years have been the warmest in the region since records began, and 2018’s summer was the most extreme – 3.3°C above the long-term average. For spruce and other species that was the limit, and by 2019 even beech trees had died.

Since extreme drought and heat will become ever more likely, researchers need to decide what mix of species is going to survive and provide cover for threatened species. “This is going to take some time,” said Bernhard Schuldt, of the University of Würzburg.

Chinese and US researchers report in Nature Sustainability that they examined the same problems using a ground-up approach. They looked at 11,000 soil samples taken across 163 control and forested plots in northern China, to find that the carbon capture potential of afforestation schemes may have been overestimated. In soils low in carbon, plantation did increase the density of organic carbon. In those soils already rich in organic carbon, the planting seemed to lower carbon density.

European researchers, too, report in Science that they looked at data collected over 150 years at 6,000 locations to work out what happened to plants and animals as climate change and human intrusion transformed the world’s forests. Again, the answers are not simple.

No guarantee

“Surprisingly, we found that forest loss doesn’t always lead to biodiversity declines,” said Gergana Daskalova of the University of Edinburgh in Scotland. “Instead, when we lose forest cover, this can amplify the ongoing biodiversity change. For example, if a plant or animal species was declining before forest loss, its decline becomes even more severe.” Species already doing well, however, seemed to do better.

But there’s little guarantee that what works now will go on working, according to Arizona scientists writing in the journal Global Change Biology. So far, forests have helped contain climate change. But they found that North America’s most prolific tree, the Douglas fir, will absorb less carbon in future and do less to slow climate change.

They based their finding on examination of 2.7 million tree rings from 2,700 sites in the fir’s enormous ecological range. At the southern and warmest and driest end of this range, the decline in annual growth could be as high as 30%.

“More warming for trees could mean more stress, more tree death and less capacity to slow global warming,” said Margaret Evans, of the University of Arizona.

“Up until now, forests have stabilised the climate, but as they become more drought-stressed, they could become a destabilising carbon source.” − Climate News Network

Forests help to slow the challenge of climate change, don’t they? Only if climate change doesn’t fell the forests first.

LONDON, 7 July, 2020 − There could be big problems with national and international plans to plant forests to deal with climate change. One of them is uncertainty about how climate change is going to deal with the forests.

In six new studies of what might be called the plantation carbon conundrum, independent groups of researchers warn that:

That the loss of natural forests worldwide is a driver of global heating and climate change has never been in doubt. And climate scientists continue to count tomorrow’s forests as part of the answer to the threat of catastrophic climate change.

But researchers have already warned that a vow to plant one trillion trees is not of itself a readymade answer, and that national plans to conserve existing forest are less than effective.

So the challenge for foresters and ecologists is to decide what works best – and what would not. Researchers in the US argue in the journal Science that governments and policymakers need a masterplan to confront the risks forests face from the consequences of rising temperatures: drought, fire and insect disturbance.

Flying blind

Forests and other natural ecosystems absorb about one-third of all the greenhouse gas emissions that human actions release each year. New forests must be part of the answer, but only if the new timber goes on and on absorbing carbon.

“There’s a very real chance that many of those forest projects could go up in flames or to bugs or drought stress or hurricanes in the coming decades,” said William Anderegg of the University of Utah, who led the study. “Without good science to tell us what the risks are, we’re flying blind and not making the best policy decisions.”

The other papers look at aspects of the hazard, and of well-intentioned policies to combat climate change. The Bonn Challenge aims to restore an area of forest eight times the size of California, but 80% of the commitments so far involve plantations of single species or of exploitable species: fruit, for instance, and rubber on what might have been natural forest land, grassland or savannahs that support biodiversity.

Californian and Chilean researchers report in the journal Nature Sustainability that they looked at the role of long-running Chilean government subsidies in afforestation and found an uncomfortable result: exotic species flourished at the expense of native wilderness.

“Chile’s forest subsidies probably decreased biodiversity without increasing total carbon stored in aboveground biomass,” they conclude, bluntly. And one of the paper’s authors, Eric Lambin of Stanford University, spelled it out: “That’s the exact opposite of what these policies are aiming for.”

“Up until now, forests have stabilised the climate, but as they become more drought-stressed, they could become a destabilising carbon source”

German scientists report in the journal Basic and Applied Ecology that a warmer world has already delivered dramatic consequences for the forests of Germany, Austria and Switzerland.

The past five years have been the warmest in the region since records began, and 2018’s summer was the most extreme – 3.3°C above the long-term average. For spruce and other species that was the limit, and by 2019 even beech trees had died.

Since extreme drought and heat will become ever more likely, researchers need to decide what mix of species is going to survive and provide cover for threatened species. “This is going to take some time,” said Bernhard Schuldt, of the University of Würzburg.

Chinese and US researchers report in Nature Sustainability that they examined the same problems using a ground-up approach. They looked at 11,000 soil samples taken across 163 control and forested plots in northern China, to find that the carbon capture potential of afforestation schemes may have been overestimated. In soils low in carbon, plantation did increase the density of organic carbon. In those soils already rich in organic carbon, the planting seemed to lower carbon density.

European researchers, too, report in Science that they looked at data collected over 150 years at 6,000 locations to work out what happened to plants and animals as climate change and human intrusion transformed the world’s forests. Again, the answers are not simple.

No guarantee

“Surprisingly, we found that forest loss doesn’t always lead to biodiversity declines,” said Gergana Daskalova of the University of Edinburgh in Scotland. “Instead, when we lose forest cover, this can amplify the ongoing biodiversity change. For example, if a plant or animal species was declining before forest loss, its decline becomes even more severe.” Species already doing well, however, seemed to do better.

But there’s little guarantee that what works now will go on working, according to Arizona scientists writing in the journal Global Change Biology. So far, forests have helped contain climate change. But they found that North America’s most prolific tree, the Douglas fir, will absorb less carbon in future and do less to slow climate change.

They based their finding on examination of 2.7 million tree rings from 2,700 sites in the fir’s enormous ecological range. At the southern and warmest and driest end of this range, the decline in annual growth could be as high as 30%.

“More warming for trees could mean more stress, more tree death and less capacity to slow global warming,” said Margaret Evans, of the University of Arizona.

“Up until now, forests have stabilised the climate, but as they become more drought-stressed, they could become a destabilising carbon source.” − Climate News Network

Fewer blizzards for North America as snow lessens

A warming world means milder winters and softer springs. It will also mean fewer blizzards, with milder impacts.

LONDON, 12 June, 2020 – It could soon be safe to think with nostalgia of the snows of yesteryear. Snowstorms in the future in the US could happen less often, with less intensity. And they would be of a smaller size.

This is on the assumption that humans go on burning ever more fossil fuels to release ever more greenhouse gases into the atmosphere to fuel global heating.

Although winters – especially in the central US and on the Eastern Seaboard – will continue to bring snowfall, ice storms and cold snaps, by the end of the century there will be, on average, 28% fewer snowstorms. And with this drop will come a fall of a third in the precipitation of snow or frozen sleet, and the area covered by snowfall will have been reduced by 38%.

A White Christmas will also begin to seem like a happy memory, as winters begin later and spring happens ever earlier.

“If we do little to mitigate climate change, the winter season will lose much of its punch in the future,” said Walker Ashley, of Northern Illinois University.

“Annual reductions in snowfall and snow cover could amplify potential warming”

“The snow season will start later and end earlier. Generally, what we consider an abnormally mild winter now, in terms of the number and intensity of snowstorms, will be the harshest of winters late this century.

“There will be fewer snowstorms, with less overall precipitation that falls as snow, and almost a complete removal of snow events in the southern tier of the United States.”

Severe winters are part of the natural pattern of life in much of North America, and for nearly two centuries meteorologists have observed a pattern of very severe blizzards indeed: sudden calamitous snowfalls that have claimed hundreds of lives and caused billions in damage.

And although temperatures have on average risen, researchers have also repeatedly pointed out that with a rise in average warming comes a greater frequency and intensity of “extreme events”. In a continental winter, any extreme event is usually likely to be harsh. Even if there is less snow over a shorter cold season, blizzards will still happen.

Global impacts

Professor Ashley and colleagues report in the journal Nature Climate Change that they tracked snowstorms for 12 winters earlier in this century: they then used supercomputer simulations to see what would happen to their sample of actual events in a climate that had warmed by around 5°C, the predicted rise if greenhouse emissions go on unchecked.

They ended with a tally of 2,200 snowstorms across central and eastern North America over a map with a grid space of about 4kms, over a period of 24 years – a sequence that embraces the past and the future.

The simulations told a clear story. There would be less snow, across smaller snowstorm tracks, and dramatically fewer falls in the months of October, November and April.

Chicago, Boston and New York will continue to see snowstorms, but the probability of vast snowdrifts and silent streets continues to decrease. Winter travel will become safer and easier, but agriculture and other industries that depend on freshwater delivered by melting snow will feel the cost. So could the rest of the world.

“There are also climate feedbacks to consider,” said Professor Ashley. “Snow cover reflects solar radiation and helps cool the environment. So annual reductions in snowfall and snow cover could amplify potential warming.” – Climate News Network

A warming world means milder winters and softer springs. It will also mean fewer blizzards, with milder impacts.

LONDON, 12 June, 2020 – It could soon be safe to think with nostalgia of the snows of yesteryear. Snowstorms in the future in the US could happen less often, with less intensity. And they would be of a smaller size.

This is on the assumption that humans go on burning ever more fossil fuels to release ever more greenhouse gases into the atmosphere to fuel global heating.

Although winters – especially in the central US and on the Eastern Seaboard – will continue to bring snowfall, ice storms and cold snaps, by the end of the century there will be, on average, 28% fewer snowstorms. And with this drop will come a fall of a third in the precipitation of snow or frozen sleet, and the area covered by snowfall will have been reduced by 38%.

A White Christmas will also begin to seem like a happy memory, as winters begin later and spring happens ever earlier.

“If we do little to mitigate climate change, the winter season will lose much of its punch in the future,” said Walker Ashley, of Northern Illinois University.

“Annual reductions in snowfall and snow cover could amplify potential warming”

“The snow season will start later and end earlier. Generally, what we consider an abnormally mild winter now, in terms of the number and intensity of snowstorms, will be the harshest of winters late this century.

“There will be fewer snowstorms, with less overall precipitation that falls as snow, and almost a complete removal of snow events in the southern tier of the United States.”

Severe winters are part of the natural pattern of life in much of North America, and for nearly two centuries meteorologists have observed a pattern of very severe blizzards indeed: sudden calamitous snowfalls that have claimed hundreds of lives and caused billions in damage.

And although temperatures have on average risen, researchers have also repeatedly pointed out that with a rise in average warming comes a greater frequency and intensity of “extreme events”. In a continental winter, any extreme event is usually likely to be harsh. Even if there is less snow over a shorter cold season, blizzards will still happen.

Global impacts

Professor Ashley and colleagues report in the journal Nature Climate Change that they tracked snowstorms for 12 winters earlier in this century: they then used supercomputer simulations to see what would happen to their sample of actual events in a climate that had warmed by around 5°C, the predicted rise if greenhouse emissions go on unchecked.

They ended with a tally of 2,200 snowstorms across central and eastern North America over a map with a grid space of about 4kms, over a period of 24 years – a sequence that embraces the past and the future.

The simulations told a clear story. There would be less snow, across smaller snowstorm tracks, and dramatically fewer falls in the months of October, November and April.

Chicago, Boston and New York will continue to see snowstorms, but the probability of vast snowdrifts and silent streets continues to decrease. Winter travel will become safer and easier, but agriculture and other industries that depend on freshwater delivered by melting snow will feel the cost. So could the rest of the world.

“There are also climate feedbacks to consider,” said Professor Ashley. “Snow cover reflects solar radiation and helps cool the environment. So annual reductions in snowfall and snow cover could amplify potential warming.” – Climate News Network

3 bn people may face Saharan heat levels by 2070

For three billion people or more, heat levels could prove almost impossible for human civilisation – in half a century.

LONDON, 3 June, 2020 – If humans go on burning ever more fossil fuels to put ever higher concentrations of greenhouse gases into the atmosphere, then one third of the world’s population may face – within 50 years – heat levels that could be all but intolerable.

By 2070, 19% of the land area of the planet, home to 3.5 billion people, could be faced with a mean annual temperature of 29°C. That is, although there would be seasons in which temperatures fell well below this average, these would be followed by summers in which the thermometer went much higher.

Right now, only 0.8% of the land surface of the planet experiences such a mean annual temperature, and most of this space is located in the Saharan desert region of North Africa. But population growth – already highest in the poorest and hottest parts of the globe – and the projected increases in planetary average temperatures will expand this danger zone to almost one fifth of the planet’s land area, to embrace a third of the world’s people.

The conclusion – published in the Proceedings of the National Academy of Sciences – sounds like a dramatic advance on repeated warnings that planetary average temperatures could be 3°C above the long-term average for almost all of human history. But it may not be.

One important difference is that climate science forecasts tend to describe the entire planet. But almost three fourths of the planet is ocean, which is warming much more slowly than the land surfaces. Another is that climate forecasts predict average change for a sphere with a circumference of 40,000 kms. And the third factor is that such predictions do not specifically address where humans choose to live.

“Our computations show that each degree of warming above present levels corresponds to roughly one billion people falling outside of the climate niche”

Xu Chi of Nanjing University in China and his European co-authors started from the premise that humans – like all animal species – have a preferred climate niche. They looked back through 6000 years of the history of civilisation and concluded that most of humankind flourished within a climate space between annual averages of 11°C and 15°C. A much smaller number of people lived in places where the average temperature was between 20°C and 25°C.

And they found that – although civilisations rose and fell, whole peoples disappeared, wars, plagues and famines struck, and entire populations migrated to or invaded other homes – nearly all of humankind continued to prefer to live in land zones at between 11°C and 15°C.

“This strikingly constant climate niche likely represents fundamental constraints on what humans need to survive and thrive,” said Marten Scheffer of Wageningen University in the Netherlands.

But in the next 50 years, the average temperature experienced by an average human is expected to rise by 7.5°C. And because population growth is highest in the already hottest regions, these temperature rises will affect more and more people.

Warnings mount

By 2070 this total could reach 3.5bn people, across 19% of the planet’s land surface, many of them exposed to temperatures and climate conditions that right now would be considered difficult to survive.

In just the last six or seven weeks, climate scientists have warned that rising temperatures present a direct threat to the natural ecosystems on which human civilisation depends; that the number of days that US farmworkers will find dangerously hot will almost double; that potentially lethal combinations of heat and humidity trailed as a future hazard may already have arrived, in limited locations for brief periods; that some will find more heat brings more extremes of rainfall, while other regions will become increasingly arid; and that South Asia, in particular, is at increasing hazard from ever more extreme temperatures and choking pollution, thanks to global climate change.

But the latest attempt to look at the big picture trumps all of these already bleak findings. As usual, other climate researchers will question their assumptions and challenge their conclusions, but the authors are fairly sure of their ground.

“We were frankly blown away by our initial results,” said Dr Xu. “As our findings were striking, we took an extra year to carefully check all assumptions and computations. We also decided to publish all data and computer codes for transparency and to facilitate follow-up work by others.

“The results are as important to China as they are to any other nation. Clearly we will need a global approach to safeguard our children against the potentially enormous social tensions the projected change could invoke.”

Range of pressures

This also raises issues already repeatedly raised by climate forecasters: the people most threatened by climate change are already among the world’s poorest. So there will be pressure to migrate. And there will be potential for conflict.

What will happen in the next 50 years under circumstances in which governments go on authorising fossil fuel consumption is difficult to predict with any certainty. Communities will to a certain extent adapt. Economic development could help contain some of the challenges. And governments could decide to act.

“The good news is that these impacts can be greatly reduced if humanity succeeds in curbing global warming,” said Tim Lenton, of Exeter University in the UK.

“Our computations show that each degree of warming above present levels corresponds to roughly one billion people falling outside of the climate niche.” – Climate News Network

For three billion people or more, heat levels could prove almost impossible for human civilisation – in half a century.

LONDON, 3 June, 2020 – If humans go on burning ever more fossil fuels to put ever higher concentrations of greenhouse gases into the atmosphere, then one third of the world’s population may face – within 50 years – heat levels that could be all but intolerable.

By 2070, 19% of the land area of the planet, home to 3.5 billion people, could be faced with a mean annual temperature of 29°C. That is, although there would be seasons in which temperatures fell well below this average, these would be followed by summers in which the thermometer went much higher.

Right now, only 0.8% of the land surface of the planet experiences such a mean annual temperature, and most of this space is located in the Saharan desert region of North Africa. But population growth – already highest in the poorest and hottest parts of the globe – and the projected increases in planetary average temperatures will expand this danger zone to almost one fifth of the planet’s land area, to embrace a third of the world’s people.

The conclusion – published in the Proceedings of the National Academy of Sciences – sounds like a dramatic advance on repeated warnings that planetary average temperatures could be 3°C above the long-term average for almost all of human history. But it may not be.

One important difference is that climate science forecasts tend to describe the entire planet. But almost three fourths of the planet is ocean, which is warming much more slowly than the land surfaces. Another is that climate forecasts predict average change for a sphere with a circumference of 40,000 kms. And the third factor is that such predictions do not specifically address where humans choose to live.

“Our computations show that each degree of warming above present levels corresponds to roughly one billion people falling outside of the climate niche”

Xu Chi of Nanjing University in China and his European co-authors started from the premise that humans – like all animal species – have a preferred climate niche. They looked back through 6000 years of the history of civilisation and concluded that most of humankind flourished within a climate space between annual averages of 11°C and 15°C. A much smaller number of people lived in places where the average temperature was between 20°C and 25°C.

And they found that – although civilisations rose and fell, whole peoples disappeared, wars, plagues and famines struck, and entire populations migrated to or invaded other homes – nearly all of humankind continued to prefer to live in land zones at between 11°C and 15°C.

“This strikingly constant climate niche likely represents fundamental constraints on what humans need to survive and thrive,” said Marten Scheffer of Wageningen University in the Netherlands.

But in the next 50 years, the average temperature experienced by an average human is expected to rise by 7.5°C. And because population growth is highest in the already hottest regions, these temperature rises will affect more and more people.

Warnings mount

By 2070 this total could reach 3.5bn people, across 19% of the planet’s land surface, many of them exposed to temperatures and climate conditions that right now would be considered difficult to survive.

In just the last six or seven weeks, climate scientists have warned that rising temperatures present a direct threat to the natural ecosystems on which human civilisation depends; that the number of days that US farmworkers will find dangerously hot will almost double; that potentially lethal combinations of heat and humidity trailed as a future hazard may already have arrived, in limited locations for brief periods; that some will find more heat brings more extremes of rainfall, while other regions will become increasingly arid; and that South Asia, in particular, is at increasing hazard from ever more extreme temperatures and choking pollution, thanks to global climate change.

But the latest attempt to look at the big picture trumps all of these already bleak findings. As usual, other climate researchers will question their assumptions and challenge their conclusions, but the authors are fairly sure of their ground.

“We were frankly blown away by our initial results,” said Dr Xu. “As our findings were striking, we took an extra year to carefully check all assumptions and computations. We also decided to publish all data and computer codes for transparency and to facilitate follow-up work by others.

“The results are as important to China as they are to any other nation. Clearly we will need a global approach to safeguard our children against the potentially enormous social tensions the projected change could invoke.”

Range of pressures

This also raises issues already repeatedly raised by climate forecasters: the people most threatened by climate change are already among the world’s poorest. So there will be pressure to migrate. And there will be potential for conflict.

What will happen in the next 50 years under circumstances in which governments go on authorising fossil fuel consumption is difficult to predict with any certainty. Communities will to a certain extent adapt. Economic development could help contain some of the challenges. And governments could decide to act.

“The good news is that these impacts can be greatly reduced if humanity succeeds in curbing global warming,” said Tim Lenton, of Exeter University in the UK.

“Our computations show that each degree of warming above present levels corresponds to roughly one billion people falling outside of the climate niche.” – Climate News Network

Global heating means a wetter and warmer world

A wetter and even warmer world will result from faster global warming. The evidence is in the sands of time.

LONDON, 14 May, 2020 – A warmer world may not be just a wetter one. It may get even warmer as well. New studies suggest the heavier rain that will accompany ever-higher global average atmospheric temperatures is in itself likely to trigger ever more carbon dioxide release from tropical soils.

This is what engineers call positive feedback. The very symptoms of a warming world become part of the fuel for accelerating global temperature change.

And the warning is derived not just from models of climate change, but once again from evidence from the past.

Scientists from the US, Canada and Switzerland report in the journal Nature that for the past 18,000 years, the “time of residence” of carbon in the soils of the Ganges-Brahmaputra river basin has been controlled by India’s summer monsoon rainfall.

The lower the rainfall, the higher the length of stored carbon. But as levels of downpour go up, so does the activity of the microbes that turn vegetable matter back into carbon dioxide, and the levels of stored soil carbon go down.

“Climate change is likely to increase rainfall in tropical regions, further accelerating respiration of soil carbon, and adding even more CO2 to the atmosphere”

Right now, global atmospheric concentrations of carbon dioxide have risen from 285 parts per million – the average for most of human history – to 416 ppm as humans clear ever more forest and burn ever more fossil fuels. This 416ppm adds up to about 750 billion tonnes of carbon. The planet’s soils are home to an estimated 3,500 bn tonnes: more than four times as much.

“Our results suggest that future hydroclimate changes in tropical regions are likely to accelerate soil carbon destabilisation, further increasing carbon dioxide concentrations,” the scientists warn.

As temperatures rise, the atmosphere’s capacity to absorb moisture also increases. As temperatures rise, so does direct evaporation from oceans, lakes, rivers and soils. This water vapour will eventually fall as rain, but unevenly: those regions already rainy will become rainier, while drylands are likely to become increasingly arid.

The Ganges and Brahmaputra carry more than a billion tonnes of sediment – most of it eroded from the Himalayan mountain chain – into the Bay of Bengal each year, and cores of sediment taken from the sea floor provide a good record of climate conditions for the last 18,000 years, as the Ice Age began to wane, and the glaciers retreated to permit a hunter-gatherer species to cultivate cereals, domesticate animals, build permanent settlements and found human civilisation.

Radiocarbon readings mean that researchers can date the sediments, and preserved organic molecules from land plants provide an indicator of conditions at those dates.

Methane adds speed

Scientists have repeatedly warned that climate change in the Arctic – the fastest-warming zone of all – is likely to be matched by the release of soil carbon in the form of the greenhouse gas methane from the thawing permafrost, to accelerate yet more warming.

As the once-frozen ground warms up, and vegetation moves further and further north, an estimated 600 million tonnes of carbon is released into the atmosphere every year.

Now, and for different reasons, the same could be true of the tropics, and the evidence is in the sands of time, deposited by one of the world’s great river systems. As the Ice Age ended, monsoon rains began to increase and in 2,600 years soil respiration – and therefore carbon release – doubled. Since then, monsoon rainfall has increased threefold.

“We found that shifts toward a warmer and wetter climate in the drainage basin of the Ganges and Brahmaputra rivers over the last 18,000 years enhanced rates of soil respiration and decreased stocks of soil carbon,” said Christopher Hein, of the Virginia Institute of Marine Science, who led the study.

“This has direct implications for the Earth’s future, as climate change is likely to increase rainfall in tropical regions, further accelerating respiration of soil carbon, and adding even more CO2 to the atmosphere than that directly added by humans.” – Climate News Network

A wetter and even warmer world will result from faster global warming. The evidence is in the sands of time.

LONDON, 14 May, 2020 – A warmer world may not be just a wetter one. It may get even warmer as well. New studies suggest the heavier rain that will accompany ever-higher global average atmospheric temperatures is in itself likely to trigger ever more carbon dioxide release from tropical soils.

This is what engineers call positive feedback. The very symptoms of a warming world become part of the fuel for accelerating global temperature change.

And the warning is derived not just from models of climate change, but once again from evidence from the past.

Scientists from the US, Canada and Switzerland report in the journal Nature that for the past 18,000 years, the “time of residence” of carbon in the soils of the Ganges-Brahmaputra river basin has been controlled by India’s summer monsoon rainfall.

The lower the rainfall, the higher the length of stored carbon. But as levels of downpour go up, so does the activity of the microbes that turn vegetable matter back into carbon dioxide, and the levels of stored soil carbon go down.

“Climate change is likely to increase rainfall in tropical regions, further accelerating respiration of soil carbon, and adding even more CO2 to the atmosphere”

Right now, global atmospheric concentrations of carbon dioxide have risen from 285 parts per million – the average for most of human history – to 416 ppm as humans clear ever more forest and burn ever more fossil fuels. This 416ppm adds up to about 750 billion tonnes of carbon. The planet’s soils are home to an estimated 3,500 bn tonnes: more than four times as much.

“Our results suggest that future hydroclimate changes in tropical regions are likely to accelerate soil carbon destabilisation, further increasing carbon dioxide concentrations,” the scientists warn.

As temperatures rise, the atmosphere’s capacity to absorb moisture also increases. As temperatures rise, so does direct evaporation from oceans, lakes, rivers and soils. This water vapour will eventually fall as rain, but unevenly: those regions already rainy will become rainier, while drylands are likely to become increasingly arid.

The Ganges and Brahmaputra carry more than a billion tonnes of sediment – most of it eroded from the Himalayan mountain chain – into the Bay of Bengal each year, and cores of sediment taken from the sea floor provide a good record of climate conditions for the last 18,000 years, as the Ice Age began to wane, and the glaciers retreated to permit a hunter-gatherer species to cultivate cereals, domesticate animals, build permanent settlements and found human civilisation.

Radiocarbon readings mean that researchers can date the sediments, and preserved organic molecules from land plants provide an indicator of conditions at those dates.

Methane adds speed

Scientists have repeatedly warned that climate change in the Arctic – the fastest-warming zone of all – is likely to be matched by the release of soil carbon in the form of the greenhouse gas methane from the thawing permafrost, to accelerate yet more warming.

As the once-frozen ground warms up, and vegetation moves further and further north, an estimated 600 million tonnes of carbon is released into the atmosphere every year.

Now, and for different reasons, the same could be true of the tropics, and the evidence is in the sands of time, deposited by one of the world’s great river systems. As the Ice Age ended, monsoon rains began to increase and in 2,600 years soil respiration – and therefore carbon release – doubled. Since then, monsoon rainfall has increased threefold.

“We found that shifts toward a warmer and wetter climate in the drainage basin of the Ganges and Brahmaputra rivers over the last 18,000 years enhanced rates of soil respiration and decreased stocks of soil carbon,” said Christopher Hein, of the Virginia Institute of Marine Science, who led the study.

“This has direct implications for the Earth’s future, as climate change is likely to increase rainfall in tropical regions, further accelerating respiration of soil carbon, and adding even more CO2 to the atmosphere than that directly added by humans.” – Climate News Network

Heatwaves too hot and wet for human life are here

Lethal heatwaves carrying air turned too hot and wet to survive are a threat which has arrived, thanks to climate change.

LONDON, 11 May, 2020 – Scientists who have repeatedly warned of future lethal conditions of temperature and humidity caused by heatwaves in a world of climate change have grim news: that future has already arrived.

They have combed through local records to identify thousands of episodes in which the dangerous combination of high temperatures and high humidity has risen to levels at which humans could not in theory survive for long. These have happened in Asia, Africa, South and North America and Australia.

More than a dozen such episodes have already been recorded around the Persian Gulf, a region that – researchers warned years ago – could one day become deadly for outdoor workers.

These outbreaks of both sweltering heat and stifling humidity have, researchers report in the journal Science Advances, so far been confined to localised areas and have lasted only hours, but they are now increasing in frequency and intensity.

There are many ways in which extreme heat can lead to death – one group has identified as many as 27 – but at its simplest, a species adapted to maintain a stable temperature by shivering when cold and perspiring when too hot can be overwhelmed by very high temperatures, or in conditions in which the body can no longer lose heat because the air is too moist for perspiration to evaporate.

“Previous studies projected that this would happen several decades from now, but this shows it’s happening right now”

Scientists measure such hazards by what they call a “wet bulb” temperature, and even the strongest and best adapted humans cannot work safely outdoors when this hits 32°C.

Potentially fatal readings identified in hourly reports from 7,877 weather stations between 1979 and 2017 confirm that such temperatures have already reached dangerous levels – and even as high as 35°C – in Saudi Arabia, Doha in Qatar, in the United Arab Emirates, in Texas, Louisiana, Mississippi, Alabama and Florida in the US, India and Bangladesh, south China, northwest Australia and Iran.

Researchers began warning years ago of the notional threat of extreme heat and extreme humidity in a world in which humans continue to burn fossil fuels and increase greenhouse gases’ concentrations in the atmosphere, and repeated studies have confirmed the reality of the hazard.

Humans cannot survive outdoor “wet bulb” conditions of 35°C for long. The number of readings beyond 30°C has doubled since 1979. There have been 1,000 readings of 31°C and 80 of 33°C.

“Previous studies projected that this would happen several decades from now, but this shows it’s happening right now,” said Colin Raymond, who completed the research at the Lamont-Doherty Earth Observatory at Columbia University, but who is now at Nasa’s Jet Propulsion Laboratory.

“The times these events last will increase, and the areas they affect will grow, in direct correlation with global warming.” – Climate News Network

Lethal heatwaves carrying air turned too hot and wet to survive are a threat which has arrived, thanks to climate change.

LONDON, 11 May, 2020 – Scientists who have repeatedly warned of future lethal conditions of temperature and humidity caused by heatwaves in a world of climate change have grim news: that future has already arrived.

They have combed through local records to identify thousands of episodes in which the dangerous combination of high temperatures and high humidity has risen to levels at which humans could not in theory survive for long. These have happened in Asia, Africa, South and North America and Australia.

More than a dozen such episodes have already been recorded around the Persian Gulf, a region that – researchers warned years ago – could one day become deadly for outdoor workers.

These outbreaks of both sweltering heat and stifling humidity have, researchers report in the journal Science Advances, so far been confined to localised areas and have lasted only hours, but they are now increasing in frequency and intensity.

There are many ways in which extreme heat can lead to death – one group has identified as many as 27 – but at its simplest, a species adapted to maintain a stable temperature by shivering when cold and perspiring when too hot can be overwhelmed by very high temperatures, or in conditions in which the body can no longer lose heat because the air is too moist for perspiration to evaporate.

“Previous studies projected that this would happen several decades from now, but this shows it’s happening right now”

Scientists measure such hazards by what they call a “wet bulb” temperature, and even the strongest and best adapted humans cannot work safely outdoors when this hits 32°C.

Potentially fatal readings identified in hourly reports from 7,877 weather stations between 1979 and 2017 confirm that such temperatures have already reached dangerous levels – and even as high as 35°C – in Saudi Arabia, Doha in Qatar, in the United Arab Emirates, in Texas, Louisiana, Mississippi, Alabama and Florida in the US, India and Bangladesh, south China, northwest Australia and Iran.

Researchers began warning years ago of the notional threat of extreme heat and extreme humidity in a world in which humans continue to burn fossil fuels and increase greenhouse gases’ concentrations in the atmosphere, and repeated studies have confirmed the reality of the hazard.

Humans cannot survive outdoor “wet bulb” conditions of 35°C for long. The number of readings beyond 30°C has doubled since 1979. There have been 1,000 readings of 31°C and 80 of 33°C.

“Previous studies projected that this would happen several decades from now, but this shows it’s happening right now,” said Colin Raymond, who completed the research at the Lamont-Doherty Earth Observatory at Columbia University, but who is now at Nasa’s Jet Propulsion Laboratory.

“The times these events last will increase, and the areas they affect will grow, in direct correlation with global warming.” – Climate News Network

North Pole may be clear water by mid-century

This story is a part of Covering Climate Now’s week of coverage focused on Climate Solutions, to mark the 50th anniversary of Earth Day. Covering Climate Now is a global journalism collaboration committed to strengthening coverage of the climate story.

 

Within 30 years, there could be clear blue water over the North Pole – not good news for most of the planet.

LONDON, 25 April, 2020 – Within three decades, the North Pole could be free of sea ice in the late summer. The latest and most advanced climate simulations, tested by 21 research institutes from around the world, predict that if humans go on emitting ever-greater volumes of carbon dioxide from fossil fuel combustion and other actions, then before 2050, for the first time in human history, there could be no ice over the North Pole.

And a team of research scientists aboard a ship intent on spending a year observing the drift of sea ice across the Arctic Ocean has been warned that they may have to finish early: the ice supposed to hold the ship fast could melt too soon.

The loss of sea ice promises devastating consequences for the rich life in the most northern waters. The ice reflects sunlight back into space and keeps the Arctic cool. It also provides space for seals on which to haul out, and hunting grounds for blubber-hungry polar bears.

And although human inaction in the climate emergency makes the loss of polar ice ever more probable, so much greenhouse gas has already built up in the planetary atmosphere that it could happen anyway.

Taken aback

“If we reduce global emissions rapidly and substantially, and thus keep our warming below 2°C relative to pre-industrial levels, sea ice will nevertheless likely disappear occasionally in summer even before 2050,” said Dirk Notz, of the University of Hamburg in Germany, who led the study. “This really surprised us.”

Climate scientists first warned of the accelerating loss of Arctic sea ice two decades ago, and have repeatedly re-examined the climate predictions, each time with much the same outcome.

The loss of ice promises new trade routes between Atlantic and Pacific Oceans, but the cost of a warming Arctic could have catastrophic economic consequences.

The pattern of the northern hemisphere climate is driven by the temperature difference between the Arctic and the tropics, and rapid polar warming both disturbs temperate climate regimes and brings ever higher sea levels, with accelerating ice loss from Greenland, which right now bears enough ice to raise global sea levels by more than seven metres.

“The changes in the Arctic system are so incredibly rapid that even our satellite observations from 15 years ago are unlike the Arctic today”

Dr Notz and his co-authors report in the journal Geophysical Research Letters that they used the very latest climate model developed for the Intergovernmental Panel on Climate Change and tested it on a range of 40 possible climate outcomes.

In most simulations, the Arctic sea ice was reduced to less than a million square kilometres – polar researchers call this “practically sea-ice free” – in the month of September for the first time before 2050. Even if human fossil fuel use was sharply reduced, the ocean could be free of ice some years; if not, the pole could become open water most years.

And a second study, in the journal The Cryosphere, offers a measure of the sea ice loss even now. More than a century ago, the great explorer Fridtjof Nansen sailed his ship the Fram into the polar ice, became fast, and travelled with the floe across the Arctic Ocean.

His became the first scientific observation of a phenomenon called the trans-Polar drift, which takes algae, sediments and nutrients – and increasingly, plastic pollution – across the Arctic from Siberia to Canada and Greenland.

Melted out

In October a team of international researchers boarded a vessel called Polarstern with the intention of measuring the ice movement in the modern Arctic in more detail. They had planned for a year fast in the ice. Their project even has a name: Mosaic, or Multidisciplinary drifting Observatory for the Study of Arctic Climate.

But climate simulations by the US scientists reveal that in every sense, the project is on thin ice and could end prematurely. The flow of ice could be faster, and carry the ship further, than expected: nearly one in five of the simulations also predicted that the ship could melt out of the ice in less than a year.

“The changes in the Arctic system are so incredibly rapid that even our satellite observations from 15 years ago are unlike the Arctic today,” said one of the authors, Marika Holland of the US National Center for Atmospheric Research.

“Now there is thinner ice, which moves more quickly, and there is less snow cover. It is a totally different ice regime.” – Climate News Network

This story is a part of Covering Climate Now’s week of coverage focused on Climate Solutions, to mark the 50th anniversary of Earth Day. Covering Climate Now is a global journalism collaboration committed to strengthening coverage of the climate story.

 

Within 30 years, there could be clear blue water over the North Pole – not good news for most of the planet.

LONDON, 25 April, 2020 – Within three decades, the North Pole could be free of sea ice in the late summer. The latest and most advanced climate simulations, tested by 21 research institutes from around the world, predict that if humans go on emitting ever-greater volumes of carbon dioxide from fossil fuel combustion and other actions, then before 2050, for the first time in human history, there could be no ice over the North Pole.

And a team of research scientists aboard a ship intent on spending a year observing the drift of sea ice across the Arctic Ocean has been warned that they may have to finish early: the ice supposed to hold the ship fast could melt too soon.

The loss of sea ice promises devastating consequences for the rich life in the most northern waters. The ice reflects sunlight back into space and keeps the Arctic cool. It also provides space for seals on which to haul out, and hunting grounds for blubber-hungry polar bears.

And although human inaction in the climate emergency makes the loss of polar ice ever more probable, so much greenhouse gas has already built up in the planetary atmosphere that it could happen anyway.

Taken aback

“If we reduce global emissions rapidly and substantially, and thus keep our warming below 2°C relative to pre-industrial levels, sea ice will nevertheless likely disappear occasionally in summer even before 2050,” said Dirk Notz, of the University of Hamburg in Germany, who led the study. “This really surprised us.”

Climate scientists first warned of the accelerating loss of Arctic sea ice two decades ago, and have repeatedly re-examined the climate predictions, each time with much the same outcome.

The loss of ice promises new trade routes between Atlantic and Pacific Oceans, but the cost of a warming Arctic could have catastrophic economic consequences.

The pattern of the northern hemisphere climate is driven by the temperature difference between the Arctic and the tropics, and rapid polar warming both disturbs temperate climate regimes and brings ever higher sea levels, with accelerating ice loss from Greenland, which right now bears enough ice to raise global sea levels by more than seven metres.

“The changes in the Arctic system are so incredibly rapid that even our satellite observations from 15 years ago are unlike the Arctic today”

Dr Notz and his co-authors report in the journal Geophysical Research Letters that they used the very latest climate model developed for the Intergovernmental Panel on Climate Change and tested it on a range of 40 possible climate outcomes.

In most simulations, the Arctic sea ice was reduced to less than a million square kilometres – polar researchers call this “practically sea-ice free” – in the month of September for the first time before 2050. Even if human fossil fuel use was sharply reduced, the ocean could be free of ice some years; if not, the pole could become open water most years.

And a second study, in the journal The Cryosphere, offers a measure of the sea ice loss even now. More than a century ago, the great explorer Fridtjof Nansen sailed his ship the Fram into the polar ice, became fast, and travelled with the floe across the Arctic Ocean.

His became the first scientific observation of a phenomenon called the trans-Polar drift, which takes algae, sediments and nutrients – and increasingly, plastic pollution – across the Arctic from Siberia to Canada and Greenland.

Melted out

In October a team of international researchers boarded a vessel called Polarstern with the intention of measuring the ice movement in the modern Arctic in more detail. They had planned for a year fast in the ice. Their project even has a name: Mosaic, or Multidisciplinary drifting Observatory for the Study of Arctic Climate.

But climate simulations by the US scientists reveal that in every sense, the project is on thin ice and could end prematurely. The flow of ice could be faster, and carry the ship further, than expected: nearly one in five of the simulations also predicted that the ship could melt out of the ice in less than a year.

“The changes in the Arctic system are so incredibly rapid that even our satellite observations from 15 years ago are unlike the Arctic today,” said one of the authors, Marika Holland of the US National Center for Atmospheric Research.

“Now there is thinner ice, which moves more quickly, and there is less snow cover. It is a totally different ice regime.” – Climate News Network

Cloudless skies hasten Greenland’s ice loss

This story is a part of Covering Climate Now’s week of coverage focused on Climate Solutions, to mark the 50th anniversary of Earth Day. Covering Climate Now is a global journalism collaboration committed to strengthening coverage of the climate story.

 

The bad news about Greenland’s ice loss has just got even worse. Blame it on mischief by blue skies all day long.

LONDON, 22 April, 2020 – Greenland’s ice loss reached record levels in 2019, and scientists think they’ve identified the culprit: the good weather which normally brings the snow-bearing clouds to the High Arctic.

The huge island, the biggest bank of ice in the northern hemisphere, has been losing ice at an ever-increasing rate in a rapidly warming world. Last year it shed more ice than ever, and this time because the skies were unusually clear.

There is enough ice on Greenland to raise global sea levels by more than seven metres. A recent study established that in the years between 1992 and 2018, rates of polar ice loss have risen six-fold, and so much water has flowed off the Greenland ice surface that sea levels have risen by more than 10mm everywhere.

Now a new study by US and Belgian scientists in the journal The Cryosphere confirms that 2019 was even worse. Because of good weather and cloudless skies, only enough snow fell to deposit 50 billion tonnes of ice into the island’s profit-and-loss ice account. The average annual deposit between 1981 and 2010 was about 375bn tonnes.

But glaciers still flowed towards the sea at an ever-increasing rate, summer snow melt continued to flow off the ice sheet, and icebergs continued to calve, so on balance the island lost 600 billion tonnes of ice: enough to raise global sea levels by 1.5mm. This is the biggest overall loss of ice since records in Greenland began in 1948.

“These atmospheric conditions are becoming more and more frequent over the past few decades. It is very likely that this is due to the waviness of the jet stream”

The cause: unusual spells of high atmospheric pressure over the island for unusually long periods of time. That stopped the formation of clouds, and that meant less precipitation, in the form of snow. Snow reflects solar radiation more effectively than ice, so the surface absorbed more heat and melting also accelerated.

The pattern of warm moist clouds trapped over northern Greenland by the heat that would normally radiate off the ice, instead of releasing snow, also emitted their own heat, to make things worse. The worst year for surface melting remains 2012, but the summer of 2019 was a good second.

The implication is that things could get worse, and losses of Greenland ice could accelerate.

“These atmospheric conditions are becoming more and more frequent over the past few decades,” said Marco Tedesco, of the Lamont-Doherty Earth Observatory at the University of Columbia in the US, the lead author.

“It is very likely that this is due to the waviness of the jet stream, which we think is related to, among other things, the disappearance of snow cover in Siberia, the disappearance of sea ice, and the difference in the rate at which temperature is increasing in the Arctic versus the mid-latitudes.” – Climate News Network

This story is a part of Covering Climate Now’s week of coverage focused on Climate Solutions, to mark the 50th anniversary of Earth Day. Covering Climate Now is a global journalism collaboration committed to strengthening coverage of the climate story.

 

The bad news about Greenland’s ice loss has just got even worse. Blame it on mischief by blue skies all day long.

LONDON, 22 April, 2020 – Greenland’s ice loss reached record levels in 2019, and scientists think they’ve identified the culprit: the good weather which normally brings the snow-bearing clouds to the High Arctic.

The huge island, the biggest bank of ice in the northern hemisphere, has been losing ice at an ever-increasing rate in a rapidly warming world. Last year it shed more ice than ever, and this time because the skies were unusually clear.

There is enough ice on Greenland to raise global sea levels by more than seven metres. A recent study established that in the years between 1992 and 2018, rates of polar ice loss have risen six-fold, and so much water has flowed off the Greenland ice surface that sea levels have risen by more than 10mm everywhere.

Now a new study by US and Belgian scientists in the journal The Cryosphere confirms that 2019 was even worse. Because of good weather and cloudless skies, only enough snow fell to deposit 50 billion tonnes of ice into the island’s profit-and-loss ice account. The average annual deposit between 1981 and 2010 was about 375bn tonnes.

But glaciers still flowed towards the sea at an ever-increasing rate, summer snow melt continued to flow off the ice sheet, and icebergs continued to calve, so on balance the island lost 600 billion tonnes of ice: enough to raise global sea levels by 1.5mm. This is the biggest overall loss of ice since records in Greenland began in 1948.

“These atmospheric conditions are becoming more and more frequent over the past few decades. It is very likely that this is due to the waviness of the jet stream”

The cause: unusual spells of high atmospheric pressure over the island for unusually long periods of time. That stopped the formation of clouds, and that meant less precipitation, in the form of snow. Snow reflects solar radiation more effectively than ice, so the surface absorbed more heat and melting also accelerated.

The pattern of warm moist clouds trapped over northern Greenland by the heat that would normally radiate off the ice, instead of releasing snow, also emitted their own heat, to make things worse. The worst year for surface melting remains 2012, but the summer of 2019 was a good second.

The implication is that things could get worse, and losses of Greenland ice could accelerate.

“These atmospheric conditions are becoming more and more frequent over the past few decades,” said Marco Tedesco, of the Lamont-Doherty Earth Observatory at the University of Columbia in the US, the lead author.

“It is very likely that this is due to the waviness of the jet stream, which we think is related to, among other things, the disappearance of snow cover in Siberia, the disappearance of sea ice, and the difference in the rate at which temperature is increasing in the Arctic versus the mid-latitudes.” – Climate News Network

Tree rings and weather data warn of megadrought

Farmers in the US West know they have a drought, but may not yet realise these arid years could become a megadrought.

LONDON, 17 April, 2020 – Climate change could be pushing the US west and northern Mexico towards the most severe and most extended period of drought observed in a thousand years of US history, a full-blown megadrought.

Natural atmospheric forces have always triggered prolonged spells with little rain. But warming driven by profligate human use of fossil fuels could now be making a bad situation much worse.

The warning of what climate scientists call a megadrought – outlined in the journal Science – is based not on computer simulations but on direct testimony from more than a century of weather records and the much longer story told by 1200 consecutive years of evidence preserved in the annual growth rings of trees that provide a record of changing levels of soil moisture.

“Earlier studies were largely model projections of the future. We are no longer looking at projections, but at where we are now,” said Park Williams, a bioclimatologist at the Lamont Doherty Earth Observatory of Columbia University in the US.

“We now have enough observations of current drought and tree ring records of past drought to say we’re on the same trajectory as the worst prehistoric droughts.”

Repeating the past

Previous research has already linked catastrophic drought to turmoil among pre-Columbian civilisations in the American Southwest.

Studies by other groups have also warned that what happened in the past could happen again, as carbon dioxide emissions from fossil fuel combustion enrich the atmosphere, raise temperatures and parch the soils of the US West.

Global heating has been repeatedly linked to the last devastating drought in California, and to the possible return of Dust Bowl conditions in the Midwestern grain belt.

The latest study delivers a long-term analysis of conditions across nine US states, from Oregon and Montana in the north down to California, New Mexico and part of northern Mexico.

With the evidence preserved in old tree trunks, the scientists identified dozens of droughts in the region from 800 AD. They found four megadroughts – periods in which the conditions became extreme – between 800 and 1600. Since then there have been no droughts that could be matched with these – so far.

And then the researchers matched the megadrought tree ring evidence with soil moisture records collected in the first 19 years of this century, and compared this with any 19-year period in the prehistoric droughts.

“We’ll need more and more good luck to break out of drought, and less and less bad luck to get into drought”

They found that the current prolonged dry spell is already more pronounced than the three earliest records of megadrought. The fourth megadrought – it ran from 1575 to 1603 – may still have been the worst of all, but the match with the present years is so close that nobody can be sure.

But the team behind the Science study is sure of one thing. This drought right now is affecting wider stretches of landscape more consistently than any of the earlier megadroughts, and this, they say, is a signature of global heating. All the ancient megadroughts lasted longer, and sometimes much longer, than 19 years, but all began in a way very similar to the present.

The snowpack in the western high mountains has fallen dramatically, the flow of the rivers has dwindled, lake levels have fallen, farmers have been  hit and the wildfires have become more prolonged and more intense.

Drought and even the chance of megadrought may be a fact of life in the US West. During occasional natural atmospheric cycles, the tropical Pacific cools and storm tracks shift further north, taking rainfall away from the US drylands.

But since 2000, average air temperatures in the western states have risen by more than 1.2°C above the normal over earlier centuries. So soils already starved of rain began to lose their stored moisture at an ever-increasing rate.

Worsened by heating

Without the additional global heating, this drought might have happened anyway, and perhaps even been the 11th worst ever recorded, rather than almost the worst ever in human experience.

“It doesn’t matter if this is exactly the worst drought ever,” said Benjamin Cook, a co-author, from Nasa’s Goddard Institute for Space Studies. “What matters is that it has been made much worse than it could have been because of climate change.”

The researchers also found that the 20th century was the wettest century in the entire 1200 year record, and this relatively plentiful supply of water must have helped enrich the US West and make California, for instance, become the Golden State, the most populous in the US.

“Because the background is getting warmer, the dice are increasingly loaded towards longer and more severe droughts,” Professor Williams said. “We may get lucky, and natural variability will bring more precipitation for a while.

“But going forward, we’ll need more and more good luck to break out of drought, and less and less bad luck to get into drought.” – Climate News Network

Farmers in the US West know they have a drought, but may not yet realise these arid years could become a megadrought.

LONDON, 17 April, 2020 – Climate change could be pushing the US west and northern Mexico towards the most severe and most extended period of drought observed in a thousand years of US history, a full-blown megadrought.

Natural atmospheric forces have always triggered prolonged spells with little rain. But warming driven by profligate human use of fossil fuels could now be making a bad situation much worse.

The warning of what climate scientists call a megadrought – outlined in the journal Science – is based not on computer simulations but on direct testimony from more than a century of weather records and the much longer story told by 1200 consecutive years of evidence preserved in the annual growth rings of trees that provide a record of changing levels of soil moisture.

“Earlier studies were largely model projections of the future. We are no longer looking at projections, but at where we are now,” said Park Williams, a bioclimatologist at the Lamont Doherty Earth Observatory of Columbia University in the US.

“We now have enough observations of current drought and tree ring records of past drought to say we’re on the same trajectory as the worst prehistoric droughts.”

Repeating the past

Previous research has already linked catastrophic drought to turmoil among pre-Columbian civilisations in the American Southwest.

Studies by other groups have also warned that what happened in the past could happen again, as carbon dioxide emissions from fossil fuel combustion enrich the atmosphere, raise temperatures and parch the soils of the US West.

Global heating has been repeatedly linked to the last devastating drought in California, and to the possible return of Dust Bowl conditions in the Midwestern grain belt.

The latest study delivers a long-term analysis of conditions across nine US states, from Oregon and Montana in the north down to California, New Mexico and part of northern Mexico.

With the evidence preserved in old tree trunks, the scientists identified dozens of droughts in the region from 800 AD. They found four megadroughts – periods in which the conditions became extreme – between 800 and 1600. Since then there have been no droughts that could be matched with these – so far.

And then the researchers matched the megadrought tree ring evidence with soil moisture records collected in the first 19 years of this century, and compared this with any 19-year period in the prehistoric droughts.

“We’ll need more and more good luck to break out of drought, and less and less bad luck to get into drought”

They found that the current prolonged dry spell is already more pronounced than the three earliest records of megadrought. The fourth megadrought – it ran from 1575 to 1603 – may still have been the worst of all, but the match with the present years is so close that nobody can be sure.

But the team behind the Science study is sure of one thing. This drought right now is affecting wider stretches of landscape more consistently than any of the earlier megadroughts, and this, they say, is a signature of global heating. All the ancient megadroughts lasted longer, and sometimes much longer, than 19 years, but all began in a way very similar to the present.

The snowpack in the western high mountains has fallen dramatically, the flow of the rivers has dwindled, lake levels have fallen, farmers have been  hit and the wildfires have become more prolonged and more intense.

Drought and even the chance of megadrought may be a fact of life in the US West. During occasional natural atmospheric cycles, the tropical Pacific cools and storm tracks shift further north, taking rainfall away from the US drylands.

But since 2000, average air temperatures in the western states have risen by more than 1.2°C above the normal over earlier centuries. So soils already starved of rain began to lose their stored moisture at an ever-increasing rate.

Worsened by heating

Without the additional global heating, this drought might have happened anyway, and perhaps even been the 11th worst ever recorded, rather than almost the worst ever in human experience.

“It doesn’t matter if this is exactly the worst drought ever,” said Benjamin Cook, a co-author, from Nasa’s Goddard Institute for Space Studies. “What matters is that it has been made much worse than it could have been because of climate change.”

The researchers also found that the 20th century was the wettest century in the entire 1200 year record, and this relatively plentiful supply of water must have helped enrich the US West and make California, for instance, become the Golden State, the most populous in the US.

“Because the background is getting warmer, the dice are increasingly loaded towards longer and more severe droughts,” Professor Williams said. “We may get lucky, and natural variability will bring more precipitation for a while.

“But going forward, we’ll need more and more good luck to break out of drought, and less and less bad luck to get into drought.” – Climate News Network

Entire wild systems at risk from rising global heat

Rising global heat raises risks to the creatures and ecosystems that sustain human society. Collapse could be sudden and near-total.

LONDON, 14 April, 2020 – Worldwide, entire ecosystems could collapse as the planetary thermometer soars: rising global heat could see the Earth’s average temperature rise by 4°C (right now the world is heading for a rise of more than three degrees).

And then one in six of the complex communities of plants and animals in wetlands, grasslands, forests or oceans could drastically alter or fail.

That is because at such temperatures more than one in five of the creatures in that network of co-dependencies would in the same decade experience temperatures beyond their normal tolerance levels.

The prediction is based on data that pinpoint the geographical ranges of 30,652 birds, mammals, reptiles, amphibians, fish and plants, and climate data from 1850 to 2005.

“We found that climate change risks to biodiversity don’t increase gradually,” said Alex Pigot of Imperial College London, in the UK, who led the research.

Abrupt change

“Instead, as the climate warms, within a certain area most species will be able to cope for a while, before crossing a temperature threshold, when a large proportion of the species will suddenly face conditions they’ve never experienced before.

“It’s not a slippery slope, but a series of cliff edges, hitting different areas at different times.”

The finding – published in the journal Nature – should come as no great surprise to the world’s zoologists, botanists, ecologists, foresters, marine scientists and conservationists.

They have repeatedly warned that as global temperatures rise, and climate patterns become increasingly unstable, in response to ever-higher greenhouse gas emissions from power stations and car exhausts, and forest destruction, both individual species and even whole habitats could be exposed to loss and species extinction.

Such threats can be prefigured even in subtle changes in species behaviour. Within this month, Spanish ornithologists who have studied the nightingale Luscinia megarhynchos since 1995 report in the journal The Auk: Ornithological Advances that in two decades, as Spanish summers became hotter and more parched, the wings of each new generation of birds have become progressively shorter.

“Our findings highlight the urgent need for climate change mitigation, by immediately and drastically reducing emissions, which could help save thousands of species from extinction”

A shorter wingspan in proportion to body length creates potential survival problems for a species that breeds in Europe but prefers to fly to sub-Saharan Africa for the winter.

And across the Atlantic, another species, the American robin Turdus migratorius now takes wing 12 days earlier each spring in Mexico and the US to fly to its summer breeding grounds in Canada and Alaska.

The ornithologists report in the journal Environmental Research Letters that GPS tracking of 55 individual birds confirms that the bird may be timing its migration to the snow melt and the first arrival of insects in the high latitudes nearer the fast-warming Arctic.

So far, the planet on average has warmed around only 1°C above the long-term average for most of human history. But Dr Pigot and colleagues in the US and South Africa wanted to look at the big picture of potential change in species everywhere as global heating reaches 2°C – the upper limits that the world’s nations promised in a key international agreement reached in Paris in 2015 – and then goes on soaring.

So they took their species data, and mapped it onto a global grid divided into 100-km-square cells, and then fine-tuned the temperature predicted by climate scientists to see where species and their habitats would experience ever-rising heat beyond their comfort zone.

Unprecedented ocean heat

Any ecosystem is a network of interdependencies: insects pollinate flowers, animals disperse seed and prey upon pests and each other in an intricate set of arrangements that have evolved over tens of thousands of years in a particular pattern of temperature and precipitation. Any disturbance ripples through the entire habitat.

The scientists’ atlas of potential ecological disruption included isolated bits of the world such as the Cayman Islands in the Caribbean and the Gobi Desert in Mongolia as well as the Amazon basin and the forests and clearings in the Congo, and one of the world’s richest marine habitats, the so-called Coral Triangle bounded by the Philippines, Malaysia, Papua New Guinea and the islands of the Western Pacific.

They found that if warming could be contained to 2°C or less, only about one community in 50 would be faced with exposure to such disruption: they warn however that even this 2% includes some of the richest habitats on the planet.

They also warn that by 2030, the tropical oceans will start to experience temperature regimes that have no precedent in human history. The tropical forests could be at risk by 2050. Ominously, almost three-fourths of all the species to face unprecedented temperatures before the end of this century will all do so more or less at the same time.

“Our findings highlight the urgent need for climate change mitigation, by immediately and drastically reducing emissions, which could help save thousands of species from extinction,” Dr Pigot said. – Climate News Network

Rising global heat raises risks to the creatures and ecosystems that sustain human society. Collapse could be sudden and near-total.

LONDON, 14 April, 2020 – Worldwide, entire ecosystems could collapse as the planetary thermometer soars: rising global heat could see the Earth’s average temperature rise by 4°C (right now the world is heading for a rise of more than three degrees).

And then one in six of the complex communities of plants and animals in wetlands, grasslands, forests or oceans could drastically alter or fail.

That is because at such temperatures more than one in five of the creatures in that network of co-dependencies would in the same decade experience temperatures beyond their normal tolerance levels.

The prediction is based on data that pinpoint the geographical ranges of 30,652 birds, mammals, reptiles, amphibians, fish and plants, and climate data from 1850 to 2005.

“We found that climate change risks to biodiversity don’t increase gradually,” said Alex Pigot of Imperial College London, in the UK, who led the research.

Abrupt change

“Instead, as the climate warms, within a certain area most species will be able to cope for a while, before crossing a temperature threshold, when a large proportion of the species will suddenly face conditions they’ve never experienced before.

“It’s not a slippery slope, but a series of cliff edges, hitting different areas at different times.”

The finding – published in the journal Nature – should come as no great surprise to the world’s zoologists, botanists, ecologists, foresters, marine scientists and conservationists.

They have repeatedly warned that as global temperatures rise, and climate patterns become increasingly unstable, in response to ever-higher greenhouse gas emissions from power stations and car exhausts, and forest destruction, both individual species and even whole habitats could be exposed to loss and species extinction.

Such threats can be prefigured even in subtle changes in species behaviour. Within this month, Spanish ornithologists who have studied the nightingale Luscinia megarhynchos since 1995 report in the journal The Auk: Ornithological Advances that in two decades, as Spanish summers became hotter and more parched, the wings of each new generation of birds have become progressively shorter.

“Our findings highlight the urgent need for climate change mitigation, by immediately and drastically reducing emissions, which could help save thousands of species from extinction”

A shorter wingspan in proportion to body length creates potential survival problems for a species that breeds in Europe but prefers to fly to sub-Saharan Africa for the winter.

And across the Atlantic, another species, the American robin Turdus migratorius now takes wing 12 days earlier each spring in Mexico and the US to fly to its summer breeding grounds in Canada and Alaska.

The ornithologists report in the journal Environmental Research Letters that GPS tracking of 55 individual birds confirms that the bird may be timing its migration to the snow melt and the first arrival of insects in the high latitudes nearer the fast-warming Arctic.

So far, the planet on average has warmed around only 1°C above the long-term average for most of human history. But Dr Pigot and colleagues in the US and South Africa wanted to look at the big picture of potential change in species everywhere as global heating reaches 2°C – the upper limits that the world’s nations promised in a key international agreement reached in Paris in 2015 – and then goes on soaring.

So they took their species data, and mapped it onto a global grid divided into 100-km-square cells, and then fine-tuned the temperature predicted by climate scientists to see where species and their habitats would experience ever-rising heat beyond their comfort zone.

Unprecedented ocean heat

Any ecosystem is a network of interdependencies: insects pollinate flowers, animals disperse seed and prey upon pests and each other in an intricate set of arrangements that have evolved over tens of thousands of years in a particular pattern of temperature and precipitation. Any disturbance ripples through the entire habitat.

The scientists’ atlas of potential ecological disruption included isolated bits of the world such as the Cayman Islands in the Caribbean and the Gobi Desert in Mongolia as well as the Amazon basin and the forests and clearings in the Congo, and one of the world’s richest marine habitats, the so-called Coral Triangle bounded by the Philippines, Malaysia, Papua New Guinea and the islands of the Western Pacific.

They found that if warming could be contained to 2°C or less, only about one community in 50 would be faced with exposure to such disruption: they warn however that even this 2% includes some of the richest habitats on the planet.

They also warn that by 2030, the tropical oceans will start to experience temperature regimes that have no precedent in human history. The tropical forests could be at risk by 2050. Ominously, almost three-fourths of all the species to face unprecedented temperatures before the end of this century will all do so more or less at the same time.

“Our findings highlight the urgent need for climate change mitigation, by immediately and drastically reducing emissions, which could help save thousands of species from extinction,” Dr Pigot said. – Climate News Network

Northern Europe’s warm water flow may falter

Global heating can stop the flow of Europe’s warm water from the tropics. Happening often during the Ice Ages, it could soon recur.

LONDON, 1 April, 2020 – Oceanographers have confirmed once again that global heating could slow or shut down the flow of currents such as the Gulf Stream, ending northern Europe’s warm water supply with an unexpected and prolonged cold snap.

This time the confidence is based neither on ocean measurements made now, nor complex computer simulations of the future. There is fresh evidence from the sea floor that such an ocean shutdown happened many times in the last half a million years of Ice Ages.

The Gulf Stream is part of a much larger flow of water called the Atlantic Meridional Overturning Circulation, an ocean recycling system that both nourishes marine life and moderates the climate in two hemispheres.

For the last 10,000 years of human history, tropical water has flowed north from the Caribbean and equatorial regions and washed the shores of Europe as far north as Norway, bringing equatorial heat to soften the impact of European winters.

A former UK chief scientist once calculated that the Gulf Stream delivered the warmth of 27,000 power stations and kept Britain about 5°C warmer than its citizens had any right to expect, given the latitude at which they lived.

“These findings suggest that our climate system, which depends greatly on deep ocean circulation, is critically poised near a tipping point for abrupt disruptions”

But as that stretch of the Gulf Stream known to oceanographers as the North Atlantic drift current reaches the Greenland Sea it becomes increasingly colder and saltier and thus more dense, and sinks to the ocean floor, loaded with dissolved atmospheric carbon dioxide and oxygen, to become a southward flow called the North Atlantic Deepwater formation.

And it also mingles with fresh water melting each summer from the Greenland ice sheet. But as the rate of Arctic melting accelerates, more fresh water will plunge into the same sea, with an increasing probability that it will disrupt the ocean cycle, turn off the flow of warm tropical water, and plunge Europe into a prolonged cold spell.

In its most dramatic form, this hypothesis was the basis for a 2004 Hollywood disaster movie called The Day After Tomorrow. Climate scientists are fairly sure that such an event would not mean the sudden advance of glacial ice over much of Europe and North America. But they have repeatedly identified evidence that the flow of the northward current is beginning to weaken.

And the journal Science now carries additional evidence that the ocean circulation was repeatedly interrupted for periods of a century or more during the warm spells or interglacials that have happened during the last 450,000 years.

Shells’ signatures

The signature of ocean change is there in the tiny sea shells from marine creatures called foraminifera that rain down onto the ocean floor to form annual layers of silent testimony to past climates.

When the mix of carbon isotope ratios preserved in them is high, that is a sign that the Atlantic circulation was once vigorous. When it is low, then this overturning circulation is feeble, or has stopped altogether.

The signal from the deep ocean is that when they happen, these disruptions seem to happen very swiftly, and to linger for 100 years or more. And, the scientists say, these interruptions in the flow of the ocean – and with it, the transport of heat from the tropics – happen more easily than previously appreciated, and they occurred in past climate conditions similar to those the world may soon face.

“These findings suggest that our climate system, which depends greatly on deep ocean circulation, is critically poised near a tipping point for abrupt disruptions,” said Yair Rosenthal of Rutgers University in the US, one of the authors.

“Although the disruptions in circulation and possible coolings may be relatively short-lived – lasting maybe a century or more – the consequences might be large.” – Climate News Network

Global heating can stop the flow of Europe’s warm water from the tropics. Happening often during the Ice Ages, it could soon recur.

LONDON, 1 April, 2020 – Oceanographers have confirmed once again that global heating could slow or shut down the flow of currents such as the Gulf Stream, ending northern Europe’s warm water supply with an unexpected and prolonged cold snap.

This time the confidence is based neither on ocean measurements made now, nor complex computer simulations of the future. There is fresh evidence from the sea floor that such an ocean shutdown happened many times in the last half a million years of Ice Ages.

The Gulf Stream is part of a much larger flow of water called the Atlantic Meridional Overturning Circulation, an ocean recycling system that both nourishes marine life and moderates the climate in two hemispheres.

For the last 10,000 years of human history, tropical water has flowed north from the Caribbean and equatorial regions and washed the shores of Europe as far north as Norway, bringing equatorial heat to soften the impact of European winters.

A former UK chief scientist once calculated that the Gulf Stream delivered the warmth of 27,000 power stations and kept Britain about 5°C warmer than its citizens had any right to expect, given the latitude at which they lived.

“These findings suggest that our climate system, which depends greatly on deep ocean circulation, is critically poised near a tipping point for abrupt disruptions”

But as that stretch of the Gulf Stream known to oceanographers as the North Atlantic drift current reaches the Greenland Sea it becomes increasingly colder and saltier and thus more dense, and sinks to the ocean floor, loaded with dissolved atmospheric carbon dioxide and oxygen, to become a southward flow called the North Atlantic Deepwater formation.

And it also mingles with fresh water melting each summer from the Greenland ice sheet. But as the rate of Arctic melting accelerates, more fresh water will plunge into the same sea, with an increasing probability that it will disrupt the ocean cycle, turn off the flow of warm tropical water, and plunge Europe into a prolonged cold spell.

In its most dramatic form, this hypothesis was the basis for a 2004 Hollywood disaster movie called The Day After Tomorrow. Climate scientists are fairly sure that such an event would not mean the sudden advance of glacial ice over much of Europe and North America. But they have repeatedly identified evidence that the flow of the northward current is beginning to weaken.

And the journal Science now carries additional evidence that the ocean circulation was repeatedly interrupted for periods of a century or more during the warm spells or interglacials that have happened during the last 450,000 years.

Shells’ signatures

The signature of ocean change is there in the tiny sea shells from marine creatures called foraminifera that rain down onto the ocean floor to form annual layers of silent testimony to past climates.

When the mix of carbon isotope ratios preserved in them is high, that is a sign that the Atlantic circulation was once vigorous. When it is low, then this overturning circulation is feeble, or has stopped altogether.

The signal from the deep ocean is that when they happen, these disruptions seem to happen very swiftly, and to linger for 100 years or more. And, the scientists say, these interruptions in the flow of the ocean – and with it, the transport of heat from the tropics – happen more easily than previously appreciated, and they occurred in past climate conditions similar to those the world may soon face.

“These findings suggest that our climate system, which depends greatly on deep ocean circulation, is critically poised near a tipping point for abrupt disruptions,” said Yair Rosenthal of Rutgers University in the US, one of the authors.

“Although the disruptions in circulation and possible coolings may be relatively short-lived – lasting maybe a century or more – the consequences might be large.” – Climate News Network