Tag Archives: Drought

A warmer, drier world’s deeper wells spell trouble

A warmer world could for billions be drier. The resultant deeper wells spell trouble for those reliant on groundwater.

LONDON, 26 April, 2021 − As many as one fifth of the world’s wells could be about to run dry, as levels of the subterranean water table continue to fall. And if they do, the resultant deeper wells spell trouble for billions of people who will face diminishing supplies of clean water, and water for their crops.

Most of the world’s freshwater is truly out of sight: 96% of all available water is held in aquifers, rock and sediment layers just below, and sometimes well below, the Earth’s surface. It sustains almost half of global agriculture. The world’s drylands are also home to more than a third of all humanity.

All this is at risk because in many places water tables are falling. According to a new study in the journal Science, if groundwater levels decline a few metres more, then the wells will run dry. Somewhere between 6% and 20% of the world’s wells are no more than five metres deeper than the water table.

And water levels almost certainly will decline. Researchers have for years been warning about global demand for groundwater. In urban areas the demand has been so great that many cities are literally going downhill: throughout the 20th century Tokyo sank by four metres, Shanghai in China and New Orleans in the US by two to three metres.

“Wells are already running dry because of groundwater level declines”

Climate change − which promises to distort global rainfall patterns still further − is steadily scorching the world’s already parched regions and as a consequence groundwater is being extracted at an accelerated rate.

And that means more water stress for millions. All the evidence is that, as greenhouse gas emissions rise as a consequence of profligate fossil fuel use, things could get a lot worse.

Californian scientists report that they compiled 39 million records of groundwater well locations, along with their depths, the reasons they were sunk, and the dates they were dug, in 40 countries that collectively make up 40% of all the lands free of ice. This landscape accounts for probably half of all groundwater extraction.

To test their simulations of overall groundwater availability, they compiled and analysed 100 million measurements made in a million wells monitored individually, and they found that in half of these there were seasonal fluctuations of around a metre or more.

Newer means deeper

They checked the big picture of water table decline against 15 years of data from the US space agency Nasa’s Gravity Recovery and Climate Experiment satellites.

They also looked at the age data of their sample, to find that in many areas, the newer the well, the more likely it was to be deeper than an old well. That alone was evidence of gradually falling water tables.

“From India to the United States, wells are already running dry because of groundwater level declines,” the authors write. “In California’s Central Valley and several other agricultural hubs around the globe, typical agricultural wells are deeper than domestic wells; as a result, domestic wells are running dry…”

Where wells are already running dry, that decline will continue, and even expand into areas that have not yet seen any depletion. And, they warn, it may not help to simply sink even deeper wells: the costs would become prohibitive and the water quality at greater depth might anyway be not good enough. − Climate News Network

A warmer world could for billions be drier. The resultant deeper wells spell trouble for those reliant on groundwater.

LONDON, 26 April, 2021 − As many as one fifth of the world’s wells could be about to run dry, as levels of the subterranean water table continue to fall. And if they do, the resultant deeper wells spell trouble for billions of people who will face diminishing supplies of clean water, and water for their crops.

Most of the world’s freshwater is truly out of sight: 96% of all available water is held in aquifers, rock and sediment layers just below, and sometimes well below, the Earth’s surface. It sustains almost half of global agriculture. The world’s drylands are also home to more than a third of all humanity.

All this is at risk because in many places water tables are falling. According to a new study in the journal Science, if groundwater levels decline a few metres more, then the wells will run dry. Somewhere between 6% and 20% of the world’s wells are no more than five metres deeper than the water table.

And water levels almost certainly will decline. Researchers have for years been warning about global demand for groundwater. In urban areas the demand has been so great that many cities are literally going downhill: throughout the 20th century Tokyo sank by four metres, Shanghai in China and New Orleans in the US by two to three metres.

“Wells are already running dry because of groundwater level declines”

Climate change − which promises to distort global rainfall patterns still further − is steadily scorching the world’s already parched regions and as a consequence groundwater is being extracted at an accelerated rate.

And that means more water stress for millions. All the evidence is that, as greenhouse gas emissions rise as a consequence of profligate fossil fuel use, things could get a lot worse.

Californian scientists report that they compiled 39 million records of groundwater well locations, along with their depths, the reasons they were sunk, and the dates they were dug, in 40 countries that collectively make up 40% of all the lands free of ice. This landscape accounts for probably half of all groundwater extraction.

To test their simulations of overall groundwater availability, they compiled and analysed 100 million measurements made in a million wells monitored individually, and they found that in half of these there were seasonal fluctuations of around a metre or more.

Newer means deeper

They checked the big picture of water table decline against 15 years of data from the US space agency Nasa’s Gravity Recovery and Climate Experiment satellites.

They also looked at the age data of their sample, to find that in many areas, the newer the well, the more likely it was to be deeper than an old well. That alone was evidence of gradually falling water tables.

“From India to the United States, wells are already running dry because of groundwater level declines,” the authors write. “In California’s Central Valley and several other agricultural hubs around the globe, typical agricultural wells are deeper than domestic wells; as a result, domestic wells are running dry…”

Where wells are already running dry, that decline will continue, and even expand into areas that have not yet seen any depletion. And, they warn, it may not help to simply sink even deeper wells: the costs would become prohibitive and the water quality at greater depth might anyway be not good enough. − Climate News Network

Plants will be hit as a warming world turns drier

If a warming world becomes a drier one, how will the green things respond? Not well, according to a new prediction.

LONDON, 26 March, 2021 − The air of planet Earth has been gradually drying this century. If this goes on, that could be bad news for humankind. In a warming world crop harvests will dwindle, even in well-watered farmlands, and trees could shrink in height.

The prospect of stunted forests and shortages of food in a world hit by global heating, climate change and rapid population growth is ominous. But if US and Canadian scientists are right, it may be a simple consequence of plant response to a rarely-discussed worldwide phenomenon known as vapour pressure deficit, which has been rising for the past 20 years as the world has warmed.

The argument isn’t a simple one. Higher global temperatures mean more evaporation. Higher atmospheric temperatures also mean that the capacity of the atmosphere to hold moisture also rises − the rule of thumb is 7% more vapour per degree Celsius rise. So a warmer world should be a wetter world.

But climate science also predicts that although those regions already rainy will get rainier, the drylands and arid zones will get even dryer as the thermometer soars.

“As we race to increase production to feed a bigger population, this is a new hurdle. Atmospheric drying could limit yields, even in regions where irrigation or soil moisture is not limiting”

Now there is another factor in the calculations: vapour pressure deficit, or the overall drying of the atmosphere, and how plants react to the problem of dwindling atmospheric moisture.

New research in the journal Global Change Biology analyses 50 years of research and 112 plant species, and 59 physiological traits in those plants. The evidence suggests that atmospheric drying reduces plant yield, as the plants adjust to new conditions.

“When there is a high vapour pressure deficit, our atmosphere pulls water from other sources: animals, plants, etc. An increase in vapour pressure deficit places greater demand on the crop to use more water. In turn, this puts more pressure on farmers to ensure this demand for water is met − either via precipitation or irrigation − so that yields do not decrease,” said Walid Sadok, of the University of Minnesota.

“We believe a climate change-driven increase in atmospheric drying will reduce plant productivity and crop yields both in Minnesota and globally.”

The paradox is that plants can adjust to a changing world but in this case by becoming more drought-resistant. Which, in the case of wheat, maize and even birch trees, means growing less.

Less productive plants

Findings such as this are tentative, and will in any case be tested by time. But they also illustrate just how much there is yet to learn about the consequence of climate change in a complex, responsive world.

Other research teams have repeatedly observed that even in the drier regions, plants have so far responded to rising greenhouse gas emissions by an increase in global greenness. But there is nothing simple about the greenhouse effect. And there has been repeated evidence too that forest conservation and more tree plantations may not provide all the answers to the challenge of growth in an ever-warmer world.

The reasoning within the new study is that plant stomata, those tiny holes in foliage through which plants breathe and release water, adjust according to new conditions. The plants become more conservative. They grow shorter, smaller and more resistant to drought, even if there is no drought. And in parallel, they become less able to fix atmospheric carbon dioxide to provide new tissue. So, overall, plant productivity is reduced.

“As we race to increase production to feed a bigger population, this is a new hurdle that will need to be cleared,” said Dr Sadok. “Atmospheric drying could limit yields, even in regions where irrigation or soil moisture is not limiting, such as Minnesota.” − Climate News Network

If a warming world becomes a drier one, how will the green things respond? Not well, according to a new prediction.

LONDON, 26 March, 2021 − The air of planet Earth has been gradually drying this century. If this goes on, that could be bad news for humankind. In a warming world crop harvests will dwindle, even in well-watered farmlands, and trees could shrink in height.

The prospect of stunted forests and shortages of food in a world hit by global heating, climate change and rapid population growth is ominous. But if US and Canadian scientists are right, it may be a simple consequence of plant response to a rarely-discussed worldwide phenomenon known as vapour pressure deficit, which has been rising for the past 20 years as the world has warmed.

The argument isn’t a simple one. Higher global temperatures mean more evaporation. Higher atmospheric temperatures also mean that the capacity of the atmosphere to hold moisture also rises − the rule of thumb is 7% more vapour per degree Celsius rise. So a warmer world should be a wetter world.

But climate science also predicts that although those regions already rainy will get rainier, the drylands and arid zones will get even dryer as the thermometer soars.

“As we race to increase production to feed a bigger population, this is a new hurdle. Atmospheric drying could limit yields, even in regions where irrigation or soil moisture is not limiting”

Now there is another factor in the calculations: vapour pressure deficit, or the overall drying of the atmosphere, and how plants react to the problem of dwindling atmospheric moisture.

New research in the journal Global Change Biology analyses 50 years of research and 112 plant species, and 59 physiological traits in those plants. The evidence suggests that atmospheric drying reduces plant yield, as the plants adjust to new conditions.

“When there is a high vapour pressure deficit, our atmosphere pulls water from other sources: animals, plants, etc. An increase in vapour pressure deficit places greater demand on the crop to use more water. In turn, this puts more pressure on farmers to ensure this demand for water is met − either via precipitation or irrigation − so that yields do not decrease,” said Walid Sadok, of the University of Minnesota.

“We believe a climate change-driven increase in atmospheric drying will reduce plant productivity and crop yields both in Minnesota and globally.”

The paradox is that plants can adjust to a changing world but in this case by becoming more drought-resistant. Which, in the case of wheat, maize and even birch trees, means growing less.

Less productive plants

Findings such as this are tentative, and will in any case be tested by time. But they also illustrate just how much there is yet to learn about the consequence of climate change in a complex, responsive world.

Other research teams have repeatedly observed that even in the drier regions, plants have so far responded to rising greenhouse gas emissions by an increase in global greenness. But there is nothing simple about the greenhouse effect. And there has been repeated evidence too that forest conservation and more tree plantations may not provide all the answers to the challenge of growth in an ever-warmer world.

The reasoning within the new study is that plant stomata, those tiny holes in foliage through which plants breathe and release water, adjust according to new conditions. The plants become more conservative. They grow shorter, smaller and more resistant to drought, even if there is no drought. And in parallel, they become less able to fix atmospheric carbon dioxide to provide new tissue. So, overall, plant productivity is reduced.

“As we race to increase production to feed a bigger population, this is a new hurdle that will need to be cleared,” said Dr Sadok. “Atmospheric drying could limit yields, even in regions where irrigation or soil moisture is not limiting, such as Minnesota.” − Climate News Network

Extreme drought and fire risk may double by 2060

Climate change may soon double the impact of extreme drought and fire. And it’s a two-way traffic.

LONDON, 25 January, 2021 − As climate change threatens a doubling of the impact of extreme drought and fire within a generation, researchers are uncovering the influence of human activity on both these growing risks.

One study has found that human numbers exposed to the hazard of extreme drought are likely to double in the decades to come, as global heating bakes away the groundwater and limits annual snowfall.

Another team of researchers says the risks of extreme wildfire could also rise twofold in the next 40 years in the Mediterranean, southern Africa, eastern North America and the Amazon. In those places already severely scorched by frequent fire − western North America, equatorial Africa, south-east Asia and Australia − hazards could rise by 50%.

And a third, separate study warns that global temperature rise will shift the patterns of rainfall around the tropics − with the consequent risks to tropical crop harvests and to equatorial ecosystems such as rainforest and savannah.

All three studies are reminders of the intricacies of the planetary climate system and the impact of human action in the last hundred years.

“Areas of the southern hemisphere, where water scarcity is already a problem, will be disproportionately affected. We predict this will affect food security and escalate human migration and conflict.”

An international research team reports in the journal Nature Climate Change that it looked at the simple problem of global terrestrial water storage: all the moisture in the canopies of forest trees, in the mountain snows and ice, in the lakes, rivers, wetlands, and in the soil itself.

This wealth of stored water is a big player in the patterns of global flooding and drought in the monsoon climates and the arid lands alike. But, the researchers say, there has so far been no study of the potential impact of global climate change on global terrestrial water storage overall.

So researchers from the US, China, Japan and Europe began modelling tomorrow’s world. And they found that, while 3% of the planet’s people were vulnerable to extreme drought in the timespan from 1976 to 2005, later in the century this proportion could increase to 7% or even 8%.

“More and more people will suffer from extreme droughts if a medium-to-high level of global warming continues and water management is maintained in its present state,” warned Yadu Pokhrel, an engineer at Michigan State University, who led the research.

“Areas of the southern hemisphere, where water scarcity is already a problem, will be disproportionately affected. We predict this increase in water scarcity will affect food security and escalate human migration and conflict.”

Fire chances increased

Australia is a southern hemisphere country that knows about water scarcity: its wildfires in 2019 broke all records and sent a vast cloud of smoke to an altitude of 35 kms.

And, on the evidence of a new study in the journal Nature Communications, it won’t be the last such extreme event. Californian scientists, struck by the scale and intensity of Californian wildfires in 2017 and 2018, report that they took a closer look at the way greenhouse gas emissions and human land use change have played into the risks of extreme fire weather.

The simple act of setting forests afire to clear land for farm use has amplified the risk of extreme blazes in the Amazon and North America by 30% in the last century. Fires create aerosols that could, by absorbing sunlight, help cool the terrain beneath them − in some zones. But they could also affect rainfall levels and raise the chances of fire. The nature of such impacts varies from place to place.

“South-east Asia relies on the monsoon, but aerosols cause so much cooling on land that they can actually suppress a monsoon,” said Danielle Touma of the University of California at Santa Barbara. “It’s not just whether you have aerosols or not, it’s the way the regional climate interacts with aerosols.”

Aerosols − with other forces − cannot just suppress a monsoon, they can shift rain patterns permanently. The tropics, too, have begun to feel the heat of the moment.

Drought stress rises

The footprint of extreme drought and fire is massive. Californian researchers report in Nature Climate Change that, across two thirds of the globe, the tropical rainbelt is likely to shift north over eastern Africa and the Indian Ocean to cause more drought stress in south-eastern Africa and Madagascar and intensified flooding in south Asia.

In the western hemisphere, however, as the Gulf Stream current and the North Atlantic deep water formation weaken, the rain belt could move south to bring greater drought stress to Central America.

And once again, climate change driven by global heating is at work with other human influences to alter what had for most of human history been a stable pattern of climate.

“In Asia, projected reductions in aerosol emissions, glacier melting in the Himalayas and loss of snow cover in northern areas brought on by climate change will cause the atmosphere to heat up faster than in other regions,” said James Randerson of the University of California, Irvine, one of the authors.

“We know the rainbelt shifts towards this heating, and that its northward movement in the eastern hemisphere is consistent with these expected impacts of climate change.” − Climate News Network

Climate change may soon double the impact of extreme drought and fire. And it’s a two-way traffic.

LONDON, 25 January, 2021 − As climate change threatens a doubling of the impact of extreme drought and fire within a generation, researchers are uncovering the influence of human activity on both these growing risks.

One study has found that human numbers exposed to the hazard of extreme drought are likely to double in the decades to come, as global heating bakes away the groundwater and limits annual snowfall.

Another team of researchers says the risks of extreme wildfire could also rise twofold in the next 40 years in the Mediterranean, southern Africa, eastern North America and the Amazon. In those places already severely scorched by frequent fire − western North America, equatorial Africa, south-east Asia and Australia − hazards could rise by 50%.

And a third, separate study warns that global temperature rise will shift the patterns of rainfall around the tropics − with the consequent risks to tropical crop harvests and to equatorial ecosystems such as rainforest and savannah.

All three studies are reminders of the intricacies of the planetary climate system and the impact of human action in the last hundred years.

“Areas of the southern hemisphere, where water scarcity is already a problem, will be disproportionately affected. We predict this will affect food security and escalate human migration and conflict.”

An international research team reports in the journal Nature Climate Change that it looked at the simple problem of global terrestrial water storage: all the moisture in the canopies of forest trees, in the mountain snows and ice, in the lakes, rivers, wetlands, and in the soil itself.

This wealth of stored water is a big player in the patterns of global flooding and drought in the monsoon climates and the arid lands alike. But, the researchers say, there has so far been no study of the potential impact of global climate change on global terrestrial water storage overall.

So researchers from the US, China, Japan and Europe began modelling tomorrow’s world. And they found that, while 3% of the planet’s people were vulnerable to extreme drought in the timespan from 1976 to 2005, later in the century this proportion could increase to 7% or even 8%.

“More and more people will suffer from extreme droughts if a medium-to-high level of global warming continues and water management is maintained in its present state,” warned Yadu Pokhrel, an engineer at Michigan State University, who led the research.

“Areas of the southern hemisphere, where water scarcity is already a problem, will be disproportionately affected. We predict this increase in water scarcity will affect food security and escalate human migration and conflict.”

Fire chances increased

Australia is a southern hemisphere country that knows about water scarcity: its wildfires in 2019 broke all records and sent a vast cloud of smoke to an altitude of 35 kms.

And, on the evidence of a new study in the journal Nature Communications, it won’t be the last such extreme event. Californian scientists, struck by the scale and intensity of Californian wildfires in 2017 and 2018, report that they took a closer look at the way greenhouse gas emissions and human land use change have played into the risks of extreme fire weather.

The simple act of setting forests afire to clear land for farm use has amplified the risk of extreme blazes in the Amazon and North America by 30% in the last century. Fires create aerosols that could, by absorbing sunlight, help cool the terrain beneath them − in some zones. But they could also affect rainfall levels and raise the chances of fire. The nature of such impacts varies from place to place.

“South-east Asia relies on the monsoon, but aerosols cause so much cooling on land that they can actually suppress a monsoon,” said Danielle Touma of the University of California at Santa Barbara. “It’s not just whether you have aerosols or not, it’s the way the regional climate interacts with aerosols.”

Aerosols − with other forces − cannot just suppress a monsoon, they can shift rain patterns permanently. The tropics, too, have begun to feel the heat of the moment.

Drought stress rises

The footprint of extreme drought and fire is massive. Californian researchers report in Nature Climate Change that, across two thirds of the globe, the tropical rainbelt is likely to shift north over eastern Africa and the Indian Ocean to cause more drought stress in south-eastern Africa and Madagascar and intensified flooding in south Asia.

In the western hemisphere, however, as the Gulf Stream current and the North Atlantic deep water formation weaken, the rain belt could move south to bring greater drought stress to Central America.

And once again, climate change driven by global heating is at work with other human influences to alter what had for most of human history been a stable pattern of climate.

“In Asia, projected reductions in aerosol emissions, glacier melting in the Himalayas and loss of snow cover in northern areas brought on by climate change will cause the atmosphere to heat up faster than in other regions,” said James Randerson of the University of California, Irvine, one of the authors.

“We know the rainbelt shifts towards this heating, and that its northward movement in the eastern hemisphere is consistent with these expected impacts of climate change.” − Climate News Network

US pays rising costs for climate’s flood damage

America’s rainfall patterns are changing with the global climate − and making catastrophic flood damage even more costly.

LONDON, 21 January, 2021 − Climate change alone has cost the United States a total of $73 billion in flood damage in the last 30 years.

The figure is significant: floods are an expensive fact of life. But Californian scientists are now sure that more than one-third of the costs of US floods must be attributed to the global heating driven by human use of fossil fuels.

The news comes hard on the heels of a second finding: that over the last century, the count of what hydrologists call “extreme streamflow” events in Canada and the US has increased significantly. This confirms that droughts are on the increase − and so are floods.

Such findings matter to engineers and city planners, and to insurers, and each resolves some long-standing uncertainties.

Because floods and droughts are part of the challenge of living close to a constant flow of water, researchers have never been too sure whether costly floods are on the increase or are just more obvious because population growth and urban spread mean that more people with more expensive property are increasingly at risk.

“The shifts towards more extreme events are especially important given the age of our dams, bridges and roads”

A new study in the Proceedings of the National Academy of Sciences settles the matter of rising costs: researchers looked at 6,600 reports of flood damage and rainfall data between 1988 and 2017 and then applied sophisticated mathematical techniques to tease out the contribution from higher precipitation driven by higher average temperatures, driven in turn by ever-higher ratios of carbon dioxide in the atmosphere.

They decided that of the $199bn flood damage costs during those years, human-triggered climate change could account for 36%.

“The fact that extreme precipitation has been increasing and will likely increase is well-known, but what effect that has had on financial damages has been uncertain,” said Frances Davenport, of Stanford University.

“What we find is that, even in states where long-term mean precipitation hasn’t changed, in most cases the wettest events have intensified, increasing the financial damages relative to what would have occurred without the changes in precipitation.”

Higher temperatures mean more evaporation. Higher temperatures mean a bigger burden of water vapour in the atmosphere. So higher rainfall is inevitable.

Variable impacts

But repeated studies have found this will happen unevenly: those places already rainy will see more rain. Other regions can expect longer, more intense dry spells.

A second team of US researchers reports in the journal Science Advances that they looked at streamflow data from 541 North American stations since 1910.

They found that in the US west and south-east, the frequency of “extreme low-flow events” has been on the increase, particularly during summer and autumn. In zones where rivers were likely to be fed by melting snow, there was a discernible rise in flood events. Once again, this is a finding with practical consequences.

“The shifts towards more extreme events are especially important given the age of our dams, bridges and roads,” said Evan Dethier, of Dartmouth College in New Hampshire. “The changes to river flows that we found are important for those who manage or depend on this type of infrastructure.” − Climate News Network

America’s rainfall patterns are changing with the global climate − and making catastrophic flood damage even more costly.

LONDON, 21 January, 2021 − Climate change alone has cost the United States a total of $73 billion in flood damage in the last 30 years.

The figure is significant: floods are an expensive fact of life. But Californian scientists are now sure that more than one-third of the costs of US floods must be attributed to the global heating driven by human use of fossil fuels.

The news comes hard on the heels of a second finding: that over the last century, the count of what hydrologists call “extreme streamflow” events in Canada and the US has increased significantly. This confirms that droughts are on the increase − and so are floods.

Such findings matter to engineers and city planners, and to insurers, and each resolves some long-standing uncertainties.

Because floods and droughts are part of the challenge of living close to a constant flow of water, researchers have never been too sure whether costly floods are on the increase or are just more obvious because population growth and urban spread mean that more people with more expensive property are increasingly at risk.

“The shifts towards more extreme events are especially important given the age of our dams, bridges and roads”

A new study in the Proceedings of the National Academy of Sciences settles the matter of rising costs: researchers looked at 6,600 reports of flood damage and rainfall data between 1988 and 2017 and then applied sophisticated mathematical techniques to tease out the contribution from higher precipitation driven by higher average temperatures, driven in turn by ever-higher ratios of carbon dioxide in the atmosphere.

They decided that of the $199bn flood damage costs during those years, human-triggered climate change could account for 36%.

“The fact that extreme precipitation has been increasing and will likely increase is well-known, but what effect that has had on financial damages has been uncertain,” said Frances Davenport, of Stanford University.

“What we find is that, even in states where long-term mean precipitation hasn’t changed, in most cases the wettest events have intensified, increasing the financial damages relative to what would have occurred without the changes in precipitation.”

Higher temperatures mean more evaporation. Higher temperatures mean a bigger burden of water vapour in the atmosphere. So higher rainfall is inevitable.

Variable impacts

But repeated studies have found this will happen unevenly: those places already rainy will see more rain. Other regions can expect longer, more intense dry spells.

A second team of US researchers reports in the journal Science Advances that they looked at streamflow data from 541 North American stations since 1910.

They found that in the US west and south-east, the frequency of “extreme low-flow events” has been on the increase, particularly during summer and autumn. In zones where rivers were likely to be fed by melting snow, there was a discernible rise in flood events. Once again, this is a finding with practical consequences.

“The shifts towards more extreme events are especially important given the age of our dams, bridges and roads,” said Evan Dethier, of Dartmouth College in New Hampshire. “The changes to river flows that we found are important for those who manage or depend on this type of infrastructure.” − Climate News Network

More trees may do less to slow the climate crisis

In theory, more trees should mean a lower risk of dangerous climate change. In practice, it may not be so simple.

LONDON, 6 January, 2021 − The belief that more trees and better-protected forests can help contain climate change looks a little less sure − if only because climate change has already begun to affect the world’s trees and forests.

Researchers have in the last few weeks established a panoply of evidence that higher temperatures and more carbon dioxide may not be recipes for green growth in a greenhouse world.

In the tropics, as the thermometer rises, trees grow more vigorously − but overall lifespans are getting shorter. This must ultimately make the forests less efficient as absorbers of atmospheric carbon.

To compound the hazard to the rainforests, the proportion of the canopy that has always been fire-resistant is showing signs of decrease: in parts of Indonesia, only 10% of the forests remain fireproof.

Climate change and more importantly human disturbance continues to put the survival of whole groups of plants at risk: a new study finds that almost one-third of all the world’s 430 oak species are in danger of extinction.

A separate study of 447 North American trees suggests that they might not have what it takes to keep pace with changes in temperature and rainfall expected in a world of global heating.

Limited gains

And there is yet further evidence that more carbon dioxide does not inevitably mean more potential nourishment for plants: a study by the US space agency Nasa suggests that what scientists call the “carbon dioxide fertilisation effect” has been dwindling since 1982.

Finally, even the gains inevitable with rising temperatures in some regions could be limited. Another Nasa study finds that although Siberia, Canada and Alaska are becoming greener as the mercury rises, the increasing drought and tree death in the Amazon rainforest and others has offset this: another blow for those who hope more growth means more carbon absorption.

None of this should be a great surprise: the more researchers look in fine detail at the challenge of restoring natural habitat as part of the planetary arsenal against climate change, the more problems they have identified.

Although researchers have demonstrated that massive forest planting and restoration could in principle reduce the extra atmospheric carbon amassed over the last century, the details are less certain.

With more heat comes more drought which could turn some forests into sources of carbon rather than sinks. The increasing heat could affect the ability of some species to germinate, thus changing the makeup of the forests.

Trees may not only be dying younger, but growing shorter as conditions change.

“Many regions in the tropics are heating up particularly rapidly and substantial areas will become warmer, on average, than approximately 25°C”

And although spring is occurring ever earlier, so is leaf fall: all these things reduce the efficiency of forests as greedy consumers of carbon.

So the latest harvest of research is simply further confirmation that the global heating to which the world is already committed is going to change the nature of those habitats that have − until now − kept the planet at an even temperature.

That means that restoring forests is not just a matter of planting trees: foresters will need to identify the right trees for climate regimes that have yet to be established.

Tropical rainforests cover only 7% of the planet’s land surface, but they shelter and nourish around half of all the planet’s plants and animal species. Around half of the Earth’s stocks of sequestered carbon are locked in the trunks, branches, leaves and roots.

Researchers report in the Proceedings of the National Academy of Sciences that they examined growth data from more than 100,000 trees of 438 different species found at 3,433 places around the world. They found that as temperatures go beyond 25°C, tree lifespans decline.

“Many regions in the tropics are heating up particularly rapidly and substantial areas will become warmer, on average, than approximately 25°C,” said Emanuel Gloor, of the University of Leeds in the UK, one of the authors.

Human interference

“Our findings, which are the first to demonstrate that there is a temperature threshold, suggest that for trees in this region, their longevity is likely to be negatively affected.”

Rainforests maintain their own microclimates: they keep themselves humid, and therefore more or less fireproof, as long as they remain intact, even during a drought. Researchers report in Communications Earth & Environment that they found 90% of the natural forest cover of Sumatra and Kalimantan had been so badly degraded by human clearance and disturbance that it was no longer fire-resistant. What was true for Indonesia could probably be true too for Central Africa or the Amazon.

“Contrary to the widely-held perception that worsening droughts are threatening the remaining rainforests, tropical forests in Indonesia become susceptible to fire only after human disturbance,” said Tadas Nikonovas of Swansea University in Wales, who led the research.

Human disturbance of natural wilderness threatens not just forests as a whole, but individual species of trees, each of which can be a natural ecosystem, supporting other plants and animals. English oaks, for instance, provide food and shelter to more than 2,300 kinds of moss, fungus, lichen, bird, mammal and insect.

Researchers for the Morton Arboretum in Illinois in the US report that of the world’s 430 species of oak, 113 are threatened with extinction: these include 32 species in Mexico, 36 in China, 20 in Vietnam and 16 in the US.

Tropical trees have naturally faster life-cycles. Trees in cooler regions can on average survive for more than 300 years. Climate change however is likely to happen over a few decades. Can trees keep pace with change at that rate?

Plants need water

Researchers from the University of Maine report in the Journal of Biogeography that they think not. They looked at the climatic ranges most suitable for 447 North American trees and shrubs to find that overall, these were at only 48.6% of their full potential. That is, the trees are no longer in equilibrium with present climate, and must increasingly be at a disadvantage as climate change accelerates.

And although the main driver of global heating and thus climate change − ever-higher ratios of carbon dioxide in the atmosphere − confers some advantage on species that live by photosynthesis, this advantage may not be guaranteed. A space-based study in the journal Science found that over the last four decades, as CO2 ratios in the atmosphere rose, 86% of terrestrial ecosystems became progressively less efficient at absorbing the stuff.

That is, the world’s green canopies have slowed climate change, but their ability to go on doing so may be limited. That is because even though more carbon dioxide should mean more growth, unless there is more nitrogen and more soil moisture as well, a plant’s capacity to respond is limited.

And that, says a second study, in the journal AGU Advances, is less of a problem in some places than others. The Arctic is greening rapidly as average temperatures rise, and there is no shortage of moisture from the thawing permafrost, nor of partly decomposed plant material, to serve as nourishment.

A survey of growth from 1982 to 2016 found that carbon absorption increased in Canada, Alaska and Siberia. But global heating has begun to reduce soil moisture in the tropics, and the gains of the Arctic are not enough to offset losses in what had once been rainforest. Nor are the polar regions likely to go on getting ever-greener.

“I don’t expect that we have to wait another 35 years to see water limitations becoming a factor in the Arctic as well,” said one of the authors, Rolf Reichle, of the Goddard Space Flight Centre in Maryland in the US. − Climate News Network

In theory, more trees should mean a lower risk of dangerous climate change. In practice, it may not be so simple.

LONDON, 6 January, 2021 − The belief that more trees and better-protected forests can help contain climate change looks a little less sure − if only because climate change has already begun to affect the world’s trees and forests.

Researchers have in the last few weeks established a panoply of evidence that higher temperatures and more carbon dioxide may not be recipes for green growth in a greenhouse world.

In the tropics, as the thermometer rises, trees grow more vigorously − but overall lifespans are getting shorter. This must ultimately make the forests less efficient as absorbers of atmospheric carbon.

To compound the hazard to the rainforests, the proportion of the canopy that has always been fire-resistant is showing signs of decrease: in parts of Indonesia, only 10% of the forests remain fireproof.

Climate change and more importantly human disturbance continues to put the survival of whole groups of plants at risk: a new study finds that almost one-third of all the world’s 430 oak species are in danger of extinction.

A separate study of 447 North American trees suggests that they might not have what it takes to keep pace with changes in temperature and rainfall expected in a world of global heating.

Limited gains

And there is yet further evidence that more carbon dioxide does not inevitably mean more potential nourishment for plants: a study by the US space agency Nasa suggests that what scientists call the “carbon dioxide fertilisation effect” has been dwindling since 1982.

Finally, even the gains inevitable with rising temperatures in some regions could be limited. Another Nasa study finds that although Siberia, Canada and Alaska are becoming greener as the mercury rises, the increasing drought and tree death in the Amazon rainforest and others has offset this: another blow for those who hope more growth means more carbon absorption.

None of this should be a great surprise: the more researchers look in fine detail at the challenge of restoring natural habitat as part of the planetary arsenal against climate change, the more problems they have identified.

Although researchers have demonstrated that massive forest planting and restoration could in principle reduce the extra atmospheric carbon amassed over the last century, the details are less certain.

With more heat comes more drought which could turn some forests into sources of carbon rather than sinks. The increasing heat could affect the ability of some species to germinate, thus changing the makeup of the forests.

Trees may not only be dying younger, but growing shorter as conditions change.

“Many regions in the tropics are heating up particularly rapidly and substantial areas will become warmer, on average, than approximately 25°C”

And although spring is occurring ever earlier, so is leaf fall: all these things reduce the efficiency of forests as greedy consumers of carbon.

So the latest harvest of research is simply further confirmation that the global heating to which the world is already committed is going to change the nature of those habitats that have − until now − kept the planet at an even temperature.

That means that restoring forests is not just a matter of planting trees: foresters will need to identify the right trees for climate regimes that have yet to be established.

Tropical rainforests cover only 7% of the planet’s land surface, but they shelter and nourish around half of all the planet’s plants and animal species. Around half of the Earth’s stocks of sequestered carbon are locked in the trunks, branches, leaves and roots.

Researchers report in the Proceedings of the National Academy of Sciences that they examined growth data from more than 100,000 trees of 438 different species found at 3,433 places around the world. They found that as temperatures go beyond 25°C, tree lifespans decline.

“Many regions in the tropics are heating up particularly rapidly and substantial areas will become warmer, on average, than approximately 25°C,” said Emanuel Gloor, of the University of Leeds in the UK, one of the authors.

Human interference

“Our findings, which are the first to demonstrate that there is a temperature threshold, suggest that for trees in this region, their longevity is likely to be negatively affected.”

Rainforests maintain their own microclimates: they keep themselves humid, and therefore more or less fireproof, as long as they remain intact, even during a drought. Researchers report in Communications Earth & Environment that they found 90% of the natural forest cover of Sumatra and Kalimantan had been so badly degraded by human clearance and disturbance that it was no longer fire-resistant. What was true for Indonesia could probably be true too for Central Africa or the Amazon.

“Contrary to the widely-held perception that worsening droughts are threatening the remaining rainforests, tropical forests in Indonesia become susceptible to fire only after human disturbance,” said Tadas Nikonovas of Swansea University in Wales, who led the research.

Human disturbance of natural wilderness threatens not just forests as a whole, but individual species of trees, each of which can be a natural ecosystem, supporting other plants and animals. English oaks, for instance, provide food and shelter to more than 2,300 kinds of moss, fungus, lichen, bird, mammal and insect.

Researchers for the Morton Arboretum in Illinois in the US report that of the world’s 430 species of oak, 113 are threatened with extinction: these include 32 species in Mexico, 36 in China, 20 in Vietnam and 16 in the US.

Tropical trees have naturally faster life-cycles. Trees in cooler regions can on average survive for more than 300 years. Climate change however is likely to happen over a few decades. Can trees keep pace with change at that rate?

Plants need water

Researchers from the University of Maine report in the Journal of Biogeography that they think not. They looked at the climatic ranges most suitable for 447 North American trees and shrubs to find that overall, these were at only 48.6% of their full potential. That is, the trees are no longer in equilibrium with present climate, and must increasingly be at a disadvantage as climate change accelerates.

And although the main driver of global heating and thus climate change − ever-higher ratios of carbon dioxide in the atmosphere − confers some advantage on species that live by photosynthesis, this advantage may not be guaranteed. A space-based study in the journal Science found that over the last four decades, as CO2 ratios in the atmosphere rose, 86% of terrestrial ecosystems became progressively less efficient at absorbing the stuff.

That is, the world’s green canopies have slowed climate change, but their ability to go on doing so may be limited. That is because even though more carbon dioxide should mean more growth, unless there is more nitrogen and more soil moisture as well, a plant’s capacity to respond is limited.

And that, says a second study, in the journal AGU Advances, is less of a problem in some places than others. The Arctic is greening rapidly as average temperatures rise, and there is no shortage of moisture from the thawing permafrost, nor of partly decomposed plant material, to serve as nourishment.

A survey of growth from 1982 to 2016 found that carbon absorption increased in Canada, Alaska and Siberia. But global heating has begun to reduce soil moisture in the tropics, and the gains of the Arctic are not enough to offset losses in what had once been rainforest. Nor are the polar regions likely to go on getting ever-greener.

“I don’t expect that we have to wait another 35 years to see water limitations becoming a factor in the Arctic as well,” said one of the authors, Rolf Reichle, of the Goddard Space Flight Centre in Maryland in the US. − Climate News Network

Fire and flood menace parts of US and Bangladesh

Fire and flood are on the rise. Bangladesh and New York face more flooding: the American West may see more forests burn.

LONDON, 14 December, 2020 − More extreme weather is on the way for the hapless residents of Bangladesh, New York and the western US,  facing the prospect of worsening fire and flood.

There is a new future for New York. By the close of the century, thanks to sea level rise and global heating, parts of it could be swept by hurricane-driven catastrophic floods almost every year.

Things don’t look much brighter for much of Bangladesh. Scientists have recalculated the risk of flooding by the Brahmaputra river system to find that, even without the climate emergency, they had under-estimated the likelihood of devastating floods across the crowded, low-lying landscape.

And far away in the American west, US citizens face yet more and more devastating seasons of fire. The area incinerated by severe fires has increased eight-fold in the last 40 years, thanks to intensifying heat and drought. And thanks to climate change, drought will become more extended and more frequent. The temperatures, too, will go on rising.

All this emerged in just another week of routine climate science, as researchers try to gauge the difficulties to come, for national and civic authorities, for foresters and for farmers.

“The increase in these once-in-a-generation floods is so dramatic because the impact of sea-level rise will create greater flooding, even if the storms today stay the same”

In 2012, Hurricane Sandy hit the US to cause $70bn in damages, and even slammed unexpectedly into New York, to devastate parts of the city. It counted as a once-in-500 years event.

Researchers report in the journal Climatic Change that they looked at the probabilities of more flooding in Jamaica Bay, on Long Island, New York as sea levels rose, along with the sea surface temperatures that drive fiercer storm weather, through the century.

Floods that tend to happen every century could, by 2050, occur every nine years. By 2080 to 2100, they could become annual events. And 500-year events like the 2012 superstorm could by the end of the century happen perhaps once every four years.

“Future projections of the hurricane climatology suggest that climate change would lead to storms that move more slowly and are more intense than we have ever seen before hitting Jamaica Bay,” said Reza Marsooli, an environmental engineer at the Stevens Institute of Technology in Hoboken, New Jersey, a co-author.

“But the increase in these once-in-a-generation or even less frequent floods is so dramatic because the impact of sea-level rise will create greater flooding, even if the storms we are seeing today stayed the same.”

Prepare for worse

The hazard that faces Bangladesh − much of which is at sea level, on fertile floodplain created by the Ganges-Brahmaputra river system − is more insidious.

One of the great waterways of the world, it rises in the Himalayan snows and swells in the monsoon season to flood the rice paddies and replenish farmlands with nourishing sediments. Occasionally the floods become devastating: in 1998, some 70% of the nation was submerged. Floods have recurred, in 2007, 2010 and 2020.

Engineers have been monitoring the flow since the 1950s, and thought they knew the flood probabilities. But US, Australian and Chinese scientists report in the journal Nature Communications that they studied the growth rings in ancient trees to find that Bangladeshis have been living in unusual times: for much of the past 70 years, on the evidence told by old trees along the watershed, the river flow has been unusually dry − the driest in the last 700 years.

“The tree rings suggest that the long-term baseline conditions are much wetter than thought,” said Mukund Palat Rao, of the Lamont-Doherty Earth Observatory at Columbia University in New York, who led the research.

“Whether you consider climate models or natural variability, the message is the same. We should prepare for a higher frequency of flooding than we are currently predicting.”

Forests’ future threatened

In the past 40 years, thanks to global heating driven by ever-higher emissions of greenhouse gases from the combustion of fossil fuels, the state of California has experienced a series of droughts that lasted for years. The fire season too has begun earlier and lasted much longer.

Ecologists report in the journal Geophysical Research Letters that they defined high-severity fires as those that killed 95% of all trees. They then counted the most severe episodes of burning in four great regions of the western US from 1985 to 2017.

They found that by 2017, the area wiped out by severe fires had risen eight times, to more than 2,000 sq kms or 800 sq miles. Much of the tree cover of the US west is adapted to episodes of fire. But the frequency and intensity of recent blazes threatens the future of the forests altogether.

“As more area burns at high severity, the likelihood of conversion to different forest types or even to non-forest increases,” said Sean Parks of the US Forest Service Rocky Mountain Research Station, and the lead author.

“At the same time, the post-fire climate is making it increasingly difficult for seedlings to establish and survive, further reducing the potential for forests to return to their pre-fire condition.” − Climate News Network

Fire and flood are on the rise. Bangladesh and New York face more flooding: the American West may see more forests burn.

LONDON, 14 December, 2020 − More extreme weather is on the way for the hapless residents of Bangladesh, New York and the western US,  facing the prospect of worsening fire and flood.

There is a new future for New York. By the close of the century, thanks to sea level rise and global heating, parts of it could be swept by hurricane-driven catastrophic floods almost every year.

Things don’t look much brighter for much of Bangladesh. Scientists have recalculated the risk of flooding by the Brahmaputra river system to find that, even without the climate emergency, they had under-estimated the likelihood of devastating floods across the crowded, low-lying landscape.

And far away in the American west, US citizens face yet more and more devastating seasons of fire. The area incinerated by severe fires has increased eight-fold in the last 40 years, thanks to intensifying heat and drought. And thanks to climate change, drought will become more extended and more frequent. The temperatures, too, will go on rising.

All this emerged in just another week of routine climate science, as researchers try to gauge the difficulties to come, for national and civic authorities, for foresters and for farmers.

“The increase in these once-in-a-generation floods is so dramatic because the impact of sea-level rise will create greater flooding, even if the storms today stay the same”

In 2012, Hurricane Sandy hit the US to cause $70bn in damages, and even slammed unexpectedly into New York, to devastate parts of the city. It counted as a once-in-500 years event.

Researchers report in the journal Climatic Change that they looked at the probabilities of more flooding in Jamaica Bay, on Long Island, New York as sea levels rose, along with the sea surface temperatures that drive fiercer storm weather, through the century.

Floods that tend to happen every century could, by 2050, occur every nine years. By 2080 to 2100, they could become annual events. And 500-year events like the 2012 superstorm could by the end of the century happen perhaps once every four years.

“Future projections of the hurricane climatology suggest that climate change would lead to storms that move more slowly and are more intense than we have ever seen before hitting Jamaica Bay,” said Reza Marsooli, an environmental engineer at the Stevens Institute of Technology in Hoboken, New Jersey, a co-author.

“But the increase in these once-in-a-generation or even less frequent floods is so dramatic because the impact of sea-level rise will create greater flooding, even if the storms we are seeing today stayed the same.”

Prepare for worse

The hazard that faces Bangladesh − much of which is at sea level, on fertile floodplain created by the Ganges-Brahmaputra river system − is more insidious.

One of the great waterways of the world, it rises in the Himalayan snows and swells in the monsoon season to flood the rice paddies and replenish farmlands with nourishing sediments. Occasionally the floods become devastating: in 1998, some 70% of the nation was submerged. Floods have recurred, in 2007, 2010 and 2020.

Engineers have been monitoring the flow since the 1950s, and thought they knew the flood probabilities. But US, Australian and Chinese scientists report in the journal Nature Communications that they studied the growth rings in ancient trees to find that Bangladeshis have been living in unusual times: for much of the past 70 years, on the evidence told by old trees along the watershed, the river flow has been unusually dry − the driest in the last 700 years.

“The tree rings suggest that the long-term baseline conditions are much wetter than thought,” said Mukund Palat Rao, of the Lamont-Doherty Earth Observatory at Columbia University in New York, who led the research.

“Whether you consider climate models or natural variability, the message is the same. We should prepare for a higher frequency of flooding than we are currently predicting.”

Forests’ future threatened

In the past 40 years, thanks to global heating driven by ever-higher emissions of greenhouse gases from the combustion of fossil fuels, the state of California has experienced a series of droughts that lasted for years. The fire season too has begun earlier and lasted much longer.

Ecologists report in the journal Geophysical Research Letters that they defined high-severity fires as those that killed 95% of all trees. They then counted the most severe episodes of burning in four great regions of the western US from 1985 to 2017.

They found that by 2017, the area wiped out by severe fires had risen eight times, to more than 2,000 sq kms or 800 sq miles. Much of the tree cover of the US west is adapted to episodes of fire. But the frequency and intensity of recent blazes threatens the future of the forests altogether.

“As more area burns at high severity, the likelihood of conversion to different forest types or even to non-forest increases,” said Sean Parks of the US Forest Service Rocky Mountain Research Station, and the lead author.

“At the same time, the post-fire climate is making it increasingly difficult for seedlings to establish and survive, further reducing the potential for forests to return to their pre-fire condition.” − Climate News Network

China and Australia face a climate tipping point

Once again, scientists warn that at least part of the world could be facing a climate tipping point. Two parts, in fact.

LONDON, 8 December 2020 − The grasslands of northern China and Mongolia could be about to lurch into a climate tipping point, an irreversible sequence of heat and drought.

This is a landscape that helped shape world history. The Hun forces that humbled the western Roman Empire 16 centuries ago, and the conquering hordes led by Genghis Khan that commanded most of the Asian continent and threatened Europe eight centuries later, both emerged from tribes of nomad herdsmen from its grasslands. Now it could itself be about to be reconfigured by human-driven climate change.

And that same anthropogenic climate tipping point poses the same threat to great tracts of south-east Australia: water could become more scarce, bush fires could become more frequent, and winds could begin to blow away the parched soils in droughts that could last decades, or even centuries.

Both studies are based on evidence from the past, and both on the story told by preserved annual growth rings. The warning from inner East Asia is based on the testimony of tree stumps and timbers from the last 260 years, say researchers in the journal Science.

“They’re alarming findings, in a long list of alarming findings…if humans continue to warm the planet, this is the future we may all be looking at”

The patterns of tree growth suggest that the recent consecutive summers marked by both heat and drought are new events, and could increase in frequency.

The high plains of central Asia can be very cold in winter, very hot in summer. But soil moisture normally evaporates to cool the air at the surface. In a sustained drought, the air becomes hotter. In recent years, the region’s lakes have been shrinking in extent − and in number.

“The result is more heatwaves, which means more soil water losses, which means more heatwaves − and where this might end, we cannot say,” said Deliang Chen of the University of Gothenburg in Sweden, one of the research team.

He and his co-authors warn bluntly that the double impact of sustained heat and prolonged drought “is potentially irreversible beyond a tipping point in the East Asian climate system.”

Mega-drought link

The evidence from Australia is based on a much more distant past, and preserved in stalagmites deep in a cave in New South Wales. Researchers write in the journal Scientific Reports that during a warm interval in the last Ice Age, from 129,000 to 116,000 years ago, global temperatures rose to levels much as they are today, and perhaps slightly warmer.

And the record of lower falls of snow, higher temperatures and ever-scarcer water, preserved in the ancient annual growths of underground calcium carbonate, provided the scientists with a hint of what to expect in a world of global heating driven by ever-increasing use of fossil fuels, and ever-greater destruction of natural ecosystems.

“We found that, in the past, a similar amount of warming has been associated with mega-drought conditions all over south-eastern Australia. These drier conditions prevailed for centuries, sometimes for more than 1000 years,” said Hamish McGowan of the University of Queensland, who led the study.

“They’re alarming findings, in a long list of alarming findings that climate scientists have released over the last few decades. We hope that this new research allows for new insights to our future climate and the risks it may bring, such as drought and associated bushfires. But importantly, if humans continue to warm the planet, this is the future we may all be looking at.” − Climate News Network

Once again, scientists warn that at least part of the world could be facing a climate tipping point. Two parts, in fact.

LONDON, 8 December 2020 − The grasslands of northern China and Mongolia could be about to lurch into a climate tipping point, an irreversible sequence of heat and drought.

This is a landscape that helped shape world history. The Hun forces that humbled the western Roman Empire 16 centuries ago, and the conquering hordes led by Genghis Khan that commanded most of the Asian continent and threatened Europe eight centuries later, both emerged from tribes of nomad herdsmen from its grasslands. Now it could itself be about to be reconfigured by human-driven climate change.

And that same anthropogenic climate tipping point poses the same threat to great tracts of south-east Australia: water could become more scarce, bush fires could become more frequent, and winds could begin to blow away the parched soils in droughts that could last decades, or even centuries.

Both studies are based on evidence from the past, and both on the story told by preserved annual growth rings. The warning from inner East Asia is based on the testimony of tree stumps and timbers from the last 260 years, say researchers in the journal Science.

“They’re alarming findings, in a long list of alarming findings…if humans continue to warm the planet, this is the future we may all be looking at”

The patterns of tree growth suggest that the recent consecutive summers marked by both heat and drought are new events, and could increase in frequency.

The high plains of central Asia can be very cold in winter, very hot in summer. But soil moisture normally evaporates to cool the air at the surface. In a sustained drought, the air becomes hotter. In recent years, the region’s lakes have been shrinking in extent − and in number.

“The result is more heatwaves, which means more soil water losses, which means more heatwaves − and where this might end, we cannot say,” said Deliang Chen of the University of Gothenburg in Sweden, one of the research team.

He and his co-authors warn bluntly that the double impact of sustained heat and prolonged drought “is potentially irreversible beyond a tipping point in the East Asian climate system.”

Mega-drought link

The evidence from Australia is based on a much more distant past, and preserved in stalagmites deep in a cave in New South Wales. Researchers write in the journal Scientific Reports that during a warm interval in the last Ice Age, from 129,000 to 116,000 years ago, global temperatures rose to levels much as they are today, and perhaps slightly warmer.

And the record of lower falls of snow, higher temperatures and ever-scarcer water, preserved in the ancient annual growths of underground calcium carbonate, provided the scientists with a hint of what to expect in a world of global heating driven by ever-increasing use of fossil fuels, and ever-greater destruction of natural ecosystems.

“We found that, in the past, a similar amount of warming has been associated with mega-drought conditions all over south-eastern Australia. These drier conditions prevailed for centuries, sometimes for more than 1000 years,” said Hamish McGowan of the University of Queensland, who led the study.

“They’re alarming findings, in a long list of alarming findings that climate scientists have released over the last few decades. We hope that this new research allows for new insights to our future climate and the risks it may bring, such as drought and associated bushfires. But importantly, if humans continue to warm the planet, this is the future we may all be looking at.” − Climate News Network

Drylands hit harder by poverty than richer regions

The arrival of the rains leaves the drylands hit harder than richer areas. Once again, climate change sows injustice.

LONDON, 7 December, 2020 − Not even the climate can be even-handed. When the rains come they leave the world’s drylands hit harder: the wealthier fare better and the poorest get relatively a little poorer. And the evidence is visible literally at the grassroots.

European scientists have been measuring vegetation growth as recorded in fine detail by satellite observation over the last 20 years. And they report that in the developing world, the vegetation that sprouts after rainfall on arid lands is more meagre, while in the better-off nations the same rainfall on the same kind of dryland terrain produces more healthy growth.

The consequence, researchers warn in the journal Nature Sustainability, could result in more food shortages, more disruption, and growing numbers of climate refugees.

“We observe a clear trend of arid areas developing in a negative direction in the most economically challenged countries,” said Rasmus Fensholt, of the University of Copenhagen, one of the authors.

“Here it is apparent that the growth of vegetation has become increasingly decoupled from the water resources available, and that there is simply less vegetation in relation to the amount of rainfall. The opposite is the case in the wealthiest countries.”

“One consequence of declining vegetation in the world’s poorer arid regions may be an increase in climate refugees from various African countries. There is no indication that the problem will diminish”

Roughly 40% of the Earth’s habitable land is arid or semi-arid, and the global drylands are home to almost a third of all humanity, around half of all the planet’s birds and mammals, as well as providing range for livestock and land for crops. Most of the world’s drylands are also home to many of the world’s least developed countries, and many of the poorest citizenry.

And, in a world of climate change driven by ever-rising global temperatures, fuelled in turn by greenhouse gas emissions from increasing fossil fuel use, things don’t look promising.

Research from the last four decades has repeatedly predicted that although global rainfall may be higher in total, those regions already well-watered will tend to become wetter, while those that have adapted to arid climate regimes will get drier. By the end of this century the proportion defined as dryland may have expanded by 23%.

And although higher temperatures, higher levels of atmospheric carbon and changes in rainfall regimes have had the overall effect of “greening” many of the drylands, those already struggling to survive are getting less benefit from any rain that falls.

The scientists, from Denmark, Norway, Sweden and the Netherlands, made a close analysis of satellite imagery from 2000 to 2015 to identify not rainfall changes, but vegetation productivity in relation to rainfall: they found pronounced differences across regions and continents. Drylands in Africa and Asia fared proportionately less well compared to South America and Australia.

Upward trend reversed

What made the difference, they think, is the number and the plight of the people on whom the rain fell. Rapid population growth in Africa meant greater pressure on land less suitable for agriculture, and more intense grazing on already fragile grassland cover.

In the richer nations, conversely, farms had expanded and intensified with help from fertiliser and irrigation.

This is not the first study to find that in a world of climate change, the poorest − among them those who have contributed least to global heating − will be hit hardest. The match of more people with less productive land can only mean more competition for less food at higher prices.

“One consequence of declining vegetation in the world’s poorer arid regions may be an increase in climate refugees from various African countries. According to what we have seen in this study, there is no indication that the problem will diminish in future,” Professor Fensholt said.

“We have been pleased to see that, for a number of years, vegetation has been on an upwards trend in arid regions. But if we dig only a tiny bit deeper and look at how successfully precipitation has translated into vegetation, then climate change seems to be hitting unevenly, which is troubling.” − Climate News Network

The arrival of the rains leaves the drylands hit harder than richer areas. Once again, climate change sows injustice.

LONDON, 7 December, 2020 − Not even the climate can be even-handed. When the rains come they leave the world’s drylands hit harder: the wealthier fare better and the poorest get relatively a little poorer. And the evidence is visible literally at the grassroots.

European scientists have been measuring vegetation growth as recorded in fine detail by satellite observation over the last 20 years. And they report that in the developing world, the vegetation that sprouts after rainfall on arid lands is more meagre, while in the better-off nations the same rainfall on the same kind of dryland terrain produces more healthy growth.

The consequence, researchers warn in the journal Nature Sustainability, could result in more food shortages, more disruption, and growing numbers of climate refugees.

“We observe a clear trend of arid areas developing in a negative direction in the most economically challenged countries,” said Rasmus Fensholt, of the University of Copenhagen, one of the authors.

“Here it is apparent that the growth of vegetation has become increasingly decoupled from the water resources available, and that there is simply less vegetation in relation to the amount of rainfall. The opposite is the case in the wealthiest countries.”

“One consequence of declining vegetation in the world’s poorer arid regions may be an increase in climate refugees from various African countries. There is no indication that the problem will diminish”

Roughly 40% of the Earth’s habitable land is arid or semi-arid, and the global drylands are home to almost a third of all humanity, around half of all the planet’s birds and mammals, as well as providing range for livestock and land for crops. Most of the world’s drylands are also home to many of the world’s least developed countries, and many of the poorest citizenry.

And, in a world of climate change driven by ever-rising global temperatures, fuelled in turn by greenhouse gas emissions from increasing fossil fuel use, things don’t look promising.

Research from the last four decades has repeatedly predicted that although global rainfall may be higher in total, those regions already well-watered will tend to become wetter, while those that have adapted to arid climate regimes will get drier. By the end of this century the proportion defined as dryland may have expanded by 23%.

And although higher temperatures, higher levels of atmospheric carbon and changes in rainfall regimes have had the overall effect of “greening” many of the drylands, those already struggling to survive are getting less benefit from any rain that falls.

The scientists, from Denmark, Norway, Sweden and the Netherlands, made a close analysis of satellite imagery from 2000 to 2015 to identify not rainfall changes, but vegetation productivity in relation to rainfall: they found pronounced differences across regions and continents. Drylands in Africa and Asia fared proportionately less well compared to South America and Australia.

Upward trend reversed

What made the difference, they think, is the number and the plight of the people on whom the rain fell. Rapid population growth in Africa meant greater pressure on land less suitable for agriculture, and more intense grazing on already fragile grassland cover.

In the richer nations, conversely, farms had expanded and intensified with help from fertiliser and irrigation.

This is not the first study to find that in a world of climate change, the poorest − among them those who have contributed least to global heating − will be hit hardest. The match of more people with less productive land can only mean more competition for less food at higher prices.

“One consequence of declining vegetation in the world’s poorer arid regions may be an increase in climate refugees from various African countries. According to what we have seen in this study, there is no indication that the problem will diminish in future,” Professor Fensholt said.

“We have been pleased to see that, for a number of years, vegetation has been on an upwards trend in arid regions. But if we dig only a tiny bit deeper and look at how successfully precipitation has translated into vegetation, then climate change seems to be hitting unevenly, which is troubling.” − Climate News Network

Africa’s resistance grows as climate crisis worsens

Battered by storms and droughts during a tough 2019, Africa’s resistance to the climate crisis left no room for passivity.

LONDON, 29 October, 2020 – Attempting to come to any general conclusions on the state of a vast, varied and complex continent may be a tricky business, but Africa’s resistance to the climate crisis shows it rejects any idea of settling for victimhood.

A new report, State of the Climate in Africa 2019, published by the World Meteorological Organization (WMO), makes that clear.

It reaches some grim conclusions. Increased temperatures, changing rainfall patterns, rising sea levels and more extreme weather are threatening human health and safety across the continent, says the report.

“Climate change is having a growing impact on the African continent, hitting the most vulnerable hardest and contributing to food insecurity, population displacement and stress on water resources”, says Petteri Taalas, the WMO secretary-general.

“In recent months we have seen devastating floods, an invasion of desert locusts and now face the looming spectre of drought because of a La Niña event”, he says. “The human and economic toll has been aggravated by the Covid-19 pandemic.”

Killer cyclone

Drought caused considerable damage in 2019, particularly across southern Africa. Much of East Africa also suffered drought but then, late in the year, there was torrential rain and serious flooding and landslides in the region.

The trend, says the report, is for continuing increases in temperature: 2019 was among the three warmest years ever recorded in Africa. The WMO predicts that rainfall is likely to decrease over northern and southern regions but increase over the Sahel.

There are also likely to be more weather-related extreme events. In March 2019 Cyclone Idai hit the coast of Mozambique and went on to devastate large areas of Malawi, Zimbabwe and surrounding countries.

Described as the most destructive cyclone ever recorded in the southern hemisphere, Idai killed hundreds of people and displaced several hundred thousand.

“Climate change is having a growing impact on the African continent, hitting the most vulnerable hardest”

Sea levels are rising well above the global average in many parts of Africa, the report says. Coastal degradation and erosion is a major challenge, particularly in West Africa. More than 50% of the coastlines in Benin, Côte d’Ivoire, Senegal and Togo are eroding – a trend likely to continue in future years.

The knock-on effects of these changes in climate are considerable. Approximately 60% of the total population of Africa is dependent on agriculture for a living.

Heat and drought, plus flood damage in some areas, are likely to reduce crop productivity. Changes in climate are also leading to pest outbreaks.

In what it describes as the worst case climate change scenario, the report says crop yields could drop by 13% by mid-century across West and Central Africa, 11% in North Africa and 8% in the eastern and southern regions of the continent. Rice and wheat crops would be particularly badly affected.

Combatting the crisis

Increased heat and continually changing rainfall patterns are also likely to lead to the spread of disease – and a fall-off in economic production in many countries.

But the report does point to some positive changes, showing Africa’s resistance to the crisis. Though the continent is responsible for only a small percentage of the world’s greenhouse gas emissions, many countries in Africa are taking measures aimed at tackling climate change.

Solar power is becoming more widespread, with several large-scale projects planned. Early warning systems monitoring the approach of such cataclysmic events as Cyclone Idai are being installed across the continent.
Farm incomes in many areas are increasing, due to the application of more efficient cultivation methods, such as micro-irrigation. But good planning, based on reliable data, is essential, the report says.

“The limited uptake and use of climate information services in development planning and practice in Africa is due in part to the paucity of reliable and timely climate information”, says Vera Songwe, the executive secretary of the United Nations Economic Commission for Africa. – Climate News Network

Battered by storms and droughts during a tough 2019, Africa’s resistance to the climate crisis left no room for passivity.

LONDON, 29 October, 2020 – Attempting to come to any general conclusions on the state of a vast, varied and complex continent may be a tricky business, but Africa’s resistance to the climate crisis shows it rejects any idea of settling for victimhood.

A new report, State of the Climate in Africa 2019, published by the World Meteorological Organization (WMO), makes that clear.

It reaches some grim conclusions. Increased temperatures, changing rainfall patterns, rising sea levels and more extreme weather are threatening human health and safety across the continent, says the report.

“Climate change is having a growing impact on the African continent, hitting the most vulnerable hardest and contributing to food insecurity, population displacement and stress on water resources”, says Petteri Taalas, the WMO secretary-general.

“In recent months we have seen devastating floods, an invasion of desert locusts and now face the looming spectre of drought because of a La Niña event”, he says. “The human and economic toll has been aggravated by the Covid-19 pandemic.”

Killer cyclone

Drought caused considerable damage in 2019, particularly across southern Africa. Much of East Africa also suffered drought but then, late in the year, there was torrential rain and serious flooding and landslides in the region.

The trend, says the report, is for continuing increases in temperature: 2019 was among the three warmest years ever recorded in Africa. The WMO predicts that rainfall is likely to decrease over northern and southern regions but increase over the Sahel.

There are also likely to be more weather-related extreme events. In March 2019 Cyclone Idai hit the coast of Mozambique and went on to devastate large areas of Malawi, Zimbabwe and surrounding countries.

Described as the most destructive cyclone ever recorded in the southern hemisphere, Idai killed hundreds of people and displaced several hundred thousand.

“Climate change is having a growing impact on the African continent, hitting the most vulnerable hardest”

Sea levels are rising well above the global average in many parts of Africa, the report says. Coastal degradation and erosion is a major challenge, particularly in West Africa. More than 50% of the coastlines in Benin, Côte d’Ivoire, Senegal and Togo are eroding – a trend likely to continue in future years.

The knock-on effects of these changes in climate are considerable. Approximately 60% of the total population of Africa is dependent on agriculture for a living.

Heat and drought, plus flood damage in some areas, are likely to reduce crop productivity. Changes in climate are also leading to pest outbreaks.

In what it describes as the worst case climate change scenario, the report says crop yields could drop by 13% by mid-century across West and Central Africa, 11% in North Africa and 8% in the eastern and southern regions of the continent. Rice and wheat crops would be particularly badly affected.

Combatting the crisis

Increased heat and continually changing rainfall patterns are also likely to lead to the spread of disease – and a fall-off in economic production in many countries.

But the report does point to some positive changes, showing Africa’s resistance to the crisis. Though the continent is responsible for only a small percentage of the world’s greenhouse gas emissions, many countries in Africa are taking measures aimed at tackling climate change.

Solar power is becoming more widespread, with several large-scale projects planned. Early warning systems monitoring the approach of such cataclysmic events as Cyclone Idai are being installed across the continent.
Farm incomes in many areas are increasing, due to the application of more efficient cultivation methods, such as micro-irrigation. But good planning, based on reliable data, is essential, the report says.

“The limited uptake and use of climate information services in development planning and practice in Africa is due in part to the paucity of reliable and timely climate information”, says Vera Songwe, the executive secretary of the United Nations Economic Commission for Africa. – Climate News Network

Drought and heat together menace American West

Climate change really is a burning issue. Simultaneous drought and heat are increasingly likely for more of the American West.

LONDON, 13 October, 2020 − The American West is about to get hotter. It is also about to get drier. To make things worse, extremes of heat and of drought will happen more often at the same time.

And to compound the damage, such simultaneous assaults are likely to extend over larger areas and become more intense and more frequent, thanks to climate change driven by profligate use of fossil fuels and other human decisions.

This is not a prediction based on computer simulations of the future. It is already happening, and the story can be traced − according to the journal Science Advances − in the narrative of hot spells and dry weather over the entire contiguous United States for the last 122 years.

Not only have combined hot and dry episodes increased in frequency, they have also grown in size in geographic terms. Where once they happened in confined localities, they now extend over whole regions, such as the entire West Coast, and parts too of the Northeast and the Southeast.

Another Dust Bowl?

“Dry-hot events can cause large fires. Add wind and a source of ignition, and this results in ‘megafires’ like the 2020 fires across the west coast of the United States. Drought and record-breaking heatwaves, coupled with a storm that brought strong winds and 12,000 lightning events in a span of 72 hours, caused more than 500 wildfires,” said Mohammad Reza Alizadeh, of McGill University in Canada, who led the research.

Heat extremes can be damaging or even devastating. So can drought. When the two coincide, their compound impact can be tragic. The study also suggested that in some way such double jeopardy events could be self-propagating: they could spread downwind, seriously bad news for the American West and other areas at risk.

Long before any fears of the climate emergency, the US Midwest was scarred by drought, and in the 1930s Oklahoma and Kansas in particular became a “Dust Bowl” and inspired the classic novel The Grapes of Wrath by the American writer John Steinbeck.

“We observed that concurrent dry and hot events of similar intensity are becoming more frequent,” said Mojtaba Sadegh, an engineer at Boise State University in Idaho, and the senior author.

“Our results point to an urgent need to take action to enhance resilience to compound hot and dry events”

“The difference is that, in the 1930s, lack of precipitation led to the local atmosphere becoming hotter, whereas in recent decades increased temperatures are driving aridity. The triggering mechanism for compound dry-hot events is changing from lack of precipitation to excess heat.”

The warning of worse to come coincides with news that California’s fires have become so bad that they warrant a new classification: the “gigafire”, with so much smoke emitted from the combined fires of California and Oregon that fumes have been detected in New York, in northern Europe, and far into the Pacific.

Researchers have repeatedly warned of the double hazard of heat and drought and the combined impact on the US, as a consequence of climate change driven by greenhouse gas emissions from power station chimneys and automobile exhausts, as well as destruction of the natural wilderness.

“This research raises an alarm about increasing frequency and intensity of compound hot and dry events,” said Dr Sadegh. “Three such events between 2011-2013 in the US caused $60bn (£46bn) in damages. Our results point to an urgent need to take action to enhance resilience to compound hot and dry events.” − Climate News Network

Climate change really is a burning issue. Simultaneous drought and heat are increasingly likely for more of the American West.

LONDON, 13 October, 2020 − The American West is about to get hotter. It is also about to get drier. To make things worse, extremes of heat and of drought will happen more often at the same time.

And to compound the damage, such simultaneous assaults are likely to extend over larger areas and become more intense and more frequent, thanks to climate change driven by profligate use of fossil fuels and other human decisions.

This is not a prediction based on computer simulations of the future. It is already happening, and the story can be traced − according to the journal Science Advances − in the narrative of hot spells and dry weather over the entire contiguous United States for the last 122 years.

Not only have combined hot and dry episodes increased in frequency, they have also grown in size in geographic terms. Where once they happened in confined localities, they now extend over whole regions, such as the entire West Coast, and parts too of the Northeast and the Southeast.

Another Dust Bowl?

“Dry-hot events can cause large fires. Add wind and a source of ignition, and this results in ‘megafires’ like the 2020 fires across the west coast of the United States. Drought and record-breaking heatwaves, coupled with a storm that brought strong winds and 12,000 lightning events in a span of 72 hours, caused more than 500 wildfires,” said Mohammad Reza Alizadeh, of McGill University in Canada, who led the research.

Heat extremes can be damaging or even devastating. So can drought. When the two coincide, their compound impact can be tragic. The study also suggested that in some way such double jeopardy events could be self-propagating: they could spread downwind, seriously bad news for the American West and other areas at risk.

Long before any fears of the climate emergency, the US Midwest was scarred by drought, and in the 1930s Oklahoma and Kansas in particular became a “Dust Bowl” and inspired the classic novel The Grapes of Wrath by the American writer John Steinbeck.

“We observed that concurrent dry and hot events of similar intensity are becoming more frequent,” said Mojtaba Sadegh, an engineer at Boise State University in Idaho, and the senior author.

“Our results point to an urgent need to take action to enhance resilience to compound hot and dry events”

“The difference is that, in the 1930s, lack of precipitation led to the local atmosphere becoming hotter, whereas in recent decades increased temperatures are driving aridity. The triggering mechanism for compound dry-hot events is changing from lack of precipitation to excess heat.”

The warning of worse to come coincides with news that California’s fires have become so bad that they warrant a new classification: the “gigafire”, with so much smoke emitted from the combined fires of California and Oregon that fumes have been detected in New York, in northern Europe, and far into the Pacific.

Researchers have repeatedly warned of the double hazard of heat and drought and the combined impact on the US, as a consequence of climate change driven by greenhouse gas emissions from power station chimneys and automobile exhausts, as well as destruction of the natural wilderness.

“This research raises an alarm about increasing frequency and intensity of compound hot and dry events,” said Dr Sadegh. “Three such events between 2011-2013 in the US caused $60bn (£46bn) in damages. Our results point to an urgent need to take action to enhance resilience to compound hot and dry events.” − Climate News Network