Tag Archives: Drought

Drought and famine stalk desperate Madagascar

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

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

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

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

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

Single day’s rain

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

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

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

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

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

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

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

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

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

The next pandemic

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

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

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

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

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

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

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

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

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

Single day’s rain

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

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

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

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

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

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

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

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

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

The next pandemic

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

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

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

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

Fossil fuel use leads to worse and longer droughts

Human reliance on fossil fuels is resulting in worse and longer droughts. It’s a familiar message across the world.

LONDON, 27 May, 2021 − Researchers have been busy trying to find out more about why many parts of the world are experiencing worse and longer droughts. Californian scientists had cleared up any confusion about Californian droughts. And about droughts in the rest of the Americas, the Mediterranean, western and southern Africa and east Asia.

Greenhouse gas emissions and other atmospheric pollution from human causes tend to increase the frequency of drought, the intensity of drought and the maximum duration of drought worldwide.

“There has always been natural variability in drought events around the world, but our research shows the clear human influence on drying, specifically from anthropogenic aerosols, carbon dioxide and other greenhouse gases,” said Felicia Chiang, of the University of California Irvine, and now at Nasa’s Goddard Institute for Space Studies in New York.

She and colleagues write in the journal Nature Communications that they used a computer simulation to explore drought characteristics, first with “natural” conditions, and then with extra help from atmospheric greenhouse gases from fossil fuel combustion, along with tiny atmospheric particles from power plants, car exhausts and fire to clear land and burn waste.

The “natural-only” simulations showed no regional changes from the late 19th to the late 20th centuries. But once the researchers tested their simulation with more atmospheric carbon dioxide, sulphur particles and soot, they could see statistically significant increases in drought hotpots in southern Europe, Central and South America and other regions.

“Our research shows the clear human influence on drying, specifically from anthropogenic aerosols, carbon dioxide and other greenhouse gases”

Researchers have been warning for years of the danger of increasing drought with ever-higher global average temperatures. The eastern Mediterranean recently went through its worst drought in 900 years, while California has been afflicted by devastating heat, prolonged dry spells and dreadful forest fires.

Drought has been so frequent in the Amazon that one scientist has warned that the entire rainforest ecosystem might collapse. So the latest study is just another confirmation of a familiar story.

“Knowing where, how and why droughts have been worsening around the world is important, because these events directly and indirectly impact everything from wildlife habitats to agricultural production to our economy,” said Amir AghaKouchak, a co-author at UC Irvine.

And a third contributor, his colleague Omid Mazdiyasni, now with the Los Angeles county department of public works, added: “If droughts over the past century have been worsened by human-sourced pollution, then there is a strong possibility that the problem can be mitigated by limiting these emissions.” − Climate News Network

Human reliance on fossil fuels is resulting in worse and longer droughts. It’s a familiar message across the world.

LONDON, 27 May, 2021 − Researchers have been busy trying to find out more about why many parts of the world are experiencing worse and longer droughts. Californian scientists had cleared up any confusion about Californian droughts. And about droughts in the rest of the Americas, the Mediterranean, western and southern Africa and east Asia.

Greenhouse gas emissions and other atmospheric pollution from human causes tend to increase the frequency of drought, the intensity of drought and the maximum duration of drought worldwide.

“There has always been natural variability in drought events around the world, but our research shows the clear human influence on drying, specifically from anthropogenic aerosols, carbon dioxide and other greenhouse gases,” said Felicia Chiang, of the University of California Irvine, and now at Nasa’s Goddard Institute for Space Studies in New York.

She and colleagues write in the journal Nature Communications that they used a computer simulation to explore drought characteristics, first with “natural” conditions, and then with extra help from atmospheric greenhouse gases from fossil fuel combustion, along with tiny atmospheric particles from power plants, car exhausts and fire to clear land and burn waste.

The “natural-only” simulations showed no regional changes from the late 19th to the late 20th centuries. But once the researchers tested their simulation with more atmospheric carbon dioxide, sulphur particles and soot, they could see statistically significant increases in drought hotpots in southern Europe, Central and South America and other regions.

“Our research shows the clear human influence on drying, specifically from anthropogenic aerosols, carbon dioxide and other greenhouse gases”

Researchers have been warning for years of the danger of increasing drought with ever-higher global average temperatures. The eastern Mediterranean recently went through its worst drought in 900 years, while California has been afflicted by devastating heat, prolonged dry spells and dreadful forest fires.

Drought has been so frequent in the Amazon that one scientist has warned that the entire rainforest ecosystem might collapse. So the latest study is just another confirmation of a familiar story.

“Knowing where, how and why droughts have been worsening around the world is important, because these events directly and indirectly impact everything from wildlife habitats to agricultural production to our economy,” said Amir AghaKouchak, a co-author at UC Irvine.

And a third contributor, his colleague Omid Mazdiyasni, now with the Los Angeles county department of public works, added: “If droughts over the past century have been worsened by human-sourced pollution, then there is a strong possibility that the problem can be mitigated by limiting these emissions.” − Climate News Network

Tide of climate refugees swells as Earth heats up

Prepare for the arrival of more displaced persons, climate refugees driven from their homes by global heating.

LONDON, 11 May, 2021 − Natural hazards − most of them driven by climate change − have forced an estimated 288 million people from their homes since 2008. That is three times the numbers displaced by war and conflict. These people have become, however briefly, climate refugees.

And the number will grow. A new study has found that for every 1°C rise in global average temperatures, the chance of displacement from river flooding alone will rise by 50%. And that calculation is based on population numbers right now. As human numbers rise, so will the risk − by 110%.

Another study makes an even more precise prediction: thanks to rising sea levels and more intense cyclonic storms, an estimated 1.3 million people in Bangladesh will be forced into migration by 2050. Many will move further inland − but many are likely to be forced across national borders, to trigger more displacement.

Drought and famine are climate-related natural disasters. So are forest fires, extreme heat waves, catastrophic windstorms and devastating floods, driven either by torrential rainfall or rising sea levels, or both.

Climate scientists, environmentalists and geographers have been warning for years that the numbers of people driven from their homes by climate change is on the increase: even in the US, as many as 13 million people could be forced from their coastal settlements by sea level rise.

“It is imperative that we have a better understanding of how the risks are changing”

Swiss scientists report in the journal Environmental Research Letters that even if the world keeps to an agreement to limit global warming to no more than 2°C, because the global population is rising, the average risk of displacement by river flooding is likely to rise by 110% by the end of the century.

If however nations take no drastic action, and go on burning ever more fossil fuels, the global average risk of being forced from home by swirling waters could rise by up to 350%.

“Because floods are a major driver of displacement, and due to the fact that they are influenced by climate change, it is imperative that we have a better understanding of how the risks are changing,” said Pui Man Kam of the Swiss Federal Institute of Technology, known as ETH Zurich, who led the study.

An estimated 680 million people worldwide live in low-lying coastal zones. Spanish, Italian and US scientists report in the journal Earth’s Future that they had developed a data model to predict the numbers likely to be displaced by any natural hazard to become climate refugees.

They tested it in the context of sea level rise, storms and floods in one low-lying country laced with rivers: Bangladesh. It is home to 163 million people, of whom 41% live at elevations lower than 10 metres above sea level.

Countrywide unrest likely

Their research found that although people in the coastal districts along the Bay of Bengal would be flooded, a surge of migration would ripple across the landscape and impact all 64 districts, including the capital, Dhaka.

Thanks to climate migration, numbers in the city should grow and eventually decline, as people moved to get away from the new arrivals. That is, flood events at the coast could ultimately trigger human unrest in the entire country.
“Droughts, desertification, floods, earthquakes, and wildfire threaten livelihoods worldwide; from wealthy to developing economies, every country is vulnerable to environmental change,” said Maurizio Porfiri of New York University’s Tandon School of Engineering.

“Mathematical models can assist in providing reliable predictions of environmental migration, which are critical for devising effective policy initiatives and improving our preparedness for future migration patterns.” − Climate News Network

Prepare for the arrival of more displaced persons, climate refugees driven from their homes by global heating.

LONDON, 11 May, 2021 − Natural hazards − most of them driven by climate change − have forced an estimated 288 million people from their homes since 2008. That is three times the numbers displaced by war and conflict. These people have become, however briefly, climate refugees.

And the number will grow. A new study has found that for every 1°C rise in global average temperatures, the chance of displacement from river flooding alone will rise by 50%. And that calculation is based on population numbers right now. As human numbers rise, so will the risk − by 110%.

Another study makes an even more precise prediction: thanks to rising sea levels and more intense cyclonic storms, an estimated 1.3 million people in Bangladesh will be forced into migration by 2050. Many will move further inland − but many are likely to be forced across national borders, to trigger more displacement.

Drought and famine are climate-related natural disasters. So are forest fires, extreme heat waves, catastrophic windstorms and devastating floods, driven either by torrential rainfall or rising sea levels, or both.

Climate scientists, environmentalists and geographers have been warning for years that the numbers of people driven from their homes by climate change is on the increase: even in the US, as many as 13 million people could be forced from their coastal settlements by sea level rise.

“It is imperative that we have a better understanding of how the risks are changing”

Swiss scientists report in the journal Environmental Research Letters that even if the world keeps to an agreement to limit global warming to no more than 2°C, because the global population is rising, the average risk of displacement by river flooding is likely to rise by 110% by the end of the century.

If however nations take no drastic action, and go on burning ever more fossil fuels, the global average risk of being forced from home by swirling waters could rise by up to 350%.

“Because floods are a major driver of displacement, and due to the fact that they are influenced by climate change, it is imperative that we have a better understanding of how the risks are changing,” said Pui Man Kam of the Swiss Federal Institute of Technology, known as ETH Zurich, who led the study.

An estimated 680 million people worldwide live in low-lying coastal zones. Spanish, Italian and US scientists report in the journal Earth’s Future that they had developed a data model to predict the numbers likely to be displaced by any natural hazard to become climate refugees.

They tested it in the context of sea level rise, storms and floods in one low-lying country laced with rivers: Bangladesh. It is home to 163 million people, of whom 41% live at elevations lower than 10 metres above sea level.

Countrywide unrest likely

Their research found that although people in the coastal districts along the Bay of Bengal would be flooded, a surge of migration would ripple across the landscape and impact all 64 districts, including the capital, Dhaka.

Thanks to climate migration, numbers in the city should grow and eventually decline, as people moved to get away from the new arrivals. That is, flood events at the coast could ultimately trigger human unrest in the entire country.
“Droughts, desertification, floods, earthquakes, and wildfire threaten livelihoods worldwide; from wealthy to developing economies, every country is vulnerable to environmental change,” said Maurizio Porfiri of New York University’s Tandon School of Engineering.

“Mathematical models can assist in providing reliable predictions of environmental migration, which are critical for devising effective policy initiatives and improving our preparedness for future migration patterns.” − Climate News Network

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