Tag Archives: Prehistory

Hotter worlds cut humans’ size − and their brains?

In a greenhouse world, humans’ size could shrink. And there is a hint of hazard to thinking capacity as well.

LONDON, 14 July, 2021 − As global temperatures rise, humankind might be about to shrink small − and possibly even think small. New research has once again linked creatures’ stature, including humans’ size, with climate conditions and, less certainly, brain size.

The finding is consistent with a biological proposition called Bergmann’s Rule, although it is more an observation than a rule: that members of a species tend to be bigger in colder climates than in warm ones.

British and German researchers report in the journal Nature Communications that they measured 300 fossils of the genus Homo found across the globe and combined their measurements with a reconstruction of the world’s regional climates for the last million years: that is, for each fossil, they were able to pinpoint the place and the temperatures in which it flourished.

And they found that humankind, whether Homo neanderthalensis or the older versions of Homo sapiens, has tended to fluctuate significantly in height and weight over the last million years, and this fluctuation is strongly linked with the temperature. When climates were cold and harsh, body sizes were larger. In warmer regimes, they were smaller.

Over the same period, brain size changed dramatically, but not in step with body size: still, the researchers could see an indirect environmental influence on brain size, possibly linked to the range of nutrients in altered environments.

Shrink for safety

“Our study indicates that climate − particularly temperature − has been the main driver of changes of body size for the past million years,” said Andrea Manica, an evolutionary ecologist at the University of Cambridge, and one of the authors.

“We can see from people living today that those in warmer climates tend to be smaller, and those living in colder climates tend to be bigger. We now know that the same climatic influences have been at work for the last million years.”

In colder climates, a larger size means more mass in relation to surface area: that is, in cold weather, large creatures lose body heat more slowly. Conversely, in hot climates, smaller animals can adjust their core temperatures by shedding heat more easily.

The finding is consistent with other studies of change over time in step with temperature. More than eight years ago, US and British scientists suggested that those species that could successfully “dwarf” would be at an advantage in an increasingly hotter world: those humans that survived what could be catastrophic climate change and ever higher temperatures could shrink to the size of J R R Tolkien’s fictional Hobbits.

“Climate − particularly temperature − has been the main driver of changes of body size for the past million years”

It was a warning, not an observation, but since then, as global average temperatures have crept up by little more than 1°C Celsius in the last century, chamois in the Italian Alps have grown on average smaller.

Another team of researchers checked the bulk of North American bison in two regions: those in grazing South Dakota were significantly heavier than their relatives much further south in Oklahoma.The team warned that this finding had costly implications for cattle farmers in an ever-warming world.

Brazilian scientists had already identified what they called “nutritional dwarfism” in north-eastern Brazil, where sustained drought four decades ago left millions in near-starving conditions. A generation of children in the region grew to an average adult height of 1.35 metres.

Diet and food supply are not separable from climatic conditions, so when it comes to brain size, the links are harder to establish. But the fossil measurement data seemed to suggest that brain size was larger when humans lived in ecologically stable areas, or in open steppes and grassland. Such people hunted large animals, which might have fuelled brain growth.

The human brain is a greedy organ: it consumes one-fifth of human energy intake. Quite how and why humans have evolved such big brains is a subject of continuous debate.

Puzzling brains

“We found that different factors determine brain size and body size − they are not under the same evolutionary pressure,” said Manuel Will, an archaeologist at the University of Tübingen in Germany, and another author.

“There is an indirect environmental influence on brain size in more stable and open areas: the amount of nutrients gained from the environment had to be sufficient to allow for the maintenance and growth of our large and energy-demanding brains.”

Human body size is still adapting: those in colder climates tend to be on average larger than those in the tropics. Brain size in humans however may have been shrinking since the end of the last Ice Age almost 12,000 years ago.

Why is not known: it might be explained by changes in human culture and social attitude; it might be connected with the invention of learning technologies. A library becomes in effect brainpower outsourced. Greater dependence on computers might drive down brain size even more. But nobody knows.

“It’s fun to speculate about what will happen to body and brain sizes in the future,” said Professor Manica, “but we should be careful not to extrapolate too much based on the last million years, because so many factors can change.” − Climate News Network

In a greenhouse world, humans’ size could shrink. And there is a hint of hazard to thinking capacity as well.

LONDON, 14 July, 2021 − As global temperatures rise, humankind might be about to shrink small − and possibly even think small. New research has once again linked creatures’ stature, including humans’ size, with climate conditions and, less certainly, brain size.

The finding is consistent with a biological proposition called Bergmann’s Rule, although it is more an observation than a rule: that members of a species tend to be bigger in colder climates than in warm ones.

British and German researchers report in the journal Nature Communications that they measured 300 fossils of the genus Homo found across the globe and combined their measurements with a reconstruction of the world’s regional climates for the last million years: that is, for each fossil, they were able to pinpoint the place and the temperatures in which it flourished.

And they found that humankind, whether Homo neanderthalensis or the older versions of Homo sapiens, has tended to fluctuate significantly in height and weight over the last million years, and this fluctuation is strongly linked with the temperature. When climates were cold and harsh, body sizes were larger. In warmer regimes, they were smaller.

Over the same period, brain size changed dramatically, but not in step with body size: still, the researchers could see an indirect environmental influence on brain size, possibly linked to the range of nutrients in altered environments.

Shrink for safety

“Our study indicates that climate − particularly temperature − has been the main driver of changes of body size for the past million years,” said Andrea Manica, an evolutionary ecologist at the University of Cambridge, and one of the authors.

“We can see from people living today that those in warmer climates tend to be smaller, and those living in colder climates tend to be bigger. We now know that the same climatic influences have been at work for the last million years.”

In colder climates, a larger size means more mass in relation to surface area: that is, in cold weather, large creatures lose body heat more slowly. Conversely, in hot climates, smaller animals can adjust their core temperatures by shedding heat more easily.

The finding is consistent with other studies of change over time in step with temperature. More than eight years ago, US and British scientists suggested that those species that could successfully “dwarf” would be at an advantage in an increasingly hotter world: those humans that survived what could be catastrophic climate change and ever higher temperatures could shrink to the size of J R R Tolkien’s fictional Hobbits.

“Climate − particularly temperature − has been the main driver of changes of body size for the past million years”

It was a warning, not an observation, but since then, as global average temperatures have crept up by little more than 1°C Celsius in the last century, chamois in the Italian Alps have grown on average smaller.

Another team of researchers checked the bulk of North American bison in two regions: those in grazing South Dakota were significantly heavier than their relatives much further south in Oklahoma.The team warned that this finding had costly implications for cattle farmers in an ever-warming world.

Brazilian scientists had already identified what they called “nutritional dwarfism” in north-eastern Brazil, where sustained drought four decades ago left millions in near-starving conditions. A generation of children in the region grew to an average adult height of 1.35 metres.

Diet and food supply are not separable from climatic conditions, so when it comes to brain size, the links are harder to establish. But the fossil measurement data seemed to suggest that brain size was larger when humans lived in ecologically stable areas, or in open steppes and grassland. Such people hunted large animals, which might have fuelled brain growth.

The human brain is a greedy organ: it consumes one-fifth of human energy intake. Quite how and why humans have evolved such big brains is a subject of continuous debate.

Puzzling brains

“We found that different factors determine brain size and body size − they are not under the same evolutionary pressure,” said Manuel Will, an archaeologist at the University of Tübingen in Germany, and another author.

“There is an indirect environmental influence on brain size in more stable and open areas: the amount of nutrients gained from the environment had to be sufficient to allow for the maintenance and growth of our large and energy-demanding brains.”

Human body size is still adapting: those in colder climates tend to be on average larger than those in the tropics. Brain size in humans however may have been shrinking since the end of the last Ice Age almost 12,000 years ago.

Why is not known: it might be explained by changes in human culture and social attitude; it might be connected with the invention of learning technologies. A library becomes in effect brainpower outsourced. Greater dependence on computers might drive down brain size even more. But nobody knows.

“It’s fun to speculate about what will happen to body and brain sizes in the future,” said Professor Manica, “but we should be careful not to extrapolate too much based on the last million years, because so many factors can change.” − Climate News Network

Nature, not humans, may cause mass extinctions

Life on Earth has been through mass extinctions before − every 27 million years. Blame it on celestial clockwork.

LONDON, 18 December, 2020 − US scientists believe they have identified a recurring pattern of mass extinctions and catastrophic climate change − and this time humans really are not to blame.

Instead, the planet and the solar system could be caught up in some deadly astronomical cycle.

They argue that every 27 million years, a high proportion of land-dwelling species − birds, mammals, reptiles and amphibians − disappear from the fossil record at around the same time.

And this disappearance seems to coincide, again according to geological evidence, with devastating eruptions of volcanic lava and violent asteroid collisions that would have had the effect of darkening the skies, lowering the temperature, depleting the ozone layer, then stimulating a greenhouse effect and starting extensive fire and acid rain.

“It seems that large-body impacts and the pulses of internal Earth activity that create flood basalt volcanism may be marching to the same 27-million-year drumbeat as the extinctions, perhaps paced by our orbit in the galaxy,” said Michael Rampino, a biologist at New York University.

Serial crises

He and colleagues used statistical analysis to identify, in the journal Historical Biology, an ominous rhythm of catastrophe in the Earth’s deep history.

Such research highlights the extraordinary nature of the present life-on-Earth survival crisis. Earth is now undergoing what naturalists and geologists see as the Sixth Great Extinction in its 500-million-year fossil history, and potentially calamitous climate change, not because of any shift in planetary orbit or galactic traffic accident, but because of the human population explosion and the 200-year-long addiction to fossil fuels.

But researchers know the present crisis to be the latest of a series of crises in the long history of life on Earth only because of the capricious evidence of the fossil record, and they have spent the last half century trying to decipher some reason how and why these might have happened.

More than 40 years ago geologists began to see what they argued seemed to be cycles of destruction, followed by the slow restoration of the biodiversity of Earth.

“The global mass extinctions were apparently caused by the largest cataclysmic impacts and massive volcanism, perhaps sometimes working in concert”

Around that time, earth scientists found evidence of an asteroid impact that appeared to have wiped out the entire dinosaur lineage, along with seven-tenths of all species on land and sea. And some began to argue that mass extinctions might not be random events, but happen according to some kind of heavenly timetable.

Most of the evidence for such happenings comes from marine sediments: evidence of extinction in the oceans every 26 million years or so. Now Professor Rampino and his colleagues have looked at the record of mass extinctions on land, and found that these seem to follow a similar cycle spaced 27.5 million years apart.

In which case, there might be an agency to take the blame: the Milky Way Galaxy, of which the solar system and planet Earth is a very small part, moving at colossal speed.

Not only does the Earth orbit the Sun at 30 kms a second, the Sun and its planets waltz around the Galaxy at 220 kms a second, and make a complete revolution, astronomers think, about every 26 million to 30 million years. That means that any galactic traffic accident guarantees a collision at very high speed.

Suspect eruptions

And it could also mean that on every round trip, the Solar System passes through some kind of unidentified hazard zone that triggers showers of comet collisions and asteroid impacts.

“In fact three of the mass annihilations of species on land and in the sea are already known to have occurred at the same times as the three largest impacts of the last 250 million years, each capable of causing disaster and resulting mass extinctions,” Professor Rampino said.

But there is another more down-to-earth factor. All eight of those episodes of mass death on land and parallel extinction in the seas also matched periods of eruptions in which hot basalts flooded across the landscape.

All volcanic eruptions release carbon dioxide: in such cases enough to create conditions of intense cold followed by greenhouse warming,  acidification of the oceans and acid rain on land, destruction of the ozone layer that normally screens the planet from dangerous ultra-violet radiation, and even marine oxygen depletion. In which case life on the planet would have to withstand a kind of double assault.

“The global mass extinctions were apparently caused by the largest cataclysmic impacts and massive volcanism, perhaps sometimes working in concert,” Professor Rampino said. − Climate News Network

Life on Earth has been through mass extinctions before − every 27 million years. Blame it on celestial clockwork.

LONDON, 18 December, 2020 − US scientists believe they have identified a recurring pattern of mass extinctions and catastrophic climate change − and this time humans really are not to blame.

Instead, the planet and the solar system could be caught up in some deadly astronomical cycle.

They argue that every 27 million years, a high proportion of land-dwelling species − birds, mammals, reptiles and amphibians − disappear from the fossil record at around the same time.

And this disappearance seems to coincide, again according to geological evidence, with devastating eruptions of volcanic lava and violent asteroid collisions that would have had the effect of darkening the skies, lowering the temperature, depleting the ozone layer, then stimulating a greenhouse effect and starting extensive fire and acid rain.

“It seems that large-body impacts and the pulses of internal Earth activity that create flood basalt volcanism may be marching to the same 27-million-year drumbeat as the extinctions, perhaps paced by our orbit in the galaxy,” said Michael Rampino, a biologist at New York University.

Serial crises

He and colleagues used statistical analysis to identify, in the journal Historical Biology, an ominous rhythm of catastrophe in the Earth’s deep history.

Such research highlights the extraordinary nature of the present life-on-Earth survival crisis. Earth is now undergoing what naturalists and geologists see as the Sixth Great Extinction in its 500-million-year fossil history, and potentially calamitous climate change, not because of any shift in planetary orbit or galactic traffic accident, but because of the human population explosion and the 200-year-long addiction to fossil fuels.

But researchers know the present crisis to be the latest of a series of crises in the long history of life on Earth only because of the capricious evidence of the fossil record, and they have spent the last half century trying to decipher some reason how and why these might have happened.

More than 40 years ago geologists began to see what they argued seemed to be cycles of destruction, followed by the slow restoration of the biodiversity of Earth.

“The global mass extinctions were apparently caused by the largest cataclysmic impacts and massive volcanism, perhaps sometimes working in concert”

Around that time, earth scientists found evidence of an asteroid impact that appeared to have wiped out the entire dinosaur lineage, along with seven-tenths of all species on land and sea. And some began to argue that mass extinctions might not be random events, but happen according to some kind of heavenly timetable.

Most of the evidence for such happenings comes from marine sediments: evidence of extinction in the oceans every 26 million years or so. Now Professor Rampino and his colleagues have looked at the record of mass extinctions on land, and found that these seem to follow a similar cycle spaced 27.5 million years apart.

In which case, there might be an agency to take the blame: the Milky Way Galaxy, of which the solar system and planet Earth is a very small part, moving at colossal speed.

Not only does the Earth orbit the Sun at 30 kms a second, the Sun and its planets waltz around the Galaxy at 220 kms a second, and make a complete revolution, astronomers think, about every 26 million to 30 million years. That means that any galactic traffic accident guarantees a collision at very high speed.

Suspect eruptions

And it could also mean that on every round trip, the Solar System passes through some kind of unidentified hazard zone that triggers showers of comet collisions and asteroid impacts.

“In fact three of the mass annihilations of species on land and in the sea are already known to have occurred at the same times as the three largest impacts of the last 250 million years, each capable of causing disaster and resulting mass extinctions,” Professor Rampino said.

But there is another more down-to-earth factor. All eight of those episodes of mass death on land and parallel extinction in the seas also matched periods of eruptions in which hot basalts flooded across the landscape.

All volcanic eruptions release carbon dioxide: in such cases enough to create conditions of intense cold followed by greenhouse warming,  acidification of the oceans and acid rain on land, destruction of the ozone layer that normally screens the planet from dangerous ultra-violet radiation, and even marine oxygen depletion. In which case life on the planet would have to withstand a kind of double assault.

“The global mass extinctions were apparently caused by the largest cataclysmic impacts and massive volcanism, perhaps sometimes working in concert,” Professor Rampino said. − Climate News Network

Ancient ice-free polar forest could soon return

An ice-free polar forest once flourished, helped by enough heat and ample greenhouse gas. It could come back.

LONDON, 10 April, 2020 – Many millions of years ago, the southern continent wasn’t frozen at all, but basked in heat balmy enough for an ice-free polar forest to thrive. And ancient pre-history could repeat itself.

Climate scientists can tell you what the world could be like were today’s greenhouse gas concentrations to triple – which they could do if humans go on clearing tropical forests and burning fossil fuels.

They know because, 90 million years ago, the last time when carbon dioxide levels in the atmosphere went past the 1200 ppm (parts per million) mark, sea levels were 170 metres higher than today and the world was so warm that dense forests grew in what is now Antarctica.

At latitude 82 South, a region where the polar night lasts for four months, there was no icecap. Instead, the continental rocks were colonised by conifer forest, with a mix of tree ferns and an understorey of flowering shrubs.

Even though at that latitude the midday sun would have been relatively low in the sky, and the forests would have had to survive sustained winter darkness for a dozen weeks or more, average temperatures would have been that of modern day Tasmania, and a good 2C° warmer than modern Germany.

“Even during months of darkness, swampy temperate forests were able to grow close to the South Pole, revealing an even warmer climate than we expected”

German and British researchers report in the journal Nature that they took a closer look at a sequence of strangely-coloured mudstone in a core drilled 30 metres below the bottom of the sea floor, off West Antarctica.

The section of sediment had been preserved from the mid-Cretaceous, around 90 million years ago, in a world dominated by dinosaurs. By then, the first mammals may have evolved, the grasses were about to emerge, and seasonal flowering plants had begun to colonise a planet dominated for aeons by evergreens.

And in the preserved silt were pollens, spores, tangled roots and other plant material so well preserved that the researchers could not just identify the plant families, but even take a guess at parallels with modern forests. Before their eyes was evidence of something like the modern rainforests of New Zealand’s South Island, but deep inside the Antarctic Circle.

“The preservation of this 90 million-year-old forest is exceptional, but even more surprising is the world it reveals,” said Tina van de Flierdt, of Imperial College London.

“Even during months of darkness, swampy temperate forests were able to grow close to the South Pole, revealing an even warmer climate than we expected.”

British rain levels

Somewhere between 115 and 85 million years ago, the whole world was a lot hotter: in the tropics temperatures reached 35°C and the average temperature of that part of the Antarctic was 13°C. This is at least two degrees higher than the average temperature for modern Germany.

Average temperatures in summer went up to 18.5°C, and the water temperatures in the swamps and rivers tipped 20°C, only 900 kms from the then South Pole. Modern Antarctica is classed as desert, with minimal precipitation: then it would have seen 1120 mm a year. People from southwestern Scotland or parts of Wales would have felt at home.

It is an axiom of earth science that the present is key to the past: if such forests today can flourish at existing temperatures, then the same must have been true in the deep past.

So climate scientists from the start have taken a close interest in the evidence of intensely warm periods in the fossil record: a mix of plant and animal remains, the ratio of chemical isotopes preserved in rock, and even the air bubbles trapped in deep ice cores can help them reconstruct the temperatures, the composition of the atmosphere and the rainfall of, for example, the warmest periods of the Pliocene, when carbon dioxide levels in the atmosphere tipped the 1000 ppm mark, and average planetary temperatures rose by 9°C.

Prehistoric encore approaching?

In the past century, atmospheric CO2 levels have swollen from 285 ppm to more than 400 ppm, and the planetary thermometer has already crept up by 1°C above the level for most of human history. If human economies continue burning fossil fuels at an ever-increasing rate, the conditions that prevailed 56 million years ago could return by 2159.

The Cretaceous evidence will help climate scientists calibrate their models of a world in which greenhouse gas emissions go on rising.

“Before our study, the general assumption was that the global carbon dioxide concentration in the Cretaceous was roughly 1000 ppm,” said Johann Klages, of the Alfred Wegener Institute centre for polar and marine research in Germany, who led the study.

“But in our model-based experiments, it took concentration levels of 1120 to 1680 ppm to reach the average temperatures back then in Antarctica.” – Climate News Network

An ice-free polar forest once flourished, helped by enough heat and ample greenhouse gas. It could come back.

LONDON, 10 April, 2020 – Many millions of years ago, the southern continent wasn’t frozen at all, but basked in heat balmy enough for an ice-free polar forest to thrive. And ancient pre-history could repeat itself.

Climate scientists can tell you what the world could be like were today’s greenhouse gas concentrations to triple – which they could do if humans go on clearing tropical forests and burning fossil fuels.

They know because, 90 million years ago, the last time when carbon dioxide levels in the atmosphere went past the 1200 ppm (parts per million) mark, sea levels were 170 metres higher than today and the world was so warm that dense forests grew in what is now Antarctica.

At latitude 82 South, a region where the polar night lasts for four months, there was no icecap. Instead, the continental rocks were colonised by conifer forest, with a mix of tree ferns and an understorey of flowering shrubs.

Even though at that latitude the midday sun would have been relatively low in the sky, and the forests would have had to survive sustained winter darkness for a dozen weeks or more, average temperatures would have been that of modern day Tasmania, and a good 2C° warmer than modern Germany.

“Even during months of darkness, swampy temperate forests were able to grow close to the South Pole, revealing an even warmer climate than we expected”

German and British researchers report in the journal Nature that they took a closer look at a sequence of strangely-coloured mudstone in a core drilled 30 metres below the bottom of the sea floor, off West Antarctica.

The section of sediment had been preserved from the mid-Cretaceous, around 90 million years ago, in a world dominated by dinosaurs. By then, the first mammals may have evolved, the grasses were about to emerge, and seasonal flowering plants had begun to colonise a planet dominated for aeons by evergreens.

And in the preserved silt were pollens, spores, tangled roots and other plant material so well preserved that the researchers could not just identify the plant families, but even take a guess at parallels with modern forests. Before their eyes was evidence of something like the modern rainforests of New Zealand’s South Island, but deep inside the Antarctic Circle.

“The preservation of this 90 million-year-old forest is exceptional, but even more surprising is the world it reveals,” said Tina van de Flierdt, of Imperial College London.

“Even during months of darkness, swampy temperate forests were able to grow close to the South Pole, revealing an even warmer climate than we expected.”

British rain levels

Somewhere between 115 and 85 million years ago, the whole world was a lot hotter: in the tropics temperatures reached 35°C and the average temperature of that part of the Antarctic was 13°C. This is at least two degrees higher than the average temperature for modern Germany.

Average temperatures in summer went up to 18.5°C, and the water temperatures in the swamps and rivers tipped 20°C, only 900 kms from the then South Pole. Modern Antarctica is classed as desert, with minimal precipitation: then it would have seen 1120 mm a year. People from southwestern Scotland or parts of Wales would have felt at home.

It is an axiom of earth science that the present is key to the past: if such forests today can flourish at existing temperatures, then the same must have been true in the deep past.

So climate scientists from the start have taken a close interest in the evidence of intensely warm periods in the fossil record: a mix of plant and animal remains, the ratio of chemical isotopes preserved in rock, and even the air bubbles trapped in deep ice cores can help them reconstruct the temperatures, the composition of the atmosphere and the rainfall of, for example, the warmest periods of the Pliocene, when carbon dioxide levels in the atmosphere tipped the 1000 ppm mark, and average planetary temperatures rose by 9°C.

Prehistoric encore approaching?

In the past century, atmospheric CO2 levels have swollen from 285 ppm to more than 400 ppm, and the planetary thermometer has already crept up by 1°C above the level for most of human history. If human economies continue burning fossil fuels at an ever-increasing rate, the conditions that prevailed 56 million years ago could return by 2159.

The Cretaceous evidence will help climate scientists calibrate their models of a world in which greenhouse gas emissions go on rising.

“Before our study, the general assumption was that the global carbon dioxide concentration in the Cretaceous was roughly 1000 ppm,” said Johann Klages, of the Alfred Wegener Institute centre for polar and marine research in Germany, who led the study.

“But in our model-based experiments, it took concentration levels of 1120 to 1680 ppm to reach the average temperatures back then in Antarctica.” – Climate News Network

Carbon dioxide triggered ancient mass die-off

The biggest extinction ever known on Earth resulted from oceans turned acid by CO2, the main gas driving human-caused climate change today. LONDON, 16 April, 2015 − Scientists have identified the lethal agency that caused the single most catastrophic event in the history of life on Earth. The mass extinction at the boundary of the Permian and Triassic eras 252 million years ago was caused by the acidification of the world’s oceans, as a consequence of an increase in atmospheric carbon dioxide. The Permian Extinction – sometimes called “the Great Dying” – seemed to all but obliterate life in the oceans, and perhaps on land. More than 90% of all species disappeared, more than 80% of all genera, and more than 50% of all marine families were extinguished in one prolonged calamity. All life on Earth today has descended from the few survivors of this far-off episode. Palaeontologists, geologists, climate scientists and astronomers have all speculated on the probable cause. The latest and most confident analysis is based on a new study of ancient marine sediments and delivers obvious parallels with processes that are – for different reasons − occurring again today. Matthew Clarkson of the University of Edinburgh in Scotland (but now at the University of Otago in New Zealand) and colleagues report in the journal Science that they examined limestone from the United Arab Emirates and found, in the isotope ratios of the element boron, evidence of ocean acidity in carbonate rocks that were laid down as sediment at the bottom of the ocean 250 million years ago. A change in the isotope ratios, they calculated, would have indicated a significant shift in seawater chemistry.

“This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions”

Over the last 40 years, researchers have introduced a whole suite of plausible triggers for the Permian extinction, but at last one team had clear evidence of increased atmospheric carbon, probably from a prolonged and convulsive series of volcanic eruptions that gave rise to vast, ancient geological formations now known as the Siberian Traps. “Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now”, said Dr Clarkson. “This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions.” There has been recent evidence that this present change in the pH of ocean waters (pH is a measure of its acidity) as a consequence of fossil fuel combustion in the last two centuries has already disturbed the behaviour of some fish species, threatened to affect oyster fisheries and coral reefs, and even to alter whole ocean ecosystems. The changes in the Permian were not sudden: ecosystems already seriously under stress because of lack of oxygen or rising temperatures were then dramatically affected by discharges of carbon dioxide that were probably much greater than all the modern world’s existing fossil fuel reserves could deliver. As the oceans became more acidic, many species were extinguished forever: among them the trilobites. The whole chain of events took 60,000 years. Humans have been burning fossil fuels for only 200 years, but, the researchers point out, in the Permian crisis, carbon was probably being released into the atmosphere at the rate of about 2.4 billion tons a year. Right now, humans are estimated to be releasing carbon from fossil fuels at the rate of 10 billion tons a year. − Climate News Network

The biggest extinction ever known on Earth resulted from oceans turned acid by CO2, the main gas driving human-caused climate change today. LONDON, 16 April, 2015 − Scientists have identified the lethal agency that caused the single most catastrophic event in the history of life on Earth. The mass extinction at the boundary of the Permian and Triassic eras 252 million years ago was caused by the acidification of the world’s oceans, as a consequence of an increase in atmospheric carbon dioxide. The Permian Extinction – sometimes called “the Great Dying” – seemed to all but obliterate life in the oceans, and perhaps on land. More than 90% of all species disappeared, more than 80% of all genera, and more than 50% of all marine families were extinguished in one prolonged calamity. All life on Earth today has descended from the few survivors of this far-off episode. Palaeontologists, geologists, climate scientists and astronomers have all speculated on the probable cause. The latest and most confident analysis is based on a new study of ancient marine sediments and delivers obvious parallels with processes that are – for different reasons − occurring again today. Matthew Clarkson of the University of Edinburgh in Scotland (but now at the University of Otago in New Zealand) and colleagues report in the journal Science that they examined limestone from the United Arab Emirates and found, in the isotope ratios of the element boron, evidence of ocean acidity in carbonate rocks that were laid down as sediment at the bottom of the ocean 250 million years ago. A change in the isotope ratios, they calculated, would have indicated a significant shift in seawater chemistry.

“This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions”

Over the last 40 years, researchers have introduced a whole suite of plausible triggers for the Permian extinction, but at last one team had clear evidence of increased atmospheric carbon, probably from a prolonged and convulsive series of volcanic eruptions that gave rise to vast, ancient geological formations now known as the Siberian Traps. “Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now”, said Dr Clarkson. “This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions.” There has been recent evidence that this present change in the pH of ocean waters (pH is a measure of its acidity) as a consequence of fossil fuel combustion in the last two centuries has already disturbed the behaviour of some fish species, threatened to affect oyster fisheries and coral reefs, and even to alter whole ocean ecosystems. The changes in the Permian were not sudden: ecosystems already seriously under stress because of lack of oxygen or rising temperatures were then dramatically affected by discharges of carbon dioxide that were probably much greater than all the modern world’s existing fossil fuel reserves could deliver. As the oceans became more acidic, many species were extinguished forever: among them the trilobites. The whole chain of events took 60,000 years. Humans have been burning fossil fuels for only 200 years, but, the researchers point out, in the Permian crisis, carbon was probably being released into the atmosphere at the rate of about 2.4 billion tons a year. Right now, humans are estimated to be releasing carbon from fossil fuels at the rate of 10 billion tons a year. − Climate News Network

Climate change 'helped to end monsoon 4,000 years ago'

FOR IMMEDIATE RELEASE
Drought appears to have played a significant part in the collapse of a vibrant community in south-west Asia several thousand years ago, British researchers say – with lessons for us today.

LONDON, 27 February – Climate change can seriously damage a civilisation. An “abrupt weakening” of the summer monsoon in north-west India accompanied the decline of the great cities of the Indus valley more than 4,000 years ago, according to new research by British scientists.

They analysed the oxygen isotopes in snail shells preserved in ancient lake sediments to build up a picture of rainfall patterns in prehistory, and found the first direct evidence that sustained drought contributed to the collapse of a great Bronze Age civilisation, they report in the journal Geology.

The Indus or Harappan civilisation – after Harappa, one of the five great ancient settlements of what is now Pakistan and western India – was marked by the world’s first “megacities”, concentrations of population in built-up areas that covered more than 80 hectares.

“They engaged in elaborate crafts, extensive local trade and long-ranging trade with regions as far away as the modern-day Middle East,” said Cameron Petrie of the University of Cambridge. “But by the mid-second millennium BC, all the great urban centres had dramatically reduced in size or been abandoned.”

The finding links the decline of the Indus civilisation to what now seems a much greater scale event: the failure of Early Bronze Age civilisation in Greece and Crete, the weakening of the Old Kingdom in Egypt, and the crumbling of the Akkadian Empire in Mesopotamia.

Common factor

Researchers last year used pollen grain sediments in an old lake bed in Cyprus to build up a picture of sustained environmental decline that accompanied the collapse of the civilisations linked with Mycenae in Greece and Knossos in Crete. In all cases, there must have been a number of factors at work, but common to them all was a pattern of drought.

Without water crops fail, populations fall and concentrations of people must disperse. Archaeological evidence in the north-west Indian sub-continent has told a story of dispersal. Palaeontological evidence from an old lake bed has confirmed the picture of a changing climate.

“We think we now have a really strong indication that a major climate change event occurred in the area where a large number of Indus settlements were situated,” said David Hodell, an earth scientist at Cambridge, and one of the authors.

“Taken with other evidence from Meghalaya in north-east India, Oman and the Arabian Sea, our results provide strong evidence for a widespread weakening of the Indian summer monsoon across large parts of India 4,100 years ago.”

The authors collected shells of the water snail Melanoides tuberculata from the sediments on an ancient lake, Kotla Dahar in Haryana, India. The changes in oxygen isotope ratios over a period of thousands of years told the researchers a story of a deep lake that became a shallower one, as evaporation accelerated and water supplies dwindled, and then all but disappeared, with an abrupt weakening of the monsoons that lasted around 200 years.

Syrian parallel?

Oxygen occurs in two isotopes: water molecules containing the lighter variant evaporate at a predictably faster rate than the heavier version. In a drought, the ratios of the heavier version increase, and this increase is preserved in the calcium carbonate of the snail shells, which can in turn be dated by radiocarbon measurements.

Archaeological evidence suggests that around the time of the 200-year drought, streets that had once been well-maintained started to fill with rubbish, craftsmanship seemed to become less sophisticated, and the locations of settlements changed.

“It is essential to understand the link between human settlement, water resources and landscape in antiquity,” said Dr Petrie. “We hope that this will hold lessons for us as we seek to find means of dealing with climate change in our own and future generations.”

Simultaneously, a French academic has argued that extended drought may have played a role in the crisis in Syria right now. Francesca de Chatel of Radboud University in the Netherlands writes in Middle Eastern Studies that in her opinion the bloodshed and turmoil in Syria is the culmination of 50 years of sustained mismanagement of water and land resources, capped by a severe drought during the years 2006-2010.

She argues “It was not the drought per se, but rather the government’s failure to respond to the ensuing humanitarian crisis that formed one of the triggers of the uprising, feeding a discontent that had long been simmering in rural areas.” – Climate News Network

FOR IMMEDIATE RELEASE
Drought appears to have played a significant part in the collapse of a vibrant community in south-west Asia several thousand years ago, British researchers say – with lessons for us today.

LONDON, 27 February – Climate change can seriously damage a civilisation. An “abrupt weakening” of the summer monsoon in north-west India accompanied the decline of the great cities of the Indus valley more than 4,000 years ago, according to new research by British scientists.

They analysed the oxygen isotopes in snail shells preserved in ancient lake sediments to build up a picture of rainfall patterns in prehistory, and found the first direct evidence that sustained drought contributed to the collapse of a great Bronze Age civilisation, they report in the journal Geology.

The Indus or Harappan civilisation – after Harappa, one of the five great ancient settlements of what is now Pakistan and western India – was marked by the world’s first “megacities”, concentrations of population in built-up areas that covered more than 80 hectares.

“They engaged in elaborate crafts, extensive local trade and long-ranging trade with regions as far away as the modern-day Middle East,” said Cameron Petrie of the University of Cambridge. “But by the mid-second millennium BC, all the great urban centres had dramatically reduced in size or been abandoned.”

The finding links the decline of the Indus civilisation to what now seems a much greater scale event: the failure of Early Bronze Age civilisation in Greece and Crete, the weakening of the Old Kingdom in Egypt, and the crumbling of the Akkadian Empire in Mesopotamia.

Common factor

Researchers last year used pollen grain sediments in an old lake bed in Cyprus to build up a picture of sustained environmental decline that accompanied the collapse of the civilisations linked with Mycenae in Greece and Knossos in Crete. In all cases, there must have been a number of factors at work, but common to them all was a pattern of drought.

Without water crops fail, populations fall and concentrations of people must disperse. Archaeological evidence in the north-west Indian sub-continent has told a story of dispersal. Palaeontological evidence from an old lake bed has confirmed the picture of a changing climate.

“We think we now have a really strong indication that a major climate change event occurred in the area where a large number of Indus settlements were situated,” said David Hodell, an earth scientist at Cambridge, and one of the authors.

“Taken with other evidence from Meghalaya in north-east India, Oman and the Arabian Sea, our results provide strong evidence for a widespread weakening of the Indian summer monsoon across large parts of India 4,100 years ago.”

The authors collected shells of the water snail Melanoides tuberculata from the sediments on an ancient lake, Kotla Dahar in Haryana, India. The changes in oxygen isotope ratios over a period of thousands of years told the researchers a story of a deep lake that became a shallower one, as evaporation accelerated and water supplies dwindled, and then all but disappeared, with an abrupt weakening of the monsoons that lasted around 200 years.

Syrian parallel?

Oxygen occurs in two isotopes: water molecules containing the lighter variant evaporate at a predictably faster rate than the heavier version. In a drought, the ratios of the heavier version increase, and this increase is preserved in the calcium carbonate of the snail shells, which can in turn be dated by radiocarbon measurements.

Archaeological evidence suggests that around the time of the 200-year drought, streets that had once been well-maintained started to fill with rubbish, craftsmanship seemed to become less sophisticated, and the locations of settlements changed.

“It is essential to understand the link between human settlement, water resources and landscape in antiquity,” said Dr Petrie. “We hope that this will hold lessons for us as we seek to find means of dealing with climate change in our own and future generations.”

Simultaneously, a French academic has argued that extended drought may have played a role in the crisis in Syria right now. Francesca de Chatel of Radboud University in the Netherlands writes in Middle Eastern Studies that in her opinion the bloodshed and turmoil in Syria is the culmination of 50 years of sustained mismanagement of water and land resources, capped by a severe drought during the years 2006-2010.

She argues “It was not the drought per se, but rather the government’s failure to respond to the ensuing humanitarian crisis that formed one of the triggers of the uprising, feeding a discontent that had long been simmering in rural areas.” – Climate News Network

Climate change ‘helped to end monsoon 4,000 years ago’

FOR IMMEDIATE RELEASE Drought appears to have played a significant part in the collapse of a vibrant community in south-west Asia several thousand years ago, British researchers say – with lessons for us today. LONDON, 27 February – Climate change can seriously damage a civilisation. An “abrupt weakening” of the summer monsoon in north-west India accompanied the decline of the great cities of the Indus valley more than 4,000 years ago, according to new research by British scientists. They analysed the oxygen isotopes in snail shells preserved in ancient lake sediments to build up a picture of rainfall patterns in prehistory, and found the first direct evidence that sustained drought contributed to the collapse of a great Bronze Age civilisation, they report in the journal Geology. The Indus or Harappan civilisation – after Harappa, one of the five great ancient settlements of what is now Pakistan and western India – was marked by the world’s first “megacities”, concentrations of population in built-up areas that covered more than 80 hectares. “They engaged in elaborate crafts, extensive local trade and long-ranging trade with regions as far away as the modern-day Middle East,” said Cameron Petrie of the University of Cambridge. “But by the mid-second millennium BC, all the great urban centres had dramatically reduced in size or been abandoned.” The finding links the decline of the Indus civilisation to what now seems a much greater scale event: the failure of Early Bronze Age civilisation in Greece and Crete, the weakening of the Old Kingdom in Egypt, and the crumbling of the Akkadian Empire in Mesopotamia.

Common factor

Researchers last year used pollen grain sediments in an old lake bed in Cyprus to build up a picture of sustained environmental decline that accompanied the collapse of the civilisations linked with Mycenae in Greece and Knossos in Crete. In all cases, there must have been a number of factors at work, but common to them all was a pattern of drought. Without water crops fail, populations fall and concentrations of people must disperse. Archaeological evidence in the north-west Indian sub-continent has told a story of dispersal. Palaeontological evidence from an old lake bed has confirmed the picture of a changing climate. “We think we now have a really strong indication that a major climate change event occurred in the area where a large number of Indus settlements were situated,” said David Hodell, an earth scientist at Cambridge, and one of the authors. “Taken with other evidence from Meghalaya in north-east India, Oman and the Arabian Sea, our results provide strong evidence for a widespread weakening of the Indian summer monsoon across large parts of India 4,100 years ago.” The authors collected shells of the water snail Melanoides tuberculata from the sediments on an ancient lake, Kotla Dahar in Haryana, India. The changes in oxygen isotope ratios over a period of thousands of years told the researchers a story of a deep lake that became a shallower one, as evaporation accelerated and water supplies dwindled, and then all but disappeared, with an abrupt weakening of the monsoons that lasted around 200 years.

Syrian parallel?

Oxygen occurs in two isotopes: water molecules containing the lighter variant evaporate at a predictably faster rate than the heavier version. In a drought, the ratios of the heavier version increase, and this increase is preserved in the calcium carbonate of the snail shells, which can in turn be dated by radiocarbon measurements. Archaeological evidence suggests that around the time of the 200-year drought, streets that had once been well-maintained started to fill with rubbish, craftsmanship seemed to become less sophisticated, and the locations of settlements changed. “It is essential to understand the link between human settlement, water resources and landscape in antiquity,” said Dr Petrie. “We hope that this will hold lessons for us as we seek to find means of dealing with climate change in our own and future generations.” Simultaneously, a French academic has argued that extended drought may have played a role in the crisis in Syria right now. Francesca de Chatel of Radboud University in the Netherlands writes in Middle Eastern Studies that in her opinion the bloodshed and turmoil in Syria is the culmination of 50 years of sustained mismanagement of water and land resources, capped by a severe drought during the years 2006-2010. She argues “It was not the drought per se, but rather the government’s failure to respond to the ensuing humanitarian crisis that formed one of the triggers of the uprising, feeding a discontent that had long been simmering in rural areas.” – Climate News Network

FOR IMMEDIATE RELEASE Drought appears to have played a significant part in the collapse of a vibrant community in south-west Asia several thousand years ago, British researchers say – with lessons for us today. LONDON, 27 February – Climate change can seriously damage a civilisation. An “abrupt weakening” of the summer monsoon in north-west India accompanied the decline of the great cities of the Indus valley more than 4,000 years ago, according to new research by British scientists. They analysed the oxygen isotopes in snail shells preserved in ancient lake sediments to build up a picture of rainfall patterns in prehistory, and found the first direct evidence that sustained drought contributed to the collapse of a great Bronze Age civilisation, they report in the journal Geology. The Indus or Harappan civilisation – after Harappa, one of the five great ancient settlements of what is now Pakistan and western India – was marked by the world’s first “megacities”, concentrations of population in built-up areas that covered more than 80 hectares. “They engaged in elaborate crafts, extensive local trade and long-ranging trade with regions as far away as the modern-day Middle East,” said Cameron Petrie of the University of Cambridge. “But by the mid-second millennium BC, all the great urban centres had dramatically reduced in size or been abandoned.” The finding links the decline of the Indus civilisation to what now seems a much greater scale event: the failure of Early Bronze Age civilisation in Greece and Crete, the weakening of the Old Kingdom in Egypt, and the crumbling of the Akkadian Empire in Mesopotamia.

Common factor

Researchers last year used pollen grain sediments in an old lake bed in Cyprus to build up a picture of sustained environmental decline that accompanied the collapse of the civilisations linked with Mycenae in Greece and Knossos in Crete. In all cases, there must have been a number of factors at work, but common to them all was a pattern of drought. Without water crops fail, populations fall and concentrations of people must disperse. Archaeological evidence in the north-west Indian sub-continent has told a story of dispersal. Palaeontological evidence from an old lake bed has confirmed the picture of a changing climate. “We think we now have a really strong indication that a major climate change event occurred in the area where a large number of Indus settlements were situated,” said David Hodell, an earth scientist at Cambridge, and one of the authors. “Taken with other evidence from Meghalaya in north-east India, Oman and the Arabian Sea, our results provide strong evidence for a widespread weakening of the Indian summer monsoon across large parts of India 4,100 years ago.” The authors collected shells of the water snail Melanoides tuberculata from the sediments on an ancient lake, Kotla Dahar in Haryana, India. The changes in oxygen isotope ratios over a period of thousands of years told the researchers a story of a deep lake that became a shallower one, as evaporation accelerated and water supplies dwindled, and then all but disappeared, with an abrupt weakening of the monsoons that lasted around 200 years.

Syrian parallel?

Oxygen occurs in two isotopes: water molecules containing the lighter variant evaporate at a predictably faster rate than the heavier version. In a drought, the ratios of the heavier version increase, and this increase is preserved in the calcium carbonate of the snail shells, which can in turn be dated by radiocarbon measurements. Archaeological evidence suggests that around the time of the 200-year drought, streets that had once been well-maintained started to fill with rubbish, craftsmanship seemed to become less sophisticated, and the locations of settlements changed. “It is essential to understand the link between human settlement, water resources and landscape in antiquity,” said Dr Petrie. “We hope that this will hold lessons for us as we seek to find means of dealing with climate change in our own and future generations.” Simultaneously, a French academic has argued that extended drought may have played a role in the crisis in Syria right now. Francesca de Chatel of Radboud University in the Netherlands writes in Middle Eastern Studies that in her opinion the bloodshed and turmoil in Syria is the culmination of 50 years of sustained mismanagement of water and land resources, capped by a severe drought during the years 2006-2010. She argues “It was not the drought per se, but rather the government’s failure to respond to the ensuing humanitarian crisis that formed one of the triggers of the uprising, feeding a discontent that had long been simmering in rural areas.” – Climate News Network