Tag Archives: Natural variability

Climate may have defeated Mongol invaders

Historical research suggests 13th-century climatic change left the grasslands of Hungary unable to provide for the Mongols’ vast invading army and forced their retreat from Europe.

LONDON, 31 May, 2016 – Climate fluctuation not only may have paved the way for Genghis Khan’s conquests of Asia in the 13th century, sudden climatic change may also have halted the Mongol invasion of Europe, according to new research.

Two scholars − one skilled in historical documents and another in interpreting tree rings to deliver weather reports through history − say that cold and heavy snowfalls may have blighted the pastureland of the Great Hungarian Plain in 1242.

This would have produced marshy conditions that would have made it difficult or impossible for 130,000 horsemen to campaign or even survive so far from home.

Genghis Khan’s vast but fleeting empire began in 1206, when the leader united the Mongol tribes, and by 1279 one hitherto impoverished group of nomads had swept across China, Russia, central Asia and Iran. Genghis died in 1227, but by 1242 an army of 130,000 Mongol cavalry had entered Hungary.

On the march

In 2014, a team of US scientists looked at tree ring and other data and found that the explosion of Mongol power from a harsh, dry homeland coincided with a mild climate spell that must have produced good pasture that was ideal for nomads on the march. So conditions made military adventure possible, they hypothesised.

Now Ulf Büntgen, a dendrochronologist at the Swiss Federal Institute for Forest, Snow and Landscape Research, and Nicola Di Cosmo, a historian at the Institute for Advanced Study at Princeton in the US, think that another change in the weather may have saved Europe from the Mongols.

They suggest in the Scientific Reports journal that local climate change may have been behind the sudden and unexplained decision of the Mongol army to withdraw to Russia.

Their study is just the latest in a long list of papers that link social turmoil and collapse of imperial power with changes in climate. Dr Büntgen himself was one of a team that recently linked the turmoil of Europe’s so-called Dark Ages with a Little Ice Age between 556 and 660 AD.

“Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility”

Such arguments are necessarily tentative: history is complex and records unreliable. But the tree ring chronologies from the period tell a story of cold, wet conditions in early 1242, when the seemingly-invincible Mongols crossed the Danube into western Hungary.

But after two months they withdrew, through Serbia and Bulgaria. And although historians have been conjecturing reasons for the retreat for the last 700 years, the Mongol generals left no record or explanation of the decision to leave Hungary alone.

So climate scientists took up the challenge. “Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility, as well as the military effectiveness of the Mongol cavalry, while despoliation and depopulation ostensibly contributed to widespread famine,” the researchers write.

“These circumstances arguably contributed to the determination of the Mongols to abandon Hungary and return to Russia.”

Initial victories

Geography certainly played a part in the Mongol advance. A great stretch of open grassland or steppe links the Mongolian homeland with the Hungarian plain, and the invaders entered Europe through the Carpathians to win convincing initial victories.

Hungary’s King Bela IV fled to Austria and the Mongol cavalry pursued him to the Dalmatian coast, and seemed to prepare for a long campaign. And then, abruptly, the Mongols departed. Some believe it may have been because of the death of the Great Khan’s successor in 1241; others believe that the Mongols were really pursuing another set of nomads, the Cumans.

But medieval armies provided for themselves only by forage and pillage, and there is also evidence that, given the climate conditions, the grasslands of Hungary could not have provided for so vast an army.

This is not the kind of debate that could ever be satisfactorily concluded, but authors of the Scientific Reports study are content that climate aspects may have played a part and contributed to withdrawal.

“Our ‘environmental hypothesis’ demonstrates the importance of minor climatic fluctuations on major historical events,” they write. – Climate News Network

Historical research suggests 13th-century climatic change left the grasslands of Hungary unable to provide for the Mongols’ vast invading army and forced their retreat from Europe.

LONDON, 31 May, 2016 – Climate fluctuation not only may have paved the way for Genghis Khan’s conquests of Asia in the 13th century, sudden climatic change may also have halted the Mongol invasion of Europe, according to new research.

Two scholars − one skilled in historical documents and another in interpreting tree rings to deliver weather reports through history − say that cold and heavy snowfalls may have blighted the pastureland of the Great Hungarian Plain in 1242.

This would have produced marshy conditions that would have made it difficult or impossible for 130,000 horsemen to campaign or even survive so far from home.

Genghis Khan’s vast but fleeting empire began in 1206, when the leader united the Mongol tribes, and by 1279 one hitherto impoverished group of nomads had swept across China, Russia, central Asia and Iran. Genghis died in 1227, but by 1242 an army of 130,000 Mongol cavalry had entered Hungary.

On the march

In 2014, a team of US scientists looked at tree ring and other data and found that the explosion of Mongol power from a harsh, dry homeland coincided with a mild climate spell that must have produced good pasture that was ideal for nomads on the march. So conditions made military adventure possible, they hypothesised.

Now Ulf Büntgen, a dendrochronologist at the Swiss Federal Institute for Forest, Snow and Landscape Research, and Nicola Di Cosmo, a historian at the Institute for Advanced Study at Princeton in the US, think that another change in the weather may have saved Europe from the Mongols.

They suggest in the Scientific Reports journal that local climate change may have been behind the sudden and unexplained decision of the Mongol army to withdraw to Russia.

Their study is just the latest in a long list of papers that link social turmoil and collapse of imperial power with changes in climate. Dr Büntgen himself was one of a team that recently linked the turmoil of Europe’s so-called Dark Ages with a Little Ice Age between 556 and 660 AD.

“Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility”

Such arguments are necessarily tentative: history is complex and records unreliable. But the tree ring chronologies from the period tell a story of cold, wet conditions in early 1242, when the seemingly-invincible Mongols crossed the Danube into western Hungary.

But after two months they withdrew, through Serbia and Bulgaria. And although historians have been conjecturing reasons for the retreat for the last 700 years, the Mongol generals left no record or explanation of the decision to leave Hungary alone.

So climate scientists took up the challenge. “Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility, as well as the military effectiveness of the Mongol cavalry, while despoliation and depopulation ostensibly contributed to widespread famine,” the researchers write.

“These circumstances arguably contributed to the determination of the Mongols to abandon Hungary and return to Russia.”

Initial victories

Geography certainly played a part in the Mongol advance. A great stretch of open grassland or steppe links the Mongolian homeland with the Hungarian plain, and the invaders entered Europe through the Carpathians to win convincing initial victories.

Hungary’s King Bela IV fled to Austria and the Mongol cavalry pursued him to the Dalmatian coast, and seemed to prepare for a long campaign. And then, abruptly, the Mongols departed. Some believe it may have been because of the death of the Great Khan’s successor in 1241; others believe that the Mongols were really pursuing another set of nomads, the Cumans.

But medieval armies provided for themselves only by forage and pillage, and there is also evidence that, given the climate conditions, the grasslands of Hungary could not have provided for so vast an army.

This is not the kind of debate that could ever be satisfactorily concluded, but authors of the Scientific Reports study are content that climate aspects may have played a part and contributed to withdrawal.

“Our ‘environmental hypothesis’ demonstrates the importance of minor climatic fluctuations on major historical events,” they write. – Climate News Network

Dead zones devour oceans’ oxygen

Marine life faces increased threats as researchers warn that warmer waters caused by climate change could seriously reduce the levels of oxygen in the world’s seas.

LONDON, 4 May, 2016 – Scientists in the US have identified a new hazard in a world in which the climates change and the oceans warm: measurable stretches of the seas could become sapped of oxygen.

They say that parts of the southern Indian Ocean, the eastern tropical Pacific and the Atlantic are already less oxygen-rich because of global warming. And oxygen deprivation could become increasingly widespread across large regions of ocean between 2030 and 2040.

Anyone who has ever kept a home aquarium knows that, in the summer, the fish in the tank are more likely to be seen gasping nearer the surface. That is because the colder the water, the greater its capacity for dissolved oxygen.

Chemistry change

Growing concentrations in the atmosphere of the greenhouse gas carbon dioxide have begun to change the ocean chemistry, making sea water gradually and alarmingly more acidic and less hospitable to many of the species adapted to ocean life.

Now Matthew Long, an oceanographer at the US National Centre for Atmospheric Research in Boulder, Colorado and colleagues report in Global Biogeochemical Cycles journal that they repeatedly modelled changes in the ocean’s oxygen content over the years 1920 to 2100.

“This new study tells us when we can expect
the impact from climate change to overwhelm
the natural variability”

Oxygen from the atmosphere gets into the sea only when it dissolves directly, or is released by photosynthesising marine plants and phytoplankton. The warmer the water, the harder life is for the creatures nearer the surface.

To make things more difficult, warmer waters are less dense, making them less likely to sink and bring the colder, more oxygen-rich waters to the surface. In unusually hot weather, “dead zones” appear in the seas, where fish and shellfish cannot survive.

The researchers warn that there will be more of these as global temperatures continue to rise. “Loss of oxygen in the ocean is one of the serious side-effects of a warming atmosphere, and a major threat to marine life,” Dr Long says.

Swiftly detectable

“Since oxygen concentrations in the ocean naturally vary, depending on variations in winds and temperature at the surface, it’s been challenging to attribute any deoxygenation to climate change. This new study tells us when we can expect the impact from climate change to overwhelm the natural variability.”

The new map suggests that even by 2100, some waters – off the east coasts of Africa and Australia and Southeast Asia, and parts of the South Atlantic, for instance – will remain oxygen-rich. But oxygen loss due to climate change will become detectable much more swiftly in northern waters in the Pacific, and parts of the Atlantic.

There are uncertainties. Oxygen measurements in the world’s oceans − and 70% of the planet is covered by blue water – are relatively sparse.

“We need comprehensive and sustained observations of what’s going on in the oceans to compare with what we’re learning from our models, and to understand the full impact of a changing climate,” Dr Long says. – Climate News Network

Marine life faces increased threats as researchers warn that warmer waters caused by climate change could seriously reduce the levels of oxygen in the world’s seas.

LONDON, 4 May, 2016 – Scientists in the US have identified a new hazard in a world in which the climates change and the oceans warm: measurable stretches of the seas could become sapped of oxygen.

They say that parts of the southern Indian Ocean, the eastern tropical Pacific and the Atlantic are already less oxygen-rich because of global warming. And oxygen deprivation could become increasingly widespread across large regions of ocean between 2030 and 2040.

Anyone who has ever kept a home aquarium knows that, in the summer, the fish in the tank are more likely to be seen gasping nearer the surface. That is because the colder the water, the greater its capacity for dissolved oxygen.

Chemistry change

Growing concentrations in the atmosphere of the greenhouse gas carbon dioxide have begun to change the ocean chemistry, making sea water gradually and alarmingly more acidic and less hospitable to many of the species adapted to ocean life.

Now Matthew Long, an oceanographer at the US National Centre for Atmospheric Research in Boulder, Colorado and colleagues report in Global Biogeochemical Cycles journal that they repeatedly modelled changes in the ocean’s oxygen content over the years 1920 to 2100.

“This new study tells us when we can expect
the impact from climate change to overwhelm
the natural variability”

Oxygen from the atmosphere gets into the sea only when it dissolves directly, or is released by photosynthesising marine plants and phytoplankton. The warmer the water, the harder life is for the creatures nearer the surface.

To make things more difficult, warmer waters are less dense, making them less likely to sink and bring the colder, more oxygen-rich waters to the surface. In unusually hot weather, “dead zones” appear in the seas, where fish and shellfish cannot survive.

The researchers warn that there will be more of these as global temperatures continue to rise. “Loss of oxygen in the ocean is one of the serious side-effects of a warming atmosphere, and a major threat to marine life,” Dr Long says.

Swiftly detectable

“Since oxygen concentrations in the ocean naturally vary, depending on variations in winds and temperature at the surface, it’s been challenging to attribute any deoxygenation to climate change. This new study tells us when we can expect the impact from climate change to overwhelm the natural variability.”

The new map suggests that even by 2100, some waters – off the east coasts of Africa and Australia and Southeast Asia, and parts of the South Atlantic, for instance – will remain oxygen-rich. But oxygen loss due to climate change will become detectable much more swiftly in northern waters in the Pacific, and parts of the Atlantic.

There are uncertainties. Oxygen measurements in the world’s oceans − and 70% of the planet is covered by blue water – are relatively sparse.

“We need comprehensive and sustained observations of what’s going on in the oceans to compare with what we’re learning from our models, and to understand the full impact of a changing climate,” Dr Long says. – Climate News Network

Plants’ heat response means fiercer heatwaves

Asia faces more extreme heat by mid-century as some plant species react unexpectedly to rising average temperatures, new research shows.

LONDON, 28 March, 2016 – Tomorrow’s heat waves could be even hotter than climate scientists have so far predicted. Maximum temperatures across the Asian continent from Europe to China could be 3°C to 5°C higher than previous estimates – because the forests and grasslands will respond in a different way.

Australian scientists report in the journal Scientific Reports that they looked at the forecasts made by the Intergovernmental Panel on Climate Change under the notorious “business-as-usual” scenario, in which the world’s nations go on burning ever more fossil fuels, to release ever more greenhouse gases.

The average global temperatures will rise steadily – but this rise will be accompanied by ever greater and more frequent extremes of heat.

But then Jatin Kala of Murdoch University in Perth, Western Australia, and colleagues factored in the responses of the plants to rising temperatures.

They looked at data from 314 species of plant from 54 research field sites. In particular, they investigated stomatas, tiny pores on the leaves through which plants absorb carbon dioxide and shed water to the atmosphere.

Response crucial

What matters is how vegetation responds to extremes of heat. Researchers have already established that plants respond, not always helpfully: extremes can alter the atmospheric chemistry unfavourably for plants, and certainly reduce crop yields

But other scientists have confirmed the so-called carbon dioxide fertilisation effect: as more carbon becomes available, plants use water more economically and so even though drylands may get drier the landscape can also get greener, and growth tends to begin ever earlier as winters get warmer, and spring arrives earlier.

Dr Kala and his fellow researchers used their field observation data to model the response of species, and types of plants, to higher temperatures, and to make some estimates of the balance of carbon taken up by the stomata, and the water released.

There has been an assumption that plants respond to temperature in roughly the same way. But there can be considerable variation.

The scientists found, overall, that the response of the plants became increasingly important: over Eurasia – they decided not to model the pattern in North America because cloudiness introduced extra uncertainties – needleleaf forests, tundra and farmland would actually release lower levels of water into the atmosphere.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures”

And since water in the atmosphere helps lower the daytime temperatures, this means that the temperatures would rise even higher than the models suggest.

“We often underestimate the role of vegetation in extreme temperature events as it has not been included in enough detail in climate models up to this point,” Dr Kala said.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures when compared to observations.”

Unexpected results invite challenge. The test will be in the replication of the findings by other groups of scientists. And the Australian scientists intend to pursue the questions too. But they see their work as one of the rewards of the interdisciplinary approach: the marriage of ecology and climate simulation.

Surprise findings

Belinda Medlyn, a theoretical biologist at Western Sydney University, and a co-author, said: “Our study of stomata was originally intended just to learn more about how plants work. We were not really expecting to find these important implications for heat waves.”

The part played by the vegetation would not affect either the frequency or the duration of the heat waves. But the traffic between stomata and atmosphere could certainly affect their intensity.

The bottom line is, the scientists conclude, that there could be increases of 5°C by 2040 to 2059, and these increases would be “additive to those likely caused by increasing greenhouse gases over the same period.” – Climate News Network

Asia faces more extreme heat by mid-century as some plant species react unexpectedly to rising average temperatures, new research shows.

LONDON, 28 March, 2016 – Tomorrow’s heat waves could be even hotter than climate scientists have so far predicted. Maximum temperatures across the Asian continent from Europe to China could be 3°C to 5°C higher than previous estimates – because the forests and grasslands will respond in a different way.

Australian scientists report in the journal Scientific Reports that they looked at the forecasts made by the Intergovernmental Panel on Climate Change under the notorious “business-as-usual” scenario, in which the world’s nations go on burning ever more fossil fuels, to release ever more greenhouse gases.

The average global temperatures will rise steadily – but this rise will be accompanied by ever greater and more frequent extremes of heat.

But then Jatin Kala of Murdoch University in Perth, Western Australia, and colleagues factored in the responses of the plants to rising temperatures.

They looked at data from 314 species of plant from 54 research field sites. In particular, they investigated stomatas, tiny pores on the leaves through which plants absorb carbon dioxide and shed water to the atmosphere.

Response crucial

What matters is how vegetation responds to extremes of heat. Researchers have already established that plants respond, not always helpfully: extremes can alter the atmospheric chemistry unfavourably for plants, and certainly reduce crop yields

But other scientists have confirmed the so-called carbon dioxide fertilisation effect: as more carbon becomes available, plants use water more economically and so even though drylands may get drier the landscape can also get greener, and growth tends to begin ever earlier as winters get warmer, and spring arrives earlier.

Dr Kala and his fellow researchers used their field observation data to model the response of species, and types of plants, to higher temperatures, and to make some estimates of the balance of carbon taken up by the stomata, and the water released.

There has been an assumption that plants respond to temperature in roughly the same way. But there can be considerable variation.

The scientists found, overall, that the response of the plants became increasingly important: over Eurasia – they decided not to model the pattern in North America because cloudiness introduced extra uncertainties – needleleaf forests, tundra and farmland would actually release lower levels of water into the atmosphere.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures”

And since water in the atmosphere helps lower the daytime temperatures, this means that the temperatures would rise even higher than the models suggest.

“We often underestimate the role of vegetation in extreme temperature events as it has not been included in enough detail in climate models up to this point,” Dr Kala said.

“These more detailed results are confronting, but they help explain why many climate models have consistently underestimated the increase in intensity of heat waves and the rise in maximum temperatures when compared to observations.”

Unexpected results invite challenge. The test will be in the replication of the findings by other groups of scientists. And the Australian scientists intend to pursue the questions too. But they see their work as one of the rewards of the interdisciplinary approach: the marriage of ecology and climate simulation.

Surprise findings

Belinda Medlyn, a theoretical biologist at Western Sydney University, and a co-author, said: “Our study of stomata was originally intended just to learn more about how plants work. We were not really expecting to find these important implications for heat waves.”

The part played by the vegetation would not affect either the frequency or the duration of the heat waves. But the traffic between stomata and atmosphere could certainly affect their intensity.

The bottom line is, the scientists conclude, that there could be increases of 5°C by 2040 to 2059, and these increases would be “additive to those likely caused by increasing greenhouse gases over the same period.” – Climate News Network

Rising seas slow the planet’s yearly journey

US scientists say climate change affects the speed at which the Earth circles the Sun and even the length of a terrestrial day.

LONDON, 17 December, 2015 – Scientists may be about to resolve one of the trickiest – and least obvious – questions of climate change: its effect on the rotation of the planet, and therefore on the length of the day.

That doesn’t mean scientists have an answer, and if they get one, it is likely to  be measured in units of time that are vanishingly small. But even if the answer is insignificant, the attempt to resolve the question is a measure of the intricacy, impact and reach of global warming as a consequence of the human combustion of fossil fuels: it even affects the axis of the planet, and it changes our days.

Jerry Mitrovica, a planetary scientist at Harvard University, and colleagues report in the journal Science Advances that they have managed to make a connection between global sea level rises of the past and the rotation of the Earth on its year-long journey around the Sun.

More precisely, they have addressed a 13-year-old puzzle known as Munk’s enigma. This study raised a simple question that cannot be answered simply: if changes on the Earth’s surface slow its rotation, surely it should be possible to detect the contribution of sea level rise?

Almost anything can affect the rotation of the planet: the 2011 Tohoku earthquake and tsunami shortened the day by 1.8 millionths of a second, but the advance and retreat of the ice ages would also have altered the clocks, had there been any clocks at the time, and the daily ocean tides have for billions of years been making the day drag on.

Fossil corals reveal that a year in the Devonian period 400 million years ago lasted more than 400 days. Now there are only 365 and a bit. 

Slowing down

Astronomers have checked ancient Babylonian, Chinese, Greek and Arab records of solar eclipses and used them to make a relatively precise calculation of the rate at which the Earth’s rotation has slowed.

They have arrived at an answer: since 500 BC, Earth time and universal time have diverged by 16,000 seconds, or 4.5 hours.

The measurement of time is one of mankind’s oldest headaches, and remains one, because the second is by its first definition a division of the minute and the hour, and a day is defined as 24 hours, and this means that if the Earth slows, the day gets longer, and so does the second.

That is why astronomers agreed to fix the second at a precise division of the year 1820, and call that universal time. And then when that wasn’t precise enough, they fixed it to the number of vibrations in a caesium-133 atom at a precise temperature.

But that then divorced the second from the 24 hours of the day. Which is why, every so often – the latest was in July 2015 – the time lords of the international scientific bureaucracy had to insert a leap second to keep universal and terrestrial time in step.

Since 1972 there have been a total of 26 leap seconds to keep the two ways of measuring time in synchronicity.

Then in 2002 Walter Munk of the Scripps Institution of Oceanography in San Diego put the question: if 40,000 billion tons of ice turned into  rising sea levels, and were changing the axis and rotation of the planet, could the effect be measured? And since it could not be measured accurately, why not?

Re-examination required

The Harvard authors now think they have an answer: the estimates on which Munk’s paper was based need to be re-examined. This re-examination involves geophysics, archaeo-astronomy and micro-measurement.

It involves dynamic processes far below the Earth’s crust, as well as a new and closer look at the message from the ancient observations of eclipse, and more detailed scrutiny of the data of sea level rise.

That doesn’t mean they have an answer to the effect of climate change upon the rotation of the Earth but, when they do, it is likely to be measured in millionths of a second per year.

So people need not adjust their watches. But the study is an indicator of the sheer range of questions raised in pursuit of the wider understanding of the science of global climate. And there may even be a pay-off in terms of more accurate climate prediction.

The Harvard team conclude: “Confronting Munk’s elegant statement of the enigma has thus improved our understanding of Earth’s rotation spanning the last three millennia and the individual sources of sea-level rise in the century before the early 1990s.

“The reconciliation also adds confidence to ongoing efforts to project this rise to the end of the current century and beyond.” – Climate News Network

US scientists say climate change affects the speed at which the Earth circles the Sun and even the length of a terrestrial day.

LONDON, 17 December, 2015 – Scientists may be about to resolve one of the trickiest – and least obvious – questions of climate change: its effect on the rotation of the planet, and therefore on the length of the day.

That doesn’t mean scientists have an answer, and if they get one, it is likely to  be measured in units of time that are vanishingly small. But even if the answer is insignificant, the attempt to resolve the question is a measure of the intricacy, impact and reach of global warming as a consequence of the human combustion of fossil fuels: it even affects the axis of the planet, and it changes our days.

Jerry Mitrovica, a planetary scientist at Harvard University, and colleagues report in the journal Science Advances that they have managed to make a connection between global sea level rises of the past and the rotation of the Earth on its year-long journey around the Sun.

More precisely, they have addressed a 13-year-old puzzle known as Munk’s enigma. This study raised a simple question that cannot be answered simply: if changes on the Earth’s surface slow its rotation, surely it should be possible to detect the contribution of sea level rise?

Almost anything can affect the rotation of the planet: the 2011 Tohoku earthquake and tsunami shortened the day by 1.8 millionths of a second, but the advance and retreat of the ice ages would also have altered the clocks, had there been any clocks at the time, and the daily ocean tides have for billions of years been making the day drag on.

Fossil corals reveal that a year in the Devonian period 400 million years ago lasted more than 400 days. Now there are only 365 and a bit. 

Slowing down

Astronomers have checked ancient Babylonian, Chinese, Greek and Arab records of solar eclipses and used them to make a relatively precise calculation of the rate at which the Earth’s rotation has slowed.

They have arrived at an answer: since 500 BC, Earth time and universal time have diverged by 16,000 seconds, or 4.5 hours.

The measurement of time is one of mankind’s oldest headaches, and remains one, because the second is by its first definition a division of the minute and the hour, and a day is defined as 24 hours, and this means that if the Earth slows, the day gets longer, and so does the second.

That is why astronomers agreed to fix the second at a precise division of the year 1820, and call that universal time. And then when that wasn’t precise enough, they fixed it to the number of vibrations in a caesium-133 atom at a precise temperature.

But that then divorced the second from the 24 hours of the day. Which is why, every so often – the latest was in July 2015 – the time lords of the international scientific bureaucracy had to insert a leap second to keep universal and terrestrial time in step.

Since 1972 there have been a total of 26 leap seconds to keep the two ways of measuring time in synchronicity.

Then in 2002 Walter Munk of the Scripps Institution of Oceanography in San Diego put the question: if 40,000 billion tons of ice turned into  rising sea levels, and were changing the axis and rotation of the planet, could the effect be measured? And since it could not be measured accurately, why not?

Re-examination required

The Harvard authors now think they have an answer: the estimates on which Munk’s paper was based need to be re-examined. This re-examination involves geophysics, archaeo-astronomy and micro-measurement.

It involves dynamic processes far below the Earth’s crust, as well as a new and closer look at the message from the ancient observations of eclipse, and more detailed scrutiny of the data of sea level rise.

That doesn’t mean they have an answer to the effect of climate change upon the rotation of the Earth but, when they do, it is likely to be measured in millionths of a second per year.

So people need not adjust their watches. But the study is an indicator of the sheer range of questions raised in pursuit of the wider understanding of the science of global climate. And there may even be a pay-off in terms of more accurate climate prediction.

The Harvard team conclude: “Confronting Munk’s elegant statement of the enigma has thus improved our understanding of Earth’s rotation spanning the last three millennia and the individual sources of sea-level rise in the century before the early 1990s.

“The reconciliation also adds confidence to ongoing efforts to project this rise to the end of the current century and beyond.” – Climate News Network

Warmer winters slow the growth of forest giants

Trees coming into leaf later and bumblebees with shorter tongues are just two of the impacts on nature that researchers are linking to global warming.
LONDON, 4 October, 2015
− Spring is arriving ever earlier as greenhouse gas levels rise and global temperatures warm, and the northern hemisphere growing season is now two weeks longer  than it was in 1900. But, paradoxically, new research shows that forest giants that once responded to the early spring are beginning to slow down – because they miss the chill. Yongshuo Fu, an Earth system scientist at Peking University, Beijing, and colleagues report in Nature journal that they have measured a slowdown in the response of oaks and other forest citizens to the change in temperatures and carbon dioxide levels. Where these species, on average, unfolded their first leaves four days earlier, with every 1˚C rise in temperature, they now do so only 2.3 days earlier for every additional 1˚C.

Ever-earlier spring

The reason is that, to take full advantage of the ever-earlier spring, these deciduous species first need to feel a period of chill. And as temperatures on average rise, the extent of true winter chill diminishes. The researchers concede that there may be other or additional reasons why alder (Alnus glutinosa), silver birch (Betula pendula), horse chestnut (Aesculus hippocastanum), beech (Fagus sylvatica), lime (Tilia cordata), oak (Quercus robur) and ash (Fraxinus excelsior) seem to be slowing in their leafy response. But since many deciduous trees depend on a frosty spell to release them from their periods of dormancy, it seems a likely factor.

The scientists show once again that as humans change the climate, they are also changing the ecosystems that support all life on Earth

To identify the slowdown, the researchers used data from the Pan-European Phenology Project, which for 33 years has monitored the unfolding of the first leaves of all seven species at 1,245 sites across central Europe. The scientists used direct observation, and confirmed their hypothesis with computer models to show once again that as humans change the climate, by increasing carbon dioxide levels in the atmosphere as a consequence of the combustion of fossil fuels, they are also changing the ecosystems that support all life on Earth. And in the same week, US scientists report that as global warming begins to change the mix of mountain wildflowers each spring, pollinating insects too are beginning to respond. Nicole Miller-Struttmann, a biologist at the State University of New York, and colleagues report in Science journal that, in the last 40 years, the tongues of two species of alpine bumblebee have grown shorter. Bumblebees need long tongues to reach deep into the flower tubes of the plants they favour. But warmer summers have meant that the flowers they favour most in the Rocky Mountains have become less frequent, and pollinators that once specialised have now become generalist foragers, grabbing honey where they can. In the course of doing so, two that are commonly found at high altitudes, species Bombus balteatus and B. sylvicola, have evolved shorter tongues.

Gaining altitude

The mix of flowers at lower altitudes has become impoverished, and although mountain flowers have been gaining altitude over the decades, the gain in higher growth has not been enough to offset the loss for the bees. The research confirms a wider picture of change as a consequence of global warming. In the Americas, plants are colonising higher slopes, and in Europe the bumblebee has also been feeling the heat, and losing part of its range. In general, high altitude sites seem to be warming faster than the lowlands. Research of this kind provides a local snapshot of global change, and what it means for individual species in nature’s mix. “We see broader bumblebee foraging niches, immigration by short-tongued bumblebees, and shorter tongue length within resident bee populations as floral resources have dwindled,” the scientists conclude. “In remote mountain habitats − largely isolated from habitat destruction, toxins, and pathogens − evolution is helping wild bees keep pace with climate change.” – Climate News Network

Trees coming into leaf later and bumblebees with shorter tongues are just two of the impacts on nature that researchers are linking to global warming.
LONDON, 4 October, 2015
− Spring is arriving ever earlier as greenhouse gas levels rise and global temperatures warm, and the northern hemisphere growing season is now two weeks longer  than it was in 1900. But, paradoxically, new research shows that forest giants that once responded to the early spring are beginning to slow down – because they miss the chill. Yongshuo Fu, an Earth system scientist at Peking University, Beijing, and colleagues report in Nature journal that they have measured a slowdown in the response of oaks and other forest citizens to the change in temperatures and carbon dioxide levels. Where these species, on average, unfolded their first leaves four days earlier, with every 1˚C rise in temperature, they now do so only 2.3 days earlier for every additional 1˚C.

Ever-earlier spring

The reason is that, to take full advantage of the ever-earlier spring, these deciduous species first need to feel a period of chill. And as temperatures on average rise, the extent of true winter chill diminishes. The researchers concede that there may be other or additional reasons why alder (Alnus glutinosa), silver birch (Betula pendula), horse chestnut (Aesculus hippocastanum), beech (Fagus sylvatica), lime (Tilia cordata), oak (Quercus robur) and ash (Fraxinus excelsior) seem to be slowing in their leafy response. But since many deciduous trees depend on a frosty spell to release them from their periods of dormancy, it seems a likely factor.

The scientists show once again that as humans change the climate, they are also changing the ecosystems that support all life on Earth

To identify the slowdown, the researchers used data from the Pan-European Phenology Project, which for 33 years has monitored the unfolding of the first leaves of all seven species at 1,245 sites across central Europe. The scientists used direct observation, and confirmed their hypothesis with computer models to show once again that as humans change the climate, by increasing carbon dioxide levels in the atmosphere as a consequence of the combustion of fossil fuels, they are also changing the ecosystems that support all life on Earth. And in the same week, US scientists report that as global warming begins to change the mix of mountain wildflowers each spring, pollinating insects too are beginning to respond. Nicole Miller-Struttmann, a biologist at the State University of New York, and colleagues report in Science journal that, in the last 40 years, the tongues of two species of alpine bumblebee have grown shorter. Bumblebees need long tongues to reach deep into the flower tubes of the plants they favour. But warmer summers have meant that the flowers they favour most in the Rocky Mountains have become less frequent, and pollinators that once specialised have now become generalist foragers, grabbing honey where they can. In the course of doing so, two that are commonly found at high altitudes, species Bombus balteatus and B. sylvicola, have evolved shorter tongues.

Gaining altitude

The mix of flowers at lower altitudes has become impoverished, and although mountain flowers have been gaining altitude over the decades, the gain in higher growth has not been enough to offset the loss for the bees. The research confirms a wider picture of change as a consequence of global warming. In the Americas, plants are colonising higher slopes, and in Europe the bumblebee has also been feeling the heat, and losing part of its range. In general, high altitude sites seem to be warming faster than the lowlands. Research of this kind provides a local snapshot of global change, and what it means for individual species in nature’s mix. “We see broader bumblebee foraging niches, immigration by short-tongued bumblebees, and shorter tongue length within resident bee populations as floral resources have dwindled,” the scientists conclude. “In remote mountain habitats − largely isolated from habitat destruction, toxins, and pathogens − evolution is helping wild bees keep pace with climate change.” – Climate News Network

The global warming slowdown is an illusion

Researchers say the world is continuing to warm, and evidence shows claims of a slowdown are unequivocally illusory.

LONDON, 19 September, 2015 – Global warming has not slowed. The so-called hiatus remains just that – so-called. The world is warming as predicted and any apparent evidence that it is not doing so is a statistical illusion, according to US scientists.

They report in the journal Climatic Change that they applied “rigorous, comprehensive, statistical analysis” to the global temperature data and came up with this unequivocal conclusion.

And although normally scientists like to spell out the caveats, the margins of error and the uncertainties in their conclusions, the team get to the point with unprecedented firmness.

“We find compelling evidence that recent claims of a ‘hiatus’ in global warming lack sound scientific basis. Our analysis reveals that there is no hiatus in the increase in the global mean temperature, no statistically significant difference in trends, no stalling of the global mean temperature, and no change in year-to-year temperature increases,” they write.

The very-much discussed and so-called pause, hiatus or slowdown in global warming has puzzled climate scientists for years. During the 1990s, annual global temperatures increased palpably, and at a measurable rate. In the early years of this century, the rate of increase began to slow.

Non-stop warming

It did not, as some have claimed, stop. Thirteen of the hottest 14 years ever have occurred this century, and 2014 was the warmest on record. But the rate of increase, expressed as fractions of a degree Celsius, averaged over the whole planet, certainly seemed to have slowed.

Since the levels of carbon dioxide in the atmosphere had continued steadily to increase, as a consequence of the combustion of fossil fuels, the rise in global temperatures should have kept pace, and scientists began to puzzle over the process.

One favourite explanation – and there have been many – was that some long-term natural oceanic or atmospheric cycle had been at play, taking any new atmospheric warmth to the deepest parts of the seas.

Another proposed that an increase in small volcanic eruptions had polluted the atmosphere and imperceptibly blocked incoming sunlight to cool the Earth from above. A third strand of argument proposed that even if there had been a slowdown, there was greater warming to come.

Yet others had begun to wonder about the completeness of the available data. And in June, a team led by the US National Oceanographic and Atmospheric Administration (NOAA) re-examined the available data, applied corrections they thought necessary,  and reported that there had been no slowdown at all

Now Bala Rajaratnam of Stanford University in California and colleagues have come to the same conclusion. They did some advanced mathematical homework, using both the measurements corrected by the NOAA group and a set of older, uncorrected temperature measurements. They also devised a new statistical framework to apply to them.

“Global temperature has increased in the long term, and the recent period does not stand out as abnormal”

“By using both datasets, nobody can claim that we made up a new statistical technique in order to get a certain result,” said Dr Rajaratnam. “We saw there was a debate in the scientific community about the global warming hiatus, and we realised that the assumptions of classical statistical tools being used were not appropriate and thus could not give reliable answers.”

Collected measurements of any kind, made at different times with different techniques, tell scientists nothing: they must use statistical tools to eliminate possible bias, smooth other distortions and allow for human error. So all debate about climate change has, at bottom, been about how to interpret information.

The Stanford team’s approach involved thinking again about how to make sense of temperature readings collected unevenly from ocean and surface atmospheric temperatures, all of them influenced by chaotic weather systems, seasonal variations and long-term natural cycles.

They applied another approach that could equally be used with climate data or stock market prices, and they report that their statistical confidence in their conclusions is 100 times stronger than what was reported by the NOAA group. Once this approach was applied, the apparent alteration in the rate of warming disappeared.

“Global warming is like other noisy systems that fluctuate wildly but still follow a trend. Think of the US stock market. There have been bull markets and bear markets but overall it has grown a lot over the past century,” said Noah Diffenbaugh of the Woods Institute for the Environment at Stanford.

“What is clear from analysing the long-term data in a rigorous statistical framework is that, even though climate varies from year to year and decade to decade, global temperature has increased in the long term, and the recent period does not stand out as abnormal.” – Climate News Network

Researchers say the world is continuing to warm, and evidence shows claims of a slowdown are unequivocally illusory.

LONDON, 19 September, 2015 – Global warming has not slowed. The so-called hiatus remains just that – so-called. The world is warming as predicted and any apparent evidence that it is not doing so is a statistical illusion, according to US scientists.

They report in the journal Climatic Change that they applied “rigorous, comprehensive, statistical analysis” to the global temperature data and came up with this unequivocal conclusion.

And although normally scientists like to spell out the caveats, the margins of error and the uncertainties in their conclusions, the team get to the point with unprecedented firmness.

“We find compelling evidence that recent claims of a ‘hiatus’ in global warming lack sound scientific basis. Our analysis reveals that there is no hiatus in the increase in the global mean temperature, no statistically significant difference in trends, no stalling of the global mean temperature, and no change in year-to-year temperature increases,” they write.

The very-much discussed and so-called pause, hiatus or slowdown in global warming has puzzled climate scientists for years. During the 1990s, annual global temperatures increased palpably, and at a measurable rate. In the early years of this century, the rate of increase began to slow.

Non-stop warming

It did not, as some have claimed, stop. Thirteen of the hottest 14 years ever have occurred this century, and 2014 was the warmest on record. But the rate of increase, expressed as fractions of a degree Celsius, averaged over the whole planet, certainly seemed to have slowed.

Since the levels of carbon dioxide in the atmosphere had continued steadily to increase, as a consequence of the combustion of fossil fuels, the rise in global temperatures should have kept pace, and scientists began to puzzle over the process.

One favourite explanation – and there have been many – was that some long-term natural oceanic or atmospheric cycle had been at play, taking any new atmospheric warmth to the deepest parts of the seas.

Another proposed that an increase in small volcanic eruptions had polluted the atmosphere and imperceptibly blocked incoming sunlight to cool the Earth from above. A third strand of argument proposed that even if there had been a slowdown, there was greater warming to come.

Yet others had begun to wonder about the completeness of the available data. And in June, a team led by the US National Oceanographic and Atmospheric Administration (NOAA) re-examined the available data, applied corrections they thought necessary,  and reported that there had been no slowdown at all

Now Bala Rajaratnam of Stanford University in California and colleagues have come to the same conclusion. They did some advanced mathematical homework, using both the measurements corrected by the NOAA group and a set of older, uncorrected temperature measurements. They also devised a new statistical framework to apply to them.

“Global temperature has increased in the long term, and the recent period does not stand out as abnormal”

“By using both datasets, nobody can claim that we made up a new statistical technique in order to get a certain result,” said Dr Rajaratnam. “We saw there was a debate in the scientific community about the global warming hiatus, and we realised that the assumptions of classical statistical tools being used were not appropriate and thus could not give reliable answers.”

Collected measurements of any kind, made at different times with different techniques, tell scientists nothing: they must use statistical tools to eliminate possible bias, smooth other distortions and allow for human error. So all debate about climate change has, at bottom, been about how to interpret information.

The Stanford team’s approach involved thinking again about how to make sense of temperature readings collected unevenly from ocean and surface atmospheric temperatures, all of them influenced by chaotic weather systems, seasonal variations and long-term natural cycles.

They applied another approach that could equally be used with climate data or stock market prices, and they report that their statistical confidence in their conclusions is 100 times stronger than what was reported by the NOAA group. Once this approach was applied, the apparent alteration in the rate of warming disappeared.

“Global warming is like other noisy systems that fluctuate wildly but still follow a trend. Think of the US stock market. There have been bull markets and bear markets but overall it has grown a lot over the past century,” said Noah Diffenbaugh of the Woods Institute for the Environment at Stanford.

“What is clear from analysing the long-term data in a rigorous statistical framework is that, even though climate varies from year to year and decade to decade, global temperature has increased in the long term, and the recent period does not stand out as abnormal.” – Climate News Network

Prehistoric dogs learned new tricks as climate changed

Scientists have found evidence that profound changes in climate caused ancient predators to evolve into the ancestors of today’s dogs. LONDON, 24 August, 2015 – Man-made climate change is expected to have a “significant effect” on the wildlife of the planet. And, if fossil evidence is anything to go by, it could seriously alter the course of evolution. The hunting habits of the wolf – ancestor of man’s best friend, the dog – evolved over millions of years to cope with profound climate change, according to new research. Borja Figueirido, of the Department of Ecology and Geology at the University of Malaga in Spain, and colleagues report in Nature Communications that they examined the elbows and teeth of 32 native North American species of the dog family from between 39 million and 2 million years ago.

Ambush and pursuit

What they found was clear evidence that, in response to changing climate and foliage cover, dogs evolved from ambush predators that survived by surprising their prey, to pursuit predators that wore them down. The story begins with a warm, wooded North America in which a canine creature with flexible forelimbs, and not much bigger than a mongoose, used stealth to surprise and pounce cat-like on its dinner. Ultimately, it gave way to animals like wolves, which could chase a deer all day.

“It’s reinforcing the idea that predators may be as directly sensitive to climate and habitat as herbivores”

In the course of those 37 million years, the climate cooled, the forests gave way to savannah and prairie, and the dog family began to evolve new strategies − including the short pursuit-and-pounce technique of the coyote or the fox, and the long-distance stamina hunting of the wolf. “It’s reinforcing the idea that predators may be as directly sensitive to climate and habitat as herbivores,” says Christine Janis, professor of ecology and evolutionary biology at Brown University in the US, and a co-author of the report. “Although this seems logical, it hadn’t been demonstrated before.” The scientists backed up their conclusions by studying the teeth and forelimb structures of a wide range of hunting animals, including cheetah, hyena and wild dog in Africa, the tiger and snow leopard in Asia, and the jaguar, puma and wolverine in the Americas.

Conservation worries

Their formal conclusion is that when things changed for the herbivores that shaped the landscape, the predators also responded. Such research confirms the worries of wildlife conservationists that man-made climate change in response to rising levels of carbon dioxide in the atmosphere − as a consequence of the burning of fossil fuels − could seriously alter the evolutionary conditions and the ecosystems from which civilised humankind and its domestic animals emerged. The scientists say their studies demonstrate that “long periods of profound climatic change are critical for the emergence of ecological innovations, and could alter the direction of lineage evolution”. – Climate News Network

Scientists have found evidence that profound changes in climate caused ancient predators to evolve into the ancestors of today’s dogs. LONDON, 24 August, 2015 – Man-made climate change is expected to have a “significant effect” on the wildlife of the planet. And, if fossil evidence is anything to go by, it could seriously alter the course of evolution. The hunting habits of the wolf – ancestor of man’s best friend, the dog – evolved over millions of years to cope with profound climate change, according to new research. Borja Figueirido, of the Department of Ecology and Geology at the University of Malaga in Spain, and colleagues report in Nature Communications that they examined the elbows and teeth of 32 native North American species of the dog family from between 39 million and 2 million years ago.

Ambush and pursuit

What they found was clear evidence that, in response to changing climate and foliage cover, dogs evolved from ambush predators that survived by surprising their prey, to pursuit predators that wore them down. The story begins with a warm, wooded North America in which a canine creature with flexible forelimbs, and not much bigger than a mongoose, used stealth to surprise and pounce cat-like on its dinner. Ultimately, it gave way to animals like wolves, which could chase a deer all day.

“It’s reinforcing the idea that predators may be as directly sensitive to climate and habitat as herbivores”

In the course of those 37 million years, the climate cooled, the forests gave way to savannah and prairie, and the dog family began to evolve new strategies − including the short pursuit-and-pounce technique of the coyote or the fox, and the long-distance stamina hunting of the wolf. “It’s reinforcing the idea that predators may be as directly sensitive to climate and habitat as herbivores,” says Christine Janis, professor of ecology and evolutionary biology at Brown University in the US, and a co-author of the report. “Although this seems logical, it hadn’t been demonstrated before.” The scientists backed up their conclusions by studying the teeth and forelimb structures of a wide range of hunting animals, including cheetah, hyena and wild dog in Africa, the tiger and snow leopard in Asia, and the jaguar, puma and wolverine in the Americas.

Conservation worries

Their formal conclusion is that when things changed for the herbivores that shaped the landscape, the predators also responded. Such research confirms the worries of wildlife conservationists that man-made climate change in response to rising levels of carbon dioxide in the atmosphere − as a consequence of the burning of fossil fuels − could seriously alter the evolutionary conditions and the ecosystems from which civilised humankind and its domestic animals emerged. The scientists say their studies demonstrate that “long periods of profound climatic change are critical for the emergence of ecological innovations, and could alter the direction of lineage evolution”. – Climate News Network

Earth has warmed as usual, with no slowdown

US scientists re-examine the collection of data which seemed to show global warming slowing since 1998 and say temperatures have continued to rise steadily. LONDON, 7 June, 2015 − Forget about the so-called “hiatus” in global warming. The planet’s average temperatures are notching up as swiftly now as they did 20 or 30 years ago. A team of US researchers has looked again not just at the data for the last 60 years but at how it has been collected, and done the sums again. They conclude, in the journal Science,  that the “estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a ‘slowdown’ in the increase of global surface temperature rise.” But first, the story-so-far. Climate sceptics have repeatedly claimed that global warming has slowed or stopped. This was not the case: 13 of the hottest years ever recorded have all occurred in the last 14 years, and 2014 was the hottest of them all. But when climate scientists looked at a graph of the rise of temperatures in the last 60 years, they saw – or thought they saw – a distinct drop in the rate of increase in global average temperatures in the last 15 years. This apparent dip became the subject of a whole series of studies. Researchers had never expected the rise to follow a straight line – all sorts of natural climate cycles would naturally affect annual records – but the rate of increase was slower, and more sustained in its slowness, than anyone could explain, especially as there had been no drop in the greenhouse gas emissions that drive global warming.

Data anomalies

Some proposed that the expected extra heat in the atmosphere had been drawn down into the great oceans and others that an unnoticed increase in volcanic activity had helped screen the sunlight and cool the atmosphere unexpectedly. Yet another group looked not at average temperature patterns but the change in the frequency of heat waves and saw a different kind of rise. Yet another group wondered if the problem might be only apparent: more complete data from many more parts of the world might combine to tell a different story. Thomas Karl and colleagues at the National Oceanographic and Atmospheric Administration in the US made this their starting point. They looked again at how the data had been collected, and the gaps that might have appeared. Sea surface temperatures, for instance, were at different periods collected by bucket from a ship’s deck, by readings aboard surface drifting and moored buoys or by engine-intake thermometers in ships’ engine rooms, and there could be subtle differences not accounted for. There were very few readings from the Arctic, yet the Arctic is by far the fastest-warming region of the planet, and the pattern of land-based temperature readings, too, repaid re-examination. By the time the NOAA team had finished, the recalibrated figures told a different story. Between 1998 and 2012, the world warmed at the rate of 0.086°C per decade, more than twice the rate of 0.039°C per decade measured by the Intergovernmental Panel on Climate Change.

“We need to look really carefully at data quality and issues of instrument change”

The new figure is much closer to the rate estimated for the decades 1950 to 1999, at 0.113°C per decade. And the new analysis lifts the rate of warming from 2000 to 2014 to 0.116°C per decade, which if anything is an acceleration, not a slowdown. British climate scientists have welcomed the finding: it is however the finding of just one group and, like all such research, will be accepted more readily if it can be separately replicated. “This study makes the important point that we need to look really carefully at data quality and issues of instrument change,” said Piers Forster, professor of climate change at the University of Leeds, UK. ”Yet there are several legitimate judgment calls made when combining datasets to make a global mean-time series. I still don’t think this study will be the last word on this complex subject.” But Peter Wadhams, a professor of ocean physics at the University of Cambridge, UK, called the study careful and persuasive, and said: “I think it shows clearly that the so-called ‘hiatus’ does not exist and that global warming has continued over the past few years at the same rate as in earlier years.” − Climate News Network

US scientists re-examine the collection of data which seemed to show global warming slowing since 1998 and say temperatures have continued to rise steadily. LONDON, 7 June, 2015 − Forget about the so-called “hiatus” in global warming. The planet’s average temperatures are notching up as swiftly now as they did 20 or 30 years ago. A team of US researchers has looked again not just at the data for the last 60 years but at how it has been collected, and done the sums again. They conclude, in the journal Science,  that the “estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a ‘slowdown’ in the increase of global surface temperature rise.” But first, the story-so-far. Climate sceptics have repeatedly claimed that global warming has slowed or stopped. This was not the case: 13 of the hottest years ever recorded have all occurred in the last 14 years, and 2014 was the hottest of them all. But when climate scientists looked at a graph of the rise of temperatures in the last 60 years, they saw – or thought they saw – a distinct drop in the rate of increase in global average temperatures in the last 15 years. This apparent dip became the subject of a whole series of studies. Researchers had never expected the rise to follow a straight line – all sorts of natural climate cycles would naturally affect annual records – but the rate of increase was slower, and more sustained in its slowness, than anyone could explain, especially as there had been no drop in the greenhouse gas emissions that drive global warming.

Data anomalies

Some proposed that the expected extra heat in the atmosphere had been drawn down into the great oceans and others that an unnoticed increase in volcanic activity had helped screen the sunlight and cool the atmosphere unexpectedly. Yet another group looked not at average temperature patterns but the change in the frequency of heat waves and saw a different kind of rise. Yet another group wondered if the problem might be only apparent: more complete data from many more parts of the world might combine to tell a different story. Thomas Karl and colleagues at the National Oceanographic and Atmospheric Administration in the US made this their starting point. They looked again at how the data had been collected, and the gaps that might have appeared. Sea surface temperatures, for instance, were at different periods collected by bucket from a ship’s deck, by readings aboard surface drifting and moored buoys or by engine-intake thermometers in ships’ engine rooms, and there could be subtle differences not accounted for. There were very few readings from the Arctic, yet the Arctic is by far the fastest-warming region of the planet, and the pattern of land-based temperature readings, too, repaid re-examination. By the time the NOAA team had finished, the recalibrated figures told a different story. Between 1998 and 2012, the world warmed at the rate of 0.086°C per decade, more than twice the rate of 0.039°C per decade measured by the Intergovernmental Panel on Climate Change.

“We need to look really carefully at data quality and issues of instrument change”

The new figure is much closer to the rate estimated for the decades 1950 to 1999, at 0.113°C per decade. And the new analysis lifts the rate of warming from 2000 to 2014 to 0.116°C per decade, which if anything is an acceleration, not a slowdown. British climate scientists have welcomed the finding: it is however the finding of just one group and, like all such research, will be accepted more readily if it can be separately replicated. “This study makes the important point that we need to look really carefully at data quality and issues of instrument change,” said Piers Forster, professor of climate change at the University of Leeds, UK. ”Yet there are several legitimate judgment calls made when combining datasets to make a global mean-time series. I still don’t think this study will be the last word on this complex subject.” But Peter Wadhams, a professor of ocean physics at the University of Cambridge, UK, called the study careful and persuasive, and said: “I think it shows clearly that the so-called ‘hiatus’ does not exist and that global warming has continued over the past few years at the same rate as in earlier years.” − Climate News Network

Science puzzles over recent rapid Antarctic thaw

Part of Antarctica has begun thawing unusually fast, leaving scientists unsure whether a natural cycle or human-caused climate change is responsible. LONDON, 31 May, 2015 − Antarctic glaciers once thought relatively stable are starting to melt. Evidence from a five-year satellite study of the frozen rivers on the southern Antarctic Peninsula now reveal that these are shedding ice at the rate of 60 cubic kilometres a year: altogether around 300 trillion litres of water has moved from the frozen continent to the oceans. Bert Wouters of the University of Bristol, UK, and colleagues report in the journal Science  that they used data from two very different research satellites to confirm their findings. The European Space Agency’s CryoSat-2 has been orbiting the polar world since April 2010, bouncing radar signals off the surface and measuring the return travel time. An examination of five years of results shows that the glacial surfaces are sinking, in some places by as much as four metres a year. There could be two reasons for that: either the snow is compacting or the ice is flowing faster.

“The glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings”

But results from the US space agency Nasa’s GRACE mission – the acronym stands for Gravity Recovery and Climate Experiment – settle the matter. The mass of ice lost in the region is so large that it changes the local gravity field, and the changes in the sheer weight of 750 kilometres of glaciers in the region can be measured from space. “To date, the glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings combined,” Dr Wouters said. “The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us. It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted.”

Melting maintained

That the southern continent is responding to climate change of some kind is not in doubt: another study has put the overall mass loss at 92 billion tons a year, and twin assaults of warmer air above, and warmer waters around the continent, continue the attrition. What is not yet certain is whether scientists are looking at the consequences of human-made global warming or at the see-saw conditions inherent in some kind of as-yet-unidentified natural cycle. But ice loss on that scale cannot be easily explained by changes in snowfall or air temperatures, so suspicion falls on the effect of warmer waters. The glaciers flow into seas that are surrounded by ice shelves. The ice shelves have lost one fifth of their thickness in recent decades, so they offer less resistance to the land-based ice, allowing the glaciers to accelerate. There is a second factor: some of the glaciers are grounded on continental bedrock that is depressed below sea level, which means that warmer ocean waters can penetrate further inland and melt the glaciers from below.

Cautious response

There are questions that have yet to be resolved. As usual in science, the interpretations are open to debate. “Although these latest CryoSat measurements of Antarctic thinning agree with findings from two studies reported last year, I think the new estimates of ice loss computed from them are far too high, because the glaciers in this sector just haven’t speeded up that much,” said Andy Shepherd, professor of earth observation at the University of Leeds in the UK and principal scientific advisor to the CryoSat mission. “It could be that a bigger chunk of the thinning is down to snowfall fluctuations than the authors have accounted for, and so I would be cautious about the new numbers until more information is to hand.” Dr Wouters agrees that more research is necessary. “It appears that some time around 2009, the ice shelf thinning and the subsurface melting of the glaciers passed a critical threshold which triggered the sudden ice loss. However, compared to other regions in Antarctica, the Southern Peninsula is rather understudied, exactly because it did not show any changes in the past, ironically,” he said. “To pinpoint the cause of the changes, more data need to be collected. A detailed knowledge of the geometry of the local ice shelves, the ocean floor topography, ice sheet thickness and glacier flow speeds are crucial to tell how much longer the thinning will continue.” − Climate News Network

Part of Antarctica has begun thawing unusually fast, leaving scientists unsure whether a natural cycle or human-caused climate change is responsible. LONDON, 31 May, 2015 − Antarctic glaciers once thought relatively stable are starting to melt. Evidence from a five-year satellite study of the frozen rivers on the southern Antarctic Peninsula now reveal that these are shedding ice at the rate of 60 cubic kilometres a year: altogether around 300 trillion litres of water has moved from the frozen continent to the oceans. Bert Wouters of the University of Bristol, UK, and colleagues report in the journal Science  that they used data from two very different research satellites to confirm their findings. The European Space Agency’s CryoSat-2 has been orbiting the polar world since April 2010, bouncing radar signals off the surface and measuring the return travel time. An examination of five years of results shows that the glacial surfaces are sinking, in some places by as much as four metres a year. There could be two reasons for that: either the snow is compacting or the ice is flowing faster.

“The glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings”

But results from the US space agency Nasa’s GRACE mission – the acronym stands for Gravity Recovery and Climate Experiment – settle the matter. The mass of ice lost in the region is so large that it changes the local gravity field, and the changes in the sheer weight of 750 kilometres of glaciers in the region can be measured from space. “To date, the glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings combined,” Dr Wouters said. “The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us. It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted.”

Melting maintained

That the southern continent is responding to climate change of some kind is not in doubt: another study has put the overall mass loss at 92 billion tons a year, and twin assaults of warmer air above, and warmer waters around the continent, continue the attrition. What is not yet certain is whether scientists are looking at the consequences of human-made global warming or at the see-saw conditions inherent in some kind of as-yet-unidentified natural cycle. But ice loss on that scale cannot be easily explained by changes in snowfall or air temperatures, so suspicion falls on the effect of warmer waters. The glaciers flow into seas that are surrounded by ice shelves. The ice shelves have lost one fifth of their thickness in recent decades, so they offer less resistance to the land-based ice, allowing the glaciers to accelerate. There is a second factor: some of the glaciers are grounded on continental bedrock that is depressed below sea level, which means that warmer ocean waters can penetrate further inland and melt the glaciers from below.

Cautious response

There are questions that have yet to be resolved. As usual in science, the interpretations are open to debate. “Although these latest CryoSat measurements of Antarctic thinning agree with findings from two studies reported last year, I think the new estimates of ice loss computed from them are far too high, because the glaciers in this sector just haven’t speeded up that much,” said Andy Shepherd, professor of earth observation at the University of Leeds in the UK and principal scientific advisor to the CryoSat mission. “It could be that a bigger chunk of the thinning is down to snowfall fluctuations than the authors have accounted for, and so I would be cautious about the new numbers until more information is to hand.” Dr Wouters agrees that more research is necessary. “It appears that some time around 2009, the ice shelf thinning and the subsurface melting of the glaciers passed a critical threshold which triggered the sudden ice loss. However, compared to other regions in Antarctica, the Southern Peninsula is rather understudied, exactly because it did not show any changes in the past, ironically,” he said. “To pinpoint the cause of the changes, more data need to be collected. A detailed knowledge of the geometry of the local ice shelves, the ocean floor topography, ice sheet thickness and glacier flow speeds are crucial to tell how much longer the thinning will continue.” − Climate News Network

US farmers given early warning about hungry crop pest

Biologists say a destructive insect is likely to cause even more damage than usual as rising temperatures prompt leaves to sprout earlier. LONDON, 24 May, 2015 − It is small, bright green and an unwelcome visitor. But global warming means that this particular agricultural menace arrives earlier than ever − and consumes more than ever. New research has confirmed that the potato leafhopper now turns up to devour US crops on average 10 days earlier than it did 60 years ago. Despite its informal name, Empoasca fabae is known to have developed an appetite not just for potatoes, but for anything from rhubarb to red maple trees. It survives over the winter in the southernmost states, then moves north as the temperatures begin to rise and crops begin to sprout. It has been observed to reproduce itself on around 200 plant species, and it also has a taste for apples, celery, beans, grapes, hops and the important perennial forage crop alfalfa, sometimes also known as lucerne.

Severe infestation

Three biologists from two US universities report in PLOS One, the Public Library of Science journal, that leafhopper infestation is more severe in the warmest years, and that the damage caused by the tiny insect is likely to increase as average temperatures continue to rise. It arrives in the growing season and pierces the plant leaf tissue to get at the sap. Its saliva carries a toxin that can cause the leaf to dry, curl and rot, and the consequent damage is called “hopperburn”.

“You don’t realise they’re even there until you see the damage to the plants . . . By then it’s too late”

“Earlier arrival dates make it particularly important for farmers to get out early in the season and scout for leafhoppers,” says William Lamp, associate professor of entomology at the University of Maryland, and one of the three authors of the study. “They’re tiny, flighty and very hard to see. You don’t realise they’re even there until you see the damage to the plants, which can take up to a week to manifest. By then it’s too late.” The researchers combed the records between 1951 and 2012 to track the dates in which the pest was recorded in each of 19 affected US states, and matched this with weather records over the same timespan. Such a finding was  possible only because scientists had access to systematic data. Dilip Venugopal, an ecologist, and colleague of Lamp at the University of Maryland, says: “The historical records on agricultural pests are a gold mine, made possible by decades of hard work by agricultural research and extension personnel who collect this data. There has been a decline in data collection activity over the past decade, and we would love to see an effort to ramp this up again.” Global average temperatures have risen by 0.74°C since 1951, and the last decade has been the warmest since climate records began.

Changed behaviour

The leafhopper is only one of many long-distance migratory pests likely to change behaviour in response to climate change. Other researchers have already observed crop pests’ steady movement towards higher latitudes in recent decades. “Climate change is not just costly because temperatures and oceans rise, but because it makes it harder to feed ourselves,” says report co-author Mitchell Baker, assistant professor of biology at Queens College, City University of New York. “Increased pest pressure in agriculture is one of the complex effects of continued warming. Predicting arrival time and severity is critical to managing this pest and others like it.” – Climate News Network

Biologists say a destructive insect is likely to cause even more damage than usual as rising temperatures prompt leaves to sprout earlier. LONDON, 24 May, 2015 − It is small, bright green and an unwelcome visitor. But global warming means that this particular agricultural menace arrives earlier than ever − and consumes more than ever. New research has confirmed that the potato leafhopper now turns up to devour US crops on average 10 days earlier than it did 60 years ago. Despite its informal name, Empoasca fabae is known to have developed an appetite not just for potatoes, but for anything from rhubarb to red maple trees. It survives over the winter in the southernmost states, then moves north as the temperatures begin to rise and crops begin to sprout. It has been observed to reproduce itself on around 200 plant species, and it also has a taste for apples, celery, beans, grapes, hops and the important perennial forage crop alfalfa, sometimes also known as lucerne.

Severe infestation

Three biologists from two US universities report in PLOS One, the Public Library of Science journal, that leafhopper infestation is more severe in the warmest years, and that the damage caused by the tiny insect is likely to increase as average temperatures continue to rise. It arrives in the growing season and pierces the plant leaf tissue to get at the sap. Its saliva carries a toxin that can cause the leaf to dry, curl and rot, and the consequent damage is called “hopperburn”.

“You don’t realise they’re even there until you see the damage to the plants . . . By then it’s too late”

“Earlier arrival dates make it particularly important for farmers to get out early in the season and scout for leafhoppers,” says William Lamp, associate professor of entomology at the University of Maryland, and one of the three authors of the study. “They’re tiny, flighty and very hard to see. You don’t realise they’re even there until you see the damage to the plants, which can take up to a week to manifest. By then it’s too late.” The researchers combed the records between 1951 and 2012 to track the dates in which the pest was recorded in each of 19 affected US states, and matched this with weather records over the same timespan. Such a finding was  possible only because scientists had access to systematic data. Dilip Venugopal, an ecologist, and colleague of Lamp at the University of Maryland, says: “The historical records on agricultural pests are a gold mine, made possible by decades of hard work by agricultural research and extension personnel who collect this data. There has been a decline in data collection activity over the past decade, and we would love to see an effort to ramp this up again.” Global average temperatures have risen by 0.74°C since 1951, and the last decade has been the warmest since climate records began.

Changed behaviour

The leafhopper is only one of many long-distance migratory pests likely to change behaviour in response to climate change. Other researchers have already observed crop pests’ steady movement towards higher latitudes in recent decades. “Climate change is not just costly because temperatures and oceans rise, but because it makes it harder to feed ourselves,” says report co-author Mitchell Baker, assistant professor of biology at Queens College, City University of New York. “Increased pest pressure in agriculture is one of the complex effects of continued warming. Predicting arrival time and severity is critical to managing this pest and others like it.” – Climate News Network