Weather events taken to extremes by climate change

Weather events taken to extremes by climate change

Scientists warn that global warming could greatly increase the likelihood of droughts, floods and heatwaves reaching record levels of frequency and intensity.

LONDON, 15 May, 2015 − As temperatures soar to record heights, blame it on global warming − but only about three-quarters of the time. And when the rain comes down by the bucketful, you can attribute one downpour in five to climate change.

Yet another team of research scientists has looked at the probabilities, and has linked extremes of weather with global warming.

Extremes have always happened and are, by definition, rare events. So, for the last 30 years, climate scientists have carefully explained that no particular climate event could be identified as the consequence of a rise in global average temperatures driven by the release of carbon dioxide and other greenhouse gases from the burning of fossil fuels.

But some events that were once improbable have now become statistically more probable because of global warming, according to Erich Fischer and Reno Knutti, climate scientists at ETH Zurich − the Swiss Federal Institute of Technology.

They report in Nature Climate Change that they looked at simulations of probabilities and climate records for the period 1901 to 2005, and projections for the period 2006 to 2100.

Rise in temperatures

Then they settled down to calculate the likelihood that a proportion of past heatwaves or floods could be linked to a measured average rise in planetary temperatures so far of 0.85°C.

They worked out how these proportions would change if the average planetary temperatures reach 2°C above the “normal” of the pre-industrial world, and they found that human-induced global warming could already be responsible for 18% of extremes of rain or snow, and 75% of heatwaves worldwide.

If the temperatures go up to the 2°C that nations have agreed should be the limit, then the probability of precipitation extremes that could be blamed on global warming rises to 40%. They are less precise about heatwaves, but any rise could be sharp.

“If temperatures rise globally by 2°C, we would expect twice as many extreme heat events worldwide than we would with a 1.5% increase,” Dr Fischer says.

“These global warming targets, which are discussed in climate negotiations and which differ little at first glance, therefore have a great influence on the frequency of extremes.”

The researchers are talking about probabilities: it will still be difficult ever to say that one event was a random happening, and another a result of climate change. In such research, there are definition problems. What counts as extreme heat in northern England would not be extreme in India or Saudi Arabia.

But such distinctions could become increasingly academic for people who live in the path of unusual heat and extended drought, or flash floods and catastrophic hailstorms.

A scientist recently told the European Geosciences Union that some regions of the planet will see unprecedented drought, driven once again by climate change, before 2050.

Ignored warnings

Yusuke Satoh, of the International Institute for Applied Systems Analysis, warned that under the notorious business-as-usual scenario −where nations ignore such warnings and just go on burning fossil fuels − 13 of 26 global regions would see “unprecedented hydrological drought levels” by 2050. Some would see this parching much earlier − the Mediterranean by 2027, and the western US as early as 2017.

Such studies are calculated to help provoke governments, states and water authorities into preparing for climate change, but it just may be that the western US is already feeling the heat. California, in particular, has been in the grip of unprecedented drought, and researchers have already linked this to climate change.

Reservoirs and irrigation systems are built on historical data. “But in the next few decades, these historical data may no longer give us accurate information about current conditions,” Dr Satoh says. “The earlier we take this seriously, the better we will be able to adapt.” – Climate News Network

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Climate poses new threat to survival of Arabian oryx

Climate poses new threat to survival of Arabian oryx

Global warming is the suspected cause of the series of dry years in Arabia that have brought starvation to a desert species saved from extinction.

LONDON, 7 April, 2015 − One of conservation’s triumphs – the reintroduction of the oryx to the deserts of Arabia – could be at risk because of climate change, according to a new book.

The animal already beautifully adapted by thousands of years of evolution to an arid environment met a problem on its return: even deserts have droughts.

The Arabian oryx had been hunted almost to extinction before a handful were captured in 1962 and flown to Phoenix, Arizona, as the nucleus of a captive breeding programme.

By 1972, the last wild oryx had been captured or killed in Oman, but the bloodline survived in captivity.

The first reintroductions to the wild began in 1982, and numbers began to increase. There were incursions by poachers, but there were more releases.

However, there have been so many dry years over the last two decades − according to Malcolm Smith, once chief scientist for the Countryside Commission in Wales, in his new book, Back from the Brink − that many of the newly-wild oryx have not been able to find sufficient grazing.

Closely monitored

The animal is one of the most closely monitored in the world. Of all recorded deaths, 19% have occurred in fights between males, 13% have been due to poaching, and 65% have been due to starvation.

The succession of particularly dry years in the region might be due to global warming as a consequence of human combustion of fossil fuels.

Since climate simulations seem to predict that, in general, moist regions will get more rain and dry regions will experience ever drier regimes as greenhouse gas levels build up in the atmosphere, things don’t look good for the oryx − although captive populations for the time being remain secure.

Other recently-rescued species may face even leaner times − once again, because of climate change.

Spanish and Portuguese authorities have established safe territories for the Iberian lynx and, by 2013, more than 300 lived wild in Spain, while 150 lynx paced the enclosures in the breeding centres awaiting reintroduction.

But the wild rabbit makes up 90% of the lynx’s diet, and rabbit numbers are limited by hunting and by outbreaks of myxomatosis and rabbit haemorrhagic disease.

There have been fears too, that southern Spain and Portugal may become too hot and dry to sustain the prey, let alone the predator.

Such threats to biodiversity, and to individual animals, are not new. Climate change has in various ways reportedly threatened Arctic marine mammalscreatures of the Borneo forests,  and chimpanzees in isolated woodland in West Africa.

Whole ecosystems that evolved in geographical climate zones may be doomed to sudden and rapid change.

But Malcolm Smith’s book concerns itself only with the choicest last-minute success stories of conservation bodies: with those creatures that were all but gone when the conservationists stepped in.

They were hunted, their habitats had been destroyed, and their ecosystems were always precarious. But climate change was, at the time of rescue, the least of their problems.

Large Blue butterfly (Maculinea arion). Image: PJC&Co via Wikimedia Commons

Large Blue butterfly (Maculinea arion).
Image: PJC&Co via Wikimedia Commons

One instance he explores shows just how intricate the living arrangements of charismatic species can be, and illustrates the finely-balanced play of climate and ecological stability in preserving a species.

The Large Blue butterfly (Maculinea arion) exists in respectable numbers worldwide, but became all but extinct in the UK − with changes in farming practices and land use the suspected causes.

Peculiar lifestyle

Until 1972, nobody quite understood the peculiar lifestyle of the Large Blue. It lays its eggs on the flower bud of the wild herb, thyme. A larva hatches and, after an initial vegetarian diet, falls off the plant. Thereafter, its life depends on just one species of red ant, Myrmica sabuleti.

The Large Blue grub secretes a fluid that somehow suggests that of a red ant queen grub, so the ants take it home and nurse it. The Large Blue caterpillar turns carnivore and, for 10 months, feeds on red ant larvae.

In pupate form, it makes queen ant noises and the ants continue to protect it. It hatches, gets out to the open − still protected by the ants − and flies off. It then has about a week in which to find a thyme flower bud, mate, and lay its eggs.

But the complexities multiply. The thyme flower bud that bears the eggs must be within metres of the right kind of red ant nest, or the larva perishes.

Dependent on temperature

The grass above the ant nest must be closely grazed because the ants’ survival is dependent on temperature, and if the grass grows even a centimetre ground is shaded, the nest temperature drops by 2°C to 3°C, and the ant colony is at risk − along with any parasitic caterpillars in the nest.

So the thyme has to flower at the right time, very near a red ant nest, the herbage has to be closely cropped, and the temperatures have to stay near the optimum.

If anything goes wrong, there are no surviving Large Blue larvae to pupate. If things go well, and too many Large Blue grubs are taken into a colony, the ant larvae are all consumed, and both ants and butterflies perish.

And then there’s the climate question − one that affects almost all insects.

“Overall, butterfly populations have moved northward by about 75km in the last 20 years as overall temperatures have risen,” Smith writes. “They are likely to move yet further.” – Climate News Network

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“Water Man of India” makes rivers flow again

“Water Man of India” makes rivers flow again

Revival of traditional rainwater harvesting has transformed the driest state in India, and could be used to combat the effects of climate change across the world.

Chennai, 6 April, 2015 − School textbooks in India have been telling children for generations that Rajasthan is an inhospitable state in the northwest of the country, constrained by the hot, hostile sands of the Thar Desert.

But the driest state in India has a softer, humane face as well – that of Rajendra Singh, known as the “Water Man of India”, whose untiring efforts in water conservation in arid Rajasthan have led to him being awarded the Stockholm Water Prize, commonly referred to as the Nobel Prize for Water.

Singh did not attempt to design a new technology to address Rajasthan’s water problems. He began simply by de-silting several traditional surface level rainwater storage facilities – called “johads” in the local Hindi language − that fell out of use during British colonial rule. And, in doing so, he has quenched the thirst of villages that were dying.

Thousands of villages followed his example, and so much water was captured and soaked into aquifers that dry rivers have begun to flow again.

Water wars

Singh believes that water conservation is vital to combat the effects of climate change and to avoid “water wars” in the future.

And such is his reputation on water issues that he received a call from Prince Charles, heir to the UK throne, seeking advice on how to handle the devastating summer floods in England in 2007.

In an interview with Climate News Network, Singh recalled how he began making water flow again in perennially dry Rajasthan by inculcating do-it-yourself initiatives in the villagers.

He explained: “I imbibed Gandhian ideals during my school days that emphasised working for empowerment of villages.

“As an Ayurvedic (traditional medicine system in India) doctor, I went to the Alwar district of Rajasthan early in 1982 to start a clinic and spread awareness among youth about health and hygiene.

“I was perturbed because the majority of young men had already left the village, and the rest were about to leave for green pastures in the cities as they were unable to battle the water scarcity. Besides, they also wanted to earn good money.

“Women, old people and children were left behind in the village. I reworked my doctor plans to address the water scarcity, as that would actually save people from several diseases.

A village johad in arid Rajasthan. Image: LRBurdak via Wikimedia Commons

A village johad in arid Rajasthan. Image: LRBurdak via Wikimedia Commons

“Along with the support of the villagers, I de-silted a couple of johads in Alwar. When rains filled them, people in neighbouring villages trusted my initiative and over 8,000 johads are renovated now.

“Hordes of youth have returned to their villages as water filled tanks and the standard of living in hamlets rose in a big way.”

He said that five rivers in this region had revived and started to flow again.

Johads are simple tanks built across a slope, with a high embankment on three sides and the fourth side left open for rainwater to enter. They hold water during rains and recharge the aquifer below to ensure continuous water supply to the neighbourhood in the dry season.

“Community-based water management yields
long-lasting results and is the only solution for water shortages”

But Singh explained: “After the advent of bore wells and pipelines connecting every hamlet in India, we forgot the traditional water conservation facility used by our ancestors.”

Having won the Stockholm prize, what does the future hold for the Water Man?

“My immediate plans are to take up a global-level campaign on water conservation and peace,” he said. “As predicted by several experts, the next world war will be for water. Unless every one of us starts at least now to save water and protect the water bodies, we face severe conflicts − apart from suffering climate change impacts. I will be leading the global water walk in the UK in August 2015.

“During his two visits (2004 and 2006), Prince Charles told me that he was impressed by the johad model of conservation. He then called me in 2007 to be part of his team of water engineers to work out all possibilities to address the crisis during the floods in England. They listened to my suggestions on creating the johad model on hilltops and downhill to arrest water in the hills and prevent floods in the future.”

In India, however, he is not confident that the government has the right ideas. “Our government is pushing a different idea of inter-linking of rivers, which will only politicise the water crisis. I was part of the national-level body to clean up the holy Ganga River from 2010 to 2012, but I quit as there was lack of accountability and it ended up as a toothless organisation.

“Inter-linking of rivers is not a solution for flood and drought. As far as India is concerned, it will result only in inter-linking of corruption and politics.

Hearts and brains

“What we need is inter-linking of the hearts and brains of people to take up water conservation in their homes and community. If exploitation of river water and polluting the river are stopped, every river will flow. Water engineering should be focused on conservation of each drop, and not on changing the course of rivers, which are designed by Mother Nature.”

Singh is also against the idea of privatising water supplies, and does not believe it would result in people using water more judiciously.

“Water is not a commodity,” he said. “In my own example, johads are de-silted by the people and used by people. Community-based water management yields long-lasting results and is the only solution for water shortages.

“When people realise their need and de-silt lakes and ponds as a group, they can use the water without having to pay for it. Right to water is every man’s right, and monetising water will increase conflicts in the society.

“Helping a community to have access to clean and safe water means helping the community to have a dignified life.” – Climate News Network

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Changing climate causes weather chaos in Chile

Changing climate causes weather chaos in Chile

What is being described as an environmental catastrophe is hitting Chile as torrential rains batter the north while the south suffers prolonged drought and wildfires.

LONDON, 30 March, 2015 − The Atacama desert region of northern Chile, one of the driest areas on Earth, has been hit in recent days by torrential rains and floods that have caused deaths, swept away homes and left much of the region without power.

Meanwhile, in the usually lush southern parts of the country, wildfires are raging across lands and forests parched by the longest period of drought in living memory, endangering some of the world’s richest flora and fauna.

“We are witnessing a massive environmental catastrophe,” Luis Mariano Rendon, head of the Accion Ecologica environmental group, told the AFP news agency.

Irreparable loss

“There have been whole species lost, such as the Araucaria araucana (monkey puzzle tree). They are trees that take hundreds of years to reach maturity, so this is a practically irreparable loss for current generations.”

The trees, a distant relative of the pine, are considered sacred by indigenous Mapuche people, and have been declared part of Chile’s unique natural heritage.

Scientists say the drought in the southern region – which is the powerhouse of Chile’s multi-billion dollar agricultural sector, and site of many of its famous vineyards – is a long-term trend, linked to climate change.

“There is no choice but to assume that the lack of water resources is a reality that is here to stay”

Chile’s president, Michelle Bachelet, says millions of dollars will have to be invested in desalination plants and new reservoirs to cope with the continuing drought. Canals and irrigation systems will also have to be upgraded.

“Faced with this critical situation,” he says, “there is no choice but to assume that the lack of water resources is a reality that is here to stay, and that puts at risk the development of important regions of the country.”

The Maipo river basin − which includes Santiago, Chile’s capital − contains nearly 40% of the country’s population and is an important area for agriculture, mining, and for power generation, much of which comes from hydroelectric sources.

Researchers, led by the Centre for Global Change at the Pontifical Catholic University of Chile, have been mapping the impact that climate change is likely to have on the Maipo basin.

Projections so far indicate that rainfall is likely to drop by 10% in the area over the period up to 2040, and by up to 30% by the end of the century. Meanwhile, temperatures will rise by 1˚C above the historical average over the next 25 years, and by between 2.5˚C and 3.5˚C by 2100.

Power source

The researchers have also been investigating glacier mass and melt in the Andes − the source of the bulk of the country’s water supply for millions of people in the region, and a crucial power source.

Scientists say that accelerated melting of Andean glaciers is being caused by atmospheric warming.

Water shortages are hitting not only the agricultural sector, but also mining – one of Chile’s major industries. The country is the world’s biggest producer of copper, and mining companies say they are having to invest in costly desalination plants in order to get water for processing copper concentrate from milled rock.

A drop in river levels feeding hydroelectric facilities is also leading to an increase in coal-fired power plants – a major source of climate-changing greenhouse gases.

Despite the recent rains in the north of the country, scientists are warning of the dangers of desertification in the region, with the northern desert advancing further south each year. – Climate News Network

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China ramps up the rhetoric on climate change

China ramps up the rhetoric on climate change

Senior Chinese official warns that climate-related temperature rises could seriously affect the country’s harvests and major infrastructure projects.

LONDON, 28 March, 2015 − Zheng Guogang, head of the China Meteorological Administration, says future variations in climate are likely to reduce crop yields and damage the environment.

In one of the strongest official statements to date on the challenges faced, Zheng told China’s official Xinhua news agency that climate change could have a “huge impact” on the country, with a growing risk of climate-related disasters.

“To face the challenges from past and future climate change, we must respect nature and live in harmony with it,” Zheng said. “We must promote the idea of nature, and emphasise climate security.”

Violent rainstorms

Zheng said temperature rises in China over the past century have been higher than the global average. He warned that river flows and harvests are likely to suffer as the incidence of droughts and violent rainstorms across the country increases.

In turn, this could affect major infrastructure projects such as the Three Gorges Dam on the Yangtze river, the biggest hydroelectric scheme in the world.

Other projects that could be hit by changes in climate are the rail line between the northwestern province of Qinghai and Tibet − the highest railway line in the world, and partly built on permafrost − and a massive project aimed at bringing water from the south of China to the parched towns and cities of the north.

“The safe production and operation of major strategic projects is facing a serious threat,” Zheng said.

Although millions of people in China have benefited from years of double-digit economic growth, damage to the environment has been extensive and has become a major social, health and political issue.

“To face the challenges from past and future climate change, we must respect nature
and live in harmony with it”

China is now the world’s biggest emitter of greenhouse gases − largely due to its continued reliance on coal for power generation.

There are frequent public protests about the state of the environment, particularly water and air pollution. In Beijing and several other cities, air pollution frequently exceeds internationally-recognised health safety limits.

The authorities are taking various measures to tackle the country’s considerable environmental problems, but they are nervous about public protests on the environment getting out of control.

Earlier this month, “Under the Dome” – a documentary on China’s pollution, made by one of the country’s leading investigative reporters − was taken down from the internet by the authorities after having been viewed by an estimated 100 million people.

Green development

Under China’s present five-year plan, which started in 2011, there is a focus on the need to encourage “green, cyclical and low-carbon development”.

The plan claims: “These actions will increase the strategic position of combating climate change in China’s overall economic and social development.”

In an effort to improve its environment and meet international obligations to cut emissions, China is in the midst of a renewable energy programme costing billions of dollars.

Late last year, Beijing announced for the first time a date when the country’s emissions would peak – 2030 – and then taper off in the years following.

China is also involved with the US and other countries in a wide range of energy-saving research projects aimed at combating climate change. – Climate News Network

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Changing weather patterns hit Pakistan’s crops

Changing weather patterns hit Pakistan's crops

Torrential rain and hailstorms have raised fears that Pakistan’s winter crops yield could be seriously depleted – and global warming is the likely culprit.

Islamabad, 23 March, 2015 − Anxious farmers in Pakistan waited for weeks for the rains to arrive – but when the skies finally opened, the downpour was so intense it destroyed crops and put the harvest in jeopardy.

“We weather scientists are really in shock, and so are farmers, who have suffered economic losses due to crop damage,” says Muzammil Hussain, a weather forecasting scientist at the Pakistan Meteorological Department (PMD).

“The wind from the southeast has carried moisture from the Arabian Sea. Normally, the northeast wind brings rain during winter, and the southeast wind brings monsoon rains in summer. But the pattern has changed this year because of what is believed to be global warming.”

Unusually heavy

Farmers across much of Pakistan plant winter crops of wheat, oilseed and potato late in the year and wait for rains to water the land. This year, the rains arrived more than three weeks late and were unusually heavy, accompanied by violent hailstorms. Along with the rains, temperatures also dropped.

Ibrahim Mughal, chairman of the Pakistan Agri Forum, says excessive moisture due to heavy bouts of late rain is likely to lead to outbreaks of fungus on crops, and production could be halved.

“If the rains come a month ahead of the harvesting time [April to mid-May], it is always disastrous,” he says. “It can hit production for a crop such as wheat by between 20% and 30%, and if the rain is accompanied by hailstorms and winds then the losses can escalate to more than 50%.”

Arif Mahmood, a former director general at PMD, says the onset of winter across much of Pakistan is being delayed by two to three days every year, and there is an urgent need for farmers to adapt to such changes.

“If the rains come a month ahead of the harvesting time, it is always disastrous”

“Over recent years, winter has been delayed by 25 to 30 days, and also the intensity of the cold has increased, which has affected almost every field of life − from agriculture to urban life.”

This year has also been marked by abrupt changes in temperature. Ghulam Rasul, a senior scientist at PMD, says big swings in temperature are likely to add to the problems being faced by millions of farmers in Pakistan.

“The average temperature during the first two weeks [of March] was between 11 and 13 degrees Celsius, but now it’s on a continuous upward trend and has reached 26˚C over the space of two days,” he reports.

“The winter rains in the north and central area of Pakistan, and the sudden rise and fall in temperature, are related to climate change.”

Serious damage

Similar storms and late winter rains have also caused serious damage across large areas of northern India.

The states of Uttar Pradesh and Maharashtra – the two most populous states in the country – have been particularly badly hit.

In Maharashtra, snow and landslides have blocked roads and cut off towns and villages.

In Uttar Pradesh, there are fears that more than 50% of the wheat crop has been lost in the eastern part of the state. – Climate News Network

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Forecast of less stormy weather is not good news

Forecast of less stormy weather is not good news

Scientists say intense droughts and heatwaves are the likely climate-related outcome of less frequent summer storms in recent decades.

LONDON, 14 March, 2015 − Storms on fine summer days might be unwelcome to many, but at least the rain and winds does act like a big brush on the weather system − bringing fresh air and relief from oppressive heat.

And scientists now warn that a decrease in the frequency of such storms across much of the US, Europe and Russia in recent decades − with climate change the probable cause – could mean that summer heat waves and droughts are likely to become ever more persistent and intense.

Scientists from the Potsdam Institute for Climate Impact Research (PIK) in Germany report in Science journal that storm activity data they collected from weather stations and satellites shows a clear reduction in the frequency and intensity of summer storms in the mid-latitudes of the northern hemisphere over recent decades.

Heat extremes

This makes heat extremes – such as the period of intense heat that hit Russia in 2010, causing widespread crop failure and multiple wildfires – ever more likely.

“While you might expect reduced storm activity to be something good, it turns out that this reduction leads to a greater persistence of weather systems in the northern hemisphere mid-latitudes,” says Dim Coumou, an Earth systems analyst at PIK and lead author of the study.

“In summer, storms transport moist and cool air from the oceans to the continents, bringing relief after periods of oppressive heat. Slack periods, in contrast, make warm weather conditions endure, resulting in the build-up of heat and drought.”

The PIK study looks at a particular set of turbulences − called synoptic eddy − in weather systems over the summer months, and calculates the total energy of their wind speeds.

“Climate change disturbs airstreams that are
important for shaping our weather”

It shows that the level of this energy, which measures the interplay between the intensity and frequency of high and low pressure systems in the atmosphere, has dropped by approximately 10% over the past 35 years.

Previous studies have focused mostly on winter storms, which tend to do more damage than those in summer. The PIK study found that average storm activity in the winter months in many regions is largely unchanged.

The Arctic region probably holds the key to the drop in summer storm activity, say the scientists.

Temperatures around the globe are rising due to greenhouse gas emissions caused by the burning of fossil fuels, but the rate of warming is faster in the Arctic.

As the sea ice cover in the Arctic shrinks, the surface reflects less sunlight and absorbs more heat. The warmer waters then warm the air, setting in motion a process through which the relative difference in temperature is reduced between the cold polar region and the rest of the northern hemisphere.

Air circulation

Temperature differences drive air circulation. As the difference in temperatures between the two regions decreases, so does the rate of summer storm activity.

The study also found that this reduction in the temperature differential weakens the polar jet stream, which − often travelling at speeds of more than 200 miles per hour high up in the troposphere − acts as a boundary between the cold polar air and warmer air further south.

“From whichever angle we look at the heat extremes, the evidence we find points in the same direction,” Dim Coumou says.

“The heat extremes do not just increase because we’re warming the planet, but because climate change disturbs airstreams that are important for shaping our weather.

“The reduced day-to-day variability that we observed makes weather more persistent, resulting in heat extremes on monthly timescales. So the risk of high-impact heat waves is likely to increase.” – Climate News Network

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Warming raises drought’s threat to California

Warming raises drought's threat to California

US researchers say climate change, not random chance, is likely to be causing California’s long drought, one of the worst on record.

LONDON, 3 March, 2015 –  Climate change could be driving the sustained Californian drought. Arid spells have been more frequent in the last two decades than in the preceding century. And warmer global temperatures linked to man-made climate change could be at the heart of it.

Right now, California is in the sustained grip of one of its worst-ever droughts. Noah Diffenbaugh of Stanford University in California and colleagues looked at the patterns of precipitation, temperature and drought in the historical record and report in the Proceedings of the National Academy of Sciences that the latest conditions were not just a random outcome.

In a sunlit landscape with a long record of intermittent drought, researchers make such predictions only cautiously. But the Stanford team worked through 120 years of rainfall, snowfall and temperature data to identify connections.

They found that, puzzlingly, the two sets of measurements were not directly connected: for the first 60 or 70 years of the historical record, it could be wet and warm, or cool and dry. But drought was more likely in those years that by chance were both dry and warm.

Doubled risk

“Of course low precipitation is a prerequisite for drought but less rain and snowfall alone don’t ensure a drought will happen. It really matters if the lack of precipitation happens during a warm or a cool year,” said Dr Diffenbaugh.

“We’ve seen the effects of record heat on snow and soil moisture this year in California and we know from this new research that climate change is increasing the probability of those warm and dry conditions occurring together.”

On the flip-a-coin analogy, the weather could be either wet or dry, and cold or hot. So only one time in four, the weather was both hot and dry. For most of the past two decades, years in California have been either warm, or hot.

“Now the temperature coin is coming up tails most years. So even though the precipitation coin is coming up tails only half the time, it means that over the past two decades we have gotten two tails-warm and dry in half the years, compared with only a quarter of years in the preceding century.”

Most populous

Accordingly, drought frequency has doubled. Model simulations suggest that the risk of any year being both warm and dry will continue. More frequent warm years will also increase the probability of multi-year drought.

The present drought is now in its fourth year, and is one of the longest consecutive periods during which conditions are severely dry and severely warm.

And soon California – home to one in eight Americans, and the country’s most populous state – could enter a climate regime in which the risk that every year will be warmer than the 20th century norm will be almost 100%.

The findings, said Dr Diffenbaugh, provide “very strong evidence that global warming is already making it much more likely that California experiences conditions that are similar to what we have already experienced during the current severe drought.” – Climate News Network

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Climate change is likely factor in Syria’s conflict

Climate change is likely factor in Syria’s conflict

Researchers say climate change probably caused the savage drought that affected Syria nearly a decade ago − and helped to spark the country’s current civil war. 

LONDON, 2 March, 2015 – In a dire chain of cause and effect, the drought that devastated parts of Syria from 2006 to 2010 was probably the result of climate change driven by human activities, a new study says.

And the study’s authors think that the drought may also have contributed to the outbreak of Syria’s uprising in 2011.

The drought, which was the worst ever recorded in the region, ravaged agriculture in the breadbasket region of northern Syria, driving dispossessed farmers to the cities where poverty, government mismanagement and other factors created the unrest that exploded four years ago. The conflict has left at least 200,000 people dead, and has displaced millions of others.

The study, by scientists from Lamont-Doherty Earth Observatory at Columbia University, US, is published in the Proceedings of the National Academy of Sciences.

The authors are quite clear that the climatic changes were human-driven (anthropogenic) and cannot be attributed simply to natural variability, but are careful to stress that their findings are tentative.

“We’re not saying the drought caused the war,” says Richard Seager, one of the co-authors. “We’re saying that, added to all the other stressors, it helped kick things over the threshold into open conflict.

“And a drought of that severity was made much more likely by the ongoing human-driven drying of that region.”

Link with violence

Their study, although it contains new material, is not the first to suggest a possible link between extreme weather and the likelihood of violence.

Some researchers have investigated whether there may be a link between El Niño and La Niña − the periodic Pacific weather disruptions − and outbreaks of unrest.

Syria was not the only country affected by the drought. It struck the Fertile Crescent, linking Turkey, Syria and Iraq, where agriculture and animal herding are believed to have started around 12,000 years ago.

Suggestions of a global connection between climate change and political instability is being taken seriously by two influential groups − insurers and military planners.

The Levant has always seen natural weather swings. Other research has suggested that the Akkadian empire, spanning much of the Fertile Crescent about 4,000 years ago, probably collapsed during a long drought.

Drought can lead to devastating consequences when coupled with pre-existing acute vulnerability

But the authors of the Lamont-Doherty study, using existing studies and their own research, showed that the area has warmed by between 1°C and 1.2°C since 1900, and has undergone a 10% reduction in wet-season precipitation.

They say this trend is a neat match for models of human-influenced global warming, and so cannot be attributed to natural variability.

Global warming has had two effects, they say. First, it appears to have indirectly weakened wind patterns that bring rain-laden air from the Mediterranean, reducing precipitation during the usual November-April wet season. And higher temperatures have increased the evaporation of moisture from soils during the hot summers.

The authors say an episode of this severity and length would have been unlikely without the long-term changes.

Other researchers have observed the long-term drying trend across the Mediterranean region, and have attributed at least part of it to anthropogenic warming.

The researchers say Syria was especially vulnerable because of other factors − including a huge increase in population from four million in the 1950s to 22 million in recent years.

Water-intensive crops

The government has also encouraged water-intensive export crops such as cotton, while illegal drilling of irrigation wells depleted groundwater, says co-author Shahrzad Mohtadi, an international affairs consultant at the US Department of State.

The drought’s effects were immediate and overwhelming. Agricultural production − typically, a quarter of Syria‘s gross domestic product − fell by a third. In the northeast, livestock was practically wiped out, cereal prices doubled, and nutrition-related diseases among children increased steeply.

As many as 1.5 million people fled from the countryside to cities already strained by waves of refugees from the war in neighbouring Iraq.

“Rapid demographic change encourages instability,” the authors say. “Whether it was a primary or substantial factor is impossible to know, but drought can lead to devastating consequences when coupled with pre-existing acute vulnerability.”

Solomon Hsiang, professor of public policy at the University of California, Berkeley, says the study is “the first scientific paper to make the case that human-caused climate change is already altering the risk of large-scale social unrest and violence”. – Climate News Network

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Big cities head for water crisis as populations explode

Big cities head for water crisis as populations explode

With more than half the world’s population now in cities, scientists warn that inadequate surface water supplies will leave many at increasing risk of drought.

LONDON, 21 February, 2015 − More than 40% of the world’s great cities supplied by surface water could become vulnerable to shortages and drought by 2040, according to new research. And more than three out of 10 were already vulnerable in 2010.

Meanwhile, the vital array of satellites designed to monitor rainfall and to warn of potential flooding is reported to be coming to the end of its shelf life.

For the first time in history, more than half the world’s population is now concentrated in cities, and this proportion is predicted to increase to two-thirds. Cities grow up near plentiful water supplies − and as a population explodes, so does demand. But the flow remains much the same.

Some cities are already under drought stress. Chennai in southern India had to be supplied with tankers in 2004 and 2005, and São Paulo in Brazil is now at crisis point.

Supply analysis

Environmental scientist Julie Padowski and Steven Gorelick, director of the Global Freshwater Initiative at Stanford University in California, report in Environmental Research Letters that they analysed supplies to 70 cities in 39 countries, all of them with more than 750,000 inhabitants, and all of them reliant on surface water.

They defined vulnerability as the failure of an urban supply basin to meet demands from human, environmental and agricultural users, and they set the supply target as 4,600 litres per person per day – which factors in “virtual water”, defined as the total volume of water needed to produce and process a commodity or service.

They proposed three different kinds of measure of supply. If a city failed to meet one or two of these metrics, it was considered threatened. If it failed to meet all three, it was rated as vulnerable.

Importantly, the scientists did not factor in climate change, which is likely to make conditions worse. Instead, they simply considered current demand and supply, and then projected demand in 2040.

Of their 70 cities, they found that 25 (36%) could already be considered vulnerable by 2010. By 2040, this number had grown to 31 (44%).

The six cities that will begin to face water shortages are Dublin in Ireland, Charlotte in the US, Ouagadougou in Burkina Faso, and Guangzhou, Wuhan and Nanjing in China.

Most of the cities that are already vulnerable rely on reservoirs, and the study implies that urban planners will need to think about more reservoirs, deeper wells or desalination plants, or will have to contemplate the diversion of rivers from somewhere else.

Rainfall data

Meanwhile, they cannot rely on rainfall data because – as geological engineer Patrick Reed, professor of civil and environmental engineering at Cornell University, and colleagues report in Environmental Research Letters − the network of dedicated satellites “fails to meet operational data needs for flood management”.

Four of the 10 satellites have exceeded their design life − some by more than a decade. There are already weak spots in the network, especially in developing countries, which means that floods could take people by surprise.

Space-based instruments offer a way of monitoring rainfall and ground moisture upstream, in a way that gives authorities time to predict the moment when the rivers will start to rise and flood the cities. When four fail to deliver, the potential for catastrophe will be even worse.

So the scientists call for better international co-ordination of satellite replacement.

“It is important for us to start thinking as a globe about a serious discussion on flood adaptation and aiding affected populations to reduce their risks,” Professor Reed says. “We want to give people time to evacuate, to make better choices, and to understand their conditions.” – Climate News Network

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