Record torrential rainfall linked to warming climate

Record torrential rainfall linked to warming climate

Scientists show that devastating increases in extreme rainfall over the last 30 years fit in with global temperature rise caused by greenhouse gases.

LONDON, 13 July, 2015 – If you think you’re getting an unusually hard soaking more often when you go out in the rain, you’re probably right.

A team of scientists in Germany says record-breaking heavy rainfall has been increasing strikingly in the last 30 years as global temperatures increase.

Before 1980, they say, the explanation was fluctuations in natural variability. But since then they have detected a clear upward trend in downpours that is consistent with a warming world.

The scientists, from the Potsdam Institute for Climate Impact Research (PIK), report in the journal Climatic Change that this increase is to be expected with rising global temperatures, caused by greenhouse gas emissions from burning fossil fuels.

High-impact flooding

Short-term torrential rains can lead to what the team calls “high-impact” flooding. For example, extreme rainfall in Pakistan in 2010 brought devastation that killed hundreds of people and led to a cholera outbreak.

In the same year, rainstorms in Texas caused dozens of flash floods. And no fewer than three “once-in-a-century” floods in Germany all happened in just a couple of years from 1997.

“In all of these places, the amount of rain pouring down in one day broke local records – and while each of these individual events has been caused by a number of different factors, we find a clear overall upward trend for these unprecedented hazards,” says the lead author, Jascha Lehmann, a PIK researcher into climate impacts and vulnerabilities.

Statistical analysis of rainfall data from 1901 to 2010, derived from thousands of weather stations around the globe, shows that from 1980 to 2010 there were 12% more of these intense events than would be expected in a climate without global warming. In the last year of the period the team studied, there were 26% more record-breaking daily rainfall events globally.

“One out of 10 record-breaking rainfall events in the past 30 years can only be explained if
the long-term warming is taken into account”

Not all parts of the world are experiencing a similar pattern of soaking. The PIK scientists found that − possibly not surprisingly − wet regions generally saw a bigger increase in deluges and drier regions a smaller one.

In southeast Asia, the observed increase in record-breaking rainfall events is as high as 56%, in Europe 31%, and in the central US it is a more modest, but still worrying, 24%.

In marked contrast, some regions have experienced significantly fewer record-breaking daily rainfall events. In the Mediterranean, the reduction is 27%, and in the western US it is 21%. Both regions are at risk from severe droughts.

The team says there is a simple scientific explanation for what they report. They compared their findings with existing knowledge about how much more water the atmosphere can store when temperatures rise, described by what they call the well-known Clausius-Clapeyron equation.

Put simply, warmer air holds more moisture, which can be released during short-term heavy rainfall.

The scientists show that the observed increase in unprecedented heavy rainfall generally fits with this thermodynamically expected increase under global warming.

Upward trend

“One out of 10 record-breaking rainfall events observed globally in the past 30 years can only be explained if the long-term warming is taken into account,” says co-author Dim Coumou, a PIK researcher into the links between atmospheric circulation and extreme weather events. “For the last year studied, 2010, it is even one event out of four, as the trend is upward.”

There are, of course, qualifications to the broad picture. For instance, the scientists allowed for the fact that the quality of historic weather data differs from one place to another. Unsurprisingly, rainfall measurements from the Sahara desert are scarce, so the team avoids drawing conclusions for the region.

But rainfall in regions such as Europe and the US has been carefully monitored for over a century, allowing the authors to draw conclusions with high levels of confidence

“The pronounced recent increase in record-breaking rainfall events is, of course, worrying,” Coumou says. “Yet since it is consistent with human-caused global warming, it can also be curbed if greenhouse gas emissions from fossil fuels are substantially reduced.” – Climate News Network

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Australia faces stormy future as temperatures soar

Australia faces stormy future as temperatures soar

Destructive storms and sudden floods are set to intensify across Australia as global warming plays havoc with rainfall patterns.

LONDON, 13 June, 2015 − New research into storm patterns warns that flash floods are likely to sweep across the Australian landscape with increasing intensity, particularly in urban or residential areas.

Peak rainfall is predicted to soar with rising surface temperatures as the world’s largest island – and also its smallest continent − experiences ever greater extremes of heat.

Civil engineers from the Water Research Centre at the University of New South Wales (UNSW) report in Nature Geoscience that they looked at 40,000 storms across the whole of the continent over the last 30 years and identified a pattern that warmer temperatures are linked to disruptive rainfall events.

“Our results were consistent across all the climate zones in Australia, regardless of season or storm type, without exception,” says Professor Ashish Sharma, one of the study’s authors.

Unexpected finding

“This was an unexpected finding, and it supports our hypothesis that increasing temperatures are changing rainfall patterns. It means that most people in Australia can expect to see intensification in the magnitude of flash flooding in smaller catchments, particularly in urban or residential areas.”

The researchers worked from data from the 500 largest storms as measured by total rainfall at 79 locations. They looked not so much at the total volume of rainfall during a storm as at the pattern of intensity of rainfall at 12-minute intervals during each storm’s duration.

“It’s very likely these same trends will be observed around the world”

They projected their findings into a hotter world and calculated that a 5°C rise in temperatures could be accompanied by up to 20% more flood peaks in urban catchment areas. Some cities could experience much worse: for Perth, the rise is projected at 10%, for Sydney 12%, and for Darwin a whopping 45%.

Australia is a landscape of extremes of heat and drought and occasional devastating flood. It is also a land of paradox.

Its own scientists have calculated that the island’s most recent and devastating heatwaves are a clear consequence of greenhouse gas emissions from fossil fuels, yet the government that finances such research has questioned the validity of its climate science and encouraged the increase of emissions.

Lost productivity

The 2013 extremes of heat cost the nation an estimated US$6bn in lost productivity, and there is evidence that such events could become five times more likely as global average temperatures rise.

The intensification of dangerous flash floods − which, by definition, are sudden and potentially lethal − is a consequence that nobody expected. And if the team’s finding is replicated by further studies, then the impact is not likely to be limited to Australia.

“These more intense patterns are leading to more destructive storms, which can significantly influence the severity of flood flows,” says the reports lead author, Conrad Wasko, from the UNSW School of Civil and Environmental Engineering.

“The climate zones we studied in Australia are representative of most global climates, so it’s very likely these same trends will be observed around the world.” – Climate News Network

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India’s coastal villages map out disasters strategy

India’s coastal villages map out disasters strategy

The Indian Ocean can be an angry and sometimes lethal neighbour, but those who live beside it are now learning how to prepare for its next onslaught.

CHENNAI, 26 May, 2015 – It has been over a decade since the devastating tsunami struck southeast Asia, but the horrific memories remain as vivid as ever for people in the coastal villages of the south Indian state of Tamil Nadu.

Now, in the aftermath of the 2004 tsunami and also two cyclones, local people are benefiting from the Indian government’s encouragement of international co-operation in helping vulnerable communities, and have produced a hazard map as a precaution against future disasters.

Vikas Shankar, from the fishing village of Sulerikattukuppam, remembers clearly the moment the tsunami struck.“I was engrossed in playing cricket when I saw water entering the village,” he says. “I thought it was just another day when the sea poured in. Then, suddenly, I saw my mother caught in a whirlpool and realised something was seriously wrong.”

His mother, Tilakavathy, survived the tsunami’s fury, but recalls: “I thought this was really the end of the world.”

Completely destroyed

Amazingly, no one in the village died, but fishermen lost their gear and livelihoods, and many buildings close to the shore were completely destroyed.

The tsunami prompted Tilakavathy and her husband to decide not to send their sons to sea to earn a livelihood.

When Vikas, their youngest son, was old enough, he was sent instead to the local community college, built in 2011 by the state government to provide education and alternative livelihood opportunities for the fishing community.

The local people, recognising the need for disaster preparedness, are now involved in a programme that focuses on  developing communication tools for vulnerable communities and raising awareness of other disaster-related issues.

Krishnamurthy Ramasamy, professor of applied geology at the University of Madras, was formerly the principal of the community college. He says: “We realised the need for international collaboration to build a curriculum on disaster management and field-based learning activities.”

Kyoto University in Japan was one of the universities keen to work with him, and two Australian universities, Melbourne and Victoria, also joined in, helping with funds, curriculum development and exchange visits.

“We were taught how and why cyclones and tsunamis happen. It helped us to understand disasters in the first place.”

The college itself fostered community-based preparedness by offering disaster management as an optional subject, and by helping to set up a Local Residents’ Alliance (LRA) in 2013 to mobilise villagers. Most members of this group were parents of students from the college.

Vikas Shankar says: “In the class, we were taught how and why cyclones and tsunamis happen. It helped us to understand disasters in the first place.”

To learn about other people’s best practices, Professor Ramasamy visited communities along the Japanese coast, and there he made a significant discovery. He says: “The first thing I noticed in each village was the hazard map. I thought that we needed this too.”

Back at the college, work on hazard map preparation began, and the first step was students surveying their own villages to understand the geography better.

Teams went from house to house and marked all the huts in the village. They counted the number of people in the house, with details of numbers of women, children, old and disabled people living there. All this information went on the hazard map.

Miwa Abe, from the Centre for Policy Studies at Kumamoto University, Japan, who trained the Indian students, says: “A hazard mapping exercise with local people gives them an opportunity to know their village.

“It is not only about environmental conditions, but also human relationships, social networks, architectural conditions. Usually people do not think about their own area because it is too familiar to them.”

Evacuation routes

The teams also prepared evacuation routes, and, after six months of rigorous work, the students presented the final map to the local people.

Today, as one walks into the village, the first thing to catch the eye is the big blue hazard map board at its entrance. It shows the evacuation routes to be followed during disasters, and also the village’s population distribution − crucial information so that local people will know who to rescue first, and where they live.

The village’s approach is now being used as a case study in efforts to prepare community-based disaster management (CBDM) plans for the entire district, and eventually as a model for the state. The Tamil Nadu government has given land adjacent to the college to establish permanent infrastructure and to provide better facilities for the students.

Rajalakshmi Mahadevan, a fisherman’s daughter, says: “The evacuation map can be read by anyone, even a newcomer. Now we know which house to go to, who to evacuate first, and this has lifted the fear of disaster from local people’s minds.”– Climate News Network

  • Sharada Balasubramanian, an independent journalist from Tamil Nadu, India, writes on energy, agriculture and the environment. Email: sharadawrites@gmail.com; Twitter: @sharadawrites

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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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Flood risk to nuclear sites raises meltdown fears

Flood risk to nuclear sites raises meltdown fears

Sea level rise, storm surges and bursting dams all pose an increasing danger to nuclear power stations as the climate changes.

LONDON, 5 May, 2015 – Safety checks following the Fukushima disaster in Japan in March 2011, when a 10 metre-high sea wall was overtopped by a tsunami, have shown that nuclear plants are at greater risk of catastrophic flooding as a result of climate change.

All nuclear plants need large quantities of water for cooling so all must be built close to the sea, large rivers or lakes. This makes them vulnerable to sea level rise, storm surges and to the possible collapse of large dams upstream from poor construction, floodwater or seismic activity.

Since nuclear plants are designed to operate for as long as 60 years and need around a further century to decommission, accelerating sea level rise and more intense rainfall may present serious problems.

There are currently 435 operating nuclear reactors in the world, many of them potentially vulnerable to flooding because of natural disasters. Examples from the UK, Finland and the US show that the extent of the danger is not always being disclosed.

In Britain, after discovering in May 2013 that one of their reactors would be at risk during a storm of inundation by seawater, the owners, EDF Energy, quietly shut it down. The reactor, at Dungeness and built on a shingle beach beside the English Channel, supplies 750,000 homes.

The company informed the Office for Nuclear Regulation that it was being shut down as a precaution. The reactor remained off-line until 15 October that year while a new sea wall was constructed – losing the company around £100 million in revenue.

Serious problem

Although the company did announce the closure at the time, the extent of the problem and the length of the shutdown were not announced. Later EDF admitted that the emergency works had taken place following an assessment of the flooding danger after the Fukushima disaster.

Stephen Thomas, professor of energy policy at the university of Greenwich in London,
criticised EDF for its attitude. He was quoted by the UK’s Independent newspaper as saying: “If a plant closes for five months it is not just fiddling about, it is something serious, and EDF can’t pretend it is not…we need to be told the truth.”

The same fears were raised in the US by the Union of Concerned Scientists after a report was leaked about the danger to nuclear reactors from dams bursting. According to a report by the US Nuclear Regulatory Authority (NRC), which had been withheld, more than 30 nuclear installations were in danger from flooding. The Commission was later accused of using security concerns to mask embarrassing information.

Higher odds

Among many revelations in the report was the fact that the authorities had known for a decade or more that the failure of a dam upstream from the Oconee nuclear plant in South Carolina would cause floodwater to overwhelm its three reactors, possibly causing a catastrophic meltdown. The odds of the dam bursting were far higher than the chances of the accident that devastated Fukushima.

Oconee is one of the largest nuclear plants in America and has been operating since 1983. Its owner, Duke Energy, remains confident that it could shut the plant down safely in an hour, before floodwaters from upstream could reach the reactors. The NRC has decided that this is sufficient safeguard.

Dave Lochbaum, director of the Nuclear Safety Project at the Union of Concerned Scientists, said: “The NRC knows – and has known for many years – that flooding from dam failures can disable the emergency equipment needed to prevent reactor core meltdown.

“The risk of a serious nuclear accident remains always above zero as a result of unexpected phenomena taking place”

“The agency must require plants to address known flooding hazards and thoroughly investigate other plants that may be at risk and require them to resolve any potential hazards.

“If such a flooding accident occurred, the NRC would quickly determine which other plants were vulnerable and require them to strengthen their protection against similar events. Wouldn’t it be smarter for the agency to do that before an accident occurs?”

More open about its problems is Finland’s Loviisa nuclear power plant on the Baltic Sea, which was flooded by a 1.73-metre storm surge in 2005. Since then four cooling towers have been built 10 metres above sea level to avoid inundation in a new storm surge, and new floodgates and waterproof doors have been installed to protect the reactor. A new road has been built above flood level so that emergency services can reach the plant to pump away floodwater.

Even so, the Rain Project, a consortium of experts on safety and climate change, thinks more can be done to protect against potential disaster. Christer Pursianen is professor of societal safety and environment at the Arctic University of Norway.

He says that although Finland is in the forefront of nuclear safety, more needs to be done to train staff in emergencies and to develop  links with neighbouring countries so as to gain experience in disaster prevention: “The risk of a serious nuclear accident remains always above zero as a result of unexpected phenomena taking place.” – Climate News Network

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Rich nations urged to cut temperature rise targets

Rich nations urged to cut temperature rise targets

Senior scientist says voices of poorer nations must be heard in the political tussle over reducing the “utterly inadequate” global warming limit.

LONDON, 31 March, 2015 − The official target of limiting global warming to a 2˚C rise has been described by a senior scientist as “utterly inadequate” to protect the people most at risk from climate change.

That’s the conclusion reached by one of the authors of the recent Intergovernmental Panel on Climate Change (IPCC) assessment report, in an analysis of the political tussle between rich and poor nations at last December’s UN conference on limiting temperature rise.

Richer countries were happy to limit global average temperature rises to 2˚C, while middle and low-income nations would have preferred to contain warming within 1.5˚ C or lower.

Possibilities of calamity

But Dr Petra Tschakert, associate professor at Pennsylvania State University’s Earth and Environmental Systems Institute, reports in the journal Climate Change Responses that the agreed limit contains within it the possibilities of calamity for many people.

“The consensus that transpired during this [UN conference] session was that a 2˚C danger level seemed utterly inadequate, given the already observed impacts on ecosystems, food, livelihoods and sustainable development,” Dr Tschakert says.

“A low temperature target is the best bet to prevent severe, pervasive and potentially irreversible impacts, while allowing ecosystems to adapt naturally, ensuring food production and security, and enabling economic development to proceed in a sustainable manner.”

Her analysis is not of itself new, nor is it much disputed − other leading scientists have also warned that such an international agreed limit could be disastrous.

But her commentary in the journal reveals something of the debate among the government representatives and experts who must meet and prepare for global action.

Global average temperatures have been creeping up at fractions of a degree per decade for more than 30 years, and some degree of further global warming is now inevitable.

Scientists at the IPCC have from the start warned that – without steps to dramatically reduce the combustion of fossil fuels – the planet could warm by 4˚C or more, and sea levels could rise by up to a metre by 2100. In 2009, governments met in Copenhagen and settled on a limit of 2˚C.

“This should happen now, and not only when climate change hits the rich world”

But this target has always been contested. More than 100 poorer nations and small island states − such as Tuvalu, recently pounded by a tropical cyclone Pam − have repeatedly said that a 2˚C rise is unsafe, and called for a 1.5˚C limit.

The World Health Organisation argued at the December UN meeting that, as far as human health was concerned, there was no safe limit, and people already faced hazards from undernourishment, and from food and water-borne infections.

Heatwaves, such as the one that hit Russia in 2010, may have caused 10,000 additional deaths, while floods, hurricanes and other extreme weather events are likely to be more frequent and more severe hazards in a 2˚C world.

Climate impacts

Dr Tschakert’s argument is that a global average limit may be a convenient and compelling instrument for discussing climate change impacts, but nobody in the world actually faces a global average.

Such a notional limit is the average of extremes and variation across regions, all of which are subject to different hazards − ranging from glacial melting to coral bleaching − that could be disastrous for people in those regions, many of whom are among the world’s poorest.

Dr Tschakert says: “These implications emphasise what is truly at stake – not a scientific bickering of what the most appropriate temperature target ought to be, but a commitment to protect the most vulnerable and at-risk populations and ecosystems, as well as the willingness to pay for abatement and compensation..

“This should happen now, and not only when climate change hits the rich world.” – 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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Shrinking of ice shelves raises sea level concerns

Shrinking of ice shelves raises sea level concerns

Evidence of rapid reduction of West Antarctica’s shelf ice could have serious implications for global sea levels in a warming world.

LONDON, 29 March, 2015 – Scientists in the US report that the volume of Antarctic shelf ice is diminishing, and that there has been an 18% shrinkage in the mass of some ice floating on coastal waters over the last 18 years.

And because much of the loss has been off West Antarctica, where shelf ice helps to keep the ice sheet stable, it could mean that global sea levels will rise even faster as a result of increased glacial flow into the ocean.

The findings once again raise concern about the link between man-made emissions of greenhouse gases and the dangerous new world of global warming, climate change and sea level rise.

Fernando Paolo, a researcher at the Scripps Institution of Oceanography at the University of California, San Diego, and colleagues report in the journal Science that they used continuous radar altimetry measurements − taken from three European Space Agency satellites between 1994 and 2012 − to compose a high-resolution record of shelf ice thickness.

Declined swiftly

They found that the total volume of shelf ice – the thickness multiplied by the shelf area – around Antarctica stayed more or less the same from 1994 to 2003, but then declined very swiftly.

The ice shelves of West Antarctica lost ice during the entire period, and although East Antarctica had been gaining shelf ice, these gains ceased after 2003. Some shelves had lost 18% of their volume.

“Eighteen per cent over the course of 18 years really is a substantial change,” Paolo says. “Overall, we show not only that the total ice shelf volume is decreasing, but we see an acceleration in the last decade.”

Shelf ice is frozen sea, so when it melts, it makes no difference to sea levels. But there could be an indirect effect.

“The ice shelves buttress the flow from grounded ice into the ocean, and that flow impacts sea levels rise, so that’s a key concern from our new study,” says co-author Helen Fricker, a glaciologist at the Scripps Institution.

In climate science, one such study is never enough: such conclusions need support from other studies. But the ice volume measurements are likely to add to growing concern about West Antarctica.

“The ice shelves buttress the flow from
grounded ice into the ocean, and that
flow impacts sea levels rise”

One earlier study looked at the potential loss of ice from West Antarctica by examining the “grounding lines” of the terrestrial glaciers, and found evidence of continuous and accelerating retreat. In effect, the West Antarctic ice sheet could be approaching a point of no return, scientists reported.

And a second group used other satellite measurements to calculate that ice was being lost from the southern continent at an increasing rate – around 150 cubic kilometres a year from West Antarctica.

So the Scripps study indirectly backs up earlier findings. It calculates that most mass has been lost from ice shelves in the Amundsen and Bellingshausen seas, off the coast of West Antarctica. These account for less than 20% of the total West Antarctic ice-shelf area, but contribute more than 85% of the total ice-shelf volume loss from West Antarctica.

Slow process

Were the West Antarctic ice sheet to melt completely – a long, slow process at almost any temperatures – sea levels would rise by more than three metres worldwide.

At current rates, a couple of the ice shelves off the western coast of the continent could disappear completely within 100 years, the Scripps team says.

Although the Arctic is one of the fastest-warming places on the planet, and although this warming has been directly linked to man-made climate change, the pattern of temperature shifts in the southern hemisphere has been more ambiguous.

The Scripps team have now begun to think about possible reasons for the loss of shelf ice in the far south, and one factor might be the cycle of El Niño events – natural and periodic bubbles of Pacific ocean warmth that have waxed and waned at intervals and changed the prevailing weather patterns worldwide through history.

“We’re looking into connections between El Niño events in the tropical Pacific and changes in the Antarctic ice sheet,” Paolo says. “It’s very far apart, but we know these teleconnections exist. That may ultimately allow us to improve our models for predicting future ice loss.” – Climate News Network

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Eyes in the sky see seas rising alarmingly faster

Eyes in the sky see seas rising alarmingly faster

Scientists analysing sophisticated satellite data warn that rises in sea level more rapid than expected are increasing threats to coastal cities and food security.

LONDON, 27 March, 2015 − Satellite observations show that sea level rise may have been underestimated, and that annual rises are increasing.

A collaborative effort between maritime organisations and space agencies in measuring sea level rise has come to the conclusion that it has been increasing by 3.1 millimetres a year since 1993 – higher than previous estimates.

The evidence is growing from a number of recent studies of the ice caps that sea level rise is accelerating, posing a threat to many of the world’s largest and most wealthy cities − most of which are also important ports.

Many of these in the developing world have little or no protection against rising sea levels. Some in Europe – such as London and Rotterdam − already have flood barriers to protect areas below high tide or storm surge level, but  these will need to be replaced and raised in the next 30 years.

Delta areas in Egypt, Vietnam, Bangladesh and China – vital to each of the nation’s food supply – are already losing land to the sea.

Difficult to measure

One of the problems scientists have had in getting accurate worldwide data is that the sea does not rise evenly around the globe. This, added to the fact that in some places the land is sinking and in other places is rising, makes exact information difficult to measure from tide gauges.

Since 1991, it has been possible to measure the surface of the oceans across the entire globe by using satellite altimetry, whereby the satellite emits a signal towards the ocean’s surface and receives the reflected echo. The sea level is calculated from the round-trip time between the satellite and the sea surface and the position of the satellite along its trajectory.

While the data from tide gauges provides information about local changes relative to the land, the use of altimeter satellites enables the recording of data on a global basis.

Luciana Fenoglio-Marc, a scientist specialising in physical and satellite geodesy at the Technical University of Darmstadt, Germany, uses these and other satellite geodetic observation data in her research.

She is working with the European Space Agency and the European Organisation for the Exploitation of Meteorological Satellites, and in close consultation with the German Federal Institute of Hydrology and the Federal Maritime and Hydrographic Agency of Germany.

This lends credibility to the report that European coastal cities are not sufficiently prepared for the threats that climate change poses

The increase of around 3.1mm per year since 1993 indicates a marked rise in the average sea level when compared to previously recorded values, which show a sea level rise of between 1mm and 2mm per year in the 20th century.

In its fifth Assessment Report (AR5, 2013), the Intergovernmental Panel on Climate Change (IPCC) predicted a further increase in the global sea level of 30cm to 70cm by the end of the 21st century, based on a scenario involving a medium rate of global warming.

The report predicted that increases will not be even, but will have a greater impact on some regions than on others. The result could be coastal flooding and rising groundwater levels – an outlook that makes it essential to have a reliable data basis for dealing with the dangers this poses.

Protecting coasts from the rising seas will require considerable adaptations, particularly in such low-lying coastal regions as the North Sea coast of Germany and the many low-lying islands in the tropics.

Another aspect of the work with satellites is measuring ocean density to see how much water expansion − because of warming − is leading to sea level rise. A direct estimation of mass changes in the Mediterranean Sea show expansion to be the cause of an average sea level rise of about 2.1mm per year since 1993.

According to the IPCC, about 35% of the sea level increase between 1993 and 2010 was the result of thermal expansion, and the rest was due to melting ice and increasing run-off from land. But the latest observation shows this may not be true of the Mediterranean.

Too cautious

There is wide debate about whether the IPCC estimates of sea level rise have been too cautious, suggesting that the sea level will rise more than a metre this century – and some have even suggested that the rise could be two metres.

This is mainly because there has been uncertainty about how much of the huge icecap in Greenland, and most of all in Antarctica, would contribute to sea level rise by 2100 – if at all.

Research published since the IPCC estimates were made show that both icecaps will be large net contributors to sea level rise, and possibly much quicker than previously thought.

This lends credibility to the report last week that European coastal cities are not sufficiently prepared for the threats that climate change poses. The report − titled Underfunded, Unprepared, Underwater? Cities at Risk – is by the E3G non-governmental organisation, and it says governments across the European Union are leaving their major cities exposed to danger from climate change, including floods, heat waves and sea level rise.

Since it takes an average of 30 years from planning to complete construction of a major flood barrier to protect a city, the report warns that the problem needs to be given urgent consideration and funding. – Climate News Network

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Population increases flood and drought threat to cities

Population increases flood and drought threat to cities

As cities worldwide expand to cope with rising populations, scientists predict a huge increase in urban land vulnerable either to flooding or drought by 2030.

LONDON, 11 March, 2015 − Many of the great coastal cities of America, Asia and Africa will be at increased risk of damaging floods − even without the increasing effects of climate change.

And there will be problems with the other extreme, as scientists also predict that the urban area exposed to drought would double by 2013.

Burak Güneralp, a geographer at Texas A&M University, and colleagues report in the journal Global Environmental Change that by 2030 almost 5 billion people will live in cities, and coastal urban areas will spread out over danger zones of low elevation.

In 2000, about 30% of global urban land – 200,000 square kilometres – was in high-frequency flood zones. By 2030, this will have risen to 40%, or 700,000 square kilometres. And there could also be a growth in the urban extent of drylands 500,000 square kilometres.

Exposed area

So the city regions vulnerable to flood would increase 2.7 times, while the area exposed to drought would double.

The report’s authors says that disasters due to water-related hazards – floods, droughts and windstorms − made up nearly 90% of the 1,000 most catastrophic events between 1900 and 2006 − and because of increasing urbanisation, economic losses have soared.

In the 20 years from 1992-2012, flood and drought hazards caused $600 billion in damage, and in 2013, floods and drought accounted for more than a quarter of all global insured losses.

The message from the authors to tomorrow’s urban planners is: watch where you build new developments or permit new settlement.

“Potential future changes in the extent and layout of urban areas are typically ignored in resilience planning for these cities”

“Urban areas exposed to flood and drought hazards will increase considerably due to the sheer increase in their extents, primarily by socioeconomic forces,” Dr Güneralp says. “In particular, coastal megacities will house a majority of the urban populations, and they will increasingly be hubs of significant economic activity in the coming decades.

“Yet potential future changes in the extent and layout of the urban areas are typically ignored in resilience planning for these cities.”

The Texas team made their calculations with geographic information systems, existing urban maps and city growth forecasts. They did so without factoring in climate change, but they warn that all hazards will be amplified by rising average global temperatures.

Human numbers exposed to a once-a-century flooding event in 136 port cities across the world are expected to increase threefold by 2070, and their economic infrastructure –roads, houses, power and water services, offices and factories – will increase tenfold.

Water shortages

Meanwhile, the number of city-dwellers who could face perennial water shortages is expected to increase fivefold by 2050 − to around 160 million people.

The Texas scientists considered the great delta cities of China, Vietnam and India, but they also included the American megalopolises of New York, Baltimore, Houston and Miami, which are all vulnerable in their own ways.

Their research reinforces fresh reminders – on the eve of yet another disaster risk reduction conference, in Sendai, Japan − that global disasters of all kinds claimed 700,000 lives, changed the lives of 1.7 billion people, and cost cities and states at least $1.4 trillion in the last 10 years.

And 87% of these disasters were climate-related, according to the UN International Secretariat for Disaster Reduction. − Climate News Network

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