Tag Archives: Rainfall

Emissions are fuelling Australian droughts

Water depth marker in Lake Albert, South Australia Image: Bidgee via Wikimedia Commons
Water depth marker in the dried out bed of Lake Albert, South Australia
Image: Bidgee via Wikimedia Commons

By Tim Radford

The Australian prime minister may be scathing about climate science, but new research shows that burning fossil fuels is a significant factor in the long-term rainfall decline that is leaving southern regions of the country parched and sweltering.

LONDON, 17 July, 2014 − American scientists have just confirmed that parts of Australia are being slowly parched because of greenhouse gas emissions – which means that the long-term decline in rainfall over south and south-west Australia is a consequence of fossil fuel burning and depletion of the ozone layer by human activity.

Such a finding is significant for two reasons. One remains contentious: it is one thing to make generalised predictions about the consequences overall of greenhouse gas levels, but it is quite another to pin a measured regional climatic shift directly on human causes, rather than some possible as-yet-unidentified natural cycle of climatic change.

The other is contentiously political. Australia’s prime minister, Tony Abbott, has in the past dismissed climate science as “crap”, and more recently has cut back on Australian research spending.

Australia has already experienced a pattern of heat waves and drought – punctuated by catastrophic flooding – and even now, in the Australian winter, New South Wales is being hit by bush fires.

Tom Delworth, a research scientist at the US National Oceanic and Atmospheric Administration, reports in Nature Geoscience that he and a colleague conducted a series of long-term climate simulations to study changes in rainfall across the globe.

Pattern of change

One striking pattern of change emerged in Australia, where winter and autumn rainfall patterns are increasingly a cause of distress for farmers and growers in two states.

The simulation showed that the decline in rainfall was primarily a response to man-made increases in greenhouse gases, as well as to a thinning of the stratospheric ozone layer in response to emissions of destructive gases by human sources.

The computer simulations tested a series of possible causes for this decline, such as volcanic eruptions and changes in solar radiation. But the only cause that made sense of the observed data was the greenhouse explanation.

South Australia has never been conspicuously lush and wet, but decline in precipitation set in around 1970, and this decline has increased in the last four decades. The simulations predict that the decline will go on, and that average rainfall will drop by 40% over south-west Australia later this century.

Dr Delworth described his model as “a major step forward in our effort to improve the prediction of regional climate change”.

In May, scientists proposed that greenhouse gas emissions were responsible for a change in Southern Ocean wind patterns, which in turn resets the thermostat for the world’s largest island.

Australian scientists report in Geophysical Research Letters that they, too, have been using climate models to examine Antarctic wind patterns and their possible consequence for the rest of the planet.

Temperature rise

“When we included projected Antarctic wind shifts in a detailed global ocean model, we found water up to 4°C warmer than current temperatures rose up to meet the base of the Antarctic ice shelves,” said Paul Spence, a researcher at Australian Research Council’s Centre of Excellence for Climate System Science. This temperature rise is twice previous estimates.

“This relatively warm water provides a huge reservoir of melt potential right near the grounding lines of ice shelves around Antarctica,” Dr Spence said. “It could lead to a massive increase in the rate of ice sheet melt, with direct consequences for global sea level rise.”

Since the West Antarctic ice sheet holds enough water to raise sea levels by 3.3 metres, the consequences would indeed be considerable.

“When we first saw the results it was quite a shock,” Dr Spence said. “It was one of the few cases where I hoped the science was wrong.” – Climate News Network

Climate puts US at risk of multi-billion bill

Overheating: US crops such as cotton face a %20 drop in yield Image: Wars via Wikinmedia Commons
Overheated economy: US crops such as cotton face a 20% drop in yield
Image: Wars via Wikimedia Commons

By Alex Kirby

A study of the possible cost of climate change to the US economy warns government and business that billions of dollars could be at risk through damage to property, reduced harvests and workers incapacitated by extreme heat.

LONDON, 29 June, 2014 − The sheer economic cost of climate change to Americans could be far greater than many realise, an influential study says.

The study was commissioned by the Risky Business Project, a research organisation chaired by a bi-partisan panel and supported by several former US Treasury Secretaries.

It expects climate change to have varied impacts across different regions and industries. Rising sea levels, it says, could destroy many billion dollars’ worth of coastal properties by 2050, and warming temperatures, especially in the south, south-west and mid-west, could cut the productivity of people working outdoors by 3%.

Without a change in crops, harvests in these regions could fall by 14%. But further north, in states such as North Dakota and Montana, winter temperatures will probably rise, reducing frost and cold-related deaths and lengthening the growing season for some crops.

Kate Gordon, executive director of the Risky Business Project, said : “We still live in a single integrated national economy, so just because it’s not hot where you are doesn’t mean you won’t feel the heat of climate change.”

Michael Bloomberg, a former mayor of New York, said: “Damages from storms, flooding, and heat waves are already costing local economies billions of dollars. We saw that firsthand in New York City with Hurricane Sandy.

Costs of inaction

“With the oceans rising and the climate changing, the Risky Business report details the costs of inaction in ways that are easy to understand in dollars and cents − and impossible to ignore.”

Hank Paulson, a former Treasury Secretary and co-chair of the Risky Business Project, said the report shows us that “our economy is vulnerable to an overwhelming number of risks from climate change.

“But if we act immediately, we can still avoid most of the worst impacts of climate change and significantly reduce the odds of catastrophic outcomes. But the investments we’re making today will determine our economic future.”

In a section on short-term climate threats, the authors say: “The American economy is already beginning to feel the effects of climate change. These impacts will likely grow materially over the next 5 to 25 years…”

“Just because it’s not hot where you are doesn’t mean
you won’t feel the heat of climate change”

They say there is a 1-in-20 chance of yield losses of more than 20% in corn, wheat, soya and cotton crops over that timespan.

On energy, they say changes in temperature driven by greenhouse gases will probably mean a need to build roughly 200 average coal-fired or natural gas-fired power plants between 2020 and 2045, costing up to $12 billion per year.

Climate impacts, the report says, are unusual because future risks are directly tied to present decisions. By failing to lower greenhouse gas emissions today, decision-makers put in place processes that increase overall risks tomorrow.

By 2050, on present trends, $66bn-$106bn worth of existing coastal property will probably be below sea level nationwide, with $238-$507bn worth by 2100.

By mid-century, the average American will probably see 27 to 50 days over 95°F (35°C) each year − two to more than three times the average annual number of such days seen over the last 30 years. By the end of the century, this number will probably average 45 to 96 days over 95°F each year.

But the study says that the south-west, south-east, and upper mid-west will probably see several months of 95°F days annually.

Human threshold

In the longer term, extreme heat during parts of the year could pass the threshold at which the human body can no longer maintain a normal core temperature without air conditioning. At these times, anyone who has to work outdoors, or without access to air conditioning, will face severe health risks and possible death.

The authors say they hope it will become standard practice for the American business and investment community to factor climate change into its decision-making process. They say: “We are already seeing this response from the agricultural and national security sectors; we are starting to see it from the bond markets and utilities as well.

“But business still tends to respond only to the extent that these risks intersect with core short-term financial and planning decisions.”

And the authors warn the government: “We also know that the private sector does not operate in a vacuum, and that the economy runs most smoothly when government sets a consistent policy and a regulatory framework within which business has the freedom to operate.

“Right now, cities and businesses are scrambling to adapt to a changing climate without sufficient federal government support…” − Climate News Network

Flow chart unclear for glacial rivers

 

Confluence of the Indus and Zanskar rivers that rise in Tibet SImage Sundeep Bhardway via Wikimedia Commons
Confluence of the glacial Indus and Zanskar rivers flowing from Tibet
Image: Sundeep Bhardwaj via Wikimedia Commons

By Kieran Cooke

Glaciers in the high Himalayas and on the Tibetan Plateau are a vital source of water for millions of people in Asia, but scientists question what will happen to supplies if the rate of melting continues to rise due to climate-related factors

 

LONDON, 19 June – A new study examining river basins in the Asia region suggests that amounts of water supplied to the area by glaciers and rainfall in the Himalayas will increase in the coming decades.

At first reading, that looks like good news, as an estimated 1.3 billion people in Pakistan, India, Bangladesh, Nepal, China and elsewhere are dependent for their water supplies on rivers fed by glaciers and snowmelt.

But the less welcome news is that scientists are unsure what will happen after 2050 if the rate at which glaciers melt continues to increase as a result of climate change.

Scientists say rising temperatures and more intense rainfall patterns in the higher Himalayas are causing the retreat of the majority of glaciers in the region.

Heat build-up

They say glacier melt is also being caused by black carbon – particulate matter that, in South Asia, comes mainly from cooking fires, the burning of waste, plus coal burning and diesel exhausts. The black carbon, or soot, falls on the glaciers, reducing reflectivity and increasing heat build-up.

This latest study of glacier melt and water flows, appearing in the journal Nature Climate Change, was carried out by scientists at Future Water, a Netherlands-based research group, Utrecht University, and the Nepal-based International Centre for Integrated Mountain Development.

It assesses the contribution of glacier and snowmelt to the region’s river basins, incorporating some of the world’s mightiest rivers – the Indus, the Ganges, the Brahmaputra, the Mekong and the Salween.

The scientists say that highly-sophisticated modelling techniques were used to study the river basins in unprecedented detail.

They report: “Despite large differences in runoff composition and regimes between basins and between tributaries within basins, we project an increase in runoff at least until 2050, caused primarily by an increase in precipitation in the upper Ganges, Brahmaputra, Salween and Mekong basins and from accelerated melt in the upper Indus Basin.

“These findings have immediate consequences for climate change policies where a transition towards coping with intra-annual shifts in water availability is desirable.”

Uncertain supplies

But while the study says that, up to mid-century, little change is likely in the amount of glacier melt water flowing into river basins, it is unclear what will happen thereafter to the water supplies for  what is a significant portion of the world’s population.

“Our study does not include projections after 2050,” Arthur Lutz, lead author of the study, told Climate News Network. “However, at some point in time, the contribution of glacier melt to the total flow will decrease, because of the decreasing glacier extent. When this happens, it will differ for different river basins and sub-basins.”

The study says the long-term outlook is particularly uncertain for the upper Indus basin. While glacier melt contributes only 11.5% of the total runoff in the upper basin of the Ganges river, it contributes more than 40% of total water runoff in the upper Indus basin.

The Indus river, which flows for nearly 2,000 miles from high up in the Hindu Kush-Karakoram Himalaya mountain range down to the Arabian Sea, is vital to life in Pakistan, providing water for 90% of the country’s agricultural crops. Hydro plants along the Indus also supply about half the country’s electricity. – Climate News Network

Rainforest tribes seek World Cup spotlight

 

Kayapò tribal leaders from the Amazon rainforest put their case to the media Image: Sue Cunningham/SCP
Kayapò tribal leaders from the Amazon rainforest put their case to the media
Image: Sue Cunningham/SCP

By Kieran Cooke

Tribal leaders from the Amazon rainforest are using the glare of publicity on the football World Cup in Brazil to highlight an impassioned plea for recognition of their lands and an end to dam building and deforestation

LONDON, 17 June − Chief Raoni Metuktire, head of the Kayapò indigenous group from the Xingu region, deep in the Amazon rainforest, sits in a packed lecture hall in London. With his jutting lip plate and large feather headdress, the elderly, gently-spoken tribal leader is an imposing presence.

“When I’m gone I want my children and grandchildren to live in the forest as I have done,” he says. “I ask for your help. In the past, we didn’t knock down the trees, destroy the land and build dams, but now all that is happening.

“The climate in the forest is changing: it is a lot hotter than it used to be, and the pattern of the winds is altering.”

Lungs of the world

The Amazon rainforest – often referred to as the lungs of the world – has a major influence on the world’s climate. Its trees and vegetation act as a vital carbon sink, soaking up carbon dioxide from the atmosphere.

Megaron Txucarramãe, a long-time campaigner for land rights for indigenous tribes in the Amazon region, sits alongside Chief Raoni, his uncle.

“The logging in our region is increasing,” he says. “Our lands and those of other indigenous tribes should be properly demarcated, but the Brazilian government is seeking to alter the constitution and undermine our land rights, giving more power to loggers, dam builders and mining companies.

“While the government worries about building stadiums
for the World Cup, our land is being threatened.”

“We went to Brasilia [Brazil’s capital] to protest, but we were received with rubber bullets, tear gas and pepper spray. While the government worries about building stadiums for the World Cup, our land is being threatened. I would like to ask the world to pay attention to our problems and help us.”

In a tour of European capitals that coincided with the opening of the World Cup, the two tribal leaders met Prince Albert of Monaco and, in London, Prince Charles. They also took their message to the Norwegian royal family.

The Kayapò are by far the largest ethnic group in the Xingu region. After years of campaigning and sometimes violent struggle, the group succeeded in having 19,000 square miles of land demarcated as an indigenous reserve in 1992.

The tribal leaders say the government of President Dilma Rousseff – which faces an election in October – is now threatening the land rights of indigenous groups and the health of the whole Amazon by allowing mining and other projects to go ahead.

In recent years, Brazil has embarked on a wide-ranging dam building programme in the Amazon. The Xingu river, a major tributary of the Amazon river, runs through the Kayapò’s lands. Despite various court judgements and continuing protests by the Kayapò and other groups, construction of the Belo Monte dam − which will be one of the world’s biggest when it is completed − began on the Xingu in 2011.

After years of decline in deforestation rates in the Amazon rainforest, they then increased dramatically by 28% over the 2012 to 2013 period, with many blaming controversial reforms to Brazil’s forest laws pushed through by a powerful and extremely wealthy land lobby.

Weather patterns

In recent months, large parts of Brazil have been suffering a drought that is one of the worst on record. Environmentalists say deforestation in the Amazon has disturbed weather patterns and has resulted in less rainfall in many areas.

Patrick Cunningham, who has travelled extensively through the Xingu region, photographing and documenting the lives of the indigenous tribes, is a spokesman for Tribes Alive, a group that highlights indigenous peoples’ issues.

He said: “Chief Metuktire and Megaron are not only asking for an end to the destruction of their lands, they are also campaigning to stop what is a suicidal rush to develop their region.

“Such actions will not only be a setback for them but also for the whole of Brazil as rain patterns alter farther south, in what is the most agriculturally productive region of the country.” – Climate News Network

Drought fuels World Cup blackouts fear

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Fading light at Sao Paulo's Corinthians Arena, venue for the opening WordCup match Image Edson Lopes Jr via Wikimedia Commons

Shadows and light: Sao Paulo’s Corinthians Arena, venue for the opening match of the World Cup
Image: Edson Lopes Jr via Wikimedia Commons

By Kieran Cooke

With only two weeks to go before the football World Cup kicks off in Brazil, the country’s worst drought in decades is severely reducing hydropower energy supplies as climate researchers warn of a serious trend that is also hitting agriculture

 LONDON, 29 May – Imagine the scene in the packed stadium: those magic boots dance as the winger flies down the touchline and crosses the ball perfectly into the penalty area, right on to the head of the striker. He rises, he heads the ball goalwards – and then the lights go out.

Although recent rains have brought some relief, many parts of Brazil are in the grip of the most severe drought for years, and temperatures have been unusually high. In many areas, reservoirs at hydro plants – which produce about 70% of Brazil’s power – are at record lows.

São Paulo state in the south-east, where the World Cup’s opening game will be staged on June 12, is home to more than 43 million people and is the country’s economic powerhouse. But it has been experiencing its worst drought since rainfall records began in 1930.

In order to keep the lights on, the government of President Dilma Rousseff has been desperately upping energy supplies from thermal power stations. But fears persist that blackouts will hit during the World Cup.

Public anger

If that happens, it’s likely to add to the anger felt by many Brazilians about the billions of dollars being spent on facilities for the football tournament – and on staging the Olympics next year.

To ward of public discontent, the government has been forced to spend the equivalent of more than US$5 billion to subsidise utilities that are having to replace hydro power with more expensive oil, coal and natural gas.

Analysts say consumers will have to pay substantially more for their energy, although price hikes are likely to be delayed until after elections in October. The government has also dismissed the idea of power rationing – for now at least.

While the government worries about power supplies, Brazil’s agriculture sector – which accounts for about 25% of the country’s Gross Domestic Product – is suffering potentially long-lasting drought damage.

Professor Hilton Silveira Pinto is a climate researcher at the Centre for Meteorological and Climate Research Applied to Agriculture at the University of Campinas. He told the Bloomberg news service: “This is a taste of what is to come in the future.”

Abandon lands

A study co-authored by Pinto warns that large numbers of farmers could be forced to abandon their lands and migrate to more temperate areas as temperatures rise. Coffee growers in the states of São Paulo and Minas Gerais in the south-east have seen their crops fail due to record high temperatures, combined with drought conditions.

In Bahia state and other areas in the north-east of Brazil, farmers have lost crops and large numbers of livestock as the drought has persisted.

The study says projected future warming trends indicate that Brazil’s overall production of soybeans could decline by as much as 24% by 2020, with wheat production dropping even further.

That’s not just bad news for Brazil and millions of its farmers. Over recent decades, Brazil has emerged as one of the world’s leading agricultural producers, and is now the number one exporter of soybeans, beef, sugar, orange juice − and, of course, coffee.

Prices of these goods are set to rise internationally, so Brazil’s changing climate and its drought is likely to have an impact not just on World Cup football. – Climate News Network

India’s lethal heat wave strikes again

 

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Hot spot: policeman Kumar Srinivasan directs traffic in the swetering Chennai heat Image: Pramila Krishnan

Hot spot: policeman Kumar Srinivasan directs traffic in the sweltering Chennai heat
Image: Pramila Krishnan

 

By Pramila Krishnan

Large numbers of people die in India each year because of heat waves − and as climate change takes hold and the country swelters again, doctors are warning the public to take extra precautions

Chennai, 28 May − Kumar Srinivasan, a 34-year-old policeman, is struggling to cope with the heat as he controls traffic at a busy city-centre road junction in Chennai, South India. “I feel like a roasted chicken,” he says. “But it’s actually worse, since I am alive while the chicken would have gone to rest in heaven.”

India is sizzling under hot winds as many parts of the country suffer temperatures hovering above 40˚C. And officials in the National Weather Forecasting Center of the India Metrological Department have warned that “heat waves to severe heat wave conditions would prevail in isolated parts of the country in the last week of May”.

As the latest Intergovernmental Panel on Climate Change (IPCC) reports confirm that India will continue to get hotter because of climate change, doctors are concerned that the public needs to be warned of the danger they are in.

Excess heat is already claiming many lives. Research published earlier this year in the journal Plos One showed that in May 2010, when the Indian city of Ahmedabad in the state of Gujarat experienced a heat wave with record-breaking maximum temperatures of 46.8˚C, an estimated 1,344 deaths occurred − 43% higher than expected.

Road fatalities

Another chilling statistic in 2012, recently published by the National Crime Records Bureau, is that 5.4% of the total 22,960 road fatalities in India were attributable to heat strokes. That is more than 1,000 people.

The Indian government has done its bit to make the summer slightly more bearable for policemen such as Srinivasan, providing them with packets of aerated fruit juices and buttermilk (yoghurt diluted in water), as well as sunglasses.

“I am just waiting for the summer to be over, or for some of the summer showers that sometimes happen during June,” Srinivasan says before stepping out of the shade of his little booth to start directing traffic manually again in the scorching heat because a power failure has cut out the traffic lights.

Indian politicians, trying to woo voters, put up water pandals (small stalls made of dried palm/coconut leaves) to supply water, and even buttermilk at times, to the public during the recent election period.

In fact, the Indian elections are deliberately timetabled to avoid the worst part of summer, and the entire election process this time was completed by the second week of May, when the sun was beginning to get harsh..

Doctors at the government’s Rajiv Gandhi General Hospital in Chennai have asked the public to take preventive measures to avoid heat strokes – including wearing light-coloured, loose-fitting cotton clothes, staying hydrated, and avoiding strenuous exercise during the day.

“The maximum temperature will reach 40˚C  in many places
in Tamil Nadu . . .  It’s going to be sweltering hot.”

And the Regional Meterological Centre (RMC) in Chennai has been publishing weather projections for the state of Tamil Nadu on its website, keeping people informed with with regular updates of  projections of average temperatures for one week for every district in the state. S.R. Ramanan, director of the RMC, told Climate News Network: “The maximum temperature will reach 40˚C  in many places in Tamil Nadu in the coming days.  It’s going to be sweltering hot.”

While rich and middle-class Indians go for upgraded refrigerators, air conditioners and coolers, the poor households have to settle for earthen pots to keep drinking water cool.

The plight of people is the same, or even worse, in most parts of tropical India during the hostile summers, particularly since fast-moving urbanisation is taking its toll on trees, which are being chopped down to make way for new high-rise buildings, roads and shopping malls

Loss of shade

The loss of the natural shade of avenue trees means that it’s not just humans who are suffering. The bovine population roams around the streets looking for any tiny puddle of urban gutter water to quench their thirst, and the government’s forest department has had to build concrete tanks and fill them with water to try to prevent animals from suffering dehydration.

Many milkmen live in urban areas and do not take enough care of their cows to protect them from the summer heat, and the Tamil Nadu Veterinary and Animal Sciences University has also found that many aged animals suffer kidney failures in the summer season because of dehydration.

Meanwhile, as more people die every year in India due to heat strokes, social activists are calling for the government to take up initiatives to protect people and spread awareness about preventive measures.

“Curbing privatisation of water and ensuring supply of good quality drinking water for the residents is a major step to avoid dehydration and heat strokes,” said Chennai social activist A.Devaneyan. “The government health department should conduct awareness campaigns to inform people about taking additional care of elders and children during the summer.”

Devaneyan pointed out that the rising number of players in the bottled drinking water industry has also led to rising prices. He said: “A one-litre bottle now costs 20 rupees. How many can afford that?”

Not surprisingly, the popularity of the Tamil Nadu state chief minister, Ms Jayalalithaa Jayaram, also rose after she recently ordered her government to supply water at 10 rupees per bottle − half the price of the “private” water. – Climate News Network.

  • Pramila Krishnan is based in Chennai as Principal Correspondent of the Deccan Chronicle, an English-language newspaper in India.

El Niño blows hot and cold

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A mud slide caused devastation in northern California after El Niño strick in 1998 Image: Dave Gatley/FEMA via Wikimedia Commons

Devastation caused by a mud slide after El Niño storms struck northern California  in 1998
Image: Dave Gatley/FEMA via Wikimedia Commons

By Tim Radford

Analysis of historic data about the mysterious El Niño, which periodically unleashes such devastating weather events, reveals that it has a bad local side, an even worse global side − and scientists warn that another storm may be brewing

LONDON, 26 May − El Niño, the mysterious meteorological phenomenon that periodically upsets global weather patterns, bringing catastrophic flooding to the arid lands of North and South America, and forest fires to South-east Asia, turns out to be more complicated than anyone had thought.

Sandra Banholzer and Simon Donner, environmental scientists at the University of British Columbia in Vancouver, Canada, report in Geophysical Research Letters  that some El Niño events don’t turn up the planetary thermostat, and may even contribute to the apparent and much-debated slowdown in the rates of increase in global warming.

An El Niño – Spanish for “The Child”, and given that name by Peruvian fishermen because they observed it around Christmas – is a blister or bubble of ocean surface heat that migrates from the western Pacific to the east, halting or even reversing the prevailing Pacific trade winds, with disconcerting consequences on both sides of the Pacific and Indian Oceans.

The blister analogy is physical, rather than metaphorical. As ocean temperatures rise, so does the volume, and the sea levels can be 45cms higher than the surrounding, cooler ocean.

Hottest years

But recent studies, say the new report’s two authors, have shown that there may be “different flavours” or types of El Niño. The traditional or eastern equatorial Pacific type is the one that everybody knows about (it made 1998 one of the hottest years ever recorded, and triggered tempests, floods, ice storms, droughts, harvest failures and bushfires around the world). But if an El Niño only gets as far as the central Pacific, it’s a different story, and the effects are more local.

The finding also lends a little extra authority to the forecasts that Australia, which had its hottest ever temperatures in 2013, will see more and worse extremes of heat.

The two authors looked at three sets of data to match long-term changes in global temperatures to the pattern of “hot” and “cold” El Niño events. “Historical analysis,” they say, in the deadpan language of a scientific paper, “indicated that slowdowns in the rate of global warming since the late 1800s may be related to decadal variability in the frequency of different types of El Niño events.”

Meanwhile, Nasa scientists have warned that another traditional El Niño may be on the way. They think so because of data gathered by a satellite called Jason-2, which monitors changes in sea surface height (because pressure, temperature and volume are related, sea surface height becomes another way of taking the ocean’s surface temperature).

“A pattern of sea surface heights and temperatures has formed that reminds me of the way the Pacific looked in the spring of 1997,” says Bill Patzert, of the Jet Propulsion Laboratory at Pasadena, US. “That turned out to be the precursor of a big El Niño.”

Tentative warning

The warning is tentative because it is based only on ripples of change in sea level travelling across the Pacific from Australia to South America. These are linked to changes in the trade winds, and tend to happen from time to time during the southern hemisphere winter. They normally last only a few days, but if they last for months, then an El Niño develops.

For the moment, there is no certainty that one will develop, and nor is there yet any indication of the knock-on effects on global weather patterns.

But although the phenomenon has nothing to do with global warming – it happens anyway, and climatologists have traced evidence of El Niño events back for more than 2000 years – global warming may have something to do with it.

In January, Australian scientists warned that rising levels of greenhouse gases in the atmosphere could increase the frequency of the most severe El Niño events. – Climate News Network

Ocean winds put heat on Australia

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Dry humour: a signpost made redundant by drought in South Australia Image: Peripitus via Wikimedia Commons

Dry humour: a signpost made redundant by drought in South Australia
Image: Peripitus via Wikimedia Commons

By Tim Radford

Greenhouse gases are causing changes to Southern Ocean wind patterns, keeping Antarctica cold but parching Australia by “stealing” more of its rainfall

LONDON, 16 May − The answer to one of the enduring puzzles of global warming − the apparently sluggish response of the Antarctic continent to rising greenhouse gas levels − may have been settled by Australian scientists. And, in the course of doing so, they may also have solved another problem: the parching of Australia itself.

Nerilie Abram, of the Australian National University’s Research School of Earth Sciences, and colleagues outline their findings in Nature Climate Change. They report that they looked at the pattern of climate in the southern hemisphere and have concluded that the Southern Ocean winds that normally deliver rain to South Australia are being pushed further south towards Antarctica.

Their research was focused on a meteorological phenomenon known − although probably only to climate scientists − as the Southern Annular Mode, which marks the pattern of climate variability south of the equator. For the last 25 years of climate observation, it has been obvious that changes in the northern hemisphere have not been matched by changes in the south.

There are geophysical reasons for some of the difference. For example, most of the inhabited landmass of the planet is in the northern hemisphere; the North Pole is covered by an ocean, while the South Pole is in the centre of an enormous continental landmass piled high with ice and snow; and the seasons and wind patterns of the two hemispheres run counter to each other. The two hemispheres are very different.

Weather observations

In addition, weather observations in the northern hemisphere are much more detailed and have been conducted over a much longer period than in the southern hemisphere.

Conspicuously, the Arctic has been the fastest warming region of the planet, and for more than a decade there was argument about whether the Antarctic was warming at all.

Lead researcher Dr Abram and her fellow scientists took the measure of the Southern Annular Mode by looking at annual seasonal data since AD 1000 – recorded in Antarctic ice cores and South American tree rings. They then used the information to build up a picture of the past and the changing present.

“With greenhouse warming, Antarctica is actually stealing more of Australia’s rainfall,” she reported. “It’s not good news. As greenhouse gases continue to rise, we’ll get fewer storms chased up into Australia. As the westerly winds are getting tighter, they’re actually trapping more of the cold air over Antarctica. This is why the Antarctic has bucked the trend. Every other continent is warming, and the Arctic is warming fastest of anywhere on Earth.”

Indirect evidence

Direct climate observations in Antarctica date back only about 60 years. That is why climate scientists must work with indirect evidence from ice cores and tree rings.

But although change has been hard to measure on the continent itself, glaciers have been in retreat and ice shelves have collapsed on the Antarctic peninsula and the west Antarctic is beginning to lose ice at an accelerating rate. The winds of change are blowing in the south.

“The Southern Ocean winds are now stronger than at any other time in the last 1000 years,” Dr Abram said. “The strengthening of these winds has been particularly prominent over the past 70 years, and by combining our observations with climate models we can clearly link this to rising greenhouse gas levels.” − Climate News Network

South Asian monsoon is on the change

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South Asia depends on the monsoon: Cganges could have profound consequences Image: Shajiarikkad via Wikimedia Commons

South Asia depends on the monsoon: Changes could have profound consequences
Image: Shajiarikkad via Wikimedia Commons

By Tim Radford

There is evidence that south Asia’s summer monsoon, a vital source of water for millions of people, is changing. But scientists say it is too soon yet to blame the warming climate.

LONDON, 30 April – Climate change may be having an effect on one of the world’s most important weather systems. A study of the monsoon season over the last sixty years reveals that the intensity of extremes of precipitation and the number of very dry spells have both been increasing.

The Indian subcontinent gets more than four-fifths of its annual rainfall in that great, sustained seasonal cloudburst called the south Asian summer monsoon. Since 60% of India’s people live by agriculture, and 70% of the country’s exports are agricultural products, a lot rides on the monsoon.

Extremes of rainfall can bring catastrophic flooding, death, disease and homelessness. Dry seasons can bring a threat to India’s economy, and to national and even to global food security.

So a pattern of wetter wet spells and longer dry spells would – if sustained – create problems for the one-sixth of the world’s population that depends on the timing and strength of the monsoons.

Deepti Singh of Stanford University in California and colleagues report in Nature Climate Change that they used statistical tools to compare rainfall patterns over two contrasting periods, from 1951 to 1980, and from 1981 to 2011.

No rush to judgement

The monsoon season is a complicated one: it generally begins in southern India in June, and is over by September. By mid-July, the rains cover the entire subcontinent. But what matters is how much rain falls, when it falls, and how long the intermittent dry periods last.

The researchers found that overall the total rainfall has declined, but the variability of precipitation during the peak monsoon months has increased. The wet spells are more intensely wet, and the frequency of the dry spells has increased. But it may be too early to be sure that global warming is behind the changes.

“The statistical techniques show that the changes in these characteristics are robust and that these changes are unlikely to happen purely by chance,” said Singh.

The finding matches anecdotal evidence. “My grandfather grew up in a village that is primarily dependent on agriculture, and the farmers that live there say that the monsoon rainfall pattern has changed. They’ve noticed over the last decade that rainfall occurs in heavy bursts and comes earlier in the monsoon season, and that dry spells last longer.”

And her co-author, Noah Diffenbaugh of Stanford, said: “There are many predictions that global warming should cause heavier downpours and more frequent dry spells. That’s what we’ve found here, but India is a complex region, so we want to be sure before we point the finger at global warming or any other cause.” – Climate News Network

California goes nuts for water

FOR IMMEDIATE RELEASE

California's almond orchards may not look so green before long: Growers now have to find their own water sources Image: US Dept of Agriculture Natural Resources Conservation Service via Wikimedia Commons

California’s almond orchards may not look so green before long: Growers now have to find their own water sources
Image: US Dept of Agriculture Natural Resources Conservation Service via Wikimedia Commons

By Kieran Cooke

While recent rainfall has brought welcome relief to California, the amount of precipitation has not been nearly enough to put an end to what is its worst drought on record.  The state’s $45 billion agricultural sector has been particularly hard hit.

LONDON, 27 March – Almonds are good for you. That’s the message California’s enterprising nut growers have been giving to the world – and they have been remarkably successful in their marketing efforts.

The world appetite for almonds is growing by the day – and nut farmers in the west of the US have been cashing in. According to the Almond Board of California the state now produces more than 80% of total world almond output: California’s almond crop has more than doubled since 2006 to 1.88 billion pounds last year.

The trouble is almonds – and other nut crops grown in California – need plenty of water, and right now water is in very short supply. A drought emergency is in force. The snow pack in the Sierra Nevada mountain range – a key source of the state’s water – was recently recorded as being only 24% of its normal capacity for the time of year.

At the end of January, California’s State Water Project – the largest state-built water and power development and distribution system in the US, responsible for supplying water to two-thirds of the state’s 38 million people – stopped supplying local agencies in many areas.

Scientists are busy analysing whether the drought is linked to changes in climate: President Obama, announcing a drought federal aid package, said the state provided an example of what might be in store for the rest of the country as climate change intensifies.

Left fallow

“We have to be clear”, said Obama.  “A changing climate means that weather-related disasters like droughts, wildfires, storms, floods, are potentially going to be costlier, and they’re going to be harsher.”

Under an unprecedented range of restrictions, no water from state projects is being supplied to the agricultural sector. Instead, farmers have to find their own water sources, whether from rivers or by sinking boreholes. Agricultural experts estimate that up to 800,000 acres of farmland will not be planted this year because of lack of water.

Cattle ranchers are selling off livestock due to lack of grass. The US now has its smallest cattle herd since the mid-1950s – and beef prices are at an all-time high.

But it’s perhaps the nut growers who are suffering most. In recent years California’s farmers have moved away from traditional annual vegetable crops such as tomatoes and lettuce and into the far more profitable market for almonds, pistachios and other nuts. Almonds are now California’s second most valuable crop – only sales of grapes are worth more.

The downside is that the nut trees are mainly in regions of central California classified as being under extreme drought conditions. Nut trees demand long-term investment: they need lots of water and take years to produce a crop.

Deeper cuts coming

Nut farmers are now scrubbing up portions of their tree plots in order to concentrate water resources on the remainder. They are digging wells and tapping in to already declining aquifers. In the process they are losing millions in revenue.

Meanwhile traders say prices for almonds and other nuts are likely to rise sharply on the world market next year due to drought-induced crop shortages.

Farmers’ organisations have complained that the agricultural sector has been unfairly targeted with water restrictions, while California’s cities and towns have been only partially affected.

That could be changing. In recent days the state supplier to Silicon Valley – the high-tech hub and likely home of the almond milk-flavoured café latte – announced that for the rest of the year it would be supplying only 80% of the normal amount of treated drinking water to inhabitants. – Climate News Network