African dust changes India's rainfall: Dust can affect planet's climate, research shows

A new analysis of satellite data reveals a link between dust in North Africa and West Asia and stronger monsoons in India. The study shows that dust in the air absorbs sunlight west of India, warming the air and strengthening the winds carrying moisture eastward. This results in more monsoon rainfall about a week later in India. The results explain one way that dust can affect the climate, filling in previously unknown details about Earth's system.

The study also shows that natural airborne particles can influence rainfall in unexpected ways, with changes in one location rapidly affecting weather thousands of miles away. The researchers analyzed satellite data and performed computer modeling of the region to tease out the role of dust on the Indian monsoon, they report March 16 in Nature Geoscience.

India relies heavily on its summer monsoon rains. "The difference between a monsoon flood year or a dry year is about 10 percent of the average summer rainfall in central India. Variations driven by dust may be strong enough to explain some of that year-to-year variation," said climate scientist Phil Rasch of the Department of Energy's Pacific Northwest National Laboratory.

Rasch, V. Vinoj of the Indian Institute of Technology Bhubaneswar, India, and their coauthors wanted to explore a correlation that appeared in satellite records: higher amounts of small particles called aerosols over North Africa, West Asia, and the Arabian Sea seemed to be connected to stronger rainfall over India around the same time. The team wanted to see if they could verify this and determine how those particles might affect rainfall.

To explore the connection, the team used a computer model called CAM5 and focused on the area. The model included humanmade aerosols from pollution, and natural sea salt and dust aerosols. First, the team ran the model and noted a similar connection: more aerosols in the west meant more rainfall in the east. Then they systematically turned off the contribution of each aerosol type and looked to see if the connection remained.

Dust turned out to be the necessary ingredient. The condition that re-created stronger rainfall in India was the rise of dust in North Africa and the Arabian peninsula.

To see how quickly dust worked, they ran short computer simulations with and without dust emissions. Without dust emissions, the atmospheric dust disappeared within a week compared to the simulation with dust emissions and rainfall declined in central India as well. This indicated the effect happens over a short period of time.

But there was one more mystery, how did dust do this to rainfall? To explore possibilities, the team zoomed in on the regional conditions such as air temperature and water transport through the air.

Their likeliest possibility focused on the fact that dust can absorb sunlight that would normally reach the surface, warming the air instead. This warmer dust-laden air draws moist air from the tropics northward, and strengthens the prevailing winds that move moisture from the Arabian Sea into India, where it falls as rain.

Although dust plays a role in strengthening monsoons, this natural phenomenon does not overpower many other processes that also influence monsoons, said Rasch. Other extremely important factors include the effect of temperature differences between land and ocean, land use changes, global warming, and local effects of pollution aerosols around India that can heat and cool the air, and also affect clouds, he said.

"The strength of monsoons have been declining for the last 50 years," he said. "The dust effect is unlikely to explain the systematic decline, but it may contribute."

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Solar activity not a key cause of climate change, study shows

Climate change has not been strongly influenced by variations in heat from the sun, a new scientific study shows.

The findings overturn a widely held scientific view that lengthy periods of warm and cold weather in the past might have been caused by periodic fluctuations in solar activity.

Research examining the causes of climate change in the northern hemisphere over the past 1000 years has shown that until the year 1800, the key driver of periodic changes in climate was volcanic eruptions. These tend to prevent sunlight reaching Earth, causing cool, drier weather. Since 1900, greenhouse gases have been the primary cause of climate change.

The findings show that periods of low sun activity should not be expected to have a large impact on temperatures on Earth, and are expected to improve scientists' understanding and help climate forecasting.

Scientists at the University of Edinburgh carried out the study using records of past temperatures constructed with data from tree rings and other historical sources. They compared this data record with computer-based models of past climate, featuring both significant and minor changes in the sun.

They found that their model of weak changes in the sun gave the best correlation with temperature records, indicating that solar activity has had a minimal impact on temperature in the past millennium.

The study, published in Nature GeoScience, was supported by the Natural Environment Research Council.

Dr Andrew Schurer, of the University of Edinburgh's School of GeoSciences, said: "Until now, the influence of the sun on past climate has been poorly understood. We hope that our new discoveries will help improve our understanding of how temperatures have changed over the past few centuries, and improve predictions for how they might develop in future. Links between the sun and anomalously cold winters in the UK are still being explored."

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Study shows deeper meltdown at Japan nuke reactor (AP)

TOKYO – Radioactive debris from melted fuel rods may have seeped deeper into the floor of a Japan's tsunami-hit nuclear reactor than previously thought, to within a foot from breaching the crucial steel barrier, a new simulation showed Wednesday.

The findings will not change the ongoing efforts to stabilize the reactors more than eight months after the Fukushima Dai-ichi plant was disabled, but they harshly depict the meltdowns that occurred and conditions within the reactors, which will be off-limits for years.

The plant operator Tokyo Electric Power Co. said its latest simulation showed fuel at the No. 1 reactor may have eroded part of the primary containment vessel's thick concrete floor. The vessel is a beaker-shaped steel container, set into the floor. A concrete foundation below that is the last manmade barrier before earth.

The fuel came within a foot of the container's steel bottom in the worst-case scenario but has been somewhat cooled, TEPCO's nuclear safety official Yoshihiro Oyama said at a government workshop. He said fuel rods in the No. 1 reactor were the worst damaged because it lost cooling capacity before the other two reactors, leaving its rods dry and overheated for hours before water was pumped in.

The nuclear crisis following the March 11 earthquake and tsunami caused massive radiation leaks and the relocation of some 100,000 people.

Another simulation on the structure released by the government-funded Japan Nuclear Energy Safety Organization, or JNES, said the erosion of the concrete could be deeper and the possibility of structural damage to the reactor's foundation needs to be studied.

JNES official Masanori Naito said the melting fuel rods lost their shape as they collapsed to the bottom of the vessel, then deteriorated into drops when water pumping resumed, and the fuel drops spattered and smashed against the concrete as they fell, Naito said.

TEPCO and government officials are aiming to achieve "cold shutdown" by the end of the year — a first step toward creating a stable enough environment for work to proceed on removing the reactors' nuclear fuel and closing the plant altogether.

The government estimates it will take 30 years or more to safely decommission Fukushima Dai-ichi.

Wednesday's simulations depict what happened early in the crisis and do not mean a recent deterioration of the No. 1 reactor. Oyama said, however, the results are based only on available data and may not match the actual conditions inside the reactors, which cannot be opened for years.

Some experts have raised questions about achieving the "cold shutdown," which means bringing the temperature of the pressure vessel containing healthy fuel rods to way below the benchmark 100 Celsius (212 Fahrenheit). They say the fuel is no longer there and measuring the temperature of empty cores is meaningless, while nobody knows where and how hot the melted fuel really is.

Kiyoharu Abe, a nuclear expert at JNES, said it's too early to make a conclusion and more simulations should be done to get accurate estimates.

"I don't think the simulation today was wrong, but we should look at this from various viewpoints rather than making a conclusion from one simulation," Abe said. "It's just the beginning of a long process."

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Paper shows Japan feared aftershocks at nuke plant (AP)

TOKYO – Japan feared three months after the Fukushima nuclear power plant was hit by a tsunami that aftershocks could further damage one of its fuel storage pools, causing rods inside to melt and spew radiation within hours, according to a newly released document.

The Japan Nuclear Energy Safety Organization said it carried out a simulation that showed some 1,500 mostly used fuel rods at the plant's No. 4 reactor building could start breaking in two hours if aftershocks further damaged the pool and caused cooling water to escape. The fuel rods could start melting within eight hours, the organization said in a report dated June 30 and published Friday.

The report shows that the pool remained vulnerable for nearly four months until its operator completed reinforcement work in July. Tokyo Electric Power Co. had said before then that the building could withstand major aftershocks without reinforcement, but made repairs after acknowledging structural damage and water leaks from the pool area.

The March 11 quake and tsunami triggered meltdowns at the plant's three reactors. Explosions also damaged their buildings, plus Unit 4 next to them.

The simulation was based on a scenario that cooling water was lost in the Unit 4 spent fuel storage pool, located on the top floor of the building. The Unit 4 pool was considered high risk as it contained more fuel than the other three pools, as it also stored fuel rods that had been moved from the unit's reactor core, which was being fitted with new parts.

In the report, the government-funded JNES said a loss of pool water due to additional cracks from aftershocks could cause the fuel rods to overheat. Their casings could break and start spewing radiation in about 2 hours. Fuel pellets inside each rod could start melting within 7.7 hours at about 2,800 Celsius (5,000 Fahrenheit), it said.

The report was part of hundreds of pages of documents containing simulation results on dozens of accident scenarios by JNES earlier in the crisis.

Plant workers are still struggling to contain radiation still leaking from the plant, although the amount is far less than before.

TEPCO said Friday that Unit 1 — one of the most damaged buildings — now has an outer shell made of airtight polyester designed to contain radioactive particles inside the building. Similar covers are also planned for other buildings.

Government officials are also making massive decontamination efforts in areas around the plant, from where tens of thousands of people had to evacuate.

Recent discoveries of radiation "hot spots" in and around Tokyo have also caused fears among people there, where many concerned parents routinely check their neighborhoods for radiation. In most cases the reading is estimated to be below the internationally accepted annual limit, but critics say the standard exceeds Japan's cap before the accident and the government should expand the scope of decontamination.

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U.N. nuclear report shows Japan safety shortcomings (Reuters)

VIENNA (Reuters) – Japanese nuclear regulators failed to review and approve steps taken after 2002 to protect against tsunamis at the Fukushima plant and these proved insufficient to prevent the tidal wave disaster three months ago, a U.N. report showed.

A detailed assessment by experts from the International Atomic Energy Agency -- the first outside review of Japan's nuclear crisis -- suggested several shortcomings both before and after a tidal wave crippled the power station three months ago.

But it also praised the way workers on the ground dealt with the situation at Fukushima Daiichi after the massive earthquake and huge tsunami devastated its reactors on March 11, triggering the world's worst nuclear catastrophe in a quarter of a century.

Given the extreme circumstances it is doubtful "that any better solutions than the ones actually chosen could have been realistically implemented," said the 160-page report, prepared for a ministerial nuclear safety meeting in Vienna next week.

A three-page summary was issued at the end of the 18-member team's May 24-June 2 inspector mission to Japan. It said the country underestimated the threat from tsunamis to the Fukushima plant and urged sweeping changes to its regulatory system.

Japanese authorities have been criticized for failing to plan for a tsunami that would surge over the 5.7 meter (19-ft) wall at the nuclear power station in the country's northeast, despite warnings that such a risk was looming.

The wave that crashed into the complex after the 9.0 magnitude earthquake was about 14 meters (46 feet) high.

In another setback to efforts to restore control over the quake-stricken plant, a rise in radiation halted the clean-up of radioactive water at Fukushima on Saturday only hours after it got under way.

The full IAEA report said there had been "insufficient defense-in-depth provisions" for tsunami hazards, even though they had been considered in the design and siting of the plant operated by Tokyo Electric Power Company, or Tepco.

DECISION DELAYS

Extra protective steps were taken as a result of an evaluation after 2002 -- the projected tsunami height was increased -- but they were insufficient "to cope with the high tsunami run-up values and all associated hazardous phenomena."

"Moreover, those additional protective measures were not reviewed and approved by the regulatory authority," said the report. It added: "Severe accident management provisions were not adequate to cope with multiple plant failures."

The document, obtained by Reuters, was submitted to IAEA member states on Friday but has not yet been made public.

At the June 20-24 IAEA-hosted meeting, some 150 nations will begin charting a strategy on boosting global nuclear safety, but differences on how much international action is needed may hamper follow-up efforts, diplomats say.

Japan's crisis has prompted a rethink of energy policy around the world, underlined by Germany's decision to shut down all its reactors by 2022 and an Italian vote to ban nuclear power for decades.

Three reactors at the Japanese complex went into meltdown when power and cooling functions failed, causing radiation leakage and forcing the evacuation of some 80,000 people.

Japanese officials have come under fire for their handling of the emergency and the authorities have admitted that lax standards and poor oversight contributed to the accident.

In 2007, the IAEA was ignored when it called on Japan to create a more powerful and independent nuclear regulator, and the report underlined the need for greater regulatory control.

"An updating of regulatory requirements and guidelines should be performed reflecting the experience and data obtained during the Great East Japan Earthquake and Tsunami," it said.

Japan has a well organized emergency preparedness and response system but "complicated structures and organizations can result in delays in urgent decision making," it added.

The report also listed wider lessons for improving nuclear safety worldwide and help avert any repeat of the disaster, saying reactors should be built so that they can withstand rare and "complex combinations" of external threats.

(Editing by Mark Heinrich)

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