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News & Events On Our Changing Planet


Changing Antarctic winds create new sea level threat

Credit: NASA/GRACE team/DLR/Ben Holt Sr.

New research shows projected changes in the winds circling the Antarctic may accelerate global sea level rise significantly more than previously estimated.
Changes to Antarctic winds have already been linked to southern Australia's drying climate but now it appears they may also have a profound impact on warming ocean temperatures under the ice shelves along the coastline of West and East Antarctic.
"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 lead author Dr Paul Spence from the ARC Centre of Excellence for Climate System Science (ARCCSS).
"The sub-surface warming revealed in this research is on average twice as large as previously estimated with almost all of coastal Antarctica affected. This relatively warm water provides a huge reservoir of melt potential right near the grounding lines of ice shelves around Antarctica. It could lead to a massive increase in the rate of ice sheet melt, with direct consequences for global sea level rise."
Prior to this research by Dr Spence and colleagues from Australian National University and the University of New South Wales, most sea level rise studies focused on the rate of ice shelf melting due to the general warming of the ocean over large areas.
Using super computers at Australia's National Computational Infrastructure (NCI) Facility the researchers were able to examine the impacts of changing winds on currents down to 700m around the coastline in greater detail than ever before.
Previous global models did not adequately capture these currents and the structure of water temperatures at these depths. Unexpectedly, this more detailed approach suggests changes in Antarctic coastal winds due to climate change and their impact on coastal currents could be even more important on melting of the ice shelves than the broader warming of the ocean.
"When we first saw the results it was quite a shock. It was one of the few cases where I hoped the science was wrong," Dr Spence said.
"But the processes at play are quite simple, and well-resolved by the ocean model, so this has important implications for climate and sea-level projections. What is particularly concerning is how easy it is for climate change to increase the water temperatures beside Antarctic ice sheets."
The research may help to explain a number of sudden and unexplained increases in global sea levels that occurred in the geological past.
"It is very plausible that the mechanism revealed by this research will push parts of the West Antarctic Ice Sheet beyond a point of no return," said Dr Axel Timmerman, Prof of Oceanography at University of Hawaii and an IPCC lead author who has seen the paper.
"This work suggests the Antarctic ice sheets may be less stable to future climate change than previously assumed."
Recent estimates suggest the West Antarctic Ice Sheet alone could contribute 3.3 metres to long-term global sea level rise.
With both West and East Antarctica affected by the change in currents, in the future abrupt rises in sea level become more likely.
According to another of the paper's authors, Dr Nicolas Jourdain from ARCCSS, the mechanism that leads to rapid melting may be having an impact on the Western Antarctic right now. Dr Jourdain said it may help explain why the melt rate of some of the glaciers in that region are accelerating more than scientists expected.
"Our research indicates that as global warming continues, parts of East Antarctica will also be affected by these wind-induced changes in ocean currents and temperatures," Dr Jourdain said.
"Dramatic rises in sea level are almost inevitable if we continue to emit greenhouse gases at the current rate."

Science Daily


Liberia caterpillar plague causes mass evacuation and crop destruction

A plague of caterpillars has forced thousands of people to flee their homes in northern Liberia, as well destroying crops, contaminating water and forcing schools to close. Image: One of millions of caterpillars moves through crops iin farms in Gbarpolu county, Liberia. Photograph: Ahmed Jallanzo/EPA
Residents of at least 25 villages and towns in Lofa and Gbarpolu counties have joined a mass exodus so far this month to escape the trail of caterpillar excrement, according to the Voice of America (VOA).
It is the second such invasion in five years. A state of emergency was declared in 2009 after tens of millions of caterpillars swept through at least 80 towns and villages in the centre and north of the country.
Dr Sizi Subah, deputy agriculture minister for technical services, told Liberia's The Inquirer that the caterpillars, which travel in huge numbers, have the capacity to destroy large areas since they feed on the leaves of cash crops such as coffee, cocoa and vegetables during the larva stage before developing into butterflies.
Subah linked the latest infestation to "climate change", the Inquirer reported.
The huge volume of excrement dropped by the caterpillars has contaminated wells and other fresh water sources, rendering them undrinkable. The pests have also colonised classrooms, forcing many schools in the area to shut down.
Jeremiah Toe, a nurse in one of the affected villages, told the VoA that the caterpillars pose a serious threat to public health. "The situation is alarming," he was quoted as saying. "We have informed the ministry of health. As you can see, the caterpillars are taking over the homes of residents. They have polluted the creeks. Even our clinic has been attacked by the caterpillars."
Smaller invasions of caterpillars occurred in 2011 and 2012. Winfred Hammond, a senior entomologist at the UN Food and Agriculture Organisation, told the VOA: "The biggest concern is the fact that this is becoming a regular occurrence. It's about time we seriously consider putting in place early warning systems and look at how we can contain or check this problem from becoming a big national concern. To prevent it as we've seen, you need to have a good surveillance system in place."
Liberian officials said they have begun spraying pesticides in a bid to control the plague.

The Guardian 

'India's rain pattern has changed': Researchers warn of extreme weather in future

The monsoon, which provides 80 per cent of the total rainfall in the subcontinent and on which India is completely dependent for its agriculture, is witnessing disturbing changes.
There has been a decline in the average total seasonal rain during the period 1980-2011, according to a new study.

The study was carried out by Stanford Woods Institute for the Environment, the Stanford University's hub of environment research, and published in the latest issue of Nature Climate Change. It also found changes in the atmosphere like winds and moisture which are likely to be responsible for changes in wet and dry spells.
After studying trends of monsoon rains over 60 years, the researchers have warned of extreme weather conditions in future.

They have also found that there is substantial variability within the monsoon season, including fluctuations between periods of heavy rainfall (wet spells) and low rainfall (dry spells).
"These fluctuations can cause extreme wet and dry regional conditions that adversely impact agricultural yields, water resources, infrastructure and human systems," the study said.

According to the study, the mean rainfall during July-August shows a significant (10 per cent significance level) decreasing trend since 1951 over the monsoon "core" in the data set of the India Meteorological Department (IMD) which is consistent with reported decrease in all-India rainfall.
This decrease in mean rainfall occurs despite an increase in seasonal mean low-level moisture convergence and convective available potential energy expected from increased moisture availability in response to atmospheric warming. 

In contrast, the daily rainfall variability during July-August shows a statistically significant (5 per cent significance level) increasing trend.
The study revealed that the intensity of rainfall in wet spells during 1981-2011 was significantly higher than during 1950-1980.
At the same time, dry spells became 27 per cent more frequent during 1981-2011, which had twice as many years with three or more dry spells.
Studying the pattern of monsoons in South Asia since 1980, researchers observed an increase in the intensity of wet spells and in the frequency of dry spells.
"Through a comprehensive statistical analysis of precipitation observations (1951–2011), we show that statistically significant decreases in peak-season precipitation over the core monsoon region have cooccurred with statistically significant increases in daily-scale precipitation variability," the researchers said.
The study said the changes in extreme wet and dry spell characteristics are supported by increases in convective available potential energy and low-level moisture convergence.


Plastic tide 'causing $13 bn in damage', UN says

Nairobi (AFP) - The dumping of plastic waste into the world's oceans is causing at least $13 billion a year of damage, threatening marine life, tourism and fisheries, the United Nations warned Monday at the launch of a global environment conference.
"Plastics have come to play a crucial role in modern life, but the environmental impacts of the way we use them cannot be ignored," said UN Environment Programme (UNEP) chief Achim Steiner said.
"The key course of action is to prevent plastic debris from entering the environment in the first place, which translates into a single powerful objective: reduce, reuse, recycle."
Scientists have found tiny plastic fragments trapped in sea ice in polar regions, while plastic waste has killed marine life, whether it be eaten by sea creatures such as turtles, tangled up dolphins and whales, or caused "damage to critical habitats such as coral reefs," the report read.
"There are also concerns about chemical contamination, invasive species spread by plastic fragments, and economic damage to the fishing and tourism industries in many countries—by, for example, fouling fishing equipment and polluting beaches," it added.

While much of the plastic waste ends up in vast mid-ocean rubbish patches where marine currents converge, micro-plastics -- tiny fragments less than five millimetres in diameter -- have had a growing impact that is particularly worrying, UNEP said.
"Transported by ocean currents across great distances, these contaminated particles eventually become a source of chemicals in our food," Steiner added.
Some of the tiny fragments are caused by the breakdown of plastics, but one emerging issue is the increasing use of directly created "micro beads" of plastic in toothpaste, gels and facial cleansers.
"These micro plastics tend not to be filtered out during sewage treatment, but are released directly into rivers, lakes and the ocean," the report added.
Companies should take responsibility, with experts arguing they could also boost their business savings through greater recycling efforts.
"The research unveils the need for companies to consider their plastic footprint, just as they do for carbon, water and forestry," said Andrew Russell, chief of the Plastic Disclosure Project, a UNEP backed organisation.
The UNEP report was released at its headquarters in Kenya as it opened its first week-long conference bringing together over 1,200 delegates and experts to discuss a raft of environment challenges.
The UNEP conference runs until Friday, tackling a range of subjects including sustainable consumption and production, and financing the "green economy".
It will also examine the illegal trade in wildlife and environmental rule of law.
The conference comes amid tight security in the Kenyan capital, after a series of warnings of the threat of attack by Somalia's Al-Qaeda-linked Shebab.


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