Physicists at The University of Texas at Austin have designed a new system that, when fully developed, would use fusion to eliminate most of the transuranic waste produced by nuclear power plants. The invention could help combat global warming by making nuclear power cleaner and thus a more viable replacement of carbon-heavy energy sources, such as coal. "We have created a way to use fusion to relatively inexpensively destroy the waste from nuclear fission," says Mike Kotschenreuther, senior research scientist with the Institute for Fusion Studies (IFS) and Department of Physics. "Our waste destruction system, we believe, will allow nuclear power-a low carbon source of energy-to take its place in helping us combat global warming." Toxic nuclear waste is stored at sites around the U.S. Debate surrounds the construction of a large-scale geological storage site at Yucca Mountain in Nevada, which many maintain is costly and dangerous. The storage capacity of Yucca Mountain, which is not expected to open until 2020, is set at 77,000 tons. The amount of nuclear waste generated by the U.S. will exceed this amount by 2010.
The physicists' new invention could drastically decrease the need for any additional or expanded geological repositories. "Most people cite nuclear waste as the main reason they oppose nuclear fission as a source of power," says Swadesh Mahajan, senior research scientist. The scientists propose destroying the waste using a fusion-fission hybrid reactor, the centerpiece of which is a high power Compact Fusion Neutron Source (CFNS) made possible by a crucial invention. The CFNS would provide abundant neutrons through fusion to a surrounding fission blanket that uses transuranic waste as nuclear fuel. The fusion-produced neutrons augment the fission reaction, imparting efficiency and stability to the waste incineration process. Kotschenreuther, Mahajan and Prashant Valanju, of the IFS, and Erich Schneider of the Department of Mechanical Engineering report their new system for nuclear waste destruction in the journal Fusion Engineering and Design.
There are more than 100 fission reactors, called "light water reactors" (LWRs), producing power in the United States. The nuclear waste from these reactors is stored and not reprocessed. (Some other countries, such as France and Japan, do reprocess the waste.) The scientists' waste destruction system would work in two major steps. First, 75 percent of the original reactor waste is destroyed in standard, relatively inexpensive LWRs. This step produces energy, but it does not destroy highly radiotoxic, transuranic, long-lived waste, what the scientists call "sludge." In the second step, the sludge would be destroyed in a CFNS-based fusion-fission hybrid. The hybrid's potential lies in its ability to burn this hazardous sludge, which cannot be stably burnt in conventional systems. "To burn this really hard to burn sludge, you really need to hit it with a sledgehammer, and that's what we have invented here," says Kotschenreuther. One hybrid would be needed to destroy the waste produced by 10 to 15 LWRs. The process would ultimately reduce the transuranic waste from the original fission reactors by up to 99 percent. Burning that waste also produces energy.
The CFNS is designed to be no larger than a small room, and much fewer of the devices would be needed compared to other schemes that are being investigated for similar processes. In combination with the substantial decrease in the need for geological storage, the CFNS-enabled waste-destruction system would be much cheaper and faster than other routes, say the scientists. The CFNS is based on a tokamak, which is a machine with a "magnetic bottle" that is highly successful in confining high temperature (more than 100 million degrees Celsius) fusion plasmas for sufficiently long times. The crucial invention that would pave the way for a CFNS is called the Super X Divertor. The Super X Divertor is designed to handle the enormous heat and particle fluxes peculiar to compact devices; it would enable the CFNS to safely produce large amounts of neutrons without destroying the system. "The intense heat generated in a nuclear fusion device can literally destroy the walls of the machine," says research scientist Valanju, "and that is the thing that has been holding back a highly compact source of nuclear fusion." Valanju says a fusion-fission hybrid reactor has been an idea in the physics community for a long time. "It's always been known that fusion is good at producing neutrons and fission is good at making energy," he says. "Now, we have shown that we can get fusion to produce a lot of neutrons in a small space." Producing an abundant and clean source of "pure fusion energy" continues to be a goal for fusion researchers. But the physicists say that harnessing the other product of fusion-neutrons-can be achieved in the near term. In moving their hybrid from concept into production, the scientists hope to make nuclear energy a more viable alternative to coal and oil while waiting for renewables like solar and pure fusion to ramp up.
"The hybrid we designed should be viewed as a bridge technology," says Mahajan. "Through the hybrid, we can bring fusion via neutrons to the service of the energy sector today. We can hopefully make a major contribution to the carbon-free mix dictated by the 2050 time scale set by global warming scientists." The scientists say their Super X Divertor invention has already gained acceptance in the fusion community. Several groups are considering implemented the Super X Divertor on their machines, including the MAST tokamak in the United Kingdom, and the DIIID (General Atomics) and NSTX (Princeton University) in the U.S. Next steps will include performing extended simulations, transforming the concept into an engineering project, and seeking funding for building a prototype.
The first comprehensive assessment of the climate cooling potential of different geoengineering schemes has been carried out by researchers at the University of East Anglia (UEA). Funded by the Natural Environment Research Council and published today in the journal 'Atmospheric Chemistry and Physics Discussions', the key findings include: · Enhancing carbon sinks could bring CO2 back to its pre-industrial level, but not before 2100 - and only when combined with strong mitigation of CO2 emissions · Stratospheric aerosol injections and sunshades in space have by far the greatest potential to cool the climate by 2050 - but also carry the greatest risk · Surprisingly, existing activities that add phosphorous to the ocean may have greater long-term carbon sequestration potential than deliberately adding iron or nitrogen · On land, sequestering carbon in new forests and as 'bio-char' (charcoal added back to the soil) have greater short-term cooling potential than ocean fertilisation · Increasing the reflectivity of urban areas could reduce urban heat islands but will have minimal global effect · Other globally ineffective schemes include ocean pipes and stimulating biologically-driven increases in cloud reflectivity · The beneficial effects of some geo-engineering schemes have been exaggerated in the past and significant errors made in previous calculations
"The realisation that existing efforts to mitigate the effects of human-induced climate change are proving wholly ineffectual has fuelled a resurgence of interest in geo-engineering," said lead author Prof Tim Lenton of UEA's School of Environmental Sciences. "This paper provides the first extensive evaluation of their relative merits in terms of their climate cooling potential and should help inform the prioritisation of future research." Geo-engineering is the large-scale engineering of the environment to combat the effects of climate change - in particular to counteract the effects of increased CO2 in the atmosphere. A number of schemes have been suggested including nutrient fertilisation of the oceans, cloud seeding, sunshades in space, stratospheric aerosol injections, and ocean pipes. "We found that some geoengineering options could usefully complement mitigation, and together they could cool the climate, but geoengineering alone cannot solve the climate problem," said Prof Lenton.
Injections into the stratosphere of sulphate or other manufactured particles have the greatest potential to cool the climate back to pre-industrial temperatures by 2050. However, they also carry the most risk because they would have to be continually replenished and if deployment was suddenly stopped, extremely rapid warming could ensue. Using biomass waste and new forestry plantations for energy, and combusting them in a way that captures carbon as charcoal, which is added back to the soil as 'bio-char', could have win-win benefits for soil fertility as well as the climate. A new combined heat and power plant at UEA is pioneering this type of technology. UEA's School of Environmental Sciences leads the world in climate change research and is creating a new GeoEngineering Assessment & Research initiative (GEAR) to take this groundbreaking work forward.
Taking up valuable land and growing edible crops for biofuels poses a dilemma: Is it ethical to produce inefficient renewable energies at the expense of an already malnourished population? David Pimentel and his colleagues from Cornell University in New York highlight the problems linked to converting a variety of crops into biofuels. Not only are these renewable energies inefficient, they are also economically and environmentally costly and nowhere near as productive as projected. Their findings1 are published online this week in Springer's journal Human Ecology. In the context of global shortages of fossil energy - oil and natural gas in particular - governments worldwide are focusing on biofuels as renewable energy alternatives. In parallel, almost 60 percent of the world's population is malnourished increasing the need for grains and other basic foods. Growing crops, including corn, sugarcane and soybean, for fuel uses water and energy resources vital for the production of food for human consumption.
Professor Pimentel and his team review the availability and use of land, water and current energy resources globally, and then look at the situation in the US specifically. They also analyze biomass resources and show that there is insufficient US biomass for both ethanol and biodiesel production to make the US oil independent. Their paper then looks at the efficiency and costs associated with converting a range of crops into energy and shows that in each case more energy is required for this process than they actually produce as fuel. The research finds a negative energy return of 46 percent for corn ethanol, 50 percent for switchgrass, 63 percent for soybean biodiesel and 58 percent for rapeseed. Even the most promising palm oil production results in a minus 8 percent net energy return. There are also a number of environmental problems linked to converting crops for biofuels, including water pollution from fertilizers and pesticides, global warming, soil erosion and air pollution. In the researchers' opinion, there is simply not enough land, water and energy to produce biofuels. They also argue that ironically, the US is becoming more oil-dependent, not less, as was intended through the production of biofuels. In most cases, more fossil energy is required to produce a unit of biofuel compared with the energy that it provides. As a result, the US is importing more oil and natural gas in order to make the biofuels.
The authors conclude that "Growing crops for biofuels not only ignores the need to reduce natural resource consumption, but exacerbates the problem of malnourishment worldwide by turning food grain into biofuels…Increased use of biofuels further damages the global environment and especially the world food system." Reference 1. Pimentel D et al (2009). Food versus biofuels: environmental and economic costs. Human Ecology DOI 10.1007/s10745-009-9215-8
Researchers at the UCLA School of Public Health have found the first evidence that perfluorinated chemicals, or PFCs - chemicals that are widely used in everyday items such as food packaging, pesticides, clothing, upholstery, carpets and personal care products - may be associated with infertility in women. Published online in Human Reproduction, Europe's leading reproductive medicine journal, the study found that women who had higher levels of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in their blood took longer to become pregnant than women with lower levels. The UCLA researchers used data from the Danish National Birth Cohort to assess whether levels of PFOS and PFOA in pregnant women's plasma were associated with a longer time to pregnancy.
A total of 1,240 women were included in their analyses. Blood samples were first taken between 4 and 14 weeks into the pregnancy so that concentrations of PFOS and PFOA could be measured. The researchers also interviewed the women at around the 12th week of pregnancy to find out whether the pregnancy was planned or not and how long it took them to become pregnant. Infertility was defined as a time to pregnancy of longer than 12 months or a situation in which infertility treatments were used to establish the pregnancy, and the results were adjusted for potential confounding factors such as age, lifestyle and socioeconomic status. The level of PFOS in the women's plasma ranged from 6.4 nanograms per milliliter (ng/ml) to 106.7 ng/ml, and from less than 1 ng/ml to 41.5 ng/ml for PFOA. The researchers divided the women's levels of PFOS/PFOA into four quartiles and found that, compared with women with the lowest levels of exposure, the likelihood of infertility increased by 70 to 134 percent for women in the higher three quartiles of PFOS exposure and by 60 to 154 percent for women in the higher three quartiles of PFOA exposure.
"Perfluorooctanoate and perfluorooctane sulfonate were considered to be biologically inactive, but recently, animal studies have shown that these chemicals may have a variety of toxic effects on the liver, immune system and developmental and reproductive organs," said UCLA researcher Chunyuan Fei, the study's first author. "Very few human studies have been done, but one of our earlier studies showed that PFOA, although not PFOS, may impair the growth of babies in the womb, and another two epidemiological studies linked PFOA and PFOS to impaired fetal growth." "As far as we know, this is the first study to assess the associations between PFOA and PFOS levels in plasma with time to pregnancy in humans," said principal investigator Jørn Olsen, chair of the department of epidemiology at the UCLA School of Public Health. "We are waiting for further studies to replicate our findings in order to discover whether the chemicals should be added to the list of risk factors for infertility." In addition to being found in household goods, PFCs, the class of chemicals to which PFOS and PFOA belong, are used in manufacturing processes involving industrial surfactants and emulsifiers. They persist in the environment and in the body for decades.
The researchers believe that although they measured the PFOS/PFOA levels after pregnancy was established, these levels probably did not change significantly from the time before pregnancy. Men's sperm quality could also be affected by PFCs and might, therefore, contribute to the associations between PFC levels and time to pregnancy, since couples would tend to be sharing the same lifestyles and have similar exposures. However, the researchers did not have data on PFC levels in fathers. "Studies on sperm quality and PFOA/PFOS are certainly warranted," Olsen said. The researchers say the biological mechanisms by which exposure to PFOS and PFOA might reduce fertility are unknown, but PFCs may interfere with hormones that are involved in reproduction. "Our data showed that higher proportions of women reported irregular menstrual periods in the upper three quartiles of PFOA and PFOS, compared with the lowest, and so this could indicate a possible pathway," Fei said.
Not only has the average global temperature increased in the past 50 years, but the hottest day of the year has shifted nearly two days earlier, according to a new study by scientists from the University of California, Berkeley, and Harvard University. Just as human-generated greenhouse gases appear to the be the cause of global warming, human activity may also be the cause of the shift in the cycle of seasons, according to Alexander R. Stine, a graduate student in UC Berkeley's Department of Earth and Planetary Science and first author of the report. "We see 100 years where there is a very natural pattern of variability, and then we see a large departure from that pattern at the same time as global mean temperatures start increasing, which makes us suspect that there's a human role here," he said.
Although the cause of this seasonal shift - which has occurred over land, but not the ocean - is unclear, the researchers say the shift appears to be related, in part, to a particular pattern of winds that also has been changing over the same time period. This pattern of atmospheric circulation, known as the Northern Annular Mode, is the most important wind pattern for controlling why one winter in the Northern Hemisphere is different from another. The researchers found that the mode also is important in controlling the arrival of the seasons each year.
Whatever the cause, Stine said, current Intergovernmental Panel on Climate Change (IPCC) models do not predict this phase shift in the annual temperature cycle. Temperatures at any given time of the year can be very different on land than over the ocean, Stine said, and a change in the strength and direction of the winds can move a lot of heat from the ocean onto land, which may affect the timing of the seasons. However, this seems to be only a partial explanation, he said, because the relationship between this pattern of circulation and the shift in the timing of the seasons is not strong enough to explain the magnitude of the seasonal shift. The researchers also found that the difference between summer and winter land temperatures has decreased over the same 50-year period, with winter temperatures warming more than those in summer. They found that in non-tropical regions, winter temperatures over land warmed by 1.8 degrees Celsius and summer temperatures increased by 1 degree. Ocean warming has been somewhat less.
Stine noted that the study limited its focus to non-tropical regions because the seasons are more pronounced outside the tropics. Stine, Peter Huybers, assistant professor of earth and planetary sciences at Harvard University, and Inez Fung, UC Berkeley professor of earth and planetary science and of environmental science, policy and management, and co-director of the Berkeley Institute of the Environment, based their study on a publicly available database of global surface temperature measurements over both land and ocean from 1850 to 2007 that was compiled by the University of East Anglia's Climate Research Unit in the United Kingdom. Using non-tropical data only, the team found that, while land temperatures in the 100-year period between 1850 and 1950 showed a simple pattern of variability, with the hottest day of the year in the Northern Hemisphere around July 21, temperatures in the period 1954-2007 peaked 1.7 days earlier.
Stine said that monthly temperatures follow a sinusoidal curve, rising to a peak in mid-summer, then dropping to a winter low, and finally rising again because of increased sunshine to another summer high. The temperature typically lags solar insolation by about 30 days over land and 60 days over the ocean, he said, because it takes less energy to heat the moisture in soil than to heat the ocean. Biologists have noticed large changes in the arrival time of many signs of spring over the past 50 years. Buds have been seen opening earlier, birds migrating earlier, snow melting earlier and sea ice breaking up earlier. These changes have been explained by the fact that the Earth is warming, and thus the temperature in any given month has increased. In contrast, this new study finds that individual months have been warming at different rates than others, and that as a result, the peak summer temperature and lowest winter temperature both now come earlier in the calendar year. "We're saying that, on top of the long term trend of warmer summer and winter highs, peak warming is coming earlier within the year," Fung said. "It's not just the onset of spring, but the peak."
The research team is now looking for other mechanisms to explain the observed shift in the timing of the seasons. These include a hypothesized drying of the global soils, which would cause the land surface to respond more quickly to the sun, and changes in the amount of solar energy absorbed by the atmosphere due to industrial pollution. One surprising aspect of the researchers' findings is that the changes they discuss explain so much about the changes over the last 50 years in the month-to-month pattern of temperatures around the globe. "Once we have accounted for the fact that the temperature averaged over any given year is increasing, we find that some months have been warming more than other months. We were surprised to find that over land, most of the difference in the warming of one month relative to another is simply the result of this shift in the timing of the seasons, and a decrease in the difference between summer and winter temperatures," said Stine. "The difference between summer and winter temperatures is comparable to the difference between ice age temperatures and non-ice age temperatures over much of the planet," Stine said. "Thus, small changes in the annual cycle can produce a big effect even if they do not change the annual mean temperature."
Scientists studying climate change have long believed that while most of the rest of the globe has been getting steadily warmer, a large part of Antarctica - the East Antarctic Ice Sheet - has actually been getting colder. But new research shows that for the last 50 years, much of Antarctica has been warming at a rate comparable to the rest of the world. In fact, the warming in West Antarctica is greater than the cooling in East Antarctica, meaning that on average the continent has gotten warmer, said Eric Steig, a University of Washington professor of Earth and space sciences and director of the Quaternary Research Center at the UW. "West Antarctica is a very different place than East Antarctica, and there is a physical barrier, the Transantarctic Mountains, that separates the two," said Steig, lead author of a paper documenting the warming published in the Jan. 22 edition of Nature.
For years it was believed that a relatively small area known as the Antarctic Peninsula was getting warmer, but that the rest of the continent - including West Antarctica, the ice sheet most susceptible to potential future collapse - was cooling. Steig noted that the West Antarctic Ice Sheet, with an average elevation of about 6,000 feet above sea level, is substantially lower than East Antarctica, which has an average elevation of more than 10,000 feet. While the entire continent is essentially a desert, West Antarctica is subject to relatively warm, moist storms and receives much greater snowfall than East Antarctica.
The study found that warming in West Antarctica exceeded one-tenth of a degree Celsius per decade for the last 50 years and more than offset the cooling in East Antarctica. Co-authors of the paper are David Schneider of the National Center for Atmospheric Research in Boulder, Colo., a former student of Steig's; Scott Rutherford of Roger Williams University in Bristol, R.I.; Michael Mann of Pennsylvania State University; Josefino Comiso of NASA's Goddard Space Flight Center in Greenbelt, Md.; and Drew Shindell of NASA's Goddard Institute for Space Studies in New York City. The work was supported by grants from the National Science Foundation. The researchers devised a statistical technique that uses data from satellites and from Antarctic weather stations to make a new estimate of temperature trends.
"People were calculating with their heads instead of actually doing the math," Steig said. "What we did is interpolate carefully instead of just using the back of an envelope. While other interpolations had been done previously, no one had really taken advantage of the satellite data, which provide crucial information about spatial patterns of temperature change." Satellites calculate the surface temperature by measuring the intensity of infrared light radiated by the snowpack, and they have the advantage of covering the entire continent. However, they have only been in operation for 25 years. On the other hand, a number of Antarctic weather stations have been in place since 1957, the International Geophysical Year, but virtually all of them are within a short distance of the coast and so provide no direct information about conditions in the continent's interior.
The scientists found temperature measurements from weather stations corresponded closely with satellite data for overlapping time periods. That allowed them to use the satellite data as a guide to deduce temperatures in areas of the continent without weather stations. "Simple explanations don't capture the complexity of climate," Steig said. "The thing you hear all the time is that Antarctica is cooling and that's not the case. If anything it's the reverse, but it's more complex than that. Antarctica isn't warming at the same rate everywhere, and while some areas have been cooling for a long time the evidence shows the continent as a whole is getting warmer."
A major reason most of Antarctica was thought to be cooling is because of a hole in the Earth's protective ozone layer that appears during the spring months in the Southern Hemisphere's polar region. Steig noted that it is well established that the ozone hole has contributed to cooling in East Antarctica. "However, it seems to have been assumed that the ozone hole was affecting the entire continent when there wasn't any evidence to support that idea, or even any theory to support it," he said. "In any case, efforts to repair the ozone layer eventually will begin taking effect and the hole could be eliminated by the middle of this century. If that happens, all of Antarctica could begin warming on a par with the rest of the world."
A patented Michigan State University process to pretreat corn-crop waste before conversion into ethanol means extra nutrients don't have to be added, cutting the cost of making biofuels from cellulose. The AFEX (ammonia fiber expansion) pretreatment process, developed by Bruce Dale, University Distinguished Professor of chemical engineering and materials science, uses ammonia to make the breakdown of cellulose and hemicellulose in plants 75 percent more efficient than when conventional enzymes alone are used. Cellulose in plants must be broken down into fermentable sugars before they can be turned into biofuel. "Doctoral student Ming Lau and I have shown that it's possible to use AFEX to pretreat corn stover (cobs, stalks and leaves) and then hydrolyze and ferment it to commercially relevant levels of ethanol without adding nutrients to the stover," Dale said. "It's always been assumed that agricultural residues such as corn stover didn't have enough nutrients to support fermentation. We have shown this isn't so." "The research also shows that the chemical compounds created when the stover goes through the AFEX process can improve the overall fermentation process," Lau added. "This is at odds with the general perception that these compounds are detrimental and should be removed."
The research is published in the current issue of the Proceedings of the National Academy of Sciences. Currently, pretreating cellulose with acid is a common way to break the material down into fermentable sugars. But after acid pretreatment, the resulting material must be washed and detoxified. That removes nutrients, leading to the mistaken idea that crop waste lacks the necessary nutrients, Dale said. Cellulosic material pretreated with the AFEX process doesn't have to be washed or detoxified, allowing ethanol to be created from cellulose without added nutrients or other steps. "Washing, detoxifying and adding nutrients back into the pretreated cellulose are three separate steps," Dale said. "Each step is expensive and adds to the cost of the biofuel. Breaking down cellulose into fermentable sugars cost effectively has been a major issue slowing cellulosic ethanol production. Using AFEX as the pretreatment process can dramatically reduce the cost of making biofuels from cellulose."
The next step could be a pilot plant, Dale said, perhaps at MBI International. MBI, a subsidiary of the MSU Foundation, partners with universities and companies to commercialize technology. "There are several companies - including the Mascoma Corp., which plans to open one of the nation's first cellulosic ethanol plants here in Michigan - that may be interested in using this technology," Dale said. "We are working to make the AFEX technology fit these companies' needs."
New research strengthens the link between water pollution and rising male fertility problems. The study, by Brunel University, the Universities of Exeter and Reading and the Centre for Ecology & Hydrology, shows for the first time how a group of testosterone-blocking chemicals is finding its way into UK rivers, affecting wildlife and potentially humans. The research was supported by the Natural Environment Research Council and is now published in the journal Environmental Health Perspectives. The study identified a new group of chemicals that act as 'anti-androgens'. This means that they inhibit the function of the male hormone, testosterone, reducing male fertility. Some of these are contained in medicines, including cancer treatments, pharmaceutical treatments, and pesticides used in agriculture. The research suggests that when they get into the water system, these chemicals may play a pivotal role in causing feminising effects in male fish.
Earlier research by Brunel University and the University of Exeter has shown how female sex hormones (estrogens), and chemicals that mimic estrogens, are leading to 'feminisation' of male fish. Found in some industrial chemicals and the contraceptive pill, they enter rivers via sewage treatment works. This causes reproductive problems by reducing fish breeding capability and in some cases can lead to male fish changing sex. Other studies have also suggested that there may be a link between this phenomenon and the increase in human male fertility problems caused by testicular dysgenesis syndrome. Until now, this link lacked credence because the list of suspects causing effects in fish was limited to estrogenic chemicals whilst testicular dysgenesis is known to be caused by exposure to a range of anti-androgens.
Lead author on the research paper, Dr Susan Jobling at Brunel University's Institute for the Environment, said: "We have been working intensively in this field for over ten years. The new research findings illustrate the complexities in unravelling chemical causation of adverse health effects in wildlife populations and re-open the possibility of a human - wildlife connection in which effects seen in wild fish and in humans are caused by similar combinations of chemicals. We have identified a new group of chemicals in our study on fish, but do not know where they are coming from. A principal aim of our work is now to identify the source of these pollutants and work with regulators and relevant industry to test the effects of a mixture of these chemicals and the already known environmental estrogens and help protect environmental health."
Senior author Professor Charles Tyler of the University of Exeter said: "Our research shows that a much wider range of chemicals than we previously thought is leading to hormone disruption in fish. This means that the pollutants causing these problems are likely to be coming from a wide variety of sources. Our findings also strengthen the argument for the cocktail of chemicals in our water leading to hormone disruption in fish, and contributing to the rise in male reproductive problems. There are likely to be many reasons behind the rise in male fertility problems in humans, but these findings could reveal one, previously unknown, factor." Bob Burn, Principal Statistician in the Statistical Services Centre at the University of Reading, said: "State-of- the- art statistical hierarchical modelling has allowed us to explore the complex associations between the exposure and potential effects seen in over 1000 fish sampled from 30 rivers in various parts of England."
The research took more than three years to complete and was conducted by the University of Exeter, Brunel University, University of Reading and the Centre for Ecology & Hydrology. Statistical modelling was supported by Beyond the Basics Ltd. The research team is now focusing on identifying the source of anti-androgenic chemicals, as well as continuing to study their impact on reproductive health in wildlife and humans.
Rapidly warming climate is likely to seriously alter crop yields in the tropics and subtropics by the end of this century and, without adaptation, will leave half the world's population facing serious food shortages, new research shows. To compound matters, the population of this equatorial belt - from about 35 degrees north latitude to 35 degrees south latitude - is among the poorest on Earth and is growing faster than anywhere else. "The stresses on global food production from temperature alone are going to be huge, and that doesn't take into account water supplies stressed by the higher temperatures," said David Battisti, a University of Washington atmospheric sciences professor.
Battisti is lead author of the study in the Jan. 9 edition of Science. He collaborated with Rosamond Naylor, director of Stanford University's Program on Food Security and the Environment, to examine the impact of climate change on the world's food security. "This is a compelling reason for us to invest in adaptation, because it is clear that this is the direction we are going in terms of temperature and it will take decades to develop new food crop varieties that can better withstand a warmer climate," Naylor said. "We are taking the worst of what we've seen historically and saying that in the future it is going to be a lot worse unless there is some kind of adaptation."
By combining direct observations with data from 23 global climate models that contributed to Nobel prize-winning research in 2007, Battisti and Naylor determined there is greater than a 90 percent probability that by 2100 the lowest growing-season temperatures in the tropics and subtropics will be higher than any temperatures recorded there to date. They used the data as a filter to view historic instances of severe food insecurity, and concluded such instances are likely to become more commonplace. Those include severe episodes in France in 2003 and the Ukraine in 1972. In the case of the Ukraine, a near-record heat wave reduced wheat yields and contributed to disruptions in the global cereal market that lasted two years. "I think what startled me the most is that when we looked at our historic examples there were ways to address the problem within a given year. People could always turn somewhere else to find food," Naylor said. "But in the future there's not going to be any place to turn unless we rethink our food supplies." The serious climate issues won't be limited to the tropics, the scientists conclude. As an example, they cite record temperatures that struck Western Europe in June, July and August of 2003, killing an estimated 52,000 people. The summer-long heat wave in France and Italy cut wheat yields and fodder production by one-third. In France alone, temperatures were nearly 6.5 degrees Fahrenheit above the long-term mean, and the scientists say such temperatures could be normal for France by 2100.
In the tropics, the higher temperatures can be expected to cut yields of the primary food crops, maize and rice, by 20 to 40 percent, the researchers said. But rising temperatures also are likely to play havoc with soil moisture, cutting yields even further. "We have to be rethinking agriculture systems as a whole, not only thinking about new varieties but also recognizing that many people will just move out of agriculture, and even move from the lands where they live now," Naylor said. Currently 3 billion people live in the tropics and subtropics, and their number is expected to nearly double by the end of the century. The area stretches from the southern United States to northern Argentina and southern Brazil, from northern India and southern China to southern Australia and all of Africa. The scientists said that many who now live in these areas subsist on less than $2 a day and depend largely on agriculture for their livelihoods. "When all the signs point in the same direction, and in this case it's a bad direction, you pretty much know what's going to happen," Battisti said. "You are talking about hundreds of millions of additional people looking for food because they won't be able to find it where they find it now." He said wheat makes up one-quarter of the calories consumed in India, but growth in wheat yields there have been stagnant for the last decade.
Temperature increases from climate change are expected to be less in equatorial regions than at higher latitudes, but because average temperatures in the tropics today are much higher than at midlatitudes, rising temperature will have a greater impact on crop yields in the tropics. Recent UW research has shown that even with much smaller temperature increases in the tropics, the impacts of warmer climate will be greater there because life in the tropics does not encounter much temperature variation and so is less adaptable. That makes an even stronger case to begin now searching for ways to deal with substantially warmer conditions, Battisti said. "You can let it happen and painfully adapt, or you can plan for it," he said. "You also could mitigate it and not let it happen in the first place, but we're not doing a very good job of that."
The National Science Foundation and the Tamaki Foundation funded the research. For more information, contact Battisti at (206) 543-2019, battisti@u.washington.edu, or Naylor at (650) 723-5697 or roz@stanford.edu. For more information on the Program on Food Security and the Environment, a joint program of Stanford's Woods Institute for the Environment and the Freeman Spogli Institute for International Studies, see http://fse.stanford.edu.
New research indicates that the ocean could rise in the next 100 years to a meter higher than the current sea level - which is three times higher than predictions from the UN's Intergovernmental Panel on Climate Change, IPCC. The groundbreaking new results from an international collaboration between researchers from the Niels Bohr Institute at the University of Copenhagen, England and Finland are published in the scientific journal Climate Dynamics. According to the UN's Intergovernmental Panel on Climate Change the global climate in the coming century will be 2-4 degrees warmer than today, but the ocean is much slower to warm up than the air and the large ice sheets on Greenland and Antarctica are also slower to melt. The great uncertainty in the calculation of the future rise in the sea level lies in the uncertainty over how quickly the ice sheets on land will melt and flow out to sea. The model predictions of the melting of the ice sheets are the basis for the Intergovernmental Panel on Climate Change's predictions for the rise in sea level are not capable of showing the rapid changes observed in recent years. The new research has therefore taken a different approach.
Looking at the direct correlation "Instead of making calculations based on what one believes will happen with the melting of the ice sheets we have made calculations based on what has actually happened in the past. We have looked at the direct relationship between the global temperature and the sea level 2000 years into the past", explains Aslak Grinsted, who is a geophysicist at the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen. With the help of annual growth rings of trees and analysis from ice core borings researchers have been able to calculate the temperature for the global climate 2000 years back in time. For around 300 years the sea level has been closely observed in several places around the world and in addition to that there is historical knowledge of the sea level of the past in different places in the world.
By linking the two sets of information together Aslak Grinsted could see the relationship between temperature and sea level. For example, in the Middle Ages around 12th century there was a warm period where the sea level was approximately 20 cm higher than today and in the 18th century there was the 'little ice age', where the sea level was approximately 25 cm lower than it is today. A rise in sea level in the future as in the past Assuming that the climate in the coming century will be three degrees warmer, the new model predictions indicate that the ocean will rise between 0,9 and 1,3 meters. To rise so much so quickly means that the ice sheets will melt much faster than previously believed. But it has already been observed that the ice sheets react quicker to increases in temperature than experts thought just a few years ago. And studies from the ice age show that ice sheets can melt quickly. When the ice age ended 11.700 years ago, the ice sheets melted so quickly that sea level rose 11 millimeters per year - equivalent to a meter in 100 years. In the current situation with global warming, Aslak Grinsted believes, that the sea level will rise with the same speed - that is to say a meter in the span of the next 100 years
Researchers at Rensselaer Polytechnic Institute have developed and demonstrated a new type of light emitting diode (LED) with significantly improved lighting performance and energy efficiency. The new polarization-matched LED, developed in collaboration with Samsung Electro-Mechanics, exhibits an 18 percent increase in light output and a 22 percent increase in wall-plug efficiency, which essentially measures the amount of electricity the LED converts into light. The new device achieves a notable reduction in "efficiency droop," a well-known phenomenon that provokes LEDs to be most efficient when receiving low-density currents of electricity, but then to lose efficiency as higher density currents of electricity are fed into the device. The cause of this droop is not yet fully understood, but studies have shown that electron leakage is likely a large part of the problem. "This droop is under the spotlight since today's high-brightness LEDs are operated at current densities far beyond where efficiency peaks," said project leader E. Fred Schubert, Wellfleet Senior Constellation Professor of Future Chips at Rensselaer, and head of the university's National Science Foundation-funded Smart Lighting Engineering Research Center. "This challenge has been a stumbling block, because reducing the current densities to values where LEDs are more efficient is unacceptable. Our new LED, however, which has a radically re-designed active region, namely a polarization-matched active region, tackles this issue and brings LEDs closer to being able to operate efficiently at high current densities," Schubert said.
Results of the study are explained in a paper published online this week by Applied Physics Letters. Focusing on the active region of LEDs where the light is generated, Schubert's team discovered the region contained materials with mismatched polarization. The polarization mismatch likely causes electron leakage, and therefore a loss of efficiency, Schubert said. The researchers discovered that the polarization mismatch can be strongly reduced by introducing a new quantum-barrier design. They replaced the conventional Gallium Indium Nitride/Gallium Nitride (GaInN/GaN) layer of the LED active region, and replaced it with Gallium Indium Nitride/ Gallium Indium Nitride (GaInN/GaInN). This substitution allows the layers of the active region to have a better matched polarization, and in turn reduce both electron leakage and efficiency droop.
The benefits seen by testing the new GaInN/GaInN LED were consistent with theoretical simulations showing polarization matching reducing electron leakage and efficiency droop. Schubert expects that a new wave of lighting devices based on LEDs and solid-state lighting will supplant the common light bulb in coming years, leading to vast environmental, energy, and cost benefits as well as innovations in healthcare, transportation systems, digital displays, and computer networking. Along with Schubert, co-authors on the paper include Rensselaer physics, Future Chips, and electrical engineering graduate students Jiuru Xu, Martin F. Schubert, and Ahmed N. Noemaun; Rensselaer Future Chips research assistant Di Zhu; Jong Kyu Kim, research assistant professor of electrical, computer, and systems engineering at Rensselaer; along with Samsung Electro-Mechanics researchers Min Ho Kim, Hun Jae Chung, Sukho Yoon, Cheolsoo Sone, and Yongjo Park. Funding for the project was contributed by Samsung Electro-Mechanics, the U.S. National Science Foundation, the Rensselaer Smart Lighting Engineering Research Center, Sandia National Laboratories, Rochester Institute of Technology, U.S. Department of Energy, U.S. Department of Defense, Magnolia Optics, Crystal IS, Troy Research Corporation, and New York state. For more information on Rensselaer's Future Chips Constellation, visit: http://www.rpi.edu/futurechips/index.htm. For more information on Rensselaer's Smart Lighting Center, visit: smartlighting.rpi.edu. Contact: Michael Mullaney Phone: (518) 276-6161 E-mail: mullam@rpi.edu
