TAU NEWS – Environment & Ecology
Regional cooperation key to river restoration strategy that could be emulated around the world, says TAU researcher
A new study conducted at Tel Aviv University and published in the journal Water Research argues that Israel's Jordan River may be a useful case study for the challenges facing stream restoration initiatives around the world. The Jordan River has been ravaged by unbridled population growth and defunct sewage treatment plants.
"No river enjoys better PR and has worse environmental conditions than the Jordan River," said Prof. Alon Tal, Chair of TAU's Department of Public Policy, who led the research. "The river has a biblical pedigree and the potential to bring about environmental cooperation."
The Jordan River now has only 3% of its original flow. It has been decimated by a drop in water supply as a result of population growth, climate change, and contamination from a range of pollution sources. Human wastewater and even fish ponds contribute to the extremely poor water quality.
"While the rehabilitation of the Jordan River is of mutual concern to Israel, Jordan, and the Palestinians, the benefits of this rehabilitation have been extremely difficult to convey to decisionmakers, who are aware of how much they must spend to create them," Prof. Tal said. "When the water evaporates, though, wells run dry and agricultural systems and communities quickly collapse."
According to Prof. Tal's research, a two-pronged strategy that would both remove pollution sources and increase water flow to revive associated ecosystems requires regional cooperation.
"A restoration strategy requires ensuring a minimum flow and removing all pollution sources," said Prof. Tal. "We would also need to develop a program for ecologically sensitive tourism that will provide critical justification for ongoing commitment to environmental protection by all parties, regardless of their relative levels of prosperity.
"Regional thinking is critical to overcoming the population pressures of scarcity. Only a focused strategy that engages all the countries in the watershed can lead to a sustainable future for this iconic water resource. If we can't find he political will and economic resources required to revive a small, iconic river like the Jordan, it will be that much more difficult to find politicians and donors who will provide the funds to bring less famous streams back to life."
A cautionary tale
According to Prof. Tal, the case of the Jordan River has direct bearing on water-scarce regions around the world. China alone has some 24,000 rivers that are drying up.
Desalination, the process of removing salts and minerals from saline water to produce water suitable for human consumption or irrigation, has been hailed as a game-changer in countries long suffering from freshwater scarcity and has produced unique opportunities for cooperation in the region. But while desalination facilities have been instrumental in improving water supplies for populations around the world, they have not solved the crisis facing the planet's rivers and streams, including the Jordan River.
"People are mistakenly euphoric about desalination," said Prof. Tal. "Israel recycles 86% of its wastewater and is considered revolutionary in terms of its water management, but even Israel can't get a handle on the Jordan River. Our study is a response to those who think that if you can desalinate water, you don't have a water crisis. Let them come to the Jordan River and see for themselves."
Entotheonella sequesters and neutralizes toxins within sponge host, say TAU researchers
Arsenic is the leading freshwater contaminant on the planet, affecting millions of people worldwide and causing an untold number of deaths every year. Removing arsenic from groundwater and freshwater is a major challenge still facing scientists and policymakers. Now a new Tel Aviv University study published in Nature Communications sheds light on a unique biological model of arsenic detoxification.
According to the new research, the Entotheonella bacterium that inhabits the Theonella swinhoei sponge is one of the only known cases of a bacterium protecting its host from metal poisoning. Entotheonella safeguards these sponges against the dangers of arsenic and another common toxin, barium.
"This particular sponge species, which is among the most ancient animals inhabiting the earth today, is home to a very diverse, very crowded number of microorganisms," said Prof. Micha Ilan of the Department of Zoology at TAU's Faculty of Life Sciences, who led the study. "These sedentary animals evolved to contain an in-house arsenal of chemicals and associated microbiota to deal with predators and pathologies."
A curious finding
While studying the biology of the sponge, which dwells in the Red Sea and the Indo-Pacific Ocean, Prof. Ilan and his colleague Dr. Boaz Mayzel discovered the curious ability of these sponges to accumulate and concentrate a million times more arsenic than that found in seawater. The results of that study were published in PLOS One in 2014.
Dr. Ray Keren, also of TAU's Department of Zoology and co-author of the new research with Dr. Mayzel, suspected a bacterium was involved in the detoxification. Indeed, after extensive testing, a single bacterial species was found to drive the accumulation of both arsenic and barium.
"We have not only discovered that a single bacterial species was the accumulator of both arsenic and barium. We have also found that this bacterium mineralizes the toxic elements, transforming them into inert products within its cells in a controlled manner," said Dr. Keren. "Sponges are eaten by turtles and worms, and even though they are exploding with arsenic, the bacteria renders them non-toxic. They become biologically inert. It is a very unique biological model."
The TAU scientists, in collaboration with Prof. Boaz Pokroy of the Technion Institute of Science and Dr. Sirine Fakra of the Advanced Light Source in the Lawrence Berkeley National Lab, harnessed cutting-edge technology to validate their initial findings, which were procured using the backscatter mode of a scanning electron microscope. "Prof. Pokroy took a sample of Entotheonella to the European Synchrotron Radiation Facility within a week of seeing that first image," said Dr. Keren. "There, he saw that barium is mineralized as barite and arsenic formed smaller peaks of an unknown mineral."
"More work to be done"
Subsequent diffraction analysis revealed that the mineral, crystalline arsenic, was in fact calcium arsenate. Dr. Fakra then validated the presence of these minerals under subfreezing cryogenic conditions.
"To render this unique detox method applicable to other situations, we need to somehow get rid of the sponge," said Prof. Ilan. "In other words, there is a lot more work to be done before we, human beings, can capitalize on this."
The researchers are currently researching the mechanism the bacterium uses to control the mineralization of the elements. "Once we identify the enzymes involved in the process, we can either look for them in bacteria in polluted water or find a way to grow Entotheonella in polluted areas," said Dr. Keren.
Non-indigenous organisms introduced through the Suez Canal are causing irreversible damage, say TAU researchers
Non-indigenous species (NIS) are harming indigenous species and habitats in the Mediterranean Sea, impairing potentially exploitable marine resources and raising concern about human health issues, according to a new Tel Aviv University study.
The 2015 expansion of the Suez Canal, one of the world's most important corridors of commerce, facilitated an influx of non-indigenous species into the Mediterranean Sea, according to Prof. Bella Galil of the Israel National Center for Biodiversity Studies at TAU's Steinhardt Museum of Natural History, the lead author of a study published last month in Management of Biological Invasions.
"The Mediterranean Sea is the most invaded marine basin in the world," says Prof. Galil. "The number of NIS greatly increased between 1970 and 2015. 750 multicellular non-indigenous species were recorded in the Mediterranean Sea, far more than in other European seas, because of the ever-increasing number of Red Sea species introduced through the Suez Canal. This raises concerns about the increasing introductions of additional NIS and associated degradation and loss of native populations, habitats and ecosystem services."
A slow reaction
The development and implementation of a management policy have been slow, despite a century of scientific documentation of marine bioinvasions in the Mediterranean Sea. The Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean, part of the United Nations Environment Programme (UNEP) Regional Seas Programme, adopted an "Action Plan concerning species introductions and invasive species in the Mediterranean Sea" in 2003. But the UNEP has "shied away from discussing, let alone managing, the influx of tropical non-indigenous biota introduced through the Suez Canal. So far no prevention and management measures have been implemented," according to Prof. Galil and her associates.
In their new study, the authors present data that marine-protected areas in the eastern Mediterranean, from Turkey to Libya, have been overwhelmed by non-indigenous species and serve as veritable "hot spots" of bioinvasion. Biotic communities are already fragile, suffering from manmade stressors such as pollution and overfishing. The colonization of these communities by NIS redistributes nutritional resources, removes important actors and renders them more susceptible to extinction.
Eastern Mediterranean algae-dominated rocky habitats have been decimated by large populations of herbivorous fish introduced through the Suez Canal. The two voracious grazers, Siganus luridus and S. rivulatus, have transformed lush rocky reefs into "barrens," dramatically reducing habitat complexity and altering the community structure and food web. Within 30 years, a small Red Sea mussel has replaced the native mytilid along the entire Mediterranean coast of Israel, forming dense nearly mono-specific species "carpets."
A hope for effective intervention
The authors of the study led a discussion on effective management of non-indigenous species introductions into the Mediterranean Sea at a EuroMarine workshop that took place in Ischia, Italy, in 2016. The discussion resulted in the "Ischia Declaration" that laid down principles for an effective, science-based, transboundary management. The declaration was approved by the general assembly of EuroMarine, a network of 73 research institutions and universities, funded by the European Union.
"We hope that this new research will be used to construct a science-based effective management of marine bioinvasions, and prevent, or at least minimize, the influx of additional non-indigenous species into the Mediterranean," says Prof. Galil. "Time will tell whether these aims are achieved or legislators and management continue to put off confronting this difficult issue and pass the environmental, economic and social burden to future generations."
The researchers are currently investigating pollution and other NIS-related factors.
Photo caption: A shoal of the Red Sea marbled spinefoot on an overgrazed rocky reef off northern Israel. Photo: Z. Fayer.
TAU researchers discover algae can yield mass quantities of hydrogen, the world's cleanest energy source
Researchers at Tel Aviv University have revealed how microalgae produce hydrogen, a clean fuel of the future, and suggest a possible mechanism to jumpstart mass production of this environmentally-friendly energy source. Their results have been published in back-to-back studies in Plant Physiology and Biotechnology for Biofuels.
The research was led by Dr. Iftach Yacoby, head of TAU's renewable energy laboratory, and Rinat Semyatich, Haviva Eisenberg, Iddo Weiner and Oded Liran, his students at the School of Plant Sciences and Food Security at TAU's Faculty of Life Sciences.
Researchers in the past believed that algae only produce hydrogen in the course of a single microburst at dawn lasting just a few minutes. But Dr. Yacoby and his team used highly sensitive technology to discover that algae produce hydrogen from photosynthesis all day long. Armed with this discovery, the team harnessed genetic engineering to increase algae's production of this clean energy source 400 percent.
Increasing algae's output of hydrogen
Laboratory tests revealed that algae create hydrogen with the assistance of the enzyme hydrogenase, which breaks down when oxygen is present. The researchers discovered effective mechanisms to remove oxygen so hydrogenase can keep producing hydrogen.
"The discovery of the mechanisms makes it clear that algae have a huge underutilized potential for the production of hydrogen fuel," said Dr. Yacoby. "The next question is how to beef up production for industrial purposes — to get the algae to overproduce the enzyme."
Some 99% of the hydrogen produced in the US comes from natural gas. But the methods used to draw hydrogen from natural gas are toxic — and wasteful.
Answering the need for clean energy
"I grew up on a farm, dreaming of hydrogen," said Dr. Yacoby. "Since the beginning of time, we have been using agriculture to make our own food. But when it comes to energy, we are still hunter-gatherers. Cultivating energy from agriculture is really the next revolution. There may be other ways to produce hydrogen, but this is the greenest and the only agricultural one.
"The world burns in just one year energy it took the earth over a million years to produce," Dr. Yacoby continued. "We must stop being hunters and gatherers of energy. We must start producing clean energy — for our children and for our children's children."
Dr. Yacoby is now researching synthetic enzymes capable of increasing hydrogen production from microalgae to industrial levels.
TAU researchers discover chemical found in most sunscreen lotions poses an existential threat to young corals
The daily use of sunscreen bearing an SPF of 15 or higher is widely acknowledged as essential to skin cancer prevention, not to mention skin damage associated with aging. Though this sunscreen may be very good for us, it may be very bad for the environment, a new Tel Aviv University study finds.
New research published in Archives of Environmental Contamination and Toxicology finds that a common chemical in sunscreen lotions and other cosmetic products poses an existential threat — even in minuscule concentrations — to the planet's corals and coral reefs. "The chemical, oxybenzone (benzophenone-3), is found in more than 3,500 sunscreen products worldwide. It pollutes coral reefs via swimmers who wear sunscreen or wastewater discharges from municipal sewage outfalls and coastal septic systems," said Dr. Omri Bronstein of TAU's Department of Zoology, one of the principal researchers.
The study was conducted by a team of marine scientists from TAU, including Prof. Yossi Loya, also of the Department of Zoology, the Haereticus Environmental Laboratory in Virginia, the National Aquarium (US), the US. National Oceanic & Atmospheric Administration, Ben Gurion University of the Negev, and other labs in the US.
A deadly day at the beach
A person spending the day at the beach might use between two to four ounces of sunblock if reapplied every two hours after swimming, towelling off, or sweating a significant amount. Multiply this by the number of swimmers in the water, and a serious risk to the environment emerges.
"Oxybenzone pollution predominantly occurs in swimming areas, but it also occurs on reefs 5-20 miles from the coastline as a result of submarine freshwater seeps that can be contaminated with sewage," said Dr. Bronstein, who conducted exposure experiments on coral embryos at the Inter University Institute in Eilat together with Dr. Craig Downs of the Heretics Environmental Laboratories. "The chemical is highly toxic to juvenile corals. We found four major forms of toxicity associated with exposure of baby corals to this chemical."
Forms of toxicity include coral bleaching, a phenomenon associated with high sea-surface temperature events like El Niño — and with global mass mortalities of coral reefs. The researchers found oxybenzone made the corals more susceptible to this bleaching at lower temperatures, rendering them less resilient to climate change. They also found that oxybenzone damaged the DNA of the corals, neutering their ability to reproduce and setting off a widespread decline in coral populations.
The study also pointed to oxybenzone as an "endocrine disruptor," causing young coral to encase itself in its own skeleton, causing death. Lastly, the researchers saw evidence of gross deformities caused by oxybenzone — i.e., coral mouths that expand to five times their healthy, normal size.
It only takes a drop
"We found the lowest concentration to see a toxicity effect was 62 parts per trillion — equivalent to a drop of water in six and a half Olympic-sized swimming pools," said Dr. Bronstein. The researchers found concentrations of oxybenzone in the US Virgin Islands to be 23 times higher than the minimum considered toxic to corals.
"Current concentrations of oxybenzone in these coral reef areas pose a significant ecological threat," said Dr. Bronstein. "Although the use of sunscreen is recognized as important for protection from the harmful effects of sunlight, there are alternatives — including other chemical sunscreens, as well as wearing sun clothing on the beach and in the water."
The researchers hope their study will draw awareness of the dangers posed by sunscreen to the marine environment and promote the alternative use of sun-protective swimwear.
The research, a product of the new TAU-Tsinghua XIN Center, was conducted by 150,000 volunteers at IBM's World Community Grid
Nearly 800 million people worldwide don't have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. Together, unsafe drinking water and the inadequate supply of water for hygiene purposes contribute to almost 90% of all deaths from diarrheal diseases — and effective water sanitation interventions are still challenging scientists and engineers.
A new study published in Nature Nanotechnology proposes a novel nanotechnology-based strategy to improve water filtration. The research project involves the minute vibrations of carbon nanotubes called "phonons," which greatly enhance the diffusion of water through sanitation filters. The project was the joint effort of a Tsinghua University-Tel Aviv University research team and was led by Prof. Quanshui Zheng of the Tsinghua Center for Nano and Micro Mechanics and Prof. Michael Urbakh of the TAU School of Chemistry, both of the TAU-Tsinghua XIN Center, in collaboration with Prof. Francois Grey of the University of Geneva.
Shake, rattle, and roll
"We've discovered that very small vibrations help materials, whether wet or dry, slide more smoothly past each other," said Prof. Urbakh. "Through phonon oscillations — vibrations of water-carrying nanotubes — water transport can be enhanced, and sanitation and desalination improved. Water filtration systems require a lot of energy due to friction at the nano-level. With these oscillations, however, we witnessed three times the efficiency of water transport, and, of course, a great deal of energy saved."
The research team managed to demonstrate how, under the right conditions, such vibrations produce a 300% improvement in the rate of water diffusion by using computers to simulate the flow of water molecules flowing through nanotubes. The results have important implications for desalination processes and energy conservation, e.g. improving the energy efficiency for desalination using reverse osmosis membranes with pores at the nanoscale level, or energy conservation, e.g. membranes with boron nitride nanotubes.
Crowdsourcing the solution
The project, initiated by IBM's World Community Grid, was an experiment in crowdsourced computing — carried out by over 150,000 volunteers who contributed their own computing power to the research.
"Our project won the privilege of using IBM's world community grid, an open platform of users from all around the world, to run our program and obtain precise results," said Prof. Urbakh. "This was the first project of this kind in Israel, and we could never have managed with just four students in the lab. We would have required the equivalent of nearly 40,000 years of processing power on a single computer. Instead we had the benefit of some 150,000 computing volunteers from all around the world, who downloaded and ran the project on their laptops and desktop computers.
"Crowdsourced computing is playing an increasingly major role in scientific breakthroughs," Prof. Urbakh continued. "As our research shows, the range of questions that can benefit from public participation is growing all the time."
The computer simulations were designed by Ming Ma, who graduated from Tsinghua University and is doing his postdoctoral research in Prof. Urbakh's group at TAU. Ming catalyzed the international collaboration. "The students from Tsinghua are remarkable. The project represents the very positive cooperation between the two universities, which is taking place at XIN and because of XIN," said Prof. Urbakh.
Other partners in this international project include researchers at the London Centre for Nanotechnology of University College London; the University of Geneva; the University of Sydney and Monash University in Australia; and the Xi'an Jiaotong University in China. The researchers are currently in discussions with companies interested in harnessing the oscillation knowhow for various commercial projects.
TAU researcher harnesses energy-efficient pulsed electric fields to preserve milk
Even though much of the population in developing countries is involved in agriculture, food security is virtually out of reach. Often the only resort is to purchase a cow, buffalo, or sheep, to provide a steady supply of fresh milk, a nutritious staple of a daily diet. But how to preserve it safely? Refrigeration and boiling are costly — and often impossible due to sporadic electricity.
The answers may lie in new Tel Aviv University research published in Technology, which finds that short pulsed electric fields can be used to kill milk-contaminating bacteria. Through a process called electroporation, bacterial cell membranes are selectively damaged. According to lead investigator Dr. Alexander Golberg, of TAU's Porter School of Environmental Studies, applying this process intermittently prevents bacteria proliferation in stored milk, potentially increasing its shelf life.
According to the study, pulsed electric fields, an emerging technology in the food industry that has been shown to effectively kill multiple food-born microorganisms, could provide an alternative, non-thermal pasteurization process. The stored milk is periodically exposed to high-voltage, short pulsed electric fields that kill the bacteria. The energy required can come from conventional sources or from the sun. The technology is three times more energy-efficient than boiling and almost twice as energy efficient as refrigeration.
An alternative for poorer countries
"We are on a constant hunt for new, low-cost, chemical-free technologies for milk preservation, especially for small farmers in low-income countries," said Dr. Golberg. "For 1.5 billion people without adequate access to electricity, refrigeration is simply not a possibility and boiling does not preserve milk's freshness over time."
In developed countries, bacterial growth in milk is managed with refrigeration. But certain pathogens like listeria monocytogenes are less sensitive to low temperature so can proliferate during transportation and in storage. "Refrigeration slows the bacteria's metabolism, but pulsed electric fields kill them," said Dr. Golberg. "They are a fundamentally different approach to controlling microorganisms during storage.
"Our model shows that pulsed electric fields preservation technology does not require a constant electricity supply; it can be powered for only 5.5 hours a day using small, family scale solar panels," said Dr. Golberg. "I believe that this technology can provide a robust, simple, and energy-efficient milk preservation system that would decrease the amount of wasted milk, thus increasing the income of small farmers in developing countries."
Dr. Golberg is currently exploring partnerships with interested agencies to develop an affordable device to reduce food waste and increase small farmers' incomes.
TAU researcher finds hurricanes ravaging U.S. and Canada originate as disturbances in western Africa's atmosphere
Hurricanes require moisture, the rotation of the earth, and warm ocean temperatures to grow from a mere atmospheric disturbance into a tropical storm. But where do these storm cells originate, and exactly what makes an atmospheric disturbance amp up full throttle?
A new study published in Geophysical Research Letters by Tel Aviv University's Prof. Colin Price and his graduate student Naama Reicher of the Department of Geosciences at TAU's Faculty of Exact Sciences finds most hurricanes over the Atlantic that eventually make landfall in North America actually start as intense thunderstorms in Western Africa.
"85 percent of the most intense hurricanes affecting the U.S. and Canada start off as disturbances in the atmosphere over Western Africa," says Prof. Price. "We found that the larger the area covered by the disturbances, the higher the chance they would develop into hurricanes only one to two weeks later."
Watching the clouds gather
Using data covering 2005-2010, Prof. Price analyzed images of cloud cover taken by geostationary satellites, which orbit the Earth at the precise speed of the earth's rotation and take pictures of cloud cover every 15 minutes. This enabled Prof. Price to track the variability in cloud cover blocking the earth's surface in West Africa between the months of June and November — hurricane season.
The coverage of clouds acts as an indication of atmospheric disturbances. The more clouds in an area, the larger the disturbance. Using infrared cloud-top temperature data gathered from satellites, Prof. Price assessed the temperatures of the cloud tops, which grow colder the higher they rise. He then compared his cloud data with hurricane statistics — intensity, date of generation, location, and maximum winds — from the same period using the National Hurricane Center data base.
"We first showed that the areal coverage of the cold cloud tops in tropical Africa was a good indicator of the monthly number of atmospheric disturbances — or waves — leaving the west coast of tropical Africa," said Prof. Price. "The disturbances that developed into tropical storms had a significantly larger area covered by cold cloud tops compared with non-developing waves."
What makes them special
According to Prof. Price, only 10 percent of the 60 disturbances originating in Africa every year turn into hurricanes. And while there are around 90 hurricanes globally every year, only 10 develop in the Atlantic Ocean.
"We wanted to know what was so special about these 10% of disturbances that develop into hurricanes. Was there something different about these storms at their genesis?" said Prof. Price. "By looking at each of these storms individually, we found again that the larger the cloud coverage originally in West Africa, the higher the value of the accumulated cyclone energy in a future hurricane. The conclusion, then, is that the spatial coverage of thunderstorms in West Africa can foretell the intensity of a hurricane a week later.
"If we can predict a hurricane one or two weeks in advance — the entire lifespan of a hurricane — imagine how much better prepared cities and towns can be to meet these phenomena head on," Prof. Price says. He is currently examining the thunderstorm clusters around the eyes of hurricanes to study the intensification process of those destructive phenomena.
TAU researchers discover cellular networks can be used to detect dangerous fog
When warm air comes into contact with a cool surface and chills to saturation, fog materializes. It blankets open roads and runways and dramatically reduces visibility — often causing devastating accidents.
A new study published in the Bulletin of the American Meteorological Society, by Tel Aviv University's Prof. Pinhas Alpert and Dr. Noam David of the Department of Geosciences at TAU's Faculty of Exact Sciences, and by Prof. Hagit Messer and Omry Sendik of the Department of Electrical Engineering Systems at TAU's Faculty of Engineering, reports a practical solution to fog detection can be found in cellular communication networks already in place all over the world.
Present fog monitoring tools include satellite systems and in situ sensors, but they are costly to implement and suffer from lack of precision when measuring at ground levels — where the data is most crucial. Researchers found in previous studies that the transmission of wireless microwave links in cellular networks were able to detect only the densest fog, but new advances in higher cellular communication frequencies can facilitate the detection of even light fog.
Opening a window of opportunity
"The goal of the work presented here is to reveal the potential that exists in commercial microwave systems, where higher frequencies more sensitive to fog are starting to be used," said Prof. Alpert, who supervised the study together with Prof. Messer. "We are presenting a window of opportunity to monitor fog with high resolution using technology already in place."
Commercial wireless links that operate at frequencies of tens of gigahertz form the infrastructure for data transmission between cellular base stations. These links are widely deployed across countries by cellular communication providers and are situated at ground level altitudes. Because of this, they are affected by different atmospheric phenomena at surface level — particularly fog.
"These existing systems have the potential to be utilized as an efficient fog monitoring tool," said Dr. David, who conducted the research as part of his postdoctoral study. "However, many of these systems, in their current format, have the potential to monitor only relatively heavy fog — hence the need for emerging technology to acquire more accurate observations."
Current wireless microwave links typically operate between frequencies of about 6 to 40 gigahertz, and the signal loss induced by fog at these frequency bands is relatively low. In other words, such systems have the potential to monitor only relatively heavy fog. In order to satisfy the growing demand for higher data rates and wider bandwidth, higher frequencies of around 70/80 gigahertz are beginning to be employed. "Since these higher frequencies are highly sensitive to the effects of fog, a new opportunity to potentially acquire wide-scale, high resolution observations of fog in real time has emerged," said Dr. David.
A foggy evening in Tel Aviv
To prove their concept, the researchers used a map of existing microwave links in Israel and calculated the minimum liquid water content that could be detected using signal attenuation data at 20, 38, and 80 GHz. At 80 GHz, even light fog, with a visibility of up to 750 meters, had a measurable effect on the signal. And when the researchers analyzed actual 38-GHz signal data for an evening that was foggy in Tel Aviv but clear in Jerusalem, the visibilities and fog densities they calculated were consistent with recorded observations.
"While most studies of this kind are focused on rainfall, fog is no less hazardous to people and objects in motion," said Dr. David. "Current monitoring tools are insufficient. Our new approach exposes the potential that already exists in these communication systems to provide high-resolution spatial measurements of fog."
The researchers are continuing to explore the potential of wireless communication frequencies.
TAU researcher devises method to provide continuous coverage of thunderstorms all over the planet
The Doomsday Clock, which measures the likelihood of global catastrophe, last month ticked a minute closer to "midnight" — the apocalypse. The symbolic clock was set to 11:57 by a board of atomic scientists featuring 17 Nobel Laureates, who warned that the planet, beset by climate change and nuclear proliferation, faced extraordinary and undeniable threats to its continued existence.
New research by Prof. Colin Price of Tel Aviv University's Department of Geosciences and published in Environmental Research Letters will likely be crucial to measuring the impact of climate change on thunderstorms — one of the weather occurrences most problematic for human life on the planet. The varying frequency and intensity of thunderstorms have direct repercussions for the public, agriculture, and industry.
"To date, satellites have only provided snapshots of thunderstorm incidence," said Prof. Price, whose new map of thunderstorms around the world is the first of its kind. "We want to use our algorithm to determine how climate change will affect the frequency and intensity of thunderstorms. According to climate change predictions, every one percent rise in global temperature will lead to a 10 percent increase in thunderstorm activity. This means that we could see 25 percent more lightning by the end of the century."
Keeping track of lightning
To draft a global thunderstorm map, Prof. Price and TAU graduate student Keren Mezuman used a vast global lightning network of 70 weather stations capable of detecting radio waves produced by lightning — the main feature of a thunderstorm — from thousands of miles away. The World Wide Lightning Location Network (http://wwlln.net) is run by atmospheric scientists at universities and research institutes around the world. The TAU team harnessed this ground-based system to cluster individual lightning flashes into "thunderstorm cells."
Every hour the exact GPS time of every detected lightning pulse was registered. Prof. Price and his colleagues then calculated the difference in arrival times of signals, using data from four to five different stations to locate individual lightning strokes anywhere on the globe. Finally, the researchers grouped the detected flashes into clusters of thunderstorm cells.
The WWLLN station in Israel has the ability to detect lightning as far away as central Africa.
Climate change and thunderstorms
"When we clustered the lighting strikes into storm cells, we found that there were around 1,000 thunderstorms active at any time somewhere on the globe," said Prof. Price.
The researchers, pooling seven years of data analysis, found that every day lightning activity on earth peaked at 1900 GMT, with low activity at 0300 GMT every day. While previous studies had estimated that 90 percent of lightning flashes occurred over land areas, the TAU team found that only 50 percent of the thunderstorms cells existed over land areas, implying that land storms have much more lightning than ocean storms.
"How lightning will be distributed in storms, and how the number and intensity of storms will change in the future, are questions we are working on answering," Prof. Price said.
TAU study pinpoints dominant factors informing erroneous forecasts of weather conditions around the world
The night before the Israel Defense Forces' 1976 mission rescuing over 200 hostages from hijackers in Entebbe, Uganda, Tel Aviv University's Prof. Pinhas Alpert, then head of an Israel Air Force base forecasting unit, provided intelligence that was critical to the success of the operation — the weather conditions commandos were likely to encounter en route and on the ground. Had his information been incorrect, the mission might have ended quite differently.
The inaccuracy of forecasts also has personal implications for people around the world, leaving them stranded without umbrellas, snowed in, or stuck in airports. But considering the technology available today, why do meteorologists continue to miss the mark?
New research published in the journal Land by Prof. Alpert and his PhD student Tali Hirsch-Eshkol of the Department of Geosciences at TAU's Faculty of Exact Sciences prioritizes, for the first time, reasons for forecast failures across different regions of the world. Using multi-regression-based statistics on data collected between 1979-1993 on tens of thousands of forecast points, Prof. Alpert and his team were able to quantify the causes — man-made and natural — for weather prediction inaccuracies.
The big picture
"Considering my background in forecasting, weather prediction fallacies bothered me for a long time," said Prof. Alpert. "Since joining TAU in 1982, I have been looking for a way to quantify the dominant factors that cause errors in forecasting. Until now, there has been no comprehensive analysis of these factors. They have been studied separately, but not in combination. I decided to quantify and prioritize the dominant factors for different regions, and provide this valuable information to the world scientific community."
Using statistical analysis of meteorological data over thousands of locations and the course of 15 years, Prof. Alpert identified unique factors affecting forecasts in Europe, North Africa, the Mediterranean, Asia, and East Asia. The researchers found the dominant factors clouding the accuracy of predictions comprised land-use changes (i.e. an area that had been covered in forest is suddenly bare), topography, particles in the atmosphere and population density.
"For example, when Israel's national water pipeline crossed the northern Negev in June 1964, it changed the lay of the land," said Prof. Alpert. "After a relatively short period of time, the desert was blooming, affecting the generation of clouds, precipitation, and temperature extremes. It is difficult for forecasters to incorporate changes like this. In effect, this single land-cover change altered the entire local climate over the Northern Negev, and existing forecast models had difficulty accommodating this, leading to erroneous predictions."
Gold, silver, and bronze
The researchers incorporated the dominant factors within a single equation and then monitored the model's ability to accurately predict monthly weather conditions in different regions over 15 years. Prof. Alpert and his team also created a table of "factor prioritization" — gold, silver, and bronze labels to identify dominant and less dominant factors for different regions in the world. For example, they found that in the eastern Mediterranean, particles in the atmosphere were the most important cause of forecast fallacies, followed by land cover change. They also found topography to be the most influential factor affecting weather around the world.
"The only tool the weather forecaster has is his model, and the only choice he or she has is to look at different models, each of which has strengths and weaknesses," said Prof. Alpert. "Several hundred research groups are trying to improve forecasting models all the time. These groups also seek to improve predictions of climate change and global warming. Our study provides them with information about the right topics of research to address for each region."
Prof. Alpert is continuing to investigate factors that damage the quality of forecasts, hoping to devise new methods of improving weather and climate models.
Environmental studies facility receives "Platinum" designation from U.S. Green Building Council
The U.S. Green Building Council has awarded Tel Aviv University's Porter School of Environmental Studies its highest distinction, LEED (Leadership in Energy & Environmental Design) Platinum. The Porter Building is the first in Israel, and only one of a few dozen in the world, to receive this exceptionally high measure of its long-term sustainability and environmental consciousness.
The building scored 92 out of 110 points, making it only one of 17 other structures in the world to have garnered more than 90 points towards a LEED designation. Platinum, the highest distinction, is achieved by earning over 80 points. Buildings at only a very few other universities in the world, including Harvard and Yale, have received the coveted "Platinum" status.
The LEED scale is the most widely recognized and respected rating system for green building in the world. The "Platinum" rating constitutes an official, independent certification that environmental considerations were given the highest priority in planning and construction of a building.
The building is the vision of TAU benefactor and Governor Dame Shirley Porter, the Porter family of Israel and the UK, and the Porter Foundation, who have championed the project for the past 13 years. Dame Shirley founded the Porter School of Environmental Studies in 2000 to deepen knowledge and train a new environmental leadership in Israel. Since then, it has become Israel's leading school in Israel dedicated to research, teaching and policy studies in the environmental field.
The Porter Building was designed by Alexrod-Grobman Architects, Geotectura Studio, and NCArchitects and landscaped by Braudo-Maoz Landscape Architects. It provides an ultramodern space for teaching, multidisciplinary research, exhibitions, conferences, and demonstrations of environmental technologies. The innovative structure was designed to maximize the efficient use of energy, water, cool air, and materials.
For more, read the article in NoCamels: "TAU's Porter School Of Environment Awarded LEED Platinum Designation".
High-tech accelerator program a "unique experiment" in academic and start-up cooperation
Tel Aviv University's National Research Institute for Transportation Innovation is poised to launch an accelerator program for budding entrepreneurs in the fields of intelligent transportation and alternative fuels. The new research institute, established in August in collaboration with the Alternative Fuels Administration of the Israeli Prime Minister's Office, will open the program in December.
The four-to-six-month program will be situated in the university's "capsule" building, the new home of TAU's Porter School of Environmental Studies.
"From the university's perspective, this is a unique experiment in joining hands with Israeli start-up industries, incorporating the best of the academic world with the best of hi-tech entrepreneurship," said Prof. Dan Rabinowitz, head of the Porter School and the Institute for Transportation Innovation.
The budget for the program is expected to reach NIS 1 million (about $263,000 US) annually, which will be partially funded by EcoMotion, an Israel-based community of entrepreneurs in the smart transportation industry. Each participating entrepreneurial team will receive about NIS 100,000 (about $26,000 US) in cash, as well as the consulting services of experts in business, technology, and the automotive industry. The goal is to guide entrepreneurs through the first stages of development and help them acquire their first investment at the end of the program.
"The accelerator is designed to try to cope with the lack of infrastructure supporting the realization of unique ideas in the field of intelligent transportation, and is a direct continuation of the community's activities," said EcoMotion director Boaz Mamo.
Read the story in The Jerusalem Post: "Tel Aviv University launches fuel substitutes accelerator"
TAU discovers Middle Eastern vegetation is remarkably resilient to long-term drought
Climate change predictions for the Middle East, like other arid regions of the world, are alarming. In an area known for its water scarcity, rainfall is expected to decrease even further in the near future, spelling disaster for the functioning of unique ecosystems — hotspots of biodiversity and rich genetic fodder for essential crops.
To test these dire predictions, Prof. Marcelo Sternberg of the Department of Molecular Biology and Ecology of Plants at Tel Aviv University's Faculty of Life Sciences, together with ecologists from the University of Tübingen in Germany, subjected natural ecosystems to an experimental drought over the course of nine years, simulating predicted future climate scenarios.
In the course of their experiment, conducted in four different ecosystems ranging from desert (3.5 inches of annual rainfall) to moist Mediterranean woodland (30.7 inches of annual rainfall), the researchers found that, contrary to predictions, no measurable changes in annual vegetation could be seen. None of the crucial vegetation characteristics — neither species richness and composition, nor density and biomass (particularly important for ecosystems traditionally used as rangelands) — had changed appreciably in the course of the rainfall manipulations.
"Based on our study, the going hypothesis that all semiarid regions will react strongly to climate change needs to be revised," states Prof. Sternberg. The surprising results of the study were recently published in Nature Communications.
A natural comfort zone
The affected ecosystems proved resilient, likely due to the highly variable amounts of annual rainfall for which the regions are known. The experimental climate changes, which simulated a decrease of about 30 percent of current rainfall, seem to fall within the natural "comfort zone" of wild plants.
In their experiment, the scientists were intent on testing one of the basic assumptions of climate change — that an affected plant species will migrate to more hospitable areas in order to survive. The researchers tested for two possible alternatives: first, a species dying off due to its inability to migrate to new and more suitable areas, and second, other varieties of the same species adapting to the new conditions created by the climate change.
"This second option has been overlooked by most researchers," said Prof. Sternberg, who found local adaptation to be the primary course of action for the plant communities that were tested.
Broad and extensive study
"Our experiment is likely the most extensive climate change study ever done, because of the number of sites involved, the long duration of experimental manipulations, and the immense species richness," said Prof. Sternberg.
According to Prof. Sternberg, the Mediterranean and semi-arid annual plant communities would be little affected by climate change, at least in the short to medium term. However, it cannot be ruled out that species composition could change after 20-30 years, because natural short-term climatic variations impose a different selection regime on organisms than a long-term trend of changing climate conditions.
Prof. Sternberg is currently searching for a new collaboration and funding to maintain the long-term experiment and expand its breadth and scope.
TAU researcher discovers the biological flaw that dooms fish larvae's ability to feed
"An end to seafood by 2050?" "Fish to disappear by 2050?" These sensational media headlines were the result of a 2010 report by the United Nations Environment Program, declaring that over-fishing and pollution had nearly emptied the world's fish stocks. That scarcity portends disaster for over a billion people around the world who are dependent on fish for their main source of protein.
Now, a new study by Dr. Roi Holzman and Victor China of the Department of Zoology at Tel Aviv University's George S. Wise Faculty of Life Sciences has uncovered the reason why 90% fish larvae are biologically doomed to die mere days after hatching. With this understanding of the mechanism that kills off the majority of the world's fish larvae, leaving only a marginal proportion to populate the world's oceans, "We can help find a solution to the looming fish crisis in the world," said Dr. Holzman.
The research, published in PNASand conducted at the Inter-University Institute for Marine Sciences in Eilat, Israel, suggests that "hydrodynamic starvation," or the physical inability to feed due to environmental incompatibility, is the reason so many fish larvae perish.
"By focusing on the constraints placed on larvae survival, we have a better chance of producing higher quality mariculture," a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, said Dr. Holzman. "If we can produce better fish, this will have huge implications for our ability to maintain fish populations."
Dr. Holzman based his study on the problematic nature of fish reproduction. Nearly all fish species reproduce externally — they release and abandon their sperm and eggs into the water, providing no parental care. The fertilized eggs then hatch in the water within a couple of days and the hatching larvae must sustain themselves. When attached to a yolk sac (a membranous sac attached to an embryo that provides early nourishment in the form of yolk), these premature organisms can survive for a period of two or three days, but once the larvae, with poorly developed fins and gills, open their mouths, they start dying in droves.
"We thought, something is going on during this period, in which the proportional number of larvae dying is greatest," said Dr. Holzman. "Our goal was to pinpoint the mechanism causing them to die. We saw that even under the best controlled conditions, 70% of fish larvae were dying within the two weeks known as the 'critical period,' when the larvae detach from the yolk sac and open their mouths to feed," said Dr. Holzman. "What was going on? We turned to physics as a source of the problem."
Eating soup with a fork
The physical structure of the larvae and their flawed interaction with the physical environment provided the answer Dr. Holzman was looking for. Over the course of two years, he and doctoral student Victor China observed fish larvae at three significant points in their development (at the beginning, middle, and end of that “critical period” — eight, 13, and 23 days old). They found that the "stickiness" of the water — the viscosity of the surrounding ocean water — was hampering the larvae's attempts to feed.
"All that determines the larvae's feeding ability is viscosity — not age, not development. Only their interaction with the surrounding water," said Dr. Holzman. "Because the water molecules around you have weak electrical bonds, only a thin layer sticks to your skin — a mere millimeter thick. If you're a large organism, you hardly feel it. But if you're a three-millimeter-sized larva, dragging a millimeter of water across your body will prevent you from propelling forward to feed. So really, it's all about larval size, and its ability to grow fast and escape the size where it feels the water as viscous fluid."
The researchers found that in less viscous water, the larvae improved their feeding ability. In theory, they can be expected to increase their survival rate. "We conclude that hydrodynamic starvation is the reason for their dying," said Dr. Holzman. "Imagine eating soup with a fork — that's what it's like for these larvae. They're not developed enough at the critical point to adopt the constrained feeding strategy of adult-sized, better-developed fish."
Armed with this knowledge of the larvae's biological flaw, the researchers are currently patenting a solution to maintain higher survival rates among fish larvae populations.
TAU researchers discover soft coral tissue may help protect reefs against the hazardous effects of climate change
Coral reefs are home to a rich and diverse ecosystem, providing a habitat for a wide range of marine animals. But the increasing acidification of ocean water is jeopardizing the calcified foundations of these reefs, endangering the survival of thousands upon thousands of resident species.
New research by Prof. Yehuda Benayahu, Dr. Zehava Barkay, Prof. Maoz Fine, and their jointly supervised graduate student Yasmin Gabay of Tel Aviv University's Department of Zoology, Wolfson Applied Materials Research Center and the Interuniversity Institute for Marine Sciences in Eilat has uncovered the protective properties of soft coral tissue, which proved resilient when exposed to declining oceanic pH levels. The study, published in PLOS One, provides insight into the changing face of coral reefs threatened by dropping oceanic pH levels and may provide a new approach toward preserving the harder, calcified reef foundations.
Reefs and environmental change
Acidification is caused by increased carbon dioxide emissions in the atmosphere due to global change, fossil fuel burning, and other pollution. These emissions dissolve in the ocean, resulting in a slight lowering of oceanic pH levels. This produces changes to ocean water's carbon content, destroying the calcification of reef-building stony coral.
"The rise in temperature and ocean acidification are the main concerns of environmental change," said Prof. Benayahu, the Israel Cohen Chair in Environmental Zoology, whose TAU laboratory is home to one of the world's only soft coral (octocoral) research centers. "We know the value of reefs, the massive calcium carbonate constructions that act as wave breakers, and protect against floods, erosion, hurricanes, and typhoons. While alive, they provide habitats for thousands of living organisms, from sea urchins to clams, algae to fish. Reefs are also economically important in regions like Eilat or the Caribbean."
At first, the researchers examined the effects of lowered pH levels on living colonies of soft corals. Observing no significant effects on their physiology, Gabay thought it would be interesting to consider the effects of acidification on the skeleton of these soft corals.
"We really wanted to know if something could survive dropping pH levels in the future," said Gabay. "I was curious as to whether coral tissue could protect the inner coral skeleton, which is of most use in terms of reef construction, so I conducted an experiment using live soft corals and soft coral skeletons, which were placed in tanks containing ocean water with manipulated pH levels."
Using state-of-the-art microscopy, Gabay then scanned the tissue-covered skeletons and bare skeletons of soft corals exposed to experimental acidic conditions, the same conditions the International Panel of Climate Change predicts will occur 100 years from now if carbon dioxide emissions continue to rise. She found that the bare soft coral skeletons exhibited acidic stressed symptoms — large pockets burned into their microscopic corpuscular subunits — whereas the tissue-covered skeleton revealed almost no damage to its microscopic subunits.
"We found that the soft coral's tissue may indeed protect the skeleton from declining pH levels," said Yasmin Gabay. "The organism's internal environment apparently has a mechanism that protects against the acidic conditions."
The future of "the orchestra"
According to Prof. Benayahu, the future of soft-coral reefs is still unclear. Soft corals are not primary reef builders, because their skeletons are slow to calcify. Stony corals provide the massive skeletons that create reefs. Soft corals are replacing these reef builders, because they are somehow able to survive and live under extreme environmental conditions.
"A reef is like an orchestra. Many organisms interact to create harmony," said Prof. Benayahu. "Thousands of species live together and create life together. It is hard to predict what will happen if only soft corals survive, because they simply do not calcify at same rate as stony corals."
The researchers are currently studying the potential effects of soft coral displacement of stony coral species and the subsequent ramifications for reefs.
The ionosphere, one of the regions of the upper atmosphere, plays an important role in global communications. Ionized by solar radiation, this electricity-rich region is used for the transmission of long wave communications, such as radio waves. Now Prof. Colin Price of Tel Aviv University's Department of Geophysical, Atmospheric and Planetary Sciences, working alongside PhD candidate Israel Silber, has discovered that the radio waves reflecting back to Earth from the ionosphere offer valuable news on climate change as well.
Their research shows that the strength of radio signals on the ground is a reliable indicator of temperature change above. Prof. Price and his team used simple radio antennae on the ground to measure radio waves broadcast by navigational transmitters around the globe, then compared information on the strength of these radio signals with data on temperature fluctuations in the upper atmosphere. They discovered that climate change in the upper atmosphere — caused by an abundance of greenhouse gases — may lead to a greater absorption of radio waves. Weaker signals could therefore be indicative of greater climate change.
Detailed in the Journal of Geophysical Research, this simple, cost-effective measurement can be a valuable contribution to the ongoing effort to track climate change, says Prof. Price, adding to measurements of ground and lower atmospheric temperatures to create a more holistic picture.
Global warming, upper atmospheric cooling
On the Earth's surface and in the lower atmosphere, an increase of greenhouse gases has a warming effect, the gases acting as a "blanket" and keeping heat from escaping from the Earth into space. But these gases, including carbon dioxide, are increasing in the upper atmosphere as well, where they have a cooling effect.
When cooled, the ionosphere contracts and descends into the atmosphere to where air is denser — leading to a higher absorption of radio waves, Prof. Price explains. By examining satellite-gathered data on the temperature in the upper atmosphere and comparing results to measurements of radio wave amplitudes collected on the ground, the researchers were able to uncover a clear correlation, consistent over time. As the upper atmosphere gets colder, radio signals lose their strength.
While the sun is certainly the driving force behind changes in temperature in this region, it accounts for only 60 to 70 percent of temperature variations, says Prof. Price. The remaining variability could not be systematically measured until now. By adding measurements of radio waves taken on the ground to solar radiation estimates, researchers can now explain approximately 95 percent of temperature changes in the upper atmosphere.
Degrees of change
According to Prof. Price, this new technique will be a valuable addition to current methods of monitoring climate change, such as the measurement of ground temperatures. Without the need for expensive equipment like satellites, monitoring the upper atmosphere can be done inexpensively and continuously. And because temperatures in the upper atmosphere fluctuate more dramatically than those on the ground — for every one degree of warming in the lower atmosphere, there is a corresponding ten degree cooling in the upper atmosphere — changes are far easier to monitor.
Using this system might reveal more about the ionosphere than ever before. The region is notoriously difficult to monitor; there are no weather balloons or airplanes that can go high enough, and it is too low for orbiting satellites. But with this method, it could be possible to study long and short term changes in the ionosphere, such as the impact of solar storms or thunderstorms on the upper atmosphere.
Rare amphibians recovered from development site
Tel Aviv University researchers have rescued some 800 tadpoles of a rare species of toad — the Syrian spadefoot — from one of the last remaining winter ponds in the Haifa area. The land is slated for the development of a new shopping center, with construction to begin in just a few short weeks.
When they learned that the pool was about to be built over, the researchers, led by Prof. Noga Kronfeld-Schor of TAU's Department of Zoology, approached Israel's Nature and Parks Authority and offered to conduct a rescue mission to save the pool's inhabitants. In addition to those of the spadefoot toads, tadpoles of several other endangered species were saved, including a rare salamander and the southern banded newt.
Though there were once hundreds of such pools along the Israeli coastline, a vast majority were either drained for agricultural use or construction, putting a variety of amphibian species in danger of extinction. Previous research has shown that the population of spadefoot toads in the Haifa pond was unique, says Prof. Kronfeld-Schor.
The toads have been transferred to the university and are now being cared for at TAU’s Zoological Gardens. The researchers hope to return them to the wild as soon as possible, and the Nature Authority is preparing a new site with artificial seasonal ponds for the toads in the Haifa area.
TAU's Prof. Emeritus Gideon Dagan wins Israel's top honor
Prof. Emeritus Gideon Dagan of Tel Aviv University's School of Mechanical Engineering is the recipient of the 2012 Israel Prize for Earth Science. The prize, which will be awarded at a April 2013 ceremony on the eve of Israel's Independence Day, honors his outstanding career and groundbreaking research in the field of hydraulics.
The Israel Prize Committee called Prof. Dagan one of the forefathers of the discipline of Stochastic Hydrology, which uses statistical methods to analyze and predict various field scale processes including groundwater pollution.
Education Minister Gideon Sa'ar praised Prof. Dagan's scientific contributions, saying that his work aids in Israel's understanding of available groundwater resources. Prof. Dagan's research will help scientists develop models to better manage Israel's precious groundwater in the years to come.
The future of water security
Prof. Dagan's stochastic models and analysis aid in the understanding of how groundwater moves across the Earth's topsoil layer. This data can be used to prevent groundwater contamination as well as contribute to water conservation efforts in Israel and across the globe. The situation is especially dire in the Middle East, says Israel's Energy and Water Minister Uzi Landau, who predicts that water in the region will become more valuable than oil considering the rapid population growth.
A prolific author, Prof. Dagan has published over 165 scientific articles over his career and has more than 6,000 citations. He has also lectured at top academic institutions worldwide.
Tel Aviv University is proud to number 73 recipients of the Israel Prize among its faculty. The prizes are given every year by the state of Israel to those who have displayed excellence in their fields of study or made a strong contribution to Israeli culture.
TAU team uses NASA satellites to measure pollution hovering over world's megacities
The thickest layers of global smog — caused by traffic, industry, and natural minerals, among other factors — are found over the world's megacities. But getting an accurate measurement of pollution is no easy task. On-the-ground monitoring stations do not always provide the most accurate picture — monitoring stations depend heavily on local positioning and some cities put stations in urban centers, while others build on the edge of a city.
Now Prof. Pinhas Alpert of Tel Aviv University's Department of Geophysics and Planetary Sciences and head of the Porter School of Environmental Studies, with graduate student Olga Shvainshteinand and Dr. Pavel Kishcha, is turning to three of NASA's high-tech satellites for a comprehensive view of pollutants in the atmosphere. Using eight years' worth of data collected by the satellites, the researchers tracked pollution trends for 189 megacities — metropolitan hotspots where the population exceeds 2 million. 58 of these megacities, including New York City, Tokyo, and Mumbai, have populations that exceed 5 million.
Their method, published in the American Journal of Climate Change, is the first to provide standardized global testing of pollution levels. Beyond uncovering reliable data about pollution trends, Prof. Alpert believes that this monitoring method will also hold countries accountable for their emissions and encourage more environmentally friendly practices.
A "three judge" panel
The smog which often covers megacities is actually a thick atmospheric layer several hundred meters above the Earth's surface, comprised of particles of pollutants. It's an environmental hazard and a severe health risk for those living below, who breathe in the particulates.
To accurately analyze the level of pollution over each megacity, the researchers used data gathered by three aerosol-monitoring satellites, called MODIS-Terra, MODIS-Aqua, and MISR, which NASA launched from 2000 through 2002. The combined data these satellites provide constitute an accurate survey of aerosol concentrations a few hundred meters above Earth.
Prof. Alpert likens the use of three satellites to the traditional Jewish idea of the three-judge panel. "In the Jewish tradition, individual judges don't decide cases. There must be a minimum of three. You need a majority opinion," he says. "By merging the data from three imperfect sensors, their flaws are mostly counterbalanced. In cases where the three sensors show differing signs of pollution levels, more research is required."
Winners and losers
Northeast China, India, the Middle East, and Central Africa are currently leading in pollution increase, including Bangalore, India, with a 34 percent average increase in aerosol concentration between 2002 and 2010. Ibdan, Nigeria, was also part of that group. Europe and Northeast and Central North America are seeing the largest decreases in aerosol concentrations overall. Among the cleanest cities were Houston, with a 31 percent decrease over the time period; Curitiba, Brazil, with a 26 percent decrease; and Stockholm, Sweden, with a 23 percent decrease.
Some American cities were on the list of increased pollution levels, including Portland with a 53 percent average increase and Seattle with a 32 percent average increase, but Prof. Alpert believes these numbers reflect the multiple wildfires that have been happening in the region in the second half of the period examined. In the future, he hopes to develop a method for separating such natural causes of pollution from man-made pollutants for more accurate data.
An honest view of emissions
A standardized approach to smog analysis is made difficult by often unreliable data from monitoring stations, the reluctance of politicians or government ministries to offer accurate numbers on pollution, and even a complete lack of monitoring in major parts of the world, says Prof. Alpert. When it comes to international treaties aimed at reducing pollution, this measurement method could help to keep all countries accountable for their promises by tracking compliance in an equitable way. Cities that successfully decrease pollution could be applauded for their efforts and stand as a positive example to follow, he suggests.