To do this, the scientists must surmount several fairly formidable obstacles: When fuel burns, the resulting chemical reaction releases energy; any method for reversing that process must restore the lost energy – and then some. The trick to creating a carbon-neutral cycle (one that takes as much carbon out of the atmosphere as it adds) is to not only add energy into the process but to employ renewable, non-polluting energy (such as sunlight) for that purpose. Ideally, the end product of this chemical reaction should be only the fuel and such substances as oxygen or water that won’t harm the environment.

Presently the scientists are following several avenues of inquiry into designing new catalysts – the materials facilitating chemical reactions – that will help turn CO2 into such fuels as methanol, using the sun’s energy. The scientists are starting from scratch on this project: Few have attempted to recreate hydrocarbon fuels from CO2 in any kind of continuous, sustainable manner, and none have succeeded. In fact, says Prof. Ronny Neumann, Head of the Institute’s Organic Chemistry Department, the team’s first step has been to review the scant literature on the subject and figure out where others went astray.

Although their task may seem daunting, the Institute team, all members of the Organic Chemistry Department, should be up to the challenge: Between them, Profs. Neumann and David Milstein have many years of experience in creating catalysts for a variety of industrial and scientific chemical reactions. Many of their catalysts have been designed with the aim of making these reactions safer for the environment – by working more efficiently and producing fewer polluting waste products. In fact, Milstein’s research was recently mentioned in Science magazine’s ”breakthroughs of the year” for its contribution to the field of green chemistry. Prof. Gershom (Jan) Martin's research focuses on catalysis from another angle: He develops computer simulations that reveal various potential catalyst molecules in atomic detail, a sort of ”drawing board” that allows the scientists to design and test different molecules on-screen in conjunction with lab experiments.

The scientists plan to explore several means of producing carbon-based fuel. Hydrocarbon molecules such as methanol are made of carbon atoms chemically bound to hydrogen. The chemical process to create the hydrocarbons must remove the oxygen from the CO2 molecule and force the remaining carbon atoms to bond with hydrogen. This is a multistep procedure, and the scientists are researching various routes to the end product, which should be only hydrocarbon fuel and oxygen. The team also intends, in the future, to investigate the possibility of using CO2 to produce hydrogen for fuel cells. In this case, only one oxygen atom will be split off from the CO2 molecules, creating CO. In a separate reaction, the CO will undergo a chemical reaction with water (H2O), producing hydrogen.

So far the scientists have seen some signs indicating they’re on a promising path, but Neumann cautions that the journey before them is likely to be quite a long one. Creating the technology to generate new fuels from the waste products of the old ones may require years of hard work and basic research. The research just beginning in the Weizmann Institute labs is a true investment in the future.

Prof. Lubomirsky, a researcher in the cutting-edge field of nanoscience, brings a background in materials science to his investigations of ways to diversify our energy supply. For example, he discovered that, under certain conditions, a common ceramic material called cerium gadolinium oxide behaves more like rubber than like a regular ceramic. It adjusts to an externally imposed shape, but returns to its original form once released from its constraints. And unlike an average ceramic, it does not buckle when heated or crack when cooled. The ceramic’s ability to adapt to all temperatures could be useful in devices that undergo repetitive warming and cooling, such as fuel cells that convert chemical energy directly into electricity.

With regard to alternative energy, Prof. Lubomirsky is especially interested in solving a fundamental problem: how to convert a low-density energy source to one that is high density. Wind and solar power – currently the most promising forms of renewable energy – are very dilute compared to fossil fuels, which means that it may take a large surface area, many hours, and certain weather conditions to collect the energy at a practical rate. “As a society, we’ve never tried to switch from concentrated energy sources to dilute ones,” he says. “Ideally, we should try to harvest energy from the wind and sun and convert it to something we can use in the same ways we use fuel now.”
With the support of the Weizmann Institute’s Alternative Energy Research Initiative (AERI), Prof. Lubomirsky is working toward this goal. He is trying to develop a method of storing and transporting wind and solar power. One of the main reasons these cheap, non-polluting energy sources have not yet been used on large scales is that today’s technologies convert them to electricity or heat on the spot, and the power is then fed directly into the home or community where the equipment is sited and cannot be transmitted to faraway populations. Further complicating the situation is the fact that the best locations for exploiting these types of energy tend to be under- populated, such as deserts or the middle of an ocean.

One of Prof. Lubomirsky’s solutions is to use electricity generated from the wind or sun to power the production of chemical fuel, which is a moveable form of stored energy. He is interested in a chemical reaction that would split molecules of carbon dioxide (CO2) to create carbon monoxide and oxygen. The carbon monoxide could then be easily transported to where it is needed, or converted by another simple chemical reaction into fuel for use in vehicles or power stations.

As splitting CO2 molecules directly is extremely inefficient, Prof. Lubomirsky is developing an alternative process in which CO2 is first converted into a cheap, reusable intermediate product such as soda (a common, naturally occurring mineral compound), and then split into oxygen and carbon monoxide by electrical current.

He hopes to develop a chemical process that is stable over time, non-polluting, and requires minimal maintenance. Because the gases CO2 and carbon monoxide are easy to transport, plants for producing the carbon monoxide could be located in sparsely populated deserts. They could also be anchored in oceans, where steady, year-round winds provide a constant energy source.

Prof. Lubomirsky points out that searching for new ideas on how to use renewable energy sources and adapt them to our existing infrastructure is something that the Weizmann Institute, as a basic research institution, is uniquely positioned to do. And these ideas are essential, he says, because “we cannot solve our energy problems with the same logic we used to create them. Now we need new logic.”

Last spring, a small research boat made an unusual trip – from one side to the other of the northwestern-most tip of the Red Sea. On this crossing (of the Gulf of Eilat or the Gulf of Aqaba, depending on one's map) were researchers from Jordan, Israel and the U.S. who had recently joined forces to study how water flows and mixes in the unique body of water that lies between Jordan and Israel.

Dr. Hezi Gildor of the Weizmann Institute's Environmental Sciences and Energy Research Department; Dr. Riyad Manasrah of the Marine Science Station in Aqaba, Jordan; Prof. Amatzia Genin of the Interuniversity Institute for Marine Sciences and the Hebrew University of Jerusalem, Eilat; and Dr. Stephen Monismith of Stanford University are conducting this research through the NATO Science for Peace and Security Program. Their efforts should greatly improve scientists' understanding of water currents and circulation. But the group has an immediate, practical goal as well: A detailed understanding of water movement in the Gulf can help the environmental agencies on both sides (which already cooperate to protect its unique ecology) plan a response to spills or prevent pollution from spreading.

Recent research by Gildor and Dr. Erick Fredj of the Jerusalem College of Technology has already revealed a surprise: Floating material such as oil might remain near the spill site for an extended period of time, rather than dispersing throughout the surface area of water. Using data collected from two on-shore high-frequency radar stations, Gildor created a computer map of the currents. He then added evenly spaced "particles" to a computer water-flow simulation to see where they would go. The calculation, which showed the particles moving with the currents over several days, revealed that some of the particles tended to move closer together, forming large clumps; at the same time, barriers created by the current separated particle clusters and prevented them from dispersing or mixing with other clusters. Large bodies of water don't normally lend themselves to experiments, but a set of aerial photos taken soon after a rare winter flood provided evidence for the accuracy of the model: The images show well-defined brown stains in the blue water – silt that had washed down from the nearby desert mountains into the Gulf and collected in the areas predicted in the model. In addition to the two radar stations on the Israeli side, a third is now set to go online on the Jordanian side, which will greatly increase the data available to the scientists.

"The Gulf of Eilat," says Gildor, "offers scientists an exceptional research opportunity. Although it is relatively small, it is also quite deep, and many types of ocean phenomena take place in its waters. Because of its limited size and the fact that it's almost entirely surrounded by land, detailed measurements can be obtained at a higher resolution than is possible in the open ocean. Also, there's the added advantage of being close to shore."

One such phenomenon is usually found only in places that are much harder to study, such as the waters off the Antarctic coast. Called a density current, it takes place when cold air from a nearby land mass cools the top layer of ocean, making it denser and heavier than the water below. This layer then sinks, creating a vertical current. Although density currents are confined to narrow belts of sea near land, they are important drivers of the global ocean currents that, in turn, affect global climate patterns. The Gulf of Eilat, although it is much closer to the equator than other areas that experience this phenomenon, has all the right conditions for density currents: On the one hand, the shallow strait at the entrance to the Red Sea prevents the deep, cold water of the outer ocean from flowing into the Gulf. On the other hand, the Gulf water is surrounded by desert, where atmospheric temperatures can drop to near freezing on winter nights, thus cooling the surface water. Gildor and his research team found that pulses of density current regularly occur off Eilat's shore in wintertime, and they used their observations to create a high-resolution computer model of these flows.

The Gulf is an invaluable natural laboratory – one that Gildor is turning into an important basis for improving ocean modeling – and collaboration between scientists on both sides is crucial to conducting research in its waters. Gildor: "There's no physical line down the middle of the Gulf, and its water doesn't recognize political borders. To really understand it, we need to be able to study this body of water as a whole."

Prof. Cahen explains that after the global crash in oil prices during the early- to mid-1980s, sup- port for research in alternative energy decreased drastically as well, resulting in what is now an extremely poor base on which to build new technologies. Meanwhile, the demand for energy is increasing worldwide, oil prices are unpredictable, and the burning of fossil fuels is causing pollution and releasing greenhouse gases that contribute to global warming. “We cannot afford another period of not-so-benign neglect,” he states.

To help provide this essential scientific ground- work and develop clean, efficient, affordable, and sustainable energy sources, the Weizmann Institute launched the Alternative Energy Research Initiative (AERI) in 2006. Prof. Cahen, the first scientific director of the AERI, has focused much of his own research on alternative energy. He is particularly interested in solar cells – devices that use the sun’s energy to generate electrical power – and his work includes studying how to  improve their performance and cost-effectiveness; for example, he and his colleagues recently showed how very inexpensive mirrors can help increase the utilization of sunlight by such cells.

Under Prof. Cahen’s guidance, the AERI provides support for innovative sustainable-energy research projects conducted by Weizmann scientists, with particular emphasis on work that is multidisciplinary, at an early stage, or that would otherwise be unlikely to compete successfully for funding.   

One such project is being carried out by scientists in two departments: Prof. Uri Pick of the Department of Biological Chemistry and Prof. Avihai Danon of the Department of Plant Sciences. Profs. Pick and Danon are investigating microalgae as a new source of biomass to generate biofuel. Some types of algae produce oil that can easily be converted to biodiesel. Algae have a number of advantages over other bio-fuel crops such as corn and sugarcane: it can be harvested year-round; it can be grown rapidly in saltwater or wastewater, without draining water resources; and it produces no waste byproducts.

Profs. Pick and Danon are studying the ways several strains of algae use sunlight and carbon dioxide (CO2) to store energy and to grow, and are working to identify the genes that regulate the algal metabolism. Eventually they hope to create genetically engineered algae that can be grown in a controlled and sustainable way, and
that can yield a liquid fuel source in much greater amounts than the best plant crops can produce.

Another AERI project is being conducted by Profs. Edward Bayer, Gideon Schreiber, and  Dan Tawfik of the Institute’s Department of Biological Chemistry, who are researching ways to break down cellulose – the main component of plant cell walls – so it can be used as a raw material for fuel. “When we have cellulose as fuel, we can also transport it and can even use it in fuel cells,” says Prof. Cahen.

Prof. Bayer has been conducting basic research on cellulose breakdown for more than 20 years and is one of the world’s foremost experts on the topic. He focuses on the cellulosome, a group of enzymes that degrades cellulose, and uses  genetic engineering to develop artificial cellulosomes that are more effective at breaking down, for example, manmade cellulose products such as paper. Now he is collaborating with Prof. Schreiber, an expert in designing and altering protein-protein interactions, and Prof. Tawfik, an expert in enzyme evolution, to design artificial cellulosomes with improved activity.

The most recent version of their artificial  cellulosome can turn a lab dish full of finely shredded paper into simple sugar syrup in about a day. These simple sugars are ideal for further conversion to liquid fuel, such as ethanol. In the future, the artificial cellulosome might be adapted to other cellulose-rich energy resources such as agricultural waste, and the scientists hope that liquid fuel will someday be made from recycled trash.

Another important goal of the AERI is to encourage young scientists to direct their careers to the pursuit of energy-related problems. Currently, says Prof. Cahen, few students are attracted to the field because of a dearth of funding and because relatively few top scientists pursue novel research in sustainable energy. To break this pattern, Prof. Cahen and his colleagues are making new outreach efforts, such as inviting top Israeli students to seminars. “We are planting the seeds and we hope that, in a few years, we can hire some of them as faculty,” he says.

The World Energy Council projects that worldwide energy demand will be at least double its present level by the middle of this century. The basic research conducted as part of the AERI is needed today, Prof. Cahen says, since “there’s typically a 15- to 20-year lag between a finding in the laboratory and its industrial success. Therefore, whatever we do now will be practical around 2025 or 2030, at the earliest.”

He stresses the importance of exploring many different approaches to sustainable energy. No single technology is likely to be able to supply all of the world’s future energy needs, and any solution will probably involve a mix of solar, biomass, wind, hydroelectric, nuclear, and other technologies. We need to work, Prof. Cahen says, “toward a strong, sustainable mosaic of many solutions, which, as a whole, will provide the solution.”  

Collection Techniques
Natural sunlight is a dilute energy source: to produce a large amount of electricity, solar cells must be spread out over a very wide area. If today’s expensive photovoltaic units were replaced by optical concentrators that intensified sunlight by, say, a factor of 500, then the cell needed to produce the same amount of electricity would be 500 times smaller. The savings in silicon alone would go a long way toward making solar-produced energy economically attractive.

Focusing highly concentrated sunlight onto small solar cells, Prof. Amnon Yogev found that when filters are used to split sunlight into a number of spectral ranges, heating is reduced and efficiency of the photovoltaic unit is doubled. If the unused wavelengths are exploited for other uses, such as providing the energy for the “absorption cooling” that powers some refrigeration and air conditioning systems, the savings can be even greater.

Economic factors such as these hold the key to bringing solar energy to vast areas of the world that have no existing infrastructure for power generation and transmission based on fossil fuels. The investment necessary is modest: a 10-kilowatt photovoltaic unit could support the electric lighting, refrigeration, and communications infrastructure of an entire village. Anticipating the difficulties of maintaining solar installations in isolated areas, Institute scientists envisage building photovoltaic units complete with satellite communications networks, to allow maintenance reports to be transmitted automatically.

New Materials
Today most commercial solar cells are still made of silicon, which is stable but relatively expensive; however, several other materials are being developed for future use in photovoltaics. The goal: to produce solar cells that are both cheap and durable. The front-runners are thin-film technologies, in which a thin layer of a fine-grained photoelectronic material is deposited on an inexpensive large-area surface such as window glass.

Weizmann Institute research may speed up the application of one of the most advanced thin-film materials in solar cells. Cadmium telluride-based photovoltaics are already in the pilot stage of development and may soon be manufactured commercially on a large scale in the United States and Europe; but these cells tend to deteriorate over time. Because Institute scientists had in the past managed to solve major theoretical and practical problems related to photovoltaics, the U.S. Department of Energy asked them to address the deterioration of cadmium telluride-based units. The Institute team, headed by Profs. David Cahen and Gary Hodes of the Materials and Interfaces Department, revealed how these solar cells can be rendered more stable. Using chemical and physical investigation methods, the scientists showed, for example, that the cells must be used in a dry, preferably oxygen-free environment. The researchers are conducting further studies aimed at enhancing the stability of cadmium telluride cells and understanding the basic science underlying their performance. Such an understanding may help not only to develop better cells but also to overcome the psychological barriers - particularly, concerns over reliability - impeding the acceptance of experimental solar energy technologies.

In another project, Profs. Cahen and Hodes are investigating the mechanism of action of an innovative type of solar cell invented in the early 1990s in Switzerland. The dye-sensitized solar cell, or DSSC, is made of an organic material that is incorporated into a porous thin film consisting of microscopic semi-conductor particles held together like beads on a string. DSSC cells are radically different from other solar cells in several respects, and until recently it was unclear how exactly they generated electric power. Cahen and Hodes, in collaboration with colleagues in Israel and abroad, have suggested a mechanism that may account for the formation of photovoltage in these cells: apparently, the dye functions much like chlorophyll, the natural photosynthetic pigment in plants. The Institute researchers are currently striving to understand the mechanisms involved in the movement of electrons through DSSC cells.

Improving the Surface
The efficiency of silicon solar cells is limited by two major problems: surface recombination - the tendency of electrons to become trapped in the surface of the semiconductor; and light reflection from the surface of the solar cells, which can decrease the energy available for electricity production by 10-20 percent.

Prof. David Cahen and his colleagues are improving solar cell performance by eliminating the surface defects common to fine-grained semiconductor materials. This research involves analyzing the defects caused by minute amounts of impurities in the semi-conductor, then controlling those defects on the molecular level. Together with Prof. Avi Shanzer of the Organic Chemistry Department, Cahen has succeeded in improving semiconductor performance by grafting desirable properties onto organic molecules.

Prof. Shanzer is adapting models of chlorophyll, the substance that controls photosynthesis in plants, to improve the semiconductors used in photovoltaic cells. The technique involves dipping the semiconductor into a specially prepared solution containing porphyrins - the “backbone” of chlorophyll molecules. The porphyrin binds to the semiconductor surface, causing the semiconductor to absorb light more efficiently. This in turn induces a greater electric charge in the semiconductor. Developing his approach further, Shanzer’s group is working on synthesizing organic “wires” that would link light-harvesting groups such as porphyrins to a metal ion, creating molecular “antennae” to guide photons to the semiconductor surface. (For more on photosynthesis and solar energy, see p. 49.)

Ancient Heat Wave
It’s now official: the heating up of the Earth known as global warming has begun. The 1990s were the hottest decade on record, and according to an authoritative report issued by a United Nations-sponsored panel in January 2001, worldwide temperatures continue to climb. In the panel’s worst-case scenario, by the year 2100 these temperatures may rise by almost 6 degrees C. Are humans responsible for global warming? Science has yet to provide a definitive answer, but one thing is certain: if the warming trend continues, the ecological and economic consequences are likely to be catastrophic. Increasingly frequent natural disasters, agricultural damage due to rising sea levels, and consequent stress on health care and water management could cost the world more than 300 billion dollars. Therefore, understanding global warming and reining in its causes are matters of utmost urgency.

Prof. Aldo Shemesh seeks to shed light on current environmental debates by studying the climate that prevailed in various regions of the world in the ancient past. By examining ocean deposits, Shemesh is able to determine the climate fluctuations that occurred long before modern industry began releasing large quantities of greenhouse gases into the atmosphere. Shemesh derives his evidence from microscopic marine algae called diatoms, which make up marine sediments around the world. Diatoms have hints from past millennia hidden in their skeletons: to form their shells thousands of years ago, they absorbed carbon, nitrogen, and oxygen atoms from the environment. Depending on the climate, different varieties of these atoms, called isotopes, were fixed into the creatures’ shells. Now, by analyzing the isotopic composition of the remains, Shemesh’s group can peel back the layers of time and obtain glimpses into various aspects of the ancient environment - such as seawater temperature, the presence of ice, and the level of carbon dioxide (CO2) in the atmosphere. For example, since the isotope Oxygen 18 tends to be enriched when the temperature is low, an alga shell with relatively high Oxygen 18 levels suggests a colder climate.

Using isotopic records of sediments from a high-altitude volcanic lake on Mt. Kenya, Shemesh reached the conclusion that a sudden warming of climate lasting several centuries took place in equatorial Africa some 2,000 years ago. The study revealed that the climate can warm up rapidly without any connection to human activity. Records obtained from lake sediments in the Swedish Lapland and on the Island of South Georgia also revealed climate variability caused by natural processes independent of human activity. Such research may enable scientists to distinguish between natural climate variability and global warming that results from man-made factors.

Another study has focused on the climate change that occurred during the coldest period of the last glacial age, some 20,000 years ago. By examining different ratios of certain carbon and nitrogen isotopes in diatoms in the Southern Ocean (the region surrounding Antarctica, including sectors of the Atlantic, Pacific, and Indian oceans), Shemesh was able to determine the level of CO2 in the ocean water during the last ice age. He found that Antarctic surface water was a major source of CO2 in the atmosphere. Since the Southern Ocean plays a major role in regulating the world’s CO2 levels, these findings could help us understand the gas’s current status in the atmosphere. Shemesh is now developing new isotopic tools and studying marine records from different parts of the world in different time periods.

Vanishing Villain
Atmospheric levels of carbon dioxide (CO2) stand today at an all-time high: whereas in the past 500,000 years they used to fluctuate between 180 and 280 parts per million, they have now hit 380 parts per million. This build-up is believed to be largely responsible for global warming: it exacerbates the greenhouse effect, which in turn heats up the Earth. However, in trying to determine how exactly CO2 fits into the global warming puzzle, scientists run into a quandary: only half of the 7 billion tons of carbon spewed as CO2 into the air each year accumulates in the atmosphere. The oceans appear to be responsible for dissolving about 1.5 billion tons, but what about the rest? Apparently, the remaining carbon is taken up by plants, but scientists do not yet fully understand the details of this uptake.

Along with researchers working on the problem around the world, environmental biologist Prof. Dan Yakir is determined to solve the CO2 enigma. Understanding CO2-related processes is essential for predicting climate change and for designing such environmental strategies as those aimed at controlling the levels of CO2 and other so-called “greenhouse” gases in the atmosphere. Without knowing, for example, where a large portion of global CO2 disappears to, it is impossible to tell exactly how this vanishing act affects the environment or whether it will continue indefinitely.

Prof. Yakir has designed a method for calculating the amount of CO2 consumed by the world’s vegetation. The method is based on the analysis of different isotopes, versions of the same atom, in the atmosphere. Yakir found that plants prefer to absorb CO2 that contains the light version of oxygen atoms, Oxygen 16, while the heavier version, the isotope Oxygen 18, tends to be left behind in the atmosphere. The ratio of the two oxygen isotopes in atmospheric CO2 can therefore be used to calculate the extent of CO2 consumption by plants and to follow its dynamics. However, various types of plants differ in the rate at which they consume CO2. In recent studies, Yakir and his colleagues extended the isotope method to identify the contribution of different plant categories to CO2 consumption. This approach is a valuable addition to the limited arsenal of tools available for the quantitative study of the biosphere’s response to changes in atmospheric CO2 levels.

In addition to heading CO2 studies at the Institute, Yakir coordinates the participation of several Israeli academic institutions in international networks aimed at understanding ecological processes involving carbon. In one such network, sponsored by the European Union, 30 research towers have been set up between Finland and Israel. The Israeli one, headed by Yakir, is considered the most special: its location in a transition zone between an arid and a semiarid climate ensures great sensitivity to perturbations in the environment. The 20-meter tower is located in the Yatir Forest, a plateau at the edge of the Negev desert planted with pine trees some 35 years ago. Research at the station has already yielded important findings. For example, it has revealed that high CO2 content in the air seems to improve the efficiency with which forests growing on arid land use water: to absorb the same quantities of carbon, tree leaves lose less water than they would in a low-CO2 environment. This revelation may make it possible to expand forests further into semiarid regions - an important prospect considering that forestation is a key carbon-reduction strategy under the Kyoto Protocol of the United Nations and one of the few means available for slowing down the potential climate change driven by the increase in such greenhouse gases as CO2.

Rainwater “Archives”
Records of the Earth’s past and present climate are kept in an unlikely archive: rainwater. Every drop contains a wealth of information about the origins of rain and the climatic conditions under which it was formed. The information is “stored” in the isotopic composition of the rainwater: depending on the relative amounts of oxygen and hydrogen isotopes it contains, scientists can tell whether a particular drop comes from a lake or an ocean, whether it has traveled over deserts or lush forests, and how warm the air was when the drop originally condensed. This type of knowledge is crucial for understanding the water cycle and the global climate in general. On a worldwide scale, such knowledge is collected within the framework of a program called the Global Network for Isotopes in Precipitation, or GNIP.

Israeli researchers taking part in GNIP study the water cycle in the eastern Mediterranean area. Rainfall in this region is rather anomalous: Israel and its neighbors lie in a desert belt where hardly any rain would be expected at all, yet every winter they are blessed with significant amounts of precipitation, which replenish their groundwater reserves. Where does the rain come from, and why does it fall only in winter? It turns out that the region’s winter showers result from a geophysical upheaval: the Mediterranean Sea stays warm throughout the winter, and its evaporating water meets the dry, cold air arriving from Europe; the warm vapors, striving to rise above the cold air, create turbulence and cyclones that eventually lead to rainfall.

Isotopic studies of this and other local aspects of the water cycle were launched at the Weizmann Institute in the 1960s. Several Israeli academic institutions, including Weizmann, conduct isotopic studies as part of GNIP, and these national research efforts have been coordinated by the Institute’s Prof. Emeritus Joel Gat. The Mediterranean Sea, a large body of water encircled by land, is a perfect laboratory for studying air-sea interactions. A better understanding of the water cycle sheds light on both past and present climate, helps verify global climate models, and facilitates predictions in such vital areas as the relationship between climate change and rainfall.

World Oceans and Global Climate
One of the most dramatic climate phenomena affecting our planet is the appearance of a gigantic mass of warm water in the Pacific Ocean every few years. South American fishermen have named it “El Nino,” meaning “the child” in Spanish, since the event tends to occur around Christmas time. El Nino precipitates a variety of environmental disasters: it causes floods in South America, brings droughts to Australia, ignites forest fires in Indonesia, and decimates the Peruvian fishing industry. By predicting the irregular El Nino events, scientists may be able to help the world prepare for them and reduce their global damage.

Prof. Eli Tziperman studies the effects of oceans on the Earth’s climate. Using models and observations, he seeks to understand the behavior of oceans and such climate phenomena as El Nino.

El Nino is caused by oscillating deep ocean waves that travel back and forth along the equator in the Pacific. The waves alternately warm and cool the water at the surface of the ocean, which in turn affects the winds that caused the waves in the first place. These equatorial perturbations trigger changes in atmospheric temperature, pressure, and rain patterns around the world. Graduate student Eli Galanti and Prof. Tziperman are developing a sophisticated method that makes it possible to incorporate data gathered by research ships, satellites, and moored instruments into ocean models, in order to improve El Nino prediction. The Weizmann scientists have already used this method to understand how the mixing of deep ocean water with surface water affects El Nino’s dynamics.

Another study has focused on understanding the cyclical appearance of ice ages. Graduate student Hezi Gildor and Tziperman have proposed a new explanation as to why ice ages have occurred roughly every 100,000 years in the past million years, and why glaciers tended to cover the Earth slowly with the advent of each ice age, only to recede rapidly afterward. Their hypothesis is that sea ice, which can spread over the oceans in a matter of decades, may act as a “switch” that shifts the world’s climate into and out of an ice age. A better understanding of the cyclical mechanism that governs the occurrence of ice ages could improve the ability of scientists to predict climate changes.

Dust Is in the Air

Desert dust, ash spewed by volcanoes, smoke from burning forests, and soot from power plants are all potential sources of aerosols - minute particles suspended in the atmosphere. When sufficiently large, these particles may redden sunsets or fill the air with haze. But beyond their visual manifestations, aerosols can have a profound effect on the environment. They can affect the ozone layer, harm people’s health by lodging in their lungs, or alter the Earth’s climate; by scattering sunlight back into space they can reduce the amount of energy the planet absorbs, and by changing the properties of clouds they can modify rain patterns. Yet despite their importance, the exact role of aerosols in a variety of environmental processes is not fully understood.

Weizmann Institute physical chemist Prof. Yinon Rudich studies the relationship between the chemical composition of aerosols and the effect of these suspended particles on atmospheric systems. He and his team focus on organic aerosols and their interactions with atmospheric molecules ranging from water to ozone. Recent results, for example, revealed that water molecules can accumulate in cracks on the surface of organic aerosols. Other results explained how interaction with ozone changes the surface properties of aerosols. This research helps other atmospheric scientists to understand how aerosols behave and to clarify their impact on the environment.

Much of Rudich’s research focuses on one of the greatest uncertainties in climate research: the impact of aerosols on the properties of clouds. Working with colleagues from other Israeli academic institutions, Rudich found that clouds formed in an area affected by dust did not produce rain, while clouds formed at the same time and in the same region but outside the area influenced by dust did produce rain. The researchers concluded that dust particles coated by a soluble material serve as cloud-condensation nuclei around which water drops form. The presence of many cloud-condensation nuclei leads to the formation of clouds with large numbers of small drops of water, and in such clouds, the growth of drops by coalescence - which is essential for the production of rain - is blocked. Simply put, dust storms inhibit rain formation. These findings suggest that in arid regions such as central Africa, desert expansion may follow a vicious circle: poor land management - for example, exposure and disruption of topsoil for cattle grazing and agricultural cultivation - can increase the amount of dust blown into the air; more dust, in turn, reduces rainfall, exacerbating the drought conditions and contributing to desertification.

Early Achievements
Prof. Emeritus Joel Gat participated in a United Nations project to investigate the large-scale deforestation in the Amazon basin, which is likely to adversely affect the climate both locally and on a global scale. By gathering data on the stable hydrogen and oxygen isotopes in rain and river water and in atmospheric moisture, Gat quantified water balance estimates. On the basis of these data, researchers constructed theoretical models of water movement in the basin and evaluated the long-term effects of deforestation on the climate and hydrology of the region.

Ancient wood analysis performed by Prof. Dan Yakir may have yielded an explanation of the mysterious reference to agriculture in Masada in a first-century CE historic treatise. Masada, the last Jewish fortress to hold out against the Romans after Jerusalem was conquered in 70 CE, is situated near the Dead Sea, on the eastern margin of the Judean Desert, whose extremely arid climate cannot today support agriculture. An isotopic study of the tamarisk wood the Romans used to build a ramp to the fortress revealed that the climate in the region was cooler and more humid 2,000 years ago. This historic weather report could explain how the besieged Jews were able to farm in a region that is now a desert.

Detection Goes Underground
Chemicals seeping in from toxic waste dumps, factories, gas stations, and other sources threaten underground water reservoirs. For example, one barrel of oil leaking slowly through the ground can pollute thousands of times its volume in freshwater. Considering that most of the world’s accessible freshwater is stored in underground aquifers, it is vitally important to safeguard these hidden reservoirs. Scientists usually rely on mathematical models to predict the movement of pollutants through layers of rock and soil. However, existing models are generally unreliable, largely because geological formations are extremely varied and complex.

Two professors in the Weizmann Institute’s Environmental Sciences and Energy Research Department - Brian Berkowitz, a hydrologist, and Harvey Scher, a physicist - are developing new mathematical models for predicting the movement of fluids and pollutants underground. On the basis of a theory previously used to model the passage of electrons through a disordered semiconductor, the scientists are seeking to discover how particles move through rock layers of different flow resistance. This research could help predict the consequences of leaks from nuclear waste canisters, evaluate the potential spread of contaminants from a new factory, or help engineers devise strategies for pollution containment.

Plotting the movement of pollutants through cracks or heterogeneous sediments is a tremendously uncertain business, data on the arrangement of the ground beneath the surface being generally limited and sketchy. Computer simulations help fill in the blanks, as does interdisciplinary collaboration among scientists. Using nuclear magnetic resonance imaging of fluid flow through rock fractures, and incorporating lab and field test data into their models, Berkowitz and Scher were able to predict not only how fluids move through cracks in the rock, but also how the cracks are dissolved and eroded as the fluid flows downward. The scientists have discovered that fluids flow especially quickly through such maze-like fissures and have developed models that reflect the risk of potentially catastrophic contamination.

In a separate project, Prof. Scher is studying the interface region known as the capillary fringe - a unique layer sandwiched between the rock formation that holds gases and water, and the stratum underneath that is saturated with water. He is developing models, based on theories describing the movement of a mixture of fluids through porous media, to describe the structure of the fringe and predict the transport of particles through this layer. An understanding of the capillary fringe will provide a better picture of how fluids move through the ground and how pollutants make their way into groundwater. Moreover, this research could clarify how bacteria residing underground may help degrade pollutants.

Seaside Modeling
Managing coastal aquifers is a crucial issue for seaside communities the world over. Near coastlines, seawater tends to seep into drinking water sources. Deep wells intended to pump freshwater from underground may gradually suck in salt water from the sea, endangering entire aquifers. And the problem is not limited to the coastline. Pockets of saltwater locked underground, away from the sea, may similarly endanger inland aquifers.

Prof. Brian Berkowitz is developing new quantitative models that specifically describe fluid flow and the movement of chemicals in rock formations near aquifers. This research may lead to improved management of freshwater resources along the coast or near underground sources of salinity. Such management is a particularly acute problem in Israel, a country prone to severe water shortages that derives about two-thirds of its water supply from groundwater - mainly the Coastal Aquifer, which extends some 130 kilometers along the Mediterranean, and the Yarkon-Taninim Aquifer, which runs parallel to the coastal one, under the Judean mountains. A sequence of drought years, as well as chronic overpumping, have already severely endangered the water quality in these underground reservoirs, and preventing their further deterioration is a matter of top national priority.

Averting the Metal Menace

Arsenic poisoning of drinking water has become a problem in many parts of the world, at times turning into a massive public health crisis, as occurred in Bangladesh in the 1990s. Chromium contamination has threatened water supplies in the United States; one famous case was featured in Erin Brockovich, a film in which the title character uncovers the poisoning of an entire town by a power company. These are examples of metal ion pollution, which has ravaged numerous communities around the world. Metal ions are among the deadliest water pollutants, harmful even in low quantities and tough to detect. Scientists are developing methods to detect the ions and remove them from water.

Laws against water pollution are only as good as the sensors that monitor compliance. New types of sensors for the real-time measurement of toxic metal levels in rivers and other fast-moving bodies of water are being investigated by Prof. Avi Shanzer of the Organic Chemistry Department and Prof. Israel Rubinstein of the Materials and Interfaces Department. The scientists have designed a gold electrode coated with a single layer of tightly packed metal-ion-binding molecules. When specific metal ions come into contact with the electrode, they bind to it, triggering an electrical response. Successfully tested in the laboratory with iron and copper, this metal sensor could in principle be developed into a device for detecting other toxic metals in water.

In a different approach, Prof. Shanzer is developing a method for removing metals from water. His team has demonstrated the possibility of synthesizing tailor-made organic molecules that bind to particular metal ions and has already successfully synthesized selective binders for copper, cobalt, nickel, lead, mercury, and cadmium. Currently available ion-exchange purification columns have a low capacity because they become plugged up by non-relevant metal ions; but columns based on Shanzer’s method - due to the high selectivity of his binders - are expected to have a high capacity. As a result, they should effectively remove even trace amounts of metal ions. The columns could be used, for example, to purify wells and aquifers that contain traces of poisonous ions.

A project launched by the late Prof. Abraham Warshawsky of the Organic Chemistry Department could help both detect and fight metal ion pollution. In Warshawsky’s method, water flows through a tube filled with synthetic beads that contain numerous holes. Inside the holes, two kinds of synthetic molecules, called ligands, are engaged in detection: one ligand is a collector molecule, designed to bind with a polluting metal; the other is a reporter molecule, which emits intense fluorescent light when bound to the metal. By manufacturing ligands that grab onto different ions, the scientists can make the system sensitive to a variety of pollutants. This work was conducted in Warshawsky’s lab by postdoctoral fellow Dr. Ying Wang, in collaboration with Dr. Gilad Haran of the Chemical Physics Department. The amount of light emitted by different pollutants is picked up by a photosensor, which indicates the chemicals in the water that have reached harmful levels. Metal-binding ligands may also be used to clean up pollution: if they hold on tightly to the polluting ions, they can be used to purify water in underground aquifers. This latter idea is being explored by Prof. Brian Berkowitz, who developed it originally with the late Prof. Warshawsky.

Early Achievements
Plants growing by the Dead Sea do not extract water from their immediate surroundings, which are excessively saline. Instead, they extract only winter flood water from the Judean hills, which occasionally reaches the area. This finding, by Prof. Dan Yakir, suggests that the plants are able to distinguish between salty water and non-salty flood water.

An ultrasensitive detector, developed in a collaborative study by three Weizmann Institute teams that began as a basic research project, has a wide variety of potential applications, ranging from sensing minute amounts of biomolecules to detecting pollutants in water or air. Profs. David Cahen, Ron Naaman, and Avi Shanzer of the Materials and Interfaces, Chemical Physics, and Organic Chemistry departments, respectively, led groups of researchers who succeeded in tracing the path of electrons moving from custom-made molecules to a semiconductor surface. This was accomplished by grafting a single layer of molecules onto a semiconductor, thereby creating an ultrasensitive detector for electron transfer. Cahen’s and Naaman’s groups are exploring new directions of research made possible by the innovative device, called MOCSER (MOlecular Controlled SEmiconductor Resistor), including its use as a sensor for chemicals in the brain, a detector for DNA mutations, and possibly as a DNA chip.

Deep inside the earth, there are underground pockets of groundwater similar to oil traps. The water in these geological traps, resembling a sealed bubble, has been stored underground for millions of years, safe from pollution. Prof. Emanuel Mazor, after studying underground water pockets in Australia and Israel, has reached the conclusion that they could serve as emergency reservoirs in a pollution event such as a nuclear catastrophe.

Scarcity of water in the Middle East and vulnerability of groundwater, Israel’s major water resource, to pollution have placed the country at risk of severe water shortages in the near future. Prof. Emanuel Mazor has drawn up a number of strategies for environmentally savvy water management. He has outlined a comprehensive approach: clean management of all enterprises, a nationwide campaign of water saving, special legislation, and the establishment of a research institute for water and environmental conservation.

Industrial plants, municipal waterworks, and private homes throughout the world use water-softening equipment to remove calcium from water (calcium minerals build up on pipe walls and restrict flow). However, the softening sometimes damages water quality or produces waste products, including tons of sodium-rich wastewater that pollutes underground aquifers. A new, environmentally friendly water softening method has been developed by Prof. Emeritus Ora Kedem. In her “cake filtration” approach, commercialized by an Israeli company, calcium minerals are filtered out without pollutants being released into the environment.

Oil from Algae
What are the best crops to grow for biofuels? Corn and sugarcane, presently converted to ethanol in Brazil and the USA, consume large amounts of petrochemicals and arable land in cultivation, and using them for fuel is already beginning to drive up the price of food. The contribution of soybean- and canola-based biodiesel in Europe to overall fuel consumption is small and cannot be extended. A better alternative, according to a number of scientists, may be lying under the nearest rock or floating on a stagnant pond: algae.

Algae have a number of advantages over other sources of biofuel. For one, they can be grown on marginal soil or in salt water, without draining water resources. For another, they grow rapidly and could be harvested regularly throughout the year. And there is no waste – no seeds, stems or roots to discard. Algae plantations placed near power plants would capture much of the emitted carbon dioxide to use as building blocks for biofuel, thus creating “green energy.”

Finally, some kinds of algae produce oil – up to 50% of their mass. This oil, says Prof. Avihai Danon of the Institute’s Plant Science Department, can be easily xtracted and converted to bio-diesel, which could be used in today’s diesel engines without significant investment. Algae could yield an estimated 30 times the oil output of the best crop plants, and could satisfy the fuel needs of the USA and other heavily industrialized countries around the world.

Danon and Prof. Uri Pick of the Biological Chemistry Department have begun a new project that aims to create strains of algae that will excel at generating oil for biofuel. Their first step is to understand how and when the algae produce the oil. Like green plants, algae get their energy from the sun and store it as sugars or oils. But there is a limit to how much energy one alga – a single-celled organism – can utilize. In fact, too much sunlight can overload the alga’s system, stimulating the production of free radicals that can harm or even kill the cell. This limit creates a trade-off between oil production and growth, and the cell must decide in which to invest its energy. The scientists suspect that it is in times of stress that the algae build up their stores of oil.

The researchers are working on several different strains of algae that grow in different conditions and have different traits. They are developing the tools to identify and compare the genes that regulate the algal metabolism, making decisions whether to stockpile oil or spread out, whether to take in additional sunlight or put up protective sunscreens. “Once we’ve identified the genes, we should be able to develop the means to control these processes in the algae ourselves,” says Danon, “and hopefully create algae that can be an excellent, environmentally friendly source of fuel.”

Recycled Fuel
While the debate rages over the ecological and economic value of using food crops to produce fuel, Weizmann Institute scientists are taking a different approach that could potentially solve two environmental problems with one stone – or at least one bacterial enzyme complex.

One of the obstacles to creating biofuels from organic substances such as agricultural waste is that they contain large amounts of tough materials – mainly cellulose – that do not break down easily. (Corn and sugarcane, on the other hand, are rich in starch and sugar that can easily be turned into ethanol.) Prof. Ed Bayer of the Biological Chemistry Department has been researching bacteria that chew up cellulose, converting it to sugar that they then feed on. In the 1980s Bayer, together with Prof. Raphael Lamed of Tel Aviv University, discovered how the bacteria’s cellulose-degrading machinery works. The cellulosome, as they dubbed this molecular machine, is a group of enzymes that work as a team to chop up the long chains of repeating sugar units in cellulose molecules into short sugars that can be dissolved in water.

About 50 percent of landfill material is cellulose, mostly in the form of paper, and it continues to pile up year after year. Breakdown is slow, partly due to landfill conditions and partly because the cellulose in such man-made products as paper turns out to be particularly hard for the bacterial cellulosome to digest. Bayer began tinkering with cellulosomes, adapting the bacterial machinery for turning plant cellulose into sugar into an effective tool for recycling paper. He and Lamed used genetic engineering techniques to create hundreds of different versions of the cellulosome, mixing and matching parts in their search for those that excelled at their new task. Prof. Gideon Schreiber, an expert in designing and altering protein-protein interactions, and Prof. Dan Tawfik, an expert in enzyme evolution, have joined the team to help design artificial cellulosomes with improved activity. The most recent version of the artificial cellulosome can potentially turn a lab dish full of finely shredded paper into simple sugar syrup in about a day.

Recently, this research has taken on new urgency. The simple sugars churned out in the process are ideal for conversion to ethanol, and the artificial cellulosome might be adapted to other cellulose-rich energy resources such as agricultural waste. Much research remains to be done before the process can be recreated efficiently on the industrial scale, Bayer cautions. Nonetheless, one day our cars may run on ethanol brewed from recycled trash.

Fuel of the Fittest
If algae and bacteria can be engineered to produce such bio-fuels as biodiesel and ethanol, might they also generate such futuristic energy resources as hydrogen? Hydrogen could be the cleanest fuel of all, as its combustion leaves behind only water. But most present-day methods of producing hydrogen still involve processing fossil fuels.

In an ambitious project, a consortium of scientists from France, Spain, Sweden, the UK, Portugal and Israel, including Prof. Dan Tawfik of the Biological Chemistry Department, are investigating the possibility of creating a bacterium that will produce hydrogen cleanly and economically. The researchers have started with a strain of cyanobacteria (often called blue-green algae, though they are not true algae). These photosynthetic, single-celled organisms have a long history of producing materials we need: They’re credited with releasing oxygen into the early atmosphere (paving the way for the evolution of oxygen-breathing animals), and with fixing nitrogen in soils so that plants such as rice can absorb it.

The researchers plan to use a cutting-edge approach to developing the new bacteria. Rather than adapting one or two existing genes, they aim to equip the cyanobacteria with a whole new set of biological components engineered for specific functions. The multidisciplinary team will use a slew of techniques to accomplish this, including one developed by Tawfik – directing the evolution of enzymes in cell culture to produce cellular components that are highly efficient at carrying out desirable tasks.

An additional, surprising role for dust was identified in the 1990s: As torrential rains in the Amazon region continuously wash minerals out of the soil, they are replaced by new minerals carried in dust blown over 5,000 km across the Atlantic Ocean from the largest desert in the world – the Sahara. Scientists believe that without a steady supply of vital minerals, the Amazon region would become a wet, but largely lifeless, desert.

In winter, seasonal winds lift dust into the air in the Sahel, the southern part of the Sahara, and carry it to the rainforest in South America. How much dust is expelled from the Sahara and how much of it reaches the Amazon rainforest? What turns particular desert regions into good sources of dust? These questions lie at the basis of research led by Dr. Ilan Koren of the Weizmann Institute’s Environmental Sciences and Energy Research Department. In a study conducted with the late Dr. Yoram Kaufman of NASA and other colleagues from Israel, the United Kingdom, the United States and Brazil, and published in Environmental Research Letters, the scientists focused on a particular desert region considered the largest source of dust in the world – the Bodele Valley, covering a 20,000-sq-km area in northern Chad.

Koren’s goal was to quantify, for the first time, the Bodele Valley’s contribution to the Amazon rainforest. An additional goal was to try to explain what turns this small valley into a leading “exporter” of dust. He and his colleagues combined the data collected by two different types of satellite sensors: One made it possible to cover a wide area and evaluate the extent of dust clouds and their movement; the other supplied precise optical information about the dust’s properties. In addition, satellite photographs taken at regular intervals allowed the scientists to evaluate the speed and direction of the winds and calculate the size of the dust “shipments.” Additional measurements at two spots above the Atlantic helped evaluate the amount of dust that is “lost” on the way to South America.

Analyses of the findings produced unexpected results: The Bodele Valley, which accounts for about 0.2% of the Sahara’s area, is responsible for 56% of the dust reaching the Amazon rainforest. Moreover, the total amount of dust arriving in South America from the Sahara each year is about 50 million tons – a much higher figure than the previously estimated 13 million tons and one that matches the amount thought to be needed to sustain the rainforest.

Why does the Bodele Valley supply such a significant amount of Amazon dust? “I looked at the satellite photos, and the answer was staring me in the eye,” says Koren, referring to Bodele’s unique geological shape. It is flanked on both sides by enormous basalt mountain ridges, with a narrow opening in the northeast. Winds that “drain” into the valley focus on this funnel-like opening, creating a large wind tunnel that directs the surface winds toward the dust source and accelerates them.

Though dust may not be a profitable export item, understanding its long-distance movement is a matter of global importance.

“Within five to ten years, we must provide a large-scale practical approach for renewable energy production, storage, and transport. Within 20 to 25 years, we must develop a non-proliferating source of nuclear energy using abundant material, generating low-hazard byproducts,” says Prof. Jacob Karni of the Weizmann Institute’s Department of Environmental Science and Energy Research.

Karni and his team feel the renewable energy development phase of this goal can be achieved largely by using energy from the sun as an alternative to burning fossil fuels such as oil, gas, and coal. Solar energy is the only renewable resource available in large enough quantities to replace a significant portion of the energy now supplied by fossil fuels, and therefore must be exploited worldwide on a large scale.

“Sufficient solar energy is available in many countries [and] on all continents except Antarctica. It can be turned into electricity, heat, or clean fuels that can be used or stored and transported,” says Prof. Karni. “The effort takes a multidisciplinary group, and the Weizmann Institute has the capability to bring the necessary disciplines together.”

Weizmann’s solar research laboratory, established in 1987, is the only such facility in the world located on an academic campus. The laboratory has six solar workstations, each capable of housing between one and three experiments. The results of one extensive project led to the development of a solar-thermal demonstration plant, which was installed in Nanjing, China, and began operation in November 2005. The plant implements state-of-the-art technology to convert sunlight to electricity.

The Weizmann Institute has taken a leading role in the development of practical alternative energy technologies. Regretfully, this effort is severely hindered by shrinking government support for alternative energy research.

“Research is defocused and underfunded. The problem cannot be solved this way. It is clear that we simply cannot rely on government funding,” explains Prof. Karni. “Conventional government policies say that fossil fuel consumption cannot be reduced in the next 25 years, so we need to increase efficiency. Driving hybrid cars, increasing production efficiency, reducing waste in the consumption of fuels and electricity, implementing stricter regulations, and using solar panels can help alleviate the problem to some extent, but they will not solve it,” he emphasized.

Western governments have taken baby steps to  encourage alternative energy sources, but Prof. Karni feels their efforts are a “talk tough, do little” approach.

“The Kyoto Protocol calls for a reduction in CO2 emissions by a minimum of 5 percent below 1990 levels by 2012. This will be impossible to accomplish globally when more than half the world is expected to use 2 to 5 times more energy from fossil fuels without emission restrictions,” Prof. Karni says. “We might be able to develop enough nuclear energy to provide 20 percent to 30 percent of the world’s energy requirements by 2030 to 2040, but it is not likely to happen unless we develop and implement methods to better deal with the storage of spent nuclear fuel, proliferation, safety, and security issues,” he explains.

Fossil fuels are a concern not only because recovering them is becoming increasingly costly and polluting, but because burning them produces carbon emissions. 1.5 billion people live in countries where the consumption of electricity tripled from 1990 to 2003. Another 2 billion live in countries where electric consumption doubled during the same time period. Carbon emissions in these fast-growing countries are rising quickly.

“Their governments and industries are not concerned about pollution, because they are in a losing race to supply the need of fast-expanding economies, but the world may pay a terrible price,” says Prof. Karni. He continues: “There is increasingly convincing evidence that warming from fossil fuel—the greenhouse effect—has already become a dominant factor in climate change. The mean surface temperature of the earth is higher today than at any time in the last millennium, causing large-scale melting of arctic ice. Since 1979, the size of the summer polar ice cap near the North Pole has shrunk more than 20 percent. The world gets rid of heat through storms, which have increased in number and intensified in strength.”

Solar energy can solve the world’s immediate and future energy needs, but the development of this resource requires funding.

“The cheapest level is the initial conceptual-level research, but no one wants to fund it,” says Prof. Karni. “The second development level is demonstration, like we have in China, then commercialization. It’s all within our grasp.” 

In a breakthrough study published today in the online edition of Science, scientists explain why aerosols -- tiny particles suspended in air pollution and smoke -- sometimes stop clouds from forming and in other cases increase cloud cover. Clouds not only deliver water around the globe, they also help regulate how much of the sun's warmth the planet holds. The capacity of air pollution to absorb energy from the sun is the key.

Image: Large plumes of smoke can act as "cloud killers" because the tiny particles in this form of air pollution absorb a lot of sunlight. NASA's Aqua satellite caught this cloud-suppression process in action over western Brazil and Bolivia in September 2005. Credit: NASA

"When the overall mixture of aerosol particles in pollution absorbs more sunlight, it is more effective at preventing clouds from forming. When pollutant aerosols are lighter in color and absorb less energy, they have the opposite effect and actually help clouds to form," said Lorraine Remer of NASA's Goddard Space Flight Center, Greenbelt, Md. Remer worked closely with the study's lead author, the late Yoram Kaufman of Goddard, on previous research into this perplexing "aerosol effect."

The effect of the planet's constantly changing cloud cover has long been a problem for climate scientists. How clouds change in response to greenhouse-gas warming and air pollution will have a major impact on future climate.

Using this new understanding of how aerosol pollution influences cloud cover, Kaufman and co-author Ilan Koren of Israel's Weizmann Institute estimate the impact worldwide could be as much as a 5 percent net increase in cloud cover. In polluted areas, these cloud changes can change the availability of fresh water and regional temperatures.

In previous research by the authors, the opposite effects that aerosols have on clouds were seen in different parts of the world using data from NASA satellites. But these observations alone could not confirm that the aerosols themselves were causing the clouds to change.

Image: Some types of air pollution can help clouds to form and storms to grow stronger. In this April 2006 image from the NASA Terra satellite, a plume of aerosol pollution from the Anatahan volcano in the western Pacific Ocean leaves more clouds in its wake. Credit: NASA

To tackle this problem, Kaufman and Koren assembled a massive database of global observations that strongly suggests it is the darkness (absorbs sunlight) or brightness (reflects sunlight) of aerosol pollution that cause pollution to act as a cloud killer or a cloud maker. These measurements were culled from the NASA-sponsored Aerosol Robotic Network of ground-based instruments at nearly 200 sites worldwide.

No matter where in the world the measurements were taken or in what season, the scientists saw the same pattern. There were lots of clouds when light-reflecting pollution filled the air, but many fewer clouds were recorded in the presence of light-absorbing aerosols.

NASA’s satellites, computer models, and technology will continue to advance our understanding of how aerosol pollution affects the Earth’s climate. NASA’s "A-Train" of formation-flying satellites, now with the cloud-piercing instruments onboard the Cloudsat and CALIPSO spacecrafts, is helping answer challenging questions such as the role of clouds in global warming and the influence of aerosols on rainfall and hurricanes.

Sitting in his book-lined office, Professor Jacob Karni likes to quote the French novelist Jules Verne.

"Yes, my friends," says Prof Karni, director of the Centre for Energy Research at the Weizmann Institute of Science, quoting from Verne's 1874 novel The Mysterious Island.

"I foresee that in the future, water will be used as fuel... water will be the coal of the future." The professor enthuses about the French author's vision 130 years ago that the world's reliance on fossil fuels is unsustainable. But he disagrees with Verne, famous for 20,000 Leagues Under the Sea, in one fundamental respect. Whereas the French writer saw water as the fuel for the future, the Israeli scientist says the future lies with solar energy.

Suntan

"Even if we were to dam every river in the world and put wind turbines where ever there is wind," says Prof Karni, "it wouldn't be enough to provide for our energy needs. But with solar energy we could meet the world's energy demands."

For the last 16 years, he has worked with colleagues at the Weizmann Institute, situated in a leafy campus in the Israeli city of Rehovot, to make renewable energy a viable alternative. The professor, who regularly works a 12-hour day, researches how to harness solar energy in a cost effective way and then transport the energy to the user. The institute has been researching solar panels that produce a greater yield of energy. "One of the big problems with solar energy is that the energy is very diluted," says Prof Karni. "It can give you a suntan but not much else."

Snags ahead

But one of Prof Karni's projects has been to use solar energy to produce a non-polluting synthetic fuel that could be used, for example, to power cars. Last summer, the Weizmann Institute published research that was "a step towards the solution", he says.

Using solar power energy, zinc oxide was heated to 1,200 C. The temperature splits the ore, releasing oxygen and creating gaseous zinc, which is then condensed into powder. When the zinc powder reacts with water, it produces hydrogen that could power a car. The chemical reaction produces no greenhouse gases and the zinc oxide can be recycled into zinc and the process starts all over again. Prof Karni says that the research demonstrated that the process is achievable, but problems remain. For every kilogram of hydrogen gas produced, you would need 60 kg of zinc, which is not feasible on a large scale, he insists. 

New Manhattan Project?

But with a map of China hanging in his office, Prof Karni insists we have to think big. "We could put solar panels here," he says, pointing at west China, "and this could provide the energy for the east of China where most people live. We just need to devise an effective way to transport the energy." The massive consumption in global energy coupled with rising pollution has made finding a renewable energy alternative more important, he declares.

Over 3.5 billion people live in countries where the consumption of energy more than doubled from 1990 to 2003, according to the Energy Information Administration. If countries were to form a "Manhattan project" for solar energy, employing the best minds and ploughing enormous resources into research, renewable energy could be challenging fossil fuels in five years, the professor believes. But that moment of reckoning has yet to arrive. "We will only find the solution when it's really urgent," he says.

Readers who remember their chemistry lessons may recall mixing zinc with hydrochloric acid in a test tube and standing by, lighted splint in hand, ready to ignite the hydrogen that is given off. (Metallic zinc reacts with the chlorine in the acid, leaving hydrogen behind.) Zinc reacts similarly with water − or, rather, steam − in this case stripping the oxygen from H2O and once again, leaving the hydrogen. Industrialising that process, though, relies on finding a cheap way of turning the zinc oxide that results back into metallic zinc, so that the material can be recycled. And this, courtesy of the Weizmann Institute's Solar Tower laboratory, is what Dr Epstein has done.

The tower's 64 seven-metre-wide mirrors track the sun and focus its rays into a beam with a power of up to 300 kilowatts (see picture). In Dr Epstein's experiment, which he outlined at the recent International Solar Energy Society conference in Orlando, Florida, the beam was used to heat a mixture of zinc oxide and charcoal. The charcoal (which is pure carbon) reacted with the oxygen in the zinc oxide, releasing the zinc. This instantly vaporised and was then extracted and condensed into powder.

At the moment, the cheapest way of making hydrogen is a process called reformation, which also uses steam, but reacts it with natural gas, a fossil fuel. Dr Epstein thinks that if his process were scaled up, it would cost about the same as reformation. It would also have the advantage over reformation that no fossil fuel need be involved (the charcoal can be made from agricultural waste, such as manure), and so there is no net contribution of climate-changing carbon dioxide to the atmosphere. And the other way of using solar power to make hydrogen − generating electricity using solar cells and then using that electricity to split water into its component gases − is vastly less efficient than Dr Epsteins's method.

In the meantime, the powdered zinc produced can be employed in a different form of energy technology − zinc-air batteries. These are used to power certain sorts of electronic device. So, even if your car never runs on second-hand solar energy, one day your laptop might.

“Like all good science — particularly at Weizmann — our work is curiosity driven,” he said recently, during a visit to the national ACWIS office. “For example, you have an oil spill — the oil seeps into the groundwater and starts to spread. The engineering approach is to drill holes and pump out the contaminated water — but six months later the contamination is back.” To solve the problem, he said, “You have to go back and determine how the oil behaves, how it travels, and what you can do with it. How does the oil interact with the water?”

Prof. Berkowitz has developed a highly accurate model of groundwater movement that can provide information to develop sound environmental policy. The ability to predict the flow of water and pollutants is critical for effective management and remediation of groundwater resources, and for protection against accidental exposure of radioactive and toxic wastes, as in the proposed use of Yucca Mountain in Nevada for underground repositories for radioactive and toxic wastes.

Prof. Berkowitz began his career in applied math, receiving a degree in petroleum engineering. While studying music in Israel (he is a passionate bassoon player), he happened to meet a chemical engineer. When he revealed his interest in the flow dynamics of oil, the man mentioned that he knew a world-renowned Israeli hydrologist. Reasoning that the only difference between water and oil was density and viscosity, he jumped into hydrology with both feet and has made quite a splash.

The biggest project in his lab is challenging assumptions about water and pollutant movement underground. The model in use is, quite simply, wrong, Prof. Berkowitz said. “We know it has an enormous error, and we’ve developed a new theory that seems to describe beautifully what’s going on.” His lab is developing the theory with computer software that models it, and encouraging others to adopt the theory by placing free software online.

He is also working on another legacy: last year, his parents were tragically killed in a car accident. He has taken on his late father’s work of a revolutionary way of processing oil and coal, which could have a profound impact on the coal and oil industry. “I taught myself hydrocarbon chemistry and developed a set up to test my father’s ideas — all those years it never occurred to us to work together, even though what we did was so related.”

How does he keep up with it all? “I don’t sleep much,” he said.