News this Week

Science  18 Oct 2013:
Vol. 342, Issue 6156, pp. 294

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  1. Around the World

    1 - Oslo
    Chemical Weapons Watchdog Group Wins Peace Prize
    2 - Mountain View, California
    NASA Backs Away From Meeting Ban
    3 - Richmond
    Climate Heats Up Virginia Politics
    4 - Rome
    Italy Blocks Use of Stem Cell Therapy
    5 - Livermore, California
    The NIF Breakthrough That Wasn't


    Chemical Weapons Watchdog Group Wins Peace Prize


    Ahmet Üzümcü, OPCW's director-general, comments on receiving the Nobel Peace Prize.


    For its "extensive efforts to eliminate chemical weapons," the Nobel Committee has chosen to honor the Organisation for the Prohibition of Chemical Weapons (OPCW) with the 2013 Nobel Peace Prize.

    "We are a small organisation which for over 16 years, and away from the glare of international publicity, has shouldered an onerous but noble task–to act as the guardian of the global ban on chemical weapons that took effect in 1997," said OPCW Director-General Ahmet Üzümcü in a prepared statement.

    Such international bodies are not famed for their speed and effectiveness, but OPCW's track record is impressive. Some 189 countries, representing 98% of the global population, have joined OPCW since the Chemical Weapons Convention came into force in 1997 and 82% of the world's declared stockpile of chemical agent (some 58,172 tonnes) has been destroyed. OPCW has carried out 5286 inspections at 228 chemical weapon–related and 1905 industrial sites in 86 countries. OPCW's recent mission in Syria, following the August chemical weapon attacks in Damascus, has brought it much greater public attention.

    Mountain View, California

    NASA Backs Away From Meeting Ban

    The Chinese scientists banned from an upcoming meeting at NASA's Ames Research Center will get another chance to register (Science, 11 October, p. 177). But that doesn't guarantee them a seat at next month's conference.

    The turnaround, announced last week by NASA Administrator Charles Bolden, comes after an angry letter from Representative Frank Wolf (R–VA), who chairs the panel that funds the space agency. NASA Ames officials said they were simply following language Wolf inserted into a 2011 spending bill with the goal of protecting NASA against industrial and military spying by China. But the real reason was a blanket ban that Bolden had imposed in March on visits by scientists from eight countries, including China.

    Wolf asked Bolden to "correct the record," and 2 days later Bolden extended his olive branch without acknowledging any mistake. Instead, Bolden blamed "[m]id-level managers at Ames … performing the due diligence … following a period of significant concern and scrutiny from Congress." The scientists will still need to pass a security clearance, however, a process that generally takes several weeks.


    Climate Heats Up Virginia Politics

    Hot topic.

    Climatologist Michael Mann has campaigned for Terry McAuliffe, Ken Cuccinelli's rival for Virginia governor.




    A new poll suggests that the issue of climate change may help businessman Terry McAuliffe in his campaign for governor of Virginia next month against Ken Cuccinelli, the outspoken state attorney general. McAuliffe, a Democrat, leads Cuccinelli, a Republican, by nine points, according to the media outlet POLITICO, which polled 1150 likely voters. Cuccinelli, who questions the scientific consensus that global warming poses a significant threat, has criticized McAuliffe's support for new federal rules on carbon emissions from coal plants. But the poll showed 45% in support of the regulations, versus 33% opposed.

    Meanwhile, climate scientist Michael Mann released a video last week saying that the attorney general was "doing the bidding of the fossil fuel interests" when he issued a 2010 subpoena of Mann's e-mails and other scientific documents. The subpoena, centered on grant applications Mann had filed during a previous stint at the University of Virginia, was eventually tossed out by a state judge. Now at Pennsylvania State University, University Park, Mann campaigned in support of McAuliffe earlier this year.


    Italy Blocks Use of Stem Cell Therapy

    Italy's Health Minister Beatrice Lorenzin announced on 10 October that Stamina, a foundation in Turin that developed a controversial and unproven stem cell therapy, will not be allowed to test it on humans—at least not in Italy. "We have put an end to it," Lorenzin says. "I would have liked to give patients better news, but the method has shown to be not eligible for a clinical trial."

    The treatment is based on bone marrow stem cells that Stamina's President Davide Vannoni claims can grow neurons and cure neurodegenerative diseases. In May, the government provided €3 million for a clinical trial. However, last month, an expert panel unanimously rejected the method, claiming that it lacks scientific basis (Science, 20 September 2013, p. 1324). A Health Ministry decree explains that the rejection was based on an "inadequate description of the method" and "the lack of quality controls on cells."

    The Justice Ministry has yet to rule on whether Stamina can continue to treat patients in Italy. In the meantime, Vannoni says, an African country that he declined to identify "has already given the green light to human experiments."

    Livermore, California

    The NIF Breakthrough That Wasn't

    No ignition.

    NIF "breakthrough" was overhyped.


    One side effect of the U.S. federal shutdown is that press officers at government labs aren't around to offer reality checks to news stories. Last week, media outlets jumped on a report by BBC News that the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California had passed a "nuclear fusion milestone." NIF uses the world's highest energy laser system to crush tiny pellets containing hydrogen fuel, aiming to fuse the hydrogen atoms into helium atoms, releasing energy. The goal is ignition, a self-sustaining fusion burn that produces more energy than the laser put in.

    The BBC story reported that during one recent experiment, "the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel - the first time this had been achieved at any fusion facility in the world." But although a 29 September NIF memo to collaborating labs describes a promising fusion shot that produced 75% more neutrons—a product of fusion—than any previous shot, it is not the breakthrough everyone is hoping for. Ignition, scientists say, is still a long way off.

  2. Random Sample


    The Boston-based Institute for Justice & Democracy in Haiti filed a lawsuit last week against the United Nations for inadvertently unleashing the 2010 cholera outbreak that has killed more than 8000 Haitians. Genomic studies and an independent U.N. report left little doubt that Nepalese peacekeeping forces brought the disease to the island nation.

    Remnant of a Comet


    A black, diamond-spackled pebble just a few centimeters across is the remainder of a comet that struck Earth almost 29 million years ago—making it the first direct evidence of a comet exploding in our atmosphere, scientists say. The stone, named "Hypatia" after an Alexandrine mathematician and philosopher, was found in 1996 among bits of yellow sand glass (also known as the Libyan Desert Glass) scattered across tens of kilometers in southwestern Egypt, near the border with Libya. The glass itself has been dated to 28.5 million years and has long been thought to be the result of a meteorite impact or an airburst caused by a comet breaking up in Earth's atmosphere. Scientists performed a range of tests on the tiny pebble, examining its mineralogy, bulk chemistry, carbon isotope, and noble gas content—which support not only an extraterrestrial but also a cometary origin, they report in an upcoming issue of Earth and Planetary Science Letters.

    They Said It

    "Oh, what news?"

    —Theoretical physicist Peter Higgs, to a former neighbor who hailed him from a car to congratulate him on "the news"—that he would share the Nobel Prize in physics for his work on the theory of the Higgs boson.

    Animals Get the Spotlight in CreatureCast


    Invertebrates, such as jellyfish, worms, or mollusks, don't have the same charismatic appeal as your average lion or tiger, so those who want to share their interest in the creatures often resort to the "ick factor," says Brown University evolutionary biologist Casey Dunn. "But that serves to create a distance between the organism and the audience, which is contrary to what you're trying to do."

    Dunn is trying something different with CreatureCast, a series of 3-minute animated videos largely starring invertebrates. In 2009, Dunn and some friends received a National Science Foundation grant to study mollusk phylogeny and part of it was allocated to communicating their findings. CreatureCast ( videos are produced with limited resources, often by a single writer/editor/producer who is also a student of Dunn's. (Students in his Invertebrate Biology class at Brown can produce a video as a final project.) Instead of expensive photos, the videomakers rely on hand-drawn animations, in which "imperfections are endearing instead of being a liability," Dunn notes.

    Although invertebrates dominate the video subjects, one recent effort tackled a more abstract statistical topic (explained with cartoon bunnies and dragons): an explanation of the central limit theorem (pictured), which states that under certain conditions, and with a sufficiently large sample size, the averages of samples will have an approximately normal distribution.

    The videos are now poised to hit the big time, thanks to a partnership that The New York Times initiated this summer. Each week, the paper considers available videos and may select one to appear on the online science page. "It's been really great," Dunn says. "I have no background in storytelling, and now I'm starting to bounce ideas off of editors."


    Join us on Thursday, 24 October, at 3 p.m. EDT for a live chat about new approaches for treating spinal cord injuries.

  3. Newsmakers

    Three Q's


    To rejuvenate a sagging economy, South Korean President Park Geun-hye is looking to her nation's scientific corps to tickle its creativity bone and produce more innovations. Samsung Electronics heeded the call, announcing in August that it will establish a 500 billion won ($466 million) foundation to hand out grants for basic research. The government, meanwhile, hopes to get creative juices flowing through its Institute for Basic Science (IBS), which provides generous support to handpicked top talents (see p. 302). Leading the charge is science minister Choi Mun-Kee, an expert on information and communications technology. Choi, 62, spoke with Science on 4 October in his office in Seoul.

    Q:How influential will Samsung's foundation be in coaxing scientists to innovate rather than imitate?

    C.M.-K.:We expect that Samsung could show us a new model that connects basic, applied, and development research. This is a starting point. We hope others will follow.

    Q:Why did the government establish IBS rather than strengthen existing centers of excellence in the universities, for example?

    C.M.-K.:Korea has suffered greatly from brain drain. We have established IBS to create a good environment for brain collection.

    Q:In recent months, scientific cooperation between North and South Korea has virtually ceased. With tensions on the Korean Peninsula easing, do you see an opportunity for science diplomacy?

    C.M.-K.:We are very much interested in cooperating. For example, I'd like to see a national park in the DMZ [demilitarized zone]. Cooperation in science will be no problem, if we have enough trust.

  4. Roving Into Martian Waters

    1. Richard A. Kerr

    Will the Curiosity rover discover an early Mars that was warm and wet and life-friendly or cold and icy and inhospitable?

    Destination Mount Sharp.

    This sediment pile holds a history of water on early Mars for Curiosity to read.


    The $2.5 billion Curiosity rover is on a journey to a mountain in search of the truth about ancient Mars. In the midst of the 154-kilometer-wide Gale crater, where the rover landed in August 2012, rises a 5.5-kilometer-high pile of sediment called Mount Sharp. Buried in its layers, Mars scientists believe, is a history of water on early Mars and a potential resolution to an emerging martian dispute.

    Ever since the two Viking spacecraft sent home images in the 1970s of water-cut valleys on Mars, most Mars scientists have believed that during its first billion years or so, the planet was shrouded in a thick, warm atmosphere capable of raining often enough to carve out those valleys. It was an environment seemingly hospitable to the origin and sustenance of life.

    But in the past decade, as the latest wave of Mars orbiters returned even sharper views of the surface, some planetary scientists have been advancing a far less life-friendly view. According to these cold-and-icy thinkers, early Mars never had a permanent atmosphere thick enough to drench the planet, even for brief intervals. There was water on the surface all right, but it was almost always tied up as ice. On this alternative Mars, the surface was icy, dry, and hostile for many millions of years at a time, and life would have struggled to gain a foothold there.

    A wet Mars for sure.

    While planetary scientists debate a warm and wet versus a cold and icy early Mars, they all agree that for at least a few geologically brief intervals, Mars was awash, as in this artist's concept.


    What will Curiosity find next year, as it begins to climb the slopes of Mount Sharp? "That is the $2.5 billion question," says planetary spectroscopist Ralph Milliken of Brown University. It could be a paleoclimatologist's dream: a neat stack of sediment layers recording a changing but mostly wet climate, and maybe even containing the organic remains of ancient martian life. Or it could be a pile of sediments altered by ground water pooled far below a dry, lifeless surface. Or it could be a total surprise. "We'll learn something useful and interesting," says planetary geologist Jeffrey Moore of NASA's Ames Research Center in Mountain View, California. "But it may not be what some people hoped it would be."

    Early wetness, sometimes.

    Alluvial fans, valley networks, and river deltas all required at least momentary wetness. Wind deposits did not.


    From wet to dry to wet

    Mars as 19th and early 20th century astronomers envisioned it was a world of deserts, lakes, and canals, not unlike the American West. All that turned to dust when the Mariner spacecraft of the 1960s flew past Mars and sent back the first close-ups of its surface, which seemed to show a parched, cratered terrain that looked more like the moon. A decade later, however, the image of Mars changed again with the two Viking orbiters, which revealed networks of river valleys in the martian tropics. Mars was warm and wet again—at least in its early history about 4 billion years ago.

    Planetary fluvial geologists, who study the shapes of erosion features to gauge how much water it took to carve them, concluded that early Mars must have had an atmosphere far thicker than today's. By counting the number of craters that have accumulated on martian surfaces, geologists can infer their ages—roughly when valley networks were carved, for example, or a delta deposited. They estimated that the heyday of erosion was in the Noachian period—the first several hundred million years of the martian geologic record—when enough rain fell to cut valley networks, erase craters smaller than 4 kilometers in diameter, and erode hundreds of meters of rock off of larger craters. But there couldn't have been a lot of water sloshing around, or the craters would have overflowed.

    "Early warm and wet Mars was never humid by terrestrial [Earth] standards," says planetary fluvial geologist Rossman Irwin of the Smithsonian Institution's National Air and Space Museum in Washington, D.C. But "it could have been semiarid. Mars in its heyday was like Utah or Nevada during the last ice age," when Great Salt Lake was even greater and lakes abounded.

    Even in the warm and wet scenario, Mars went downhill, climatically speaking, after the few hundred million years of the Noachian. Erosion rates fell, although one or more periods of hydrological "reactivation" interrupted the long drying. In those clearly wet times, flowing water formed crater lakes, built river deltas in some lakes, and washed debris off crater rims to form half-cone-shaped alluvial fans. In fact, Curiosity landed on the toe of a kilometers-high fan nestled against the rim of Gale crater, which formed around the end of the Noachian about 3.7 billion years ago.

    Several hundred million years later, "Mars dies," as Irwin's Air and Space colleague Robert Craddock puts it. Researchers agree that for the 3 billion years since then, Mars has remained icy and hyperarid (Science, 11 April 2003, p. 234).

    The picture of an early Mars of at least intermittent rain was reinforced 10 years ago when the Opportunity rover landed on the floor of what was taken to be an ancient shallow, salty sea. Its twin rover, Spirit, eventually discovered hot-spring deposits like Yellowstone's.

    Convincing as the evidence was to geologists, however, planetary climate modelers weren't at all sure. Their models of early Mars's climate could not produce conditions warm enough for rain or flowing water. Half again as far as Earth from a young sun that was 25% dimmer than it is now, early Mars was a perpetual ice ball, at least in the models. Even a thick carbon dioxide atmosphere could not break the planet out of its deep freeze.

    That may be changing. Climate modelers had struggled to show how liquid water could have existed on early Earth, given the faintness of the newborn sun, but they have recently succeeded in producing a temperate early Earth. The key for some modelers: enriching the model planet's atmosphere with hydrogen molecules, which—at least when they collide with lots of other molecules—can efficiently absorb radiation and act as a powerful greenhouse gas.

    Planetary climate scientists James Kasting, Ramses Mario Ramirez, and Michael Zugger of Pennsylvania State University, University Park, have followed that lead for early Mars. Their model tucks the planet up snugly in a thick carbon dioxide atmosphere that contains 10% hydrogen, the sort of atmosphere they believe likely enshrouded the planet back then. As the group reported at last December's meeting of the American Geophysical Union, a hydrogen-rich atmosphere would have kept the martian surface at the time of Gale crater's formation above freezing on average year-round.

    Icy Mars

    Planetary geologist James Head of Brown University doesn't see the need for a hydrogen blanket because he doesn't think Mars was ever permanently warm and even occasionally rainy. At last March's Lunar and Planetary Science Conference, he cited a dozen reasons from his own work and that of others for arguing that Mars was always icy and that the water world envisioned a decade ago should go the way of the 19th century martian canals.

    The eroded craters and water-cut valleys are real enough, Head says, but he thinks they could have formed during rare episodes of ice melting. That's the way the water cycle works around the year in the Dry Valleys of Antarctica, where Head does fieldwork. It's below freezing on average there, but enough ice melts in the daytime summer warmth to cut gullies in the bare earth nearby.

    In Head's scheme—which he calls Noachian icy highlands—Mars had ice near its water-cut features. He and colleagues have deduced from lingering glacial features, like sediment ridges deposited in channels beneath glacial ice, that an ice sheet did indeed circle the south pole in the late Noachian and chill the southern hemisphere.

    Planetary climate modelers François Forget and Robin Wordsworth of Pierre and Marie Curie University in Paris, with Head and others, showed how the ice might have formed. They ran an early-Mars climate model with a moderately thick carbon dioxide atmosphere. It could not warm the planet above freezing, but like Earth's atmosphere and unlike today's wisp of a martian atmosphere, it cooled with increasing altitude. That meant that snow could fall at the high elevations of the southern hemisphere, compacting into ice. And in the 28 August issue of Geophysical Research Letters, Kathleen Scanlon of Brown, Head, and colleagues report on similar climate modeling that puts snow and ice right where it was needed to supply meltwater to cut valley networks.

    To melt that snow and ice, Head calls on volcanoes or possibly large impacts. Giant impacts, of which there were lots on early Mars, scatter hot ejecta globally. That vaporizes ground ice, producing a hot, steamy atmosphere that could unleash heavy rains. Such sudden warmings had seemed too short-lived, but atmospheric scientist Teresa Segura of Space Systems/Loral LLC in Palo Alto, California, and her colleagues may have found a way around that. In the July 2012 issue of Icarus, they showed in a model how, under the right conditions, a giant impact could drive a frigid martian climate into a warm climate stable enough to get the required amount of erosion done.

    Volcanoes might work, too, warming climate by spewing greenhouse gases. The Viking orbiters discovered some of the solar system's largest volcanoes on Mars, but they appeared to have erupted quietly, like the volcanoes on Hawaii, without releasing much gas. Now, in the 3 October issue of Nature, planetary geologist Joseph Michalski of the Planetary Science Institute in Tucson, Arizona, and Jacob Bleacher of NASA's Goddard Space Flight Center in Greenbelt, Maryland, report finding the lingering calderas of as many as seven explosive, gas-rich "supervolcanoes" that erupted on early Mars. They might have pumped enough carbon dioxide and other greenhouse gases into the atmosphere to trigger brief springtimes on an otherwise frozen planet.

    With a scheme as grand as Head's, there is no shortage of critics. But fluvial geologist Craddock focuses on one very small aspect: the raindrop. The icy highlands scenario has none, but Craddock sees them as essential to explain the observed crater erosion. Only falling raindrops hitting every square centimeter of crater rim and kicking up rock particles can create the observed smooth erosion, he says; meltwater flowing out from glaciers couldn't do that.

    But to planetary spectroscopists, who analyze the spectral signatures of minerals from orbit, Head's cold, dry Mars makes sense. A decade ago, the Opportunity rover encountered sulfate minerals that formed when salty, acidic water weathered rock. At first, rover team members attributed them to shallow, salty seas on early Mars. But subsequent rover investigation failed to turn up further signs of standing water. That and mineralogical evidence from the rover persuaded team members that the telltale minerals must have formed underground. Those supposed seas were just ephemeral, briny, and often acidic puddles oozing up from ground water.

    Researchers are also rethinking another class of minerals once hailed as supporting a warm, wet early Mars: the clays that the Mars Reconnaissance Orbiter and Mars Express probes identified in deposits around Mars. Rock weathering produces clays only after prolonged exposure to water. But in the 3 November 2011 issue of Nature, Bethany Ehlmann of the California Institute of Technology in Pasadena and several other leading planetary spectroscopists say that there is little need for much standing water on early Mars.

    The types of clay detected and the way they have been exposed by impacts "all point to ground water. … We don't see high-volume flows of [surface] water for long durations," Ehlmann says. In this picture of early Mars, "the proposed warmer and wetter early Mars was largely beneath the surface," the group writes. They conclude that "frozen, arid conditions may have been hallmarks of the surface environment since the early-Noachian period"—that is, the entire known history of Mars.

    We just have to go

    That's a disappointing verdict for anyone searching the martian surface for signs of ancient life. But NASA planners picked a good spot for determining whether it will stick. Gale crater is one of the lowest spots on the planet, so if water was going to pool anywhere, that was the spot for it. Gale's alluvial fans speak of rushing waters, at least momentarily. Curiosity spotted fine-grained, layered sediments on the crater floor that look for all the world like quiet lake sediments or at least puddle deposits. Stream gullies cut the slopes of Mount Sharp. And the layers in the lower slopes of the central mound preserve a transition from clays to sulfates.

    Curiosity has the tools to read the water story in Mount Sharp: how its sediments were laid down, how long water wetted them under what conditions, and—with luck—whether the water ever teemed with life. The tools include cameras with views from the panoramic to the microscopic that can scope out how sediments were deposited. One instrument package will analyze samples drilled from the rock. Another instrument will measure chemical composition from meters away by zapping rocks with its laser. All that could take years of roving, and the story will probably be convoluted. Mars, says planetary spectroscopist Milliken, is likely "no less complicated than Earth."

  5. Climate Change

    Dr. Cool

    1. Eli Kintisch

    David Keith has helped usher geoengineering into the mainstream. Actually testing a way to cool the planet is his next big challenge.

    Sun blocker.

    Serious geoengineering research is long past due, says physicist David Keith.


    David Keith was a 26-year-old graduate student in experimental physics when he first heard of geoengineering, the concept of intentionally tinkering with Earth's climate system in order to counteract global warming. It was 1989, and some of his colleagues at the Massachusetts Institute of Technology (MIT) in Cambridge considered the idea distasteful, Keith recalls. Discussing possible experiments was "a de facto taboo" in the field.

    That didn't deter Keith, who saw the dearth of interest as a professional opportunity. Three years later, he published his first paper on the topic. Geoengineering needed a "systematic research program," Keith and a co-author concluded after analyzing the few existing studies of possible approaches, including sucking carbon dioxide out of the atmosphere with machines and releasing particles into the sky to block sunlight. Such exotic technologies, they argued, had the "potential to mitigate catastrophic climate change."

    Few others, however, paid much attention. And for the next 15 years, discussions of geoengineering drifted between the fringe of academic research and science fiction. Still, as Keith built a career as a specialist on energy and climate issues, he periodically published papers suggesting that scientists needed to take geoengineering seriously.

    Aiming high.

    A proposed experiment would use a balloon to release sulfuric acid vapor (A) and then measure its effect on ozone chemistry in successive passes (B).


    In the past 5 years, they have. As carbon dioxide continues to build up in the atmosphere, the U.S. National Academies, the United Kingdom's Royal Society, and the American Geophysical Union have all issued calls to explore expanding research into technological fixes. The number of scientists publishing on geoengineering is growing, as are citations of their work by influential groups, such as the Intergovernmental Panel on Climate Change (IPCC).

    Keith has ridden geoengineering's shift from the fringe toward the mainstream—and has helped catalyze it. In addition to publishing influential academic papers, the Canadian scientist has become geoengineering's public face, delivering sold-out lectures and vivid quotes to the media. He's also become something of a power broker, advising one of the world's richest men on climate issues and doling out some $6 million of Bill Gates's money to convene meetings and spur new research. And 2 years ago, Keith gained a high-profile perch for promoting his views, moving from the University of Calgary in Canada to Harvard University.

    Now, Keith wants to bring geoengineering out of the ivory tower and into the stratosphere. He and a partner at Harvard are proposing one of the world's first geoengineering field experiments, using a highaltitude balloon to release sun-blocking vapors into the atmosphere. And this month, Keith is releasing a book, A Case for Climate Engineering, in which he argues that "the potential upsides of geoengineering" demand greater research. Such studies "may show that these technologies will not work," he writes. "Yet the sooner we find this out the better."

    It's an audacious agenda for a scientist colleagues describe as equal parts thoughtful, unorthodox, and headstrong. And he faces a myriad of obstacles, including a lack of organized government support and fierce opposition from critics—one of whom calls Keith's sun-blocking ideas "barking mad." He's even gotten death threats.

    Further complicating matters is Keith's ownership stake in a company that is pursuing a different flavor of geoengineering—sucking carbon dioxide out of the air. That has raised questions about financial conflicts. And some wonder whether Keith has the diplomatic savvy to win over opponents. "David does not suffer fools gladly," says David Layzell, Keith's former boss at the University of Calgary. "Everybody respects him—or is a little terrified of him."

    A polymath

    Keith grew up in Ottawa, where his father and stepmother, both wildlife biologists, taught him how to stuff birds, enjoy the outdoors, and work with his hands. After earning a physics degree at the University of Toronto, Keith headed to MIT, where "he was an incredible hot shot," recalls Harvard's William Clark, an early mentor.

    But Keith was troubled by the military applications of his physics research and instead drifted toward the burgeoning field of climate and energy research. After he earned his doctorate in 1991, his eclectic interests led to an array of jobs over the next decade: policy analysis at Carnegie Mellon University in Pittsburgh, Pennsylvania; climate modeling at the National Center for Atmospheric Research in Boulder, Colorado; building atmospheric instruments at Harvard; and even a stint in environmental ethics at the University of Montana in Missoula. "A lot of rock climbing, too," Keith says.

    Along the way, he published a number of provocative papers, including a 2001 Science publication that questioned the potential of wind power to replace fossil fuels, and analyses of hydrogen fuel, natural gas, and the then-controversial concept of carbon capture and storage (CCS): capturing carbon dioxide from industrial smokestacks and pumping it underground.

    Geoengineering continued to fascinate him, Keith says, because it provided a new look at humanity's relationship with nature, which he valued personally as an outdoorsman. Geoengineering "encourages us to rethink some of our root assumptions about the means and ends of climate policy," he writes in his book.

    By 2004, when the University of Calgary recruited Keith from Carnegie Mellon, he was considered a go-to voice on geoengineering, and he began building bridges with business. In 2007, he joined with four top executives in Alberta's powerful energy industry to write a report touting the potential of CCS to curb carbon emissions. It drew darts from environmentalists, but led to a pledge to invest $3 billion in CCS technology by the Alberta and Canadian governments, which had requested the study. "I've had a deputy minister stop me and say it was amazing what David did on that report," Layzell says.

    Keith's persuasiveness came with a confidence that could be alienating, however. "David is usually right, and he has a high degree of confidence that he's right," says geochemist Ken Caldeira of the Carnegie Institution for Science in Palo Alto, California. And that can be "off-putting to some people," says Jane Long, an energy scientist at the University of California, Berkeley, who nonetheless commends Keith's "strong ability to get people to see his point of view, while seeing multiple conflicting points of view."

    In Calgary, Keith's willingness to speak his mind sometimes complicated his relationships with industry. A few firms refused to partner with the university after Keith challenged Alberta's efforts to mine its oil sands, for instance. But Keith was becoming an entrepreneur himself, launching Carbon Engineering, a startup aiming to build machines to remove carbon dioxide from the atmosphere, in 2009. One of its investors is Microsoft cofounder Bill Gates, for whom Keith has served as an informal energy adviser since 2006.

    The amount of Gates's investment in the company is undisclosed, but the mogul has also provided roughly $6 million to the informal Fund for Innovative Climate and Energy Research, managed by Keith and Caldeira. Since 2007, the fund has supported more than a dozen research projects, most on geoengineering. It also helps fund a weeklong summer school on the topic, now in its fifth year, which brings together physical and social scientists. The networking opportunity "shows David's great value" as a scientist and organizer, says Benjamin Kravitz, a climate modeler at Pacific Northwest National Laboratory in Richland, Washington, whose work is supported by the fund.

    Keith's 2011 move to Harvard, where he holds appointments in the schools of engineering and government, has brought him close to science and policy heavyweights—and students who go on to become powerful policymakers around the world. It's also an opportunity to team with some of the nation's top atmospheric scientists, and ramp up efforts on one of Keith's priorities, developing rules for governing geoengineering research. And Cambridge offers a bully pulpit for injecting the topic into international discussions. Or, as Keith put it in a 2007 TED talk: "We need a broader debate … not just a few oddballs like me."

    A low-dose supplement

    Keith hopes to jump-start that debate with A Case for Climate Engineering. In 112 pages of authoritative prose, he largely eschews figures and technical terms in a bid to reach a lay audience. He begins by casting the climate challenge in stark terms: Past emissions have already committed Earth to substantial warming, he warns; even aggressive emissions cuts—if they ever materialize—can only partly reduce climate risks. But geoengineering techniques could relatively quickly "cut the average rate of global warming in half for the next half-century," he argues.

    In particular, Keith focuses on one technique: releasing sulfuric acid vapor high in the stratosphere, where it would scatter sunlight away from Earth's surface. The approach mimics the global cooling effect of large volcanic eruptions, which spew sulfates into the stratosphere. But Keith envisions a "slow ramp scenario," gradually adding sulfur over decades to counteract about one-half the yearly climate change caused by humans. That would allow "ample time" to alter or halt the procedure if there are surprises, he notes. And the method could be relatively cheap: A 2010 study he arranged suggested that the cost of starting the plan with aircraft would be, incredibly, a few hundred million dollars—"the price of a Hollywood blockbuster," Keith writes.

    Keith highlights the risks. The particles could catalyze chemical destruction of the protective ozone layer, or—at high doses—rob the climate system of crucial energy required to drive precipitation. And even discussing the idea might undermine efforts to transition away from fossil fuels, he concedes, or even prompt international tensions. But some modeling studies, he writes, suggest sun-blocking methods could reduce the harm caused by warming, including heat stress on crops "in the hottest and poorest parts of the world."

    Still, many are skeptical. Last month, the IPCC warned that solar geoengineering could "modify the global water cycle," although it didn't specify how much sulfur it might take to cause concern. Other critics are more direct: Efforts to manipulate climate with light-scattering particles are "barking mad," says climate modeler Raymond Pierrehumbert of the University of Chicago in Illinois. One problem, he says, is sun-blocking may do little to reduce overall peak global temperature increases under many scenarios. And it could even lead to a relatively sudden global temperature spike, he warns, if the effort is interrupted by a war or calamity.

    To clarify and quantify such risks, Keith says researchers need to move beyond theoretical debate to actual field experiments. First up, he argues, should be "process studies" that would be too small to have any appreciable impact on climate—studies like the one he and chemist James Anderson of Harvard have now proposed (see graphic, p. 308). The idea is to use a balloon release less than a kilogram of sulfuric acid vapor about 20 kilometers above Earth's surface during the fall or spring, when the stratosphere is very still. Chemical sensors aboard the balloon would then measure possible effects on stratospheric ozone. The craft would also repeat the experiment with water vapor, fingered recently by Anderson as a possibly underestimated threat to ozone.

    A hazy outlook

    Gates, among other tycoons, could fund such an experiment. But Keith is adamant that governments should lead on solar geoengineering research. International oversight agreements and government funding can make "the development of solar geoengineering technologies … as public and transparent as possible," he writes. Government leadership could also prevent potential conflicts of interest, he argues, by preventing companies from winning monopolies on new technologies and keeping them in the public domain. Keith and Anderson say they will ask the U.S. government to fund their experiment.

    So far, however, U.S. agencies have held back from funding geoengineering research, and prospects overseas are dim as well. In 2010, the 197 nations that are members of the Convention on Biological Diversity adopted a resolution that asks governments to oppose "geo-engineering activities that may affect biodiversity." And one U.K.-funded effort, the Stratospheric Particle Injection for Climate Engineering project, had to cancel a 2011 field experiment after it became mired in controversy. Critics complained that researchers hadn't adequately vetted the test, which involved spreading a small quantity of water vapor from a tethered balloon, or worked out how ownership of any new technology might be handled.

    A public perch

    A publicly funded experiment subject to customary environmental review could avoid such pitfalls, Keith says. But he faces obstacles of his own. One is his stake as president of Carbon Engineering, which some observers say poses a potential conflict of interest because his call for greater investment in geoengineering research could ultimately benefit his own company. Such concerns, in fact, blocked Keith from serving on a current National Research Council panel on geoengineering. "With David straddling this academic-business divide, his company is going to hold him back," Caldeira predicts. "It's impacting his academic career."

    Keith sees "a sharp distinction in the role of private enterprise" in the two flavors of geoengineering. Because sun-blocking technologies hold global risks as well as benefits, they are no place for private enterprise, he says. His work in that area involves "open publications and no patenting." In contrast, he argues that firms serve a crucial function in developing air capture methods, which he says pose "local risks" akin to other industry.

    Such nuances are often lost in public debate. After one article criticized his proposed experiment, Harvard alumni were "writing to the [university] president … asking why these maniacs are on your faculty," Anderson says. And then there are the two death threats, apparently from people who believe Keith is part of a government conspiracy. One caller last year was "verbally abusive and drunk," says Keith's assistant Hollie Roberts, prompting a report to the police.

    Colleagues, however, appreciate Keith's increasingly public role as advocate. "It's important to have good spokespeople on geoengineering, and Keith is an independent and hyperarticulate one," says Caldeira, of Carnegie. "He's a very deep thinker," Long says. "You may not always agree with him, but you have to hear him out."

    For his part, Keith says he's learned from his time in the limelight and is taking greater care in what he says and writes. "It gets under my skin when I am made out to be the rank advocate" for geoengineering, he says. "It hurts." So now he's "trying to be more disciplined about weaving caveats in," so that others can't take his words out of context. And his book tempers boldness with humility. "I myself have concluded that it makes sense to move with deliberate haste towards deployment of geoengineering," Keith writes. "You may well reach a different conclusion. My goal is simply to convince you that it's a hard choice."