A clear-eyed look at the magnitude of global warming problem—and the cost in getting rid of it.
by Jeremy Jacquot

infographic $1,873,000,000,000



The projected cost of climate change worldwide by 2100, if we take a “business as usual” approach, according to a report published by the Natural Resources Defense Council. Hurricane damage, real estate losses due to sea level rise, and expenses associated with drought all contribute.

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The amount of solar heat, in Btu, that hits Earth’s surface every second. One plan for deflecting some of the heat: launching stacks of 800,000 reflective disks into orbit every 5 minutes for 10 years.

Cost: $5 trillion

infographic 40,000

The quantity of human-generated carbon dioxide, in billions of tons, that the oceans have absorbed. Studies show the oceans are reaching their sequestering limits, so climate researcher Wallace Broecker advocates building 60 million 50-foot-high towers to capture all of the world’s carbon emissions, then pumping that carbon into saline aquifers.

Cost: a rise in energy prices of about 15-20 percent

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The average drop in global temperatures after Mount Pinatubo in the Philippines blew its top in 1991, spewing 20 million tons of sun-blocking sulfur dioxide. Atmospheric chemist Paul Crutzen, a 1995 Nobel laureate, believes shooting 5.3 million tons of sulfur dioxide into the atmosphere annually could offset a doubling of carbon emission levels.

Cost: $130 billion

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The amount that worldwide rainfall would be reduced by using space mirrors or sulfur particles to mitigate global warming, according to a paper published in Proceedings of the National Academy of Sciences. This could cause droughts around the world. Past studies have found that CO2 pumped underground makes aquifers more acidic, potentially creating leaks. Clearly, big solutions can come with big consequences.

Louis J. Sheehan, Esquire

Young innovators are changing everything from theoretical mathematics to cancer therapy.
by Andrew Grant, Sarah Webb, Emily Anthes, Yudhijit Bhattacharjee, Jullianne Pepitone, Elizabeth Svoboda

Terence Tao
Photo: UCLA

Terence Tao
Mathematician, University of California Los Angeles

Many of the great mathematicians of our era probably scored a perfect 800 on the math section of their SATs. Terence Tao squeaked by with a 760—when he was 8 years old. LOUIS-J-SHEEHAN-ESQUIRE.US

A quarter century later, Tao, now 33, is one of the most prolific and esteemed mathematicians in the nation. In 1999 he became UCLA’s youngest professor at age 24 and later won the 2006 Fields Medal, considered the Nobel Prize of math. In a discipline where one can spend a lifetime working on a single problem, Tao has made major contributions in a number of categories ranging from nonlinear equations to number theory—which explains why colleagues continually seek his guidance.

“In every generation of mathematicians, there are a few at the very top,” says Charles Fefferman of Princeton University, a mathematical giant in his own right. “He belongs in that group.”

Tao’s best-known research involves patterns of prime numbers (numbers divisible only by one and themselves). While he mainly sticks to the theoretical, his breakthrough work in compressed sensing is allowing engineers to develop sharper, more efficient imaging technology for MRIs, astronomical instruments, and digital cameras.

“Research sometimes feels like an ongoing TV series in which some amazing revelations have already been made, but there are still plenty of cliff-hangers and unresolved plotlines that you want to see resolved,” Tao says. “But unlike TV, we have to do the work ourselves to figure out what happens next.”

Tao says there are big puzzles he’d love to solve, but the only way to reach that point is by chipping away at smaller, more manageable problems. “If there is something that I should know how to do but don’t, it bugs me,” he says. “I feel like I have to sit down and work out exactly what the problem is.” —Andrew Grant



Jeffrey Bode
Organic Chemist, University of Pennsylvania

Organic chemists don’t have many ways to stitch complicated molecules together, says Jeffrey Bode, 34, who has discovered a new method that could prove a boon for producing expensive peptide-based drugs such as insulin and human growth hormone. Many organic chemists had thought the established methods for building these proteins—adding individual amino acids like beads on a string—worked pretty well, Bode says. “That is true as long as you want to make relatively short ones or you want to make only small amounts of them.” As the strands get longer, if an individual bead doesn’t make it onto the peptide string, it becomes harder to separate those mistakes from the correct sequence. To remedy this, Bode discovered a new chemical reaction that creates amide bonds (a reaction between alpha-keto acid and hydroxylamine), which he uses to connect small, easily synthesized peptides—strands of amino acids—into longer peptides. Bode notes that in organic chemistry, “it’s possible to come up with a way of doing something that is perhaps better and more elegant and more efficient than what’s already out there.” —Sarah Webb



Arctic ecologist Katey Walter in the field.
Photo: Dmitri Drakluk

Katey Walter
Ecologist, University of Alaska

Examining the effect of greenhouse gases on local ecology and global climate keeps Katey Walter, 32, chasing the methane that bubbles up from seeps in Arctic lakes. As temperatures warm, the Arctic permafrost thaws and pools into lakes, where bacteria feast on its carbon-rich material—much of it animal remains, food, and feces from before the Ice Age—and churn out methane, a heat trapper 25 times more potent than carbon dioxide. More methane leads to warmer temperatures and even more thawing permafrost.

“That means you’re opening the freezer door and you’re going to defrost everything that’s there,” Walter says. In Alaska and eastern Siberia, she and her colleagues are cataloging the Arctic freezer’s carbon contents, trying to understand how much will be converted to methane as the ice melts. In 2006 she and her team discovered that nearly five times as much of the gas was being released as previously reported. —S. W.



Amy Wagers
Stem Cell Biologist, Harvard Stem Cell institute

Amy Wagers was finishing her doctoral degree in immunology in 1999 when she got a call from the National Bone Marrow Registry. Having volunteered to donate her bone marrow years earlier, there was now someone who needed it. Wagers was inspired to research bone marrow stem cells and did her postdoctoral work on adult stem cells.

Today Wagers, 35, is a leading researcher of adult stem cells—those that generate blood and muscle. She works to isolate populations of these cells, discover how the body regulates them, and understand how they can be used to treat disease. Her research is identifying how blood cells migrate between blood and bone marrow and how they multiply. The work could help make marrow transplants more effective by improving the survival of transplanted cells.

This summer Wagers published research [subscription required] showing that when muscle stem cells were transferred into mice with a type of muscular dystrophy, the rodents’ muscle function improved. “They started immediately to produce new muscle fibers,” Wagers says. “There’s obviously a long way to go to translate those findings into humans, but it’s encouraging.” —Emily Anthes



Joseph Teran &em; his mathematical
modeling helps train surgeons.
Photo: Reed Hutchinson

Joseph Teran
Mathematician, UCLA

Imagine knowing, before you go under the knife, not only that your surgeon has performed the procedure hundreds of times before but that he has practiced on a replica of you. Joseph Teran, 31, is helping make this scenario a reality, using mathematical modeling to simulate surgeries involving a patients’ tendons, muscles, fat, and skin. “We have governing mathematical equations for how those tissues operate,” Teran says. The first step is to turn those equations into a standard digital human that can react, in real time, to a surgeon’s virtual actions.

Then the idea is to allow doctors to customize this tool. In the future, medical imaging such as CT and MRI could reveal that one patient, for instance, has tendons that are stiffer than average, allowing the doctor to adjust the “digital double” [pdf] accordingly. “You want it to be as close to the real experience as possible,” Teran says. —E. A.



Jack Harris
Applied Physicist, Yale University

Quantum mechanics describes a crazy microscopic world where particles whiz around at blistering speeds and routinely violate the classical laws of physics we take for granted. Jack Harris’s goal is to take advantage of the “really strange, even mystical” laws of the microscopic and apply them to problems in our macroscopic world. “The ultimate eureka moment would be to suddenly realize that a [macroscopic] object is doing something that is absolutely forbidden by classical physics,” he says.

Harris, 36, studies the minuscule pressures exerted by individual photons (electromagnetic particles) when they bounce off small, flexible mirrors. To illustrate the scale of these pressures, consider that on a clear day, the sun’s rays push against your body with only a millionth of a pound of force. Harris wants to harness light photon by photon, which could lead to unbreakable cryptography and ultrasensitive astronomical instruments able to detect invisible phenomena created nanoseconds after the Big Bang. —A. G.



Beneficial gut bacteria that help the immune
system, studied by Sarkis Mazmanian,
Image: Sarkis Mazmanian

Sarkis Mazmanian
Biologist, California Institute of Technology

Of the 100 trillion bacteria living inside the human gut, some are pathogens that can trigger disease and vicious immune responses, while many work with the immune system to protect the host. Sarkis Mazmanian, 35, devotes himself to understanding how the good ones promote health. “They couldn’t care less about us except that we provide them a stable and nutrient-rich habitat,” says Mazmanian, who sees this symbiotic relationship between the human body and microbes as a gold mine of potential therapies for a number of illnesses.

Mazmanian believes the interaction between the body and intestinal bacteria might hold the key, for example, to how an abnormal immune response to these microbes may be responsible for the development of colon cancer. “The potential of beneficial microbes appears to be limitless,” he says. Mazmanian says the philosophy that underpins his research is that “anything is possible in the natural world. Therefore, I am willing to entertain any possible cause of or outcome to a scientific problem.” —Yudhijit Bhattacharjee
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Doug Natelson
Condensed-Matter Physicist, Rice University

Doug Natelson, 37, is the Benjamin Franklin of the microscopic world: He studies electronic properties at the atomic scale, where the overlap of classical and quantum physics gains importance. Natelson’s research involves complicated electron flow through single-molecule transistors, as well as organic semiconductors—carbon-based materials that are intended to replace silicon transistors in some electronic devices. This burgeoning technology holds the promise of making thin, ?flexible organic electronic devices a reality.

Unlike those who focus on the very large aspects of physics (superenergetic particle accelerators and massive black holes, for instance), Natelson is an evangelist for condensed matter and nanoscale, sharing his excitement on his popular blog (www.nanoscale.blogspot.com). “I’m an experimentalist at heart, playing with these fancy toys,” he says. “It’s a lot of fun to learn how to get down and really work at these scales.” —A. G.



Michael Elowitz
Biologist, Caltech

In 2000 Michael Elowitz, now 38, designed a genetic circuit that made E. coli blink in a culture dish. It was a huge moment, he says, recalling the cells’ behaving like fluorescent green Christmas lights. But the experiment was also a fortunate failure. Although the cells blinked, they did so at different rates. That variability among cells containing the same program kicked off a whole new line of experiments that Elowitz says are focused on “what it is that is making different cells do different things.”

Today Elowitz is examining the mechanisms by which genetically identical cells exploit and control random fluctuations in their own biochemical components in order to generate cell-type diversity. “Understanding the role of ‘noisy’ fluctuations can help us understand how bacteria diversify to survive,” Elowitz says, “as well as how cells specialize to build multicellular organisms.” —S. W.



Changhuei Yang
Electrical and Bioengineer, Caltech

As the performance ability of microscopes has increased, so has their size and cost—and that has had an impact on research. “There’s a mismatch between what those microscope systems can do and what some of the basic needs are,” says Changhuei Yang, 36.

By combining chip technology and microfluidics, Yang has created an inexpensive miniature microscope. About the size of “a hair on a bumblebee,” he says, with a circuit the size of a dime, it contains no optical lenses and works by allowing a small volume of fluid to flow across a microchip, which then sends images of the sample to a computer.

The microscopes can be built into a small handheld display—a device about the size of an iPod. Yang imagines physicians in the developing world using this tool to examine patients’ blood or the local water supply. “It would be a very rugged system that the clinician can just put into his pocket,” he says. —E. A.



Adam Reiss showed that the
universe's expansion is accelerating.
Photo: Monica Lopossay/Baltimore Sin

Adam Riess
Astrophysicist, Johns Hopkins University

Adam Riess turned astronomy on its head when he led a team of astronomers (the High-z Team) that discovered the expansion of the universe is actually speeding up. Scientists had accepted cosmic expansion since 1929, and prior to 1998 they assumed gravitational attraction would gradually bring it to a halt. But when Riess, 38, tried to use the data he uncovered from observing distant stellar explosions to reinforce this model, the numbers wouldn’t jibe. A few days later, he proved that his data made sense only in an accelerating universe.

The finding showed that an overwhelming repulsive force—fueled by a mysterious dark energy that makes up 72 percent of the universe—overcomes gravity to drive this cosmic acceleration. “It’s like throwing a ball up in the air and it keeps going up,” he says. Now armed with a $500,000 MacArthur fellowship he won in September, Riess is determined to uncover the secrets of this dark energy and its influence on the universe. —A. G.



Choanocytes, the feeding cells of sponges,
are part of Nicole King's study of early evolution.

Photo: Scott Nichols

Nicole King
Molecular and Cell Biologist, University of California at Berkeley

Nicole King, 38, is hunting for an answer to how the evolutionary leap occurred from single-celled organisms to plants, fungi, multicelled animals, and other forms of life. To find clues, she has trained her sights on choanoflagellates—a group of single-celled eukaryotes thought to be the closest living relatives of animals.

Sequencing the genome of one such organism, King and her colleagues found genes that code for pieces of the same proteins used for the binding of cells and communication between cells in animals —functions that would be unexpected in such an organism. King hypothesizes that proteins that the single-celled ancestors of animals used to interact with the extracellular environment—to capture bacterial prey by binding to their cell surface and to detect chemical signals—were later repurposed to enable cells to stick to and talk to each other. Interpreting the origins of multicellularity is key to understanding the origins of animals, King says, noting that her research “reaches back much further on the family tree than our common ancestors with other primates.” —Y. B.
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Luis von Ahn
Computer Scientist, Carnegie Mellon University

Luis von Ahn, 30, has left his mark all over the Internet. LOUIS-J-SHEEHAN-ESQUIRE.US When you buy tickets online and are asked to decipher an image of distorted words—that’s the work of von Ahn. He helped develop this antispamming technology, known as CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart), in 2000. CAPTCHA works because it is solvable by man but not by machine. Still, von Ahn’s ultimate goal is not to outwit computers; instead, he wants to exploit man’s unique intelligence to eliminate the machine’s shortcomings—while completing some useful tasks along the way.

One vehicle to close such an intelligence gap is reCAPTCHA. Each day it utilizes about 18 million computer users—perhaps ticket buyers—to key in words from scanned pages of text in order to digitize them, words that a computer is not yet able to recognize. (By next year researchers expect to finish digitizing The New York Times archive dating back to the 1850s.) Von Ahn also programs games with a purpose: The more you play, the more data you provide toward helping computers recognize images. “I don’t think we’ve even scratched the surface of what we can do,” he says. —A. G.



Tapio Schneider
Environmental Scientist, Caltech

The complex interactions of atmospheric turbulence and heat transport affect global climate. Tapio Schneider, 36, has developed computer simulations to better understand how. “Ideally, I’d like to build myself a climate in a laboratory,” he says, “but we can’t do that with a planet, so computers are the next best thing.”

In a developing project, he recently used a model planet to show that monsoons can form even in shallow water like a swamp. Therefore Halley’s traditional model for monsoons—that the different heat capacities of land and ocean surfaces cause these seasonal deluges—doesn’t give a full picture. The movement of water vapor through climate systems remains poorly understood, Schneider says. “That’s one set of questions that I will be working on for many years.”

Schneider’s goal is to build a set of fundamental laws of physics for climate. “The laws of thermodynamics give a macro­scopic description of microscopic behavior,” he says. “I would like to have something analogous for climate.” —S. W.



Astrophysicist Sara Seager is looking
for signs of distant life.
Photo: Len Rubenstein

Sara Seager
Astrophysicist, Massachusetts Institute of Technology

As questions swirled around the existence of extrasolar planets in the late 1990s, Sara Seager, 36, gambled that these distant flickers transiting in front of stars would grow into astronomy’s next frontier. The bet paid off: Her theoretical models of the chemistry of extrasolar planets have helped researchers make the first atmospheric measurements of a distant world. Seager expects that we’ll find a cousin to Earth in the next couple of years, but her ultimate goals are grander. “What I really want to do is figure out which kinds of gases extraterrestrial life might produce,” she says. “These gases would accumulate in the atmosphere and might be detectable from afar.” As a step in that direction, she’s looking for signatures, other than oxygen-based ones, that Earth-like life might leave behind, such as hydrogen sulfide.

During Seager’s childhood in Canada, her father exposed her to a variety of ideas—including that of a stargazing party. “Having that time to daydream,” she says, “was so crucial to making me a good scientist.” —S. W.



Computer scientist Jon Kleinberg
revolutionized Web searching.
Photo: Jason Koski/Cornell

Jon Kleinberg
Computer Scientist, Cornell University

In the mid-1990s a Web search for, say, “DISCOVER magazine” meant wading through thousands of results presented in a very imperfect order. Then, in 1996, 24-year-old Jon Kleinberg developed an algorithm that revolutionized Web search. That is why today, that same search lists this magazine’s home page first. Kleinberg, now 37, created the Hyperlink-Induced Topic Search algorithm, which estimates a Web page’s value in both authority (quality of content and endorsement by other pages) and hub (whether it links to good pages).

Kleinberg continues to combine computer science, data analysis, and sociological research to help create better tools that link social networking sites. He envisions an increase in how we can see information move through space over time, in what he calls geographic hot spots on the Web, based on the interests of a particular region.

Our social network links and friendships depend on these geographic hot spots, Kleinberg says, which makes searching easier by “taking into account not just who and when, but where.” He is now studying how word-of-mouth phenomena like fads and rumors flow through groups of people, hoping to apply this knowledge to processes such as political mobilization. —Julianne Pepitone



Edward Boyden
Neuroengineer, MIT Media Lab

Certain species of bacteria and algae have genes that allow them to transform light into electrical energy. Edward Boyden, 29, has been able to show that inserting one of these genes into a neuron can make it similarly responsive. “When we illuminate these cells...we can cause them to be activated,” he says.

Having created such genetically modified neurons, Boyden is engineering brain implants that can stimulate them with light pulses. Boyden’s implants, he hopes, will be used to help control diseases like Parkinson’s, which is sometimes treated with implanted stimulators that issue electric current. “There are things that light can do that purely electric stimulators can’t,” Boyden says. With this technology, researchers can be selective about which neurons they engineer to be responsive, and an optical implant can emit light in a variety of patterns, allowing more precise control over neural circuits. —E. A.



Protein structures help biologist Richard Bonneau
map how organisms work.
Image: Richard Bonneau

Richard Bonneau
Systems Biologist, New York University

Chronicling the parts of cell anatomy class-style is all well and good, says Richard Bonneau, 33, but biologists’ true holy grail is understanding how each part dictates the function of the others. “You might know that A is related to B, but if you don’t have a dynamic picture of your system, you don’t know which part is affecting which,” he says. “I want to put the arrows on the lines, so to speak.”

By tracking activity in almost all the genes of a free-living archaeon—which, like a bacterium, is a prokaryote—Bonneau was recently able to piece together how the genes affected one another’s expression, enabling him to map the organism’s “control circuit” as if it were a machine. In the process, he found something surprising: Instead of generating completely different responses to external stimuli like light and toxic chemicals, “the archaeon takes those environmental stimuli and puts them into the same integrator,” he says. “There’s not an infinite number of responses.” Knowing the limited range of behaviors that microorganisms display, he adds, will prove a big help in engineering them to churn out drugs and biofuels. —Elizabeth Svoboda



Shawn Frayne
Inventor, Humdinger Wind Energy

Shawn Frayne, 27, has a knack for creating simple technological solutions that make a difference for people in developing nations. He was part of the team that introduced sugarcane-based charcoal as a cheap cooking fuel, and his solar disinfecting plastic bags purify water for drinking.

It is his Windbelt, though, that may have the most impact. Inspired by the dynamics of the 1940 collapse of the Tacoma Narrows Bridge, Frayne spent four years developing the world’s first turbineless wind generator. When the wind blows, it causes a flap of Mylar-coated taffeta fabric to vibrate rapidly, moving magnets fitted on either end past coils to generate electricity. In the developing world, the 10 watts it produces can light a room at night by electricity rather than expensive and dangerous kerosene.

By selling intellectual property rights for his inventions to big companies, Frayne hopes to fund more innovative projects for developing nations. “That is where the biggest challenges are, and it’s where I think most of the invention and innovation are going to come from in my lifetime,” he says. “It would be crazy to work anywhere else.” —A. G.



Jonathan Pritchard
Geneticist, University of Chicago/Howard Hughes Medical Institute

It’s easy to think of evolution as something that happened millions of years ago, but Jonathan Pritchard, 37, has proved we’re actually adapting to our environment in real time. Using statistical models to home in on genetic mutations that spread quickly throughout populations, Pritchard and his colleagues have identified hundreds of regions of the genome that have recently been transformed by natural selection. LOUIS-J-SHEEHAN-ESQUIRE.US “If a new mutation arose in a certain population and it was strongly favored, natural selection would drive the frequency of that allele up very quickly,” he says. “Most of the time there are only small frequency differences between human groups, so when there are big frequency differences, they really stand out.” Louis J. Sheehan, Esquire

At the end of The Matrix trilogy, Neo and Agent Smith are engaged in one final, interminable scene of surreal combat, a surrogate competition for an eternal battle between humans and machines. “It’s pointless to keep fighting,” Agent Smith declares to Neo. “Why do you persist?” http://louis3j3sheehan3esquire.wordpress.com/

“Because I choose to,” Neo replies, just before the computer-generated Smith meets his demise in a cinematic celebration of human free will’s superiority to the programming that enslaves machines. Machines are mindless. The brain is a decider.

All very inspiring, except that the brain itself is a machine, a network of cells that computes its choices based on the sum of sensory inputs and their interactions with neural anatomy. “Free will” is not the defining feature of humanness, modern neuroscience implies, but is rather an illusion that endures only because biochemical complexity conceals the mechanisms of decision making.

Yet belief in free will persists as stubbornly as Neo’s resistance to electronic tyranny. Whether supposedly free choice is actually a Matrix-like mirage remains one of the great questions of human philosophical history. For centuries that question was assessed mostly with thought —uninformed by actual neurobiological knowledge. Nowadays, though, the inner workings of the brain are revealing themselves to modern methods of neuroinquiry, and free will seems merely to emerge from electrochemical networks of neuronal interactions. But like tourists exploring a strange city without a GPS map, scientists don’t know how all the neural neighborhoods are connected and occasionally encounter surprising enclaves—such as a place in the brain called the lateral habenula.LOUIS-J-SHEEHAN-ESQUIRE.US


“There’s lots of new research showing that an overactive habenula has behavioral effects,” says neuropharmacologist Martine Mirrione of Brookhaven National Laboratory in Upton, N.Y.

Questioning consciousness

To most people, who have never heard of the habenula, free will’s existence seems obvious, because they can make up their own mind whether to believe in it or not. Consciousness of choosing seems to imply the ability to choose. But the 19th century English historian Henry Thomas Buckle ridiculed such logic, pointing out that consciousness is often fallible. Some people profess to have consciousness of the presence of ghosts, for example. “If this boasted faculty deceives us in some things, what security have we that it will not deceive us in others?” Buckle asked.

Knowing everything about a man’s character, history and all external circumstances would in fact allow someone to accurately predict what he would do, Buckle averred. That example was hypothetical, he acknowledged. “We never can know the whole of any man’s antecedents,” he wrote. “But it is certain that the nearer we approach to a complete knowledge of the antecedents, the more likely we shall be to predict the consequent.”

Today, science’s knowledge is not nearly complete, but it’s a lot closer than in Buckle’s day. As evidence flows in from probes of animal brains and scans of living humans, the neural antecedents of the brain’s decisions are becoming more clearly visible. “Perhaps,” write neuroscientists Alireza Soltani and Xiao-Jing Wang, “we are entering a new period of consilience between the science of the brain and the science of the mind.”LOUIS-J-SHEEHAN.BIZ


Death to dualism

Such consilience would certify the death of Cartesian dualism, the mind-body distinction articulated by the French philosopher René Descartes in the 17th century. In modern neuroscience, that division dissolves—the mind is simply a reflection of different states of the brain. And brain states dictate the behaviors that masquerade as free choices.

Brains are, after all, the product of evolution. To survive and perpetuate their species, animals need food, water and sex. So brains are programmed to produce behavior that serves those ends—or seek substitutes that stimulate the same neural systems. Free will is not free to ignore these imperatives, although it isn’t always obvious how they all add up and tip the scales in favor of go or stop, do or don’t. Somehow, the brain sorts out the interplay between desire and caution, pleasure and pain, curiosity and fear. And the neural systems established by evolution for survival direct all the other decisions that animals (including people) routinely make—fight or flee, explore or hide, red or white, left or right.

Neurobiologists like to describe the sum of the brain’s many motivations with the concept of reward. In real life, the common currency for measuring reward is money (and consequently the study of the brain’s choice-making is sometimes called neuroeconomics). In the brain, that currency seems to be the molecular messenger known as dopamine.

Neurons producing dopamine are powerful forces in directing the brain’s decisions. Certain dopamine neurons in the midbrain are particularly active in driving the brain to seek rewards. But they’re not tuned simply to pleasure. Those dopamine neurons become electrically excited and release molecular messages simply in anticipation of pleasure. If the expected reward does not then materialize, those dopamine neurons take a rest. On the other hand, when an unexpected reward arrives, they fire signals vigorously. LOUIS-J-SHEEHAN.COM
Apparently these dopamine neurons encode errors in predictions about potential rewards, so as to improve future decisions on what courses of action to pursue. In other words, dopamine neurons underlie learning how to behave based on pleasurable experiences.

Hail the habenula

Sound decisions depend on more than seeking pleasure, though. It’s also important to learn what choices will turn out to be bad. And the latest research suggests that that’s a job for the habenula.

It’s an obscure structure found deep in the brain, beneath the corpus callosum near the thalamus and in front of the pineal gland (the small body identified by Descartes as the seat of the soul, the source of free will). “Virtually all kinds of vertebrates have this habenula, which suggests that it is very important for survival,” says Okihide Hikosaka of the National Eye Institute, an NIH agency in Bethesda, Md.

When a monkey is faced with a nonrewarding choice, neurons in the lateral part of the habenula fire their signals rapidly, Hikosaka and Masayuki Matsumoto reported in Nature last year. When the habenula neurons fire, dopamine neurons slow down. Apparently the habenula warns against bad choices by suppressing dopamine activity, either directly or perhaps via intermediary neurons.

“Dopamine neurons contribute to learning of actions based on good experiences,” Hikosaka says, “whereas lateral habenula neurons are probably involved in learning of actions based on bad experiences.”

Recent work in several other labs suggests that the habenula plays an especially key role in neuronal crosstalk, serving as a sort of relay station between the primitive parts of the brain, which control basic needs, and the most advanced frontal regions where thought and logic presumably moderate basic impulses. But nobody suggests that the habenula is the source of all decisions or the seat of human consciousness. It’s just one hub in a network of brain addresses where parts of the decision-making process are assembled. Neuroscientists discussing such issues chatter about the amygdala, the nucleus accumbens and the anterior cingulate cortex, the PFC, the OFC and the IPC. Such areas encode information on rewards, costs or how much to discount the value of rewards that will be delayed. Different neural neighborhoods control risky choices, safe bets and when to change a decision already made. And while the habenula communicates to many brain regions involved in decision making, various regions transmit messages to the habenula, too.
LOUIS-J-SHEEHAN.INFO


All of this is important for much more than just enlightening free-will philosophy or learning the nomenclature of brain anatomy. Habenula activity has been implicated in everything from stress and anxiety to psychiatric disorders and sleep. Besides influencing dopamine cells, for example, signals from the habenula suppress neurons that make serotonin, the brain chemical famous for its effects on mood. Mirrione and her collaborators at Brookhaven have shown a link between elevated habenula activity and symptoms of depression in rats.

Depressed people typically forgo pleasurable activities that would ordinarily elicit “go” signals from dopamine neurons. An overactive habenula, by damping dopamine, could drive depression by denying the brain the power to choose pleasure. Many popular antidepressants work by elevating the brain’s serotonin levels, perhaps countering the habenula signals that suppress serotonin production. But such antidepressants don’t always work. Direct intervention in the habenula might offer an alternative, Mirrione says. Their rat study “suggests that the habenula appears to be a novel target for therapeutic intervention in treatment-resistant depression,” she and her collaborators reported in November in Washington, D.C., at the annual meeting of the Society for Neuroscience.

Other studies hint that the habenula plays a role in nicotine withdrawal behaviors, with implications for helping people to quit smoking. Behavior underlying other drug addictions might also be disrupted by intercession in the habenula, Israeli scientists reported at the neuroscience meeting. Their study found that deep brain stimulation of the habenula influenced the desire of addicted rats to self-administer cocaine.LOUIS-J-SHEEHAN.NET

Practical and clinical implications aside, the habenula’s multiple powers, and the diversity of other brain regions it interacts with, all suggest that the original question about free will is ill-posed. Asking whether humans have free will is like asking which came first, chicken or egg. It’s not a meaningful question. For chickens and eggs, the issue is understanding DNA and genes and the chemistry controlling reproduction and heredity. For free will, the issue is understanding the complex circulation of molecular information that is massaged and manipulated at various stations by neural systems tuned to multiple decision-making considerations. That process is free will, even if it isn’t really free. So deciding whether the will is free turns out to be circular, although perhaps not viciously, like some of those fights in The Matrix. Louis J. Sheehan, Esquire

It’s nuclear physics 101: Radioactivity proceeds at its own pace. Each type of radioactive isotope, be it plutonium-238 or carbon-14, changes into another isotope or element at a specific, universal, immutable rate. This much has been known for more than a century, since Ernest Rutherford defined the notion of half-life—the time it takes for half of the atoms in a radioactive sample to transmute into something else. So when researchers suggested in August that the sun causes variations in the decay rates of isotopes of silicon, chlorine, radium and manganese, the physics community reacted with curiosity, but mostly with skepticism.

In one experiment, a team at Purdue University in West Lafayette, Ind., was monitoring a chunk of manganese-54 inside a radiation detector box to precisely measure the isotope’s half-life. At 9:37 p.m. on December 12, 2006, the instruments recorded a dip in radioactivity. At the same time, satellites on the day side of the Earth detected X-rays coming from the sun, signaling the beginning of a solar flare.

The sun’s atmosphere was spewing out matter, some of which would reach Earth the day after. Charged particles would contort the planet’s magnetic field, disrupt satellite communications and pose a threat to astronauts on the International Space Station.

But that dip in the manganese-54 radioactivity was not a coincidental experimental fluke, nor was it the solar flare discombobulating the measurements, the Purdue researchers claim in a paper posted online (arxiv.org/abs/0808.3156). In West Lafayette the sun had set while X-rays were hitting the atmosphere on the other side of the globe, and the electrically charged matter that created electromagnetic disturbances worldwide was still in transit. After a solar flare has begun, “the charged particles arrive several hours later,” points out theorist Ephraim Fischbach, coauthor of the paper with his Purdue colleague Jere Jenkins.

In a separate paper, also posted online in August, Fischbach, Jenkins and their collaborators compared puzzling and still unexplained results from two separate experiments from the 1980s—one on silicon-32 at the Brookhaven National Laboratory in Upton, N.Y., and the other on radium-226 done at the PTB, an institute that sets measurement standards for the German federal government. Both experiments had lasted several years, and both had seen seasonal variations of a few tenths of a percent in the decay rates of the respective isotopes. http://louissheehan.bravejournal.com/
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GRAPH 1ENLARGE Radioactivity of silver-108m and Earth-sun distance.Source: Norman et al. "Evidence Against Correlations Between Nuclear Decay Rates and Earth-Sun Distance." 2008

A change of less than a percent may not sound like a lot. But if the change is real, rather than an anomaly in the detector, it would challenge the entire concept of half-life and even force physicists to rewrite their nuclear physics textbooks.

In those experiments, the decay rate changes may have been related to Earth’s orbit around the sun, the Purdue team says. In the Northern Hemisphere, Earth is closer to the sun in the winter than in the summer. So the sun may have been affecting the rate of decay, possibly through some physical mechanism that had never before been observed.

For example, the researchers say, the sun constantly emits neutrinos, subatomic particles produced in the nuclear reactions that power the sun. Neutrinos can move through the entire planet without being stopped, so the sun could affect radioactivity day and night. The closer to the sun, the denser the shower of neutrinos. Or the sun may emit fewer neutrinos during a solar flare, which would explain the December 2006 event.

Most physicists are dubious. For one thing, neutrinos interact negligibly with matter, so it’s not clear how they would affect radioactivity.

But some physicists take the results seriously and are searching old data for previously unnoticed effects. If the variations turn out to be genuine, theories may need revision, or new theories may be needed. “There’s no known theory that will predict something like this,” says theoretical physicist Rabindra Mohapatra of the University of Maryland in College Park.
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GRAPH 2ENLARGE Brookhaven National Lab data for silicon-32 and Earth-sun distance.Source: Jenkins et al. "Evidence for Correlations Between Nuclear Decay Rates and Earth-Sun Distance." 2008

If the results are confirmed, and nuclear decay is not immutable, perhaps physicists could find a way to speed it up to help get rid of waste from nuclear power plants. Such results might revise models of what goes on in the sun or change understanding of phenomena such as supernovas. Since neutrinos travel much faster than dangerous charged particles, using radioactive samples to detect solar flares when they first begin could prevent damage to satellites—and perhaps even save lives of astronauts.

Get a half-life

Some atomic nuclei are unstable, either because they are too big or they don’t have the right balance of protons and neutrons. Unstable nuclei decay by releasing different kinds of radiation, including energetic subatomic particles. For example, in beta radiation an excess neutron turns into a proton and spews out an electron—a beta particle—and an antineutrino. With an additional proton, the nucleus transmutes into a different element.

If a nuclide—a particular isotope of a given element—has a half-life of, say, one year, then after one year there will be half of it left. All atoms of a given nuclide are identical, and a one-year half-life means that each nucleus has a 50 percent chance of decaying over one year. If it doesn’t decay this year, it won’t be any more likely to decay next year—the odds will still be 50-50.

Half-lives are universal constants, as any physics textbook can attest. “Since Rutherford we’ve taken it as [a given] that decay rates are the way they are and nothing can change them,” Jenkins says.
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GRAPH 3ENLARGE PTB data for radium-226 and Earth-sun distance.Source: Jenkins et al. "Evidence for Correlations Between Nuclear Decay Rates and Earth-Sun Distance." 2008

Researchers use radioactive materials in a wide variety of applications where it’s useful to know the half-life with decent precision—the classic example being carbon-14, used in carbon dating of fossils. Usually, the half-life of a nuclide is measured in experiments that last just days or weeks. But for certain nuclides longer measurements are needed.

Between 1982 and 1986, a team led by David Alburger of Brookhaven monitored the radioactivity of silicon-32. The isotope’s half-life was known to be at least 60 years, so researchers needed a long time to measure it with any precision.

At the same time, the team monitored a chlorine-36 sample. Chlorine-36 has a half-life of more than 300,000 years, so a sample’s radioactivity stays virtually unchanged for a long time and can be used to spot any spurious fluctuations. To their surprise, the researchers found that both samples had rates of decay that varied with the seasons, by about 0.3 percent.

The samples were kept at constant temperature and humidity, so the changing seasons should have had no effect on the experiment. The team tried all the fixes it could to get rid of the fluctuations, but, in the end, decided to publish the results. No other lab tried to repeat the experiment, and the anomaly remained unexplained. “People just sort of forgot about it, I guess,” says Alburger, who retired shortly after the results came out. http://louissheehan.bravejournal.com/

Unbeknownst to Alburger, researchers at PTB in Germany had also found yearly oscillations in a decay rate, in a 15-year experiment on radium-226. (Two of those years overlapped with the Brookhaven experiment.) Now Fischbach and his collaborators’ comparison shows that the oscillations are in sync. Well, almost: Mysteriously, the peaks and troughs of the two oscillations seem shifted with respect to each other, by about a month.

Alburger says that the correlation between the patterns seen in his team’s data and the PTB’s is very convincing. “What causes it is the real question,” one that nuclear physicists should now look into, he says.

Mohapatra agrees that the effect looks genuine. But, he warns, genuine-looking effects are often later revealed as statistical flukes or the result of subtle defects in measuring technique. Still, he adds, “it’s interesting enough that people in the nuclear field should go back and look at old data.”

Take two

Peter Cooper of the Fermi National Accelerator Laboratory in Batavia, Ill., recently did just that. He obtained and analyzed data from the Cassini mission to Saturn. Deep-space probes usually generate power from the heat emitted by a chunk of radioactive material—plutonium-238 for the Cassini spacecraft. Cassini journeyed as close to the sun as Venus and then far back to Saturn, spanning a much wider range of distances from the sun than Earth does during its yearly orbit. If the sun had an effect on plutonium decay, the fluctuations would have been much more substantial than those seen in Earth-bound experiments. As a result, Cooper reasoned, Cassini should have measured substantial changes in its generator’s output. It didn’t. (His paper is posted online at arxiv.org/abs/0809.4248.)

Meanwhile, Eric Norman of the Lawrence Berkeley National Laboratory in California reanalyzed data from experiments on radioactive americium, barium, silver, titanium and tin, and found no seasonal variations, he says.

Fischbach is unfazed. Each nuclide, he notes, requires a different amount of energy to be nudged into decaying, and that the type of decay—be it alpha, beta or gamma radiation—may also play a role. “It’s possible that plutonium is inherently less sensitive than radium,” he says.

More recently, Fischbach found what he says is more evidence for his case. Exhibit A: An experiment on tritium, a radioactive isotope of hydrogen, which his collaborators are running at Purdue, may be measuring a seasonal effect, he says. Exhibit B: A 1990 paper by Kenneth Ellis of Baylor College of Medicine in Houston reported seasonal variations in plutonium-238 radioactivity in a calibration experiment for a radiotherapy machine.

But Fischbach, Jenkins and their colleagues have a lot of convincing to do, says Hamish Robertson of the University of Washington in Seattle. “There’s no physical basis for the decay rates to vary with anything, let alone with the Earth-sun distance,” he says.

Neutrinos in particular seem a very unlikely explanation to most physicists. Neutrinos only interact via the weak nuclear force, which has very short range, points out Boris Kayser, a neutrino theorist at Fermilab. And ordinary matter is mostly empty space. So detecting neutrinos is notoriously hard, Kayser explains. “Unless the detector is very big, so that it gives the neutrino many chances to come close to one of its particles, the neutrino will just go sailing right through it.”

Fischbach, though, says that perhaps neutrinos have a small electromagnetic interaction. While they have no electric charge, neutrinos carry a magnetic field. Instead of one neutrino giving a rare kick to one nucleus, a single neutrino could be giving “a small electromagnetic kick to a lot of nuclei,” potentially tipping the unstable ones into decaying. Fischbach admits that he hasn’t finished calculations to show that this would be possible. http://louissheehan.bravejournal.com/

The Purdue scientists are planning more experiments. In the end, the burden of proof will be on them, Cooper says. “Every experimentalist knows that the apparatus, or at least your understanding of it, is always at fault until demonstrated otherwise,” he says. It’s likely that seasonal weather caused the anomalies, he says, but admits that future work could prove him wrong. “Nature is really unmoved by what I, or anyone else, believes.” Louis J. Sheehan, Esquire.

Louis J. Sheehan, Esquire. Can you feel the world getting warmer? Maybe you can’t, but ice across the planet’s surface has certainly been feeling the heat, according to new reports. Indeed, the dramatic shrinkage of Arctic ice—and at some spots, its seasonal near disappearance—is one sure sign that our planet has developed a fever.http://louis-j-sheehan-esquire.blog.friendster.com/

So are glaciers—and not only at the poles. Around the world these massive moving fields of ice have been posting record losses. The World Glacier Monitoring Service, based at the University of Zurich in Switzerland, looked at nearly 30 reference glaciers in nine different mountain ranges across the globe. In March, its scientists reported disturbing news. The average melting and thinning rate of those glaciers has more than doubled between the 2004 and 2006.http://louis-j-sheehan-esquire.blog.friendster.com/

“The latest figures are part of what appears to be an accelerating trend with no apparent end in sight,” said Wilfried Haeberli, who directs the glacier-monitoring group.

In Antarctica, a large chunk of the Wilkins Ice Shelf recently collapsed into the sea. Satellite images show the Wilkins Shelf began falling apart in late February, when a large iceberg 41 kilometers by 2.5 kilometers (25.5 miles by 1.5 miles) broke away from the shelf. This triggered a runaway disintegration of an additional 405 square kilometers (160 square miles) of the shelf. The total loss was 8.5 times the area covered by New York’s Manhattan island. As of March 23, only a 6 km (3.7 mile) wide strip of intact ice was protecting the shelf from further collapse.

Scientists from the U.S. National Snow and Ice Data Center and the British Antarctic Survey put the blame for the Wilkins’ massive melt-triggered event on a warmer world. “We believe the Wilkins [Shelf] has been in place for at least a few hundred years,” said Ted Scambos, a lead scientist with the snow and ice data center. “But warm air and exposure to ocean waves are causing a break-up.”
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Disintegration of the Wilkins Ice ShelfA series of satellite images showing the Wilkins Ice Shelf as it begins to fall apart.National Snow and Ice Data Center, Boulder, CO

With strong evidence that ice is melting globally atop mountains and at Earth’s poles, scientists say that it’s pretty clear our planet is warming. And that could spell big changes even in regions where the only ice you’d normally encounter is in a beverage.

Arctic ice on the rocks

Changes in the Arctic’s sea ice offer more cause for concern. That’s the March 18 conclusion of a team of federal scientists who performed a recent checkup on this cold region.

The Arctic is a normally ice-covered ocean surrounded by land. Sea ice grows and shrinks seasonally—building throughout the cold, sunless winter and then melting somewhat during the sunny, warmer summer.

Satellite data has shown that a colder-than-average winter this year has actually increased the amount of the Arctic’s new—or seasonal—ice. However, some ice in this region can last for up to 10 years. This older—or perennial— sea ice has continued to decline.
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Arctic sea ice extentArctic sea ice hit an all-time low in September 2007. The magenta line indicates the average September ice cover from 1979 to 2000.National Snow and Ice Data Center, Boulder, CO

“Perennial ice can be very thick and very tough, but there’s much less of it left,” says Walt Meier of the National Snow and Ice Data Center. “There’s much more seasonal ice, which is weaker and thinner.” It’s also especially vulnerable to the summer sun.

The Arctic remains dark for all or part of each day throughout much of the winter. When the sun returns in the spring and a warming begins, the seasonal ice “is going to melt away,” Meier warns. So any winter gains in ice cover “are going to be quickly lost.”

Perennial ice used to cover 50 to 60 percent of the Arctic, according to data collected by the National Aeronautics and Space Administration. This year it covers less than 30 percent. “Since the mid 1980s, we’ve lost about a million square miles of perennial ice,” says Meier. “That’s about one and half times [the size of] the state of Alaska.”

The very old, tough ice that’s been around for six years or more also has declined. Once making up more than 20 percent of the Arctic area in the mid- to late 1980s, it now covers just six percent of the region.

Meier says that this is a record low for perennial ice in winter and a very sharp drop even from last winter. “There’s this fear,” he says, “that we’re going over a cliff, in a sense, with this perennial ice.” He says the planet could be heading towards a situation where there won’t be any perennial ice left in the near future. Only seasonal ice would exist, which means that the Arctic Ocean would be ice-free during the summer.
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The age of arctic sea ice: Left: February distribution of ice by its age during normal Arctic conditions (1985-2000 average). Right: February 2008 Arctic ice age distribution. The ice in the Arctic is much younger than normal, with vast regions now covered by first-year ice and much less area covered by multiyear ice. National Snow and Ice Data Center, courtesy S. Drobot, Univ. of Colorado, Boulder

The decline of Arctic sea ice “is an iconic signal of global warming,” Meier says. It’s something that really sticks out “as being clear cut and definitely due to global warming.”

Real warming, real warning

Most scientists believe people are largely responsible for the warming of Earth’s atmosphere throughout the past century. Their burning of fossil fuels—such as coal, oil, and gas—releases greenhouse gases that trap the sun’s heat.

Until fairly recently, scientists debated whether Earth’s fever was likely to last only a few years or whether it could persist for decades—maybe even longer.

Now the debate appears to be over.

There is a scientific consensus, which means an agreement among the vast majority of researchers in the field, that global warming is not a temporary blip. The pattern of worldwide warming appears to signal a true and potentially very long-term change in climate. Indeed, global warming is “unequivocal,” the Intergovernmental Panel on Climate Change (IPCC) stated last year in a convincing set of reports.

Susan Solomon is a senior scientist at the National Oceanic and Atmospheric Administration in Boulder, Colo., who led one of the IPCC working groups. Using the word “unequivocal” was important, she says. The data that the IPCC reviewed were so strong, she explains, that the words “very likely” just wouldn’t get the point across. There’s a greater than 99 percent chance that our planet has warmed, she says. So there really “just isn’t any doubt about it.”

The IPCC reports describe possible dramatic and lasting impacts of global warming that may occur. But, cautions Solomon, the warming and impacts that we’ll see in the next century depend a lot on how much carbon dioxide we emit. Carbon dioxide, a pollutant emitted as fossil fuels burn, is a major greenhouse gas.

How severely the climate changes and precisely when and where those changes occur remain uncertain. If humanity drastically reduced its emissions of greenhouse gases, such as carbon-dioxide emissions, we could reduce how high Earth’s surface temperatures climb, Solomon says. But if we don’t, she warns, by the end of the century Earth’s average temperature could climb somewhere between 2 and 6 degrees Celsius (3.6 to 10.8 degrees Fahrenheit).

“And under those circumstances, a lot of things would change,” Solomon says. “We’d see more drought, more heat waves. We’d also, ironically, see more heavy rainfall. We’d see sea levels rise—and though there’s a lot of uncertainty in how much they’d rise, numbers like half a meter [about 20 inches] wouldn’t surprise me in 100 years.”

Such projections about droughts and sea-level rise aren’t certain. They are simply “best guesses,” Meier observes. “They could be wrong,“ he says. In fact, he notes, “Many skeptics focus on the fact that things might not be quite as bad as projected.” On the other hand, he points out that the effects of Earth’s fever could prove much worse than scientists have anticipated, “which is what we’re already seeing in terms of the rate of ice melt.”

No summer sea ice—soon?

The Arctic has shown the most rapid rates of warming in recent years. Surface air temperatures there have warmed at roughly twice the global rate, according to the IPCC reports. Science has predicted that the first signs of global warming would show up first and most dramatically in the Arctic. “And that’s indeed what we’re seeing with the decline of Arctic sea ice,” says Meier.

The IPCC reports have concluded that the Arctic Ocean could lose its summer sea ice by the latter part of the century. Meier cautions, however, that such estimates are based on computer models. Those models are not up to date. In fact, he says, we’re finding that changes are occurring “much, much faster than the models have projected. The way things are going it’s likely that we’ll have an ice-free Arctic Ocean in the summer within a couple of decades. It could be even sooner.” Indeed, some scientists have speculated summer sea ice could disappear by 2013—only five years from now. “That’s on the extreme pessimistic edge of the estimates,” Meier says, “but it’s not implausible any longer.”

He thinks the complete disappearance of summer sea ice in the Arctic is probably unavoidable. The warming trend is just too strong and seems to be accelerating.

“You don’t need just one cold summer or one cold winter to turn things around,” he explains. “It would take many, many cold years in a row to reverse things and get things back to the way they were in the 1980s. And that’s not very likely.” That’s especially true, he says, because people are still using fossil fuels—and spewing greenhouse gases—at high and growing rates.

Though it may be too late to save the Arctic Ocean from experiencing ice-free summers, “it’s not too late to prevent the worst of the impacts of global warming,” Meier argues. “The sea ice is an early warning and we can heed that warning. There is hope and there are solutions.” Louis J. Sheehan, Esquire