Running short of worries? Then ponder the super-volcanoes — earth-bombs that can vomit 10 or 100 or 1,000 cubic kilometers of molten rock. Super-volcanoes can change history by creating rivers of red-hot ash moving at highway speed, spreading dust across hundreds of kilometers and spewing vapors that block the sun, destroy crops and start famines.

A volcano may go dormant for thousands of years after such a huge eruption, so they may be even harder to predict than smaller ones — which are also unpredictable at this point…

But this week, Nature published a new analysis of Santorini, a Mediterranean monster, that shows the movement of molten rock that preceded the eruption.

Santorini’s sudden release of 40 to 60 cubic kilometers of rock and ash was followed by a giant collapse that left a characteristic ring of hills called a caldera. Thousands may have died in the eruption, which laid down a 60-meter layer of ash and rock.

Eruptions of this general size happen about every 300 years, says Timothy Druitt, a volcanologist at the Université Blaise Pascal in France, who lead the current study. The most recent was in 1815 at Tambora, in Indonesia.

Druitt’s new analysis of crystals within the frozen magma offers a rough schedule for the entry of molten magma into a holding tank — the magma chamber — below the volcano, which is a precursor to eruption.

Caldera-forming eruptions rival earthquakes and tsunamis as the deadliest natural disasters. “People who work in the field know these volcanoes are not rare, even on a human time scale,” says Druitt, but “we have never been able to monitor one of these big eruptions during the long buildup phase, so we are not really sure how that happens.”

The crystal analysis detects microscopic changes in chemical composition, offering a unique, after-the-fact picture of the gestation of eruption.

In the crystals

As crystals grow in the cooling magma, atoms of trace elements diffuse within them, and both growth and diffusion are affected by conditions within the hot magma, says Druitt. “These crystals grow progressively, and as they do, their chemical composition changes according to the composition of the magma around them, and the temperature and amount of water in the magma.”

The crystals revealed that a big gob of magma — perhaps 10 percent of the magma chamber’s total contents — entered in the decades before the eruption. “Looking at the crystals in this magma, we were able to reconstruct very crudely events taking place in the last few decades prior to the eruption,” Druitt says.

That final addition probably made the magma chamber unstable, leading to the eruption, Druitt explains.

If such a late, large magma movement proves typical of super-volcanoes, that could contribute to a distant early warning system for mega-eruptions, based on more conventional methods, such as seismic monitoring.

Distant early warning

But the findings also carried a caution, Druitt says, since Santorini was apparently dormant for about 18,000 years before the last apoplectic outburst. “That is a slightly alarming result. There are lot of these big caldera systems, but most are in a stage of repose.”

The upshot is more proof that a dormant volcano can still be a dangerous one, he adds. “We can imagine that a big caldera in a remote region of the world, such as the Andes, which is not monitored very well, could reawaken pretty quickly on a human time scale.”

The crystal method gives after-the-fact data on an eruption. Current attempts to anticipate eruptions rely on data about earth shaking, deformation of the crust, and release of gases.

“It’s a very timely topic, and solid science in terms of the measurements and observations,” says Bradley Singer, a volcanologist and professor of geoscience at University of Wisconsin-Madison. “They admit that there are issues about the time scales,” largely because the diffusion of strontium and titanium is imperfectly understood in the hot magma.

The study’s title, however, specifies that the final growth of the magma chamber occurs on “Decadal to monthly timescales,” Singer notes. “It could be centuries or even longer, which implies that we’d have a longer time prior to the eruption” to worry about the effects of the rising magma.

Singer concurs on the importance of understanding the relationship of magma flows, instability and eruption, and says the crystal analysis is gaining traction in volcanology.

That’s just as well, since giant caldera-forming volcanoes may be frighteningly common. The one at Yellowstone, for example, released 1,000 cubic kilometers of rock 640,000 years ago. Wouldn’t you want to know if something like that was building on your continent?

The seas’ most sought-after fish are swimming between a rock and a hard place: the fisherman’s net and an encroaching mass of suffocating water.

A recent study has uncovered a new dose of bad news for ocean fish and the fishing industry. Areas of the deep ocean with little dissolved oxygen, called dead zones, are expanding and, thus, shrinking many fishes’ watery homes.

One driving force behind the predicament is none other than that pesky climate problem.

“Climate change is actually working in tandem with overexploitation of the animals to push these populations into a real dangerous place in terms of population collapse,” said Eric Prince, a fisheries biologist with the National Oceanic and Atmospheric Administration’s Southeast Fisheries Science Center and co-author of the study.

For example, Prince and his colleagues calculated that the Atlantic blue marlin, an economically valuable fish that was a focus of their study, has lost about 15 percent of its habitat from expanding dead zones since 1960. Dwindling habitat threatens not only the lives of fishes, but also the sustainability of the already ailing fishing industry.

Breathing room

Like their above-water brethren, fish need oxygen, which is dissolved in the water. Big, predatory fish, such as the blue marlin, need more dissolved oxygen than most, because they require lots of energy to grow and survive. Without sufficient oxygen, they’ll suffocate.

The level of oxygen in the water thus partly delineates fish habitat boundaries. Dead zones often draw these borders.

As climate change causes open ocean dead zones to balloon, fish habitat deflates.

Diagram modified from one originally published in Deep Sea Research Part I: Oceanographic Research Papers, Vol 57, Issue 4, Lothar Stramma, Sunke Schmidtko, Lisa A. Levin, & Gregory C. Johnson. Ocean oxygen minima expansions and their biological impacts, 587-595, Copyright Elsevier (2010).

Technically known as oxygen minimum zones, dead zones are actually a natural occurrence. Found at depths of between 200 and 1000 meters, they are caused partly by seawater circulation and partly by the decomposition of organic matter, namely deceased sea critters that sink from surface waters.

As aerobic bacteria nosh on the organic matter, they use up the oxygen in the water. Eventually, hypoxia happens—the water becomes so depleted of oxygen that many creatures can’t survive.

Since deep-sea dead zones are insulated from the ocean’s surface, where the water borrows oxygen from the atmosphere, they can only reload with oxygen if currents make a long-distance delivery, according to Sunke Schmidtko, an oceanographer at the University of East Anglia, the other co-author of the study.

Deep-sea dead zones are different from their coastal cousins like the one in the Gulf of Mexico. Coastal dead zones form due to a buildup of agricultural fertilizer that rivers, such as the Mississippi, collect and then flush out to sea, causing abnormal blooms of plant life.

De-fizzing the ocean

But climate change is turning what Mother Nature does normally into a big problem. As the air is getting hotter, so is the water, and warmer water can hold less oxygen than colder water.

This is similar to what happens to a soft drink on a hot day. After sitting in the heat and sun, the fizz fizzles, and you are left with a flat, carbon dioxide-depleted beverage.

Also, warmer surface waters are less likely to sink to the ocean’s lower layers, because warm water is lighter than the colder water below, Schmidtko explained. In other words, as the oxygen-rich surface layers heat up, they could have a harder time delivering oxygen to the deeper ocean.

Schmidtko clarified that oceanographers are still trying to determine how exactly climate change is affecting the ocean, but with their knowledge of how water works, these represent their current speculations.

The rock below

With less oxygen to go around, oxygen minimum zones are swelling and intruding on many fishes’ living zones.

For example, marlins often dive deep to feed, sometimes as far down as 800 meters. However, in the eastern Atlantic’s growing dead zone, which is already one of the largest in the world, Prince found that marlins can’t dive as deep as their west-side counterparts.

“They need to go where the food is and where they can breathe,” he said.

With less breathing room below, the floor of their habitat rises, and they are pinned to the surface layers. With nowhere to go but up, marlins become squished into tighter, testier quarters with other predatory fish and their prey. They also find it harder to dodge a waiting fishing hook or net.

“Concentrating them makes it much easier for overexploitation by [humans],” said Prince.

The increasing concentration of animals at the top could also lead to a boost in the amount of sinking organic matter, which would further worsen the oxygen shortage below.

Softening the hard place above

As a prized catch, Atlantic blue marlins are already victims of overharvesting. In fact, their populations have dropped 60-64 percent over the past three fish generations (14-18 years).

But the growing dead zones can actually fool scientists and fishermen into thinking fish populations are doing just fine, since more fish are squeezed into a smaller area. Thus, to ensure the dead zone-fishing vise does not become their demise, Prince said scientists must more carefully monitor fish populations, as well as the expansion of the dead zones.

While fish stock assessments are starting to incorporate this information, Prince warned the pace needs to quicken.

And if the Earth is to continue warming, as most scientists predict, Schmidtko added that humans should chill out on fishing.

After all, we will never be capable of “ventilating the ocean,” he said.

Seven viewpoints

Introduction

Katharine Hayhoe

Richard Alley

John Nielsen-Gammon

John Williams

Michael Notaro

Kent McGregor

Kevin Trenberth

Drought and searing heat in Texas: Is this the face of global warming?

Courtesy Eric Bruning, Texas Tech University Atmospheric Science

The cold front that blew through Lubbock, Texas on Oct. 17 raised a dust storm not seen since the 1930s Dust Bowl. The dust storm, seen in this movie, is called a “haboob,” an event more common to Saudi Arabia than Texas.

On Oct. 17, a cold front blowing through Lubbock, Tex. raised a red dust cloud that recalled the awesome Dust Bowl of the 1930s, an epoch of drought, enormous dust storms, poverty and social upheaval that depopulated the Great Plains.

The 2011 dust storm served as an exclamation point on a cruel Texan summer, with drought, wildfires, and temperature records that would not quit. On Oct. 19, the Lower Colorado River Authority, source of much water in the Southwest, warned customers that the drought was likely to force another 20 percent cut in water supplies.

On Oct. 18, Texas Lt. Gov. David Dewhurst instructed the state legislature to study drought-related problems like helping homeowners protect against fire, and ensuring that utilities would get enough water to cool their generators.

As far as we could tell, the multi-pronged assignment did not mention something that many observers think contributes to heat waves, fires and droughts: climate change.

Many recent “natural” disasters have raised the same question: Is the no-sense-denying-it-any-longer human-caused planetary warming intensifying devastating hurricanes, giant rainfalls and snowfalls, or the deadly heat waves in Europe (2003) or Russia (2010)?

Despite political skepticism in the United States, the scientific study of changing climates has grown exponentially for 20 years. In 2009, almost 14,000 research reports focused on climate change, and 20 scientific journals are devoted to the issue.

UPDATED NOV. 18: Today, the New York Times reported that a United Nations panel has concluded that “At least some of the weather extremes being seen around the world are consequences of human-induced climate change and can be expected to worsen in coming decades. It is likely that greenhouse gas emissions related to human activity have already led to more record-high temperatures and fewer record lows, as well as to greater coastal flooding and possibly to more extremes of precipitation, the report said.”

Enough introductory blather. Let’s ask some experts: Is the hot, dry weather in Texas a reflection of global warming? Or is it just proof that the essence of weather is its natural variability? The Why Files talked to seven climate scientists. Peruse their viewpoints in the box above.

Interested in waterfront property in Southern California? A new study of a continental schism running east of Los Angeles offers a clear “buy” signal for the long-term investor: The North American continent is splitting apart along a rift, and if you got the patience, we have the real-estate-appreciation potential!

In just a few million years, as the North American continent sunders in a weak zone called the Salton Trough, the Gulf of California will stretch further north.

On our unstable Earth, not even the continents are rock solid. Instead, they shift around like blocks of sea ice that join, fissure and separate once again — over millions of years.

Geologists know the process is occurring in the Southern California desert, and we’ve just read a sophisticated analysis that finds an ominous thinning of the strong crustal layer in the Salton Trough.

Ominous, that is, unless you are planning a waterfront resort here, with a grand opening in, say, 2,002,011.

The study helps to fill a gap in our understanding of the earth, says first author Vedran Lekic, a National Science Foundation post-doctoral fellow at Brown University. “The main question is, how do continents come to break apart? This process is really fundamental to shaping how the Earth looks; if not for rifting, once Pangaea formed, it would never have broken apart and we would have only one continent.”

Pangaea is a giant agglomeration of continents that broke up about 150 million years ago, creating our current collection of continents.

Scoping out the Earth

The lithosphere, Earth’s crust and the rigid rock beneath it, essentially floats on the asthenosphere, the soft and hot outer layer of the mantle that is located tens of kilometers belowground.

As a continental rift grows, one would expect to find a thinned lithosphere at the Salton Trough. But Lekic says the actual thinning was more dramatic than expected — as much as a 50 percent reduction compared to adjacent areas.

By studying earthquake waves passing through Earth, Lekic and colleagues measured the thickness of the lithosphere by locating its lower border. They knew that one type of wave converts to a faster wave type as it passes up from the asthenosphere into the lithosphere, so the conversion could be used to mark the base of the lithosphere.

It turned out that the lithosphere measured about 40 kilometers thick beneath the Salton Trough, compared to 60 to 80 kilometers on nearby areas. That thinning translates into a weakening that will eventually allow open water into the Trough, and myriad real-estate opportunities along the new shoreline.

Previous efforts to estimate the lithosphere’s depth have relied mainly on surface data, says Lekic, and that limited our knowledge of how the continental splitsville takes place. From relying on “surface observations of faults, topography, heat flow, and some studies of the crustal structure, we have not been able to image the detailed topography of the base of the tectonic plate, as it looks during rifting.”

Rift terrific

Although the study relied on the interest in Southern California seismology that is a response to extreme seismic activity, the finding says little about earthquake probabilities.

But earthquakes are not the only tectonic game in town, says Eugene Humphreys, a professor of geophysics at the University of Oregon. “While most people know southern California is being sheared by the San Andreas and related faults, most people are not aware that the region also is being pulled apart as the Pacific plate also moves slowly away from North America. These researchers have imaged the deep structure of the plate where it is being torn apart by this process, and contrary to what many have thought, the tears go through the entire plate right where the surface expression of this rifting is seen. It’s exciting work.”

The study provides insight into deep structure and processes of fluid migration up into the plate, says Humphreys. “These lower-plate interfaces were not expected to exist at all, and the scientific community is excited but struggling to determine what could create relatively sharp interfaces.”

Although Earth warms with depth, that is unlikely to explain the weakness, Humphreys says, “so the search for other causes is on. By associating the position and shape of these interfaces with a specific deformation history, this study provides important information on the origin of these interfaces.”

Lekic, who worked with co-author Karen Fischer of Brown, on the study, says that “Even at great depth, we see the same stretching and deformation that we see near the surface. At the bottom of the lithosphere, there is this persistent weakness, in a zone that runs more or less vertically, and that’s surprising.”

But as scientists wrestle with the geological goulash that is Southern California, we suggest you send a down payment to Rift ‘n Grift Realty on the ocean-front lot of your dreams – and wait a few million years!

— David J. Tenenbaum

For advocates of space travel, the news is grim, and we’re not talking about the crash of a six-ton satellite last week, either. In July, the last U.S. space shuttle was parked, as planned. Over 30 years, the shuttles helped build the International Space, but two explosions killed 14 astronauts, and each flight cost nearly half a billion dollars.

On August 24, a clogged pipe caused the crash of a Russian Soyuz rocket. Soyuz is a reliable space-truck whose ancestor launched Sputnik, the first artificial satellite, in 1957.

With the shuttles in the old-age home, any delay of a Soyuz launch to resupply the space station, planned for Nov. 14, could force the station’s evacuation.

Abandoning the space station after a decade of continuous occupation might have limited scientific impact, as the station is not proving to be a scientific bonanza as promised. (However, on Sept. 21, NASA reported that a Japanese astronaut did perform “bubbling experiments” on green tea before staging a “traditional Japanese tea ceremony.”)

The growing problem of getting into space got more attention on Aug. 24, when a sub-orbital space taxi built by Blue Origin, a company funded by Amazon founder Jeff Bezos, crashed in West Texas, setting back the nascent space-tourism industry.

People have been going into space for 40 years, but the process is neither cheap nor routine. For comparison, 40 years after the first automobiles, millions of cars were changing the U.S. economy and landscape. And 40 years after Kitty Hawk (1903), airplanes had circled the globe and become a dominant force in World War II.

So, 40 years after Yuri Gargarin became the first space-farer, why is it so hard to get people into space?

It’s the gravity, stupid!

The first clue to the difficulty of reaching orbit is evident in the controlled explosion needed to launch anything: reaching orbit requires a speed of almost 18,000 miles per hour and overcoming gravity.

And gravity is a stern customer.

Although gravity is fixed, a changing political backdrop has deprived the space program of its historic justification, says Howard McCurdy, a professor of public administration and policy at American University, and student of the space program. “The key problem, as a political scientist, was the end of the Cold War. Now the rationale for a lot of human space program is jobs, but in the absence of Cold War competition, we get these anomalies,” like thumbing a ride to space from your former enemy.

Faced with the prospect of being stuck on Earth, on Sept. 14, NASA administrator Charles Bolden announced the Space Launch System (SLS), a heavy-lift rocket and space capsule designed to reach earth orbit and beyond. “American leadership in space will continue for at least next half century,” Bolden said. “We have laid the foundation for success.”

Better than nothing?

The reaction to SLS was a bit ho-hum. The proposal “has been controversial because some say it’s just the same old technology, a combination of Apollo, Saturn V, and the shuttle, and we really should be advancing the technology, doing something new that will get us to deep space more quickly,” says astrophysicist Jack Burns, who has served on the NASA Advisory Council science committee, and is vice-president emeritus for academic affairs and research at the University of Colorado System.

But what else is there? Burns asks. “I look at SLS as a practical vehicle that will get a lot of mass into orbit, and then to the moon, the asteroids. Having a heavy lift vehicle, for the first time since the mid ’70s, when we did away with Saturn V, should be an important part of U.S. space architecture.”

The shuttle, whose demise has forced the current concern over space launching, was hatched in 1972, by Pres. Richard Nixon, who proposed a reusable, flying bus to reach low orbit and “take the astronomical costs out of astronautics.”

Getting to orbit didn’t turn out to be cheap: NASA chalks up the average price tag on 135 shuttle launches at $450 million.

Consternation over Constellation

In 2005, faced with mission failures and an aging shuttle fleet, Pres. George W Bush called for the shuttle program to end after the space station was constructed. As a replacement, Bush proposed Constellation, a new rocket, and Ares, a new spaceship, which would visit the moon and then Mars.

However much the Mars mission was beloved by space-travel enthusiasts, it carries certain health hazards…

Cost estimates for Constellation and Ares rose faster than a rocket and by 2010, the projects had black-holed $9 billion, and the guesstimated price of launching a single Ares-1 had reached $1 billion. So Pres. Obama trash-binned the twin projects and directed NASA to come up with something cheaper and faster – which turned out to be the poetically-branded “Space Launch System.”

The proposal has, as we’ve said, met grudging acceptance at best. “This is a turning point for all kinds of reasons,” says Michael G. Smith, a space historian at Purdue University. “The shuttle program is finished after 30 years — it was too expensive, too old — and the Bush program to take us to the moon is finished.”

Although NASA has another job — the SLS — the manned space program needs goals with more focus, Smith says. Because Obama has failed to set a clear challenge before NASA, “they have nothing to prove, no short-term mission.”

In a sense, Smith adds, the Obama plan conforms to American desires. “There’s a paradox. A Gallup poll says the American public wants a space program, and is proud of it, but does not want to pay for it, and that’s the Obama Administration approach: ‘We want something, we have announced something, without a clear-cut commitment to what it is.’”

Take the money and … design?

In an era that is short of cash and jobs, however, NASA has an immense constituency in its legion of employees, contractors and their employees, Smith says. “Lawmakers with NASA investment in their districts are challenging the administration’s lack of clarity.”

But viewing a space program as a jobs program is unlikely to maximize either cost savings or scientific breakthroughs. “NASA has half-lost the ability to innovate,” says McCurdy. “People are hunkering down like turtles, protecting what they have, playing defense to hang onto the field stations [such as Marshall Space Flight Center in Alabama], and Congress is pushing them in ways that are inefficient for cost reduction. Most members want to know if contracts are still going to their districts.”

Space is inherently expensive, and McCurdy questions whether the current NASA budget will accomplish much space travel, or mainly rocket design and construction. “A big issue for NASA is whether the budget for exploration is going to be sufficient to actually develop, build and test the rocketry,” he says. “It looks like it will be sufficient to provide aerospace jobs, but they need a little bit more money to bend metal.”

Confronting costs

It’s odd, McCurdy says, that developing a new rocket and space vehicle are expected to cost $100 billion, considering that Saturn V, which launched Skylab and the moon shots, cost about $10 billion in 1960 dollars. “Multiply that by five to get today’s price — $50 billion — and that included the production line, a test vehicle and the actual rocket.”

Much engineering has been done for Constellation and previous rockets, and McCurdy, who acknowledges that the engineering and manufacturing expertise and the Saturn assembly line have long disappeared, wonders why NASA cannot produce a heavy-lift rocket for $50-billion.

Cutting the budget to the bone can be penny wise and pound foolish, McCurdy adds. “Once they got the assembly line going for Saturn V, it was very efficient, but if they build only one rocket every two years, it becomes more of a craft rocket.”

What are the other options for launching people into space?

Government rocket, private rocket

International rockets such as Ariane have gotten into the satellite-launch business, but most of them are not powerful enough to take people into orbit, or to leave earth orbit and reach the moon.

China, with one satellite orbiting the moon, and an imminent launch of an 8.5 ton component for its first space station, definitely has the lift capacity, but we’ve not heard about any discussions about launching U.S. space equipment.

Government is not the only game in town, however, and many hope that the genius of private enterprise will fill the gap, even if some of the efforts are watered with buckets of federal funds. If you place a challenge before rocket manufacturers, “both the startups and old horses, somebody may come up with a breakthrough,” says McCurdy. Even so, he adds, NASA must still “pick a winner before knowing whether it is a working design, and they are no better at that than I am at picking stocks.”

So how is the private sector faring in the human space travel biz?

the private role

Corporations are contending for two roles in space. Many are interested in space tourism, a business that began in 2001 with a seven-day visit to the International Space Station but today is focused on sub-orbital flights – spending a few minutes in micro-gravity beyond the edge of the atmosphere:

Photo: Jim Campbell/Aero-News Network

SpaceShipOne, built by Scaled Composites, slung beneath White Knight, the mother ship that lifts it toward the edge of space.

Blue Origin, a secretive operation funded by Jeff Bezos, the Amazon.com billionaire, is working on “New Shepard,” a sub-orbital vehicle. According to the website, “We’re working, patiently and step-by-step, to lower the cost of spaceflight so that many people can afford to go and so that we humans can better continue exploring the solar system. Accomplishing this mission will take a long time, and … we do not kid ourselves into thinking this will get easier as we go along.” Blue Origin has a NASA contract to develop a taxi for hauling astronauts to orbit, but recently lost a spaceship at 45,000 feet.

Scaled Composites, an advanced aircraft maker, won the $10-million X-prize in 2004 for attaining 328,000 feet twice within 10 days. The firm is working with Virgin Galactic to enhance its a sub-orbital spaceship-mother-ship combination. Virgin says 430 private-nauts are already put down a deposit for flights that will cost $200,000.

Xcor Aerospace is also selling seats on an unfinished spaceship, for a suborbital flight priced at $95,000, starting with a spare-change deposit of $20,000. Buy now, and your seat-mate could be a Victoria’s Secret model… Honest!

Let’s really go to space!

Above the sub-orbital realm, however, comes the real high-technology interest: resupplying the space station, or reaching the moon or an asteroid. In this realm, one company has grabbed most of the headlines: SpaceX, founded by PayPal founder Elon Musk.

SpaceX is developing two types of “Falcon” rockets, and has a $1.6 billion NASA contract to launch 12 loads of cargo to the space station (the first flight is scheduled for Nov. 30), in NASA’s Commercial Orbital Transportation Services program. (Orbital Science Corp. is the other contractor in the program.)

In December, 2010, SpaceX became the first private company to launch and recover a spaceship. “The technology has advanced,” says Burns, “but so far SpaceX only has a couple of launches of the Falcon 9. It’s a long way from that all the way to orbit, with real live astronauts. It’s a risky venture.”

SpaceX says it emphasizes reliability, and the business end of Falcon 9 houses nine individual rocket engines. The rocket is supposed to reach space even if one engine goes kaplooey.

A human role remains

When President Ronald Reagan proposed and promoted what is now called the International Space Station, a howl went up among scientists who called it a diversion of resources from the more productive unmanned spacecraft. Carting people around raises the price and the stakes at every stage of design, production and operation, and these scientists accurately forecast a fruitful program of robotic exploration — everything from the Hubble Space Telescope, to the Opportunity and Sojourner rovers on Mars to the Galileo spaceship that explored Jupiter.

Those robots were awesome and inspiring, says Burns. “Opportunity is U.S. technology, it’s something we all should be proud of it, it has well exceeded its lifetime, the engineers were very clever in the design and operation. That good old-fashioned American ingenuity ought to get kids excited about going into science, engineering, math, whether that gets directed to space or something else.”

The manned vs. robot argument had merit in its time, given that the space station alone has cost NASA north of $50 billion (with other countries contributing about the same amount), and NASA never has enough money for all the scientists who write grants, which leads some critics to question whether the money is well spent, or would have been more productive if spent on funding conventional science.

But the manned vs. robot dichotomy may be fading, says Steven Collicott, a professor of aeronautics and astronautics at Purdue University, who placed an experiment about the fluid flow in micro-gravity on the space station. “There is a great benefit to doing both. The astronauts who have operated space station experiments I have been involved in have been incredibly creative thinkers, problem solvers.”

The flow experiment cannot be performed on Earth, Collicott says. “We do everything we can to test on earth, or on short-duration, low-gravity [aircraft] flights, but there are times when … the camera position needs to be changed, or a liquid gets trapped. An astronaut can unbolt and shake the experiment … or act on their observations to explore a new phenomenon immediately, without reprogramming, relaunching or rebuilding, which involves years and millions of dollars.”

Human hands, eyes and brains are irreplaceable, Collicott says. “If people were not needed for research of this type, why would we be spending money to send people to Antarctica each year?”

human vs. robot — the dichotomy wanes

“I never felt comfortable with the manned versus unmanned argument,” says Purdue’s Smith. “We have always pursued both [approaches]. Satellite, probes and telescopes… There is no ICBM [inter-continental ballistic missile] system without satellites, there is no exploration of the moon or Mars without the [robotic] probes we have sent there.”

More on the manned vs. robot issue…

Yet despite the phenomenal allure of space-telescope photos, manned exploration plays a critical motivational role, Smith adds. “Without an orbital station, and the public interest and international cooperation that revolve around it, NASA can’t do anything. Satellites and probes just don’t drive that public interest.”

What Smith calls “fierce debates” between astronomers, who favor robotic exploration, and engineers who favor manned exploration are “not about policy or philosophy, they center on funding; those seem to me very parochial questions.”

Burns offers one suggestion for merging people and robots: sending astronauts to a low-gravity point above the far side of the moon (which never faces Earth), where they could control a moon rover. “Astronauts who are familiar with geological exploration could operate the rover in real time, there’s much less delay [in the radio signals]. They could visit the oldest [known] impact basin in the solar system, and it would not require a human lander, would be cheap, and would give you the kind of experience that is going to be needed” for further exploration of the solar system.

The quest to populate the solar system would entail a search for signs of life – and for water and useful minerals, Burns says. “This is going to require knowledge of geology, chemistry, astronomy and mechanical engineering; it will be very different than the first few flights to the moon that were just trying to get there. I argue that the difference between manned and unmanned travel is going to start to fade.”

Historic moment

Tele-operation, as remote-control is currently called, is being used every day by earthbound “pilots” in Nevada to fly drones in the Middle East, highlighting the firm link between space engineering and the military.

Rockets and satellites have military roots, and the space race was an early and intense focus of Cold-War competition, as the United States and Soviet Union both relied on German rocketeers who had helped the Third Reich try to conquer Europe. Now the United States and Russia, World-War II allies, then Cold-War enemies, have become allies once again, at least in terms of space cooperation.

Dating back to the late 1950s, Smith says, “Space policy has always been as much about perception as reality. It goes all the way back to the first ballistic missiles, the space race, the missile gap.”

John F. Kennedy warned about a “missile gap” while running for president, and even though it proved illusory, the fear of Soviet supremacy — Sputnik was in orbit while American rockets were exploding in front of TV cameras — supported the development of missiles that could be used for global nuclear war or putting men on the moon.

The result was lavish budgets for rockets and space.

But the easy goals have been reached, and visiting the moon is so last-century. Visiting an asteroid will answer important scientific questions, but will never have the sex appeal of visiting the man on the moon. As Smith says, today, “We are in another gap; an ambition gap.”

David J. Tenenbaum

Uganda is looking for answers as about 20 students and a teacher were killed June 28 by lightning that struck their school in this highland nation in Eastern Africa. With dozens of children also injured by electricity, Ugandans wonder if the serious string of lightning strikes is related to climate changes, or are just the consequence of an unusually heavy stream of moist air coming from the Atlantic.

We can’t answer, but the tragedy did get us Why Filers to thinking about lightning. Although lightning bolts killed “only” an average of 39 Americans over a recent 10-year stretch, the injuries, which concentrate on the vulnerable nervous system, can be severe and lifelong.

Satellites tell us that 1.2 billion lightning flashes occur in the atmosphere each year — although not all reach Earth.

What is lightning? How does it injure and kill? And what has been learned in the past few years from the millions spent studying nature’s electricity?

2003, NASA Johnson Space Center

A string of lightning flashes are seen from space.

Boom-boom room

Thunder — the cracking or rumbling you often hear — is caused by thermal expansion and contraction. Lightning bolts can get far hotter than the sun’s surface — up to 20,000° Celsius. That heats the air, causing it to expand, and starting a shock wave that moves as sound waves — thunder.

If you’re close to the lightning bolt, you’ll hear a cracking; further away, you’ll hear rumbling because that sound has come from several parts of the bolt, and been reflected from buildings and hills.

And yes, if you start counting “one Mississippi,” when you see the flash, you can estimate the distance to the bolt: Light essentially reaches you instantly, but sound takes about five seconds to travel one mile. Divide the number of seconds by five to find miles, or by three for kilometers.

Silence is — mysterious

One of the many lightning mysteries is this: Sometimes you hear the thunder, and sometimes you don’t. For example, “heat lightning” is an eerie, silent flash that often lights clouds in thunderstorms.

The sound has been gobbled by an audio version of the visual mirages that cause trekkers to see water in stone-dry desert. These visual mirages are caused by heat that bends light waves. You look straight ahead, but you actually see the sky, shimmering like a tempting lake.

Similarly, in a thunderstorm, the sharp boundaries between warm and cool air can channel sound waves away from the observer, as you can see from the nifty applet, below.

Much the same phenomenon was noticed during the Civil War, when artillery was visible in the distance but audible only in some parts of the battlefield.

Go play with lightning.

Nature’s lighting foundry

We think of clouds as billowy places, couches for angels in Renaissance paintings. In thunderclouds, however, air and water – liquid, frozen and in between — may be whizzing up and down at a furious clip — up to 100 miles an hour.

That’s a place where angels fear to tread.

The motion in these cumulonimbus clouds is powered by convection, a force that separates fluids based on density. The dense, cold air falls while the warmer air rises. Smaller water droplets hitchhike up on the updrafts, which can’t support the larger droplets.

Because smaller particles tend to carry positive charges, the movement caused by temperature, humidity and density (which can include snow, ice, and water vapor) segregates electrical charges: The top of a cloud becomes positive and the bottom negative.

Regions of different charge can only exist if surrounded by an insulator — namely air. Insulators, however, eventually fail when they are overwhelmed by electric “pressure.” In a thunderstorm, that “failure” results in lightning.

Hangin’-motor blues

Having trouble envisioning this? Imagine a chain holding a greasy V-8 motor above a ’63 Ford Fairlane in a shade-tree auto mechanic’s backyard. If the engine is too heavy, or the chain too weak, the chain will snap as it is overwhelmed by the gravitational attraction between Earth and engine.

Thunk!

Substitute air’s insulation for the chain, and electrical attraction between positive and negative charges for gravity, and you have a greasy-fingered picture of how air can separate electrical charges during a thunderstorm.

To go further, we need one hunk of physical-science jargon: electrical potential is how fast charge changes with distance, and it’s measured in volts per meter. Electrical potential is the “pressure” that’s “trying” to start an electric current between areas of opposite charge.

(Opposite electrical charges are like young lovers: They will do anything to get together.)

Just as an overweight V-8 can snap a skimpy chain, excess electrical potential can “break” air’s insulation. When that happens, an electrical current — in the form of a lightning bolt — neutralizes the opposing charges.

Flash!

Diagram: Encyclopædia Britannica, Inc.

Lightning leaps between separate negative and positive regions during a storm. Most cloud-to-ground flashes originate in the cloud’s negative regions.

In a cloud-to-ground flash, the huge electrical potential — measured in millions of volts — eventually overcomes air’s electrical resistance, and a “streamer” or “leader” begins reaching, about 50 meters at a time, toward ground. The streamer makes an ionized (conducting) pathway of plasma, allowing current to flow.

Where am I safe?

As the current approaches the ground, its electrical potential can cause a surge of oppositely-charged particles to “reach” up toward it. Because this upward current often springs from tall objects, trees and other tall objects make lousy shelter during a storm.

For a 2001 Why File on lightning, David Rust, who was then director of forecast research and development at the National Severe Storms Laboratory, told us that the safety of a building is determined by the degree of grounding. A steel building that’s securely grounded, he said, will be safer than a wooden one that’s not, even if the steel building is taller. Steel and other conductive metals provide an easy pathway to ground for the lightning, and that translates into safety.

Once the ionized pathway is established, electric currents flow back and forth between ground and cloud so quickly that they appear as flickers rather than separate bolts. (More on lightning safety.)

We’ve heard that a big cloud-to-ground bolt carries one trillion watts of electricity. If that estimate is right, during its fraction-of-a-millisecond life, the flash carries about the same current as the total U.S. generating capability. (Watts measure the flow of electric current at any instant. The more familiar watt-hours measures an hour of flow of a given current; 1 kilowatt hour equals 1,000 watt hours.)

But nobody has figured out how to put this energy to work. Though we have heard one proposal, the currents are insanely high and the strikes are too brief and too unpredictable.

Keeping a close watch on lightning

Our understanding of lightning grows with improvements in technology, and a new instrument on trusty weather balloons has pointed to a surprising source for the electric charge. The process involves a small, spongy relative of hail called graupel, says Don MacGorman a physicist at NOAA’s National Severe Storms Laboratory.

“As graupel accumulates tiny, pristine ice particles, and then falls through liquid water, there can be some charge exchange in collisions where the tiny ice particles rebound,” MacGorman says. In the lab, this interaction seems powerful enough to be main source of electricity – and therefore lightning — in large areas of the storm.

Within a few years, a better understanding of lightning formation could improve predictions, MacGorman says. “We will not be able to say lightning will a hit particular location. Lightning is too random for that, but we are getting to the place where it may be possible to say that a storm will produce a little or lot of lightning, and that would be helpful for storm safety.”

Cloudy picture

The graupel explanation, however, raises a question: If the interaction of water and ice creates the electric charge, why is lightning found in dry sectors of the storm, including the large “anvil” structure that exhausts cold, dry air above the storm? “We have seen lightning initiated almost 100 kilometers from the heavy precipitation area, so something else must be going on in the anvil,” says MacGorman. “This does not accord with how we’d viewed anvils.”

Scientists are also probing cloud flashes, caused by the flow of current between regions of clouds with opposite charges and does not hit the ground. Formerly dissed because they don’t kill people, cloud flashes are getting some respect.

For one thing, they are the most common type of lightning, accounting for perhaps one-quarter of all lightning flashes. Adding cloud-to-ground and cloud-to-cloud lightning gives a better indicator of total storm intensity than ground flashes alone, “which have very little relationship to storm severity,” says MacGorman. “You can have huge ground flashes in a relatively innocuous storm, but total lightning is well related to things that affect severity and strength: the size of the updraft, the amount of ice in the clouds, and so it gives us clues as to how intense the storm is.”

Positively speaking

The biggest recent discovery on lightning, says MacGorman, concerns storms that produce a large amount of positively charged cloud-to-ground lightning rather than the usual negative currents. During a field research program called STEPS, in a lightning-rich region of the high plains, some storms contained negative charges in places that normally would be positive, and vice versa. In these conditions, instead of dropping the normal negative charge to the ground, the lightning bolts were positive.

The unusual phenomenon could arise in clouds containing a high concentration of liquid water, MacGorman says, and that would also raise the odds of large hail. “Hail typically forms because graupel or another seed particle starts collecting liquid water faster than it can freeze, and the water spreads over the surface, then freezes into a solid layer of ice.”

These dense particles are more likely to happen in an area with a lot of liquid water, and therefore, these positive lightning strikes could be a harbinger of large, destructive, hail.

The view from on high

For the next stage in lightning observations, scientists will go to GOES-R, a series of geostationary satellites scheduled for launch in 2015. These high-orbital spyglasses will carry an optical gadget that should “see” upwards of 90 percent of total lightning activity. “The viewing area will cover pretty much all of the continental United States, and parts of Africa and South America, and eventually, half of the Pacific Ocean,” says MacGorman. “This will allow us to detect thunderstorms over the oceans, which we have not had good way to see in the past.”

That should help airplanes dodge storms, but also aid weather prediction, MacGorman says, since thunderstorms can trigger other thunderstorms. They also add water vapor to the lower atmosphere, which also feeds storms.

Nothing light about lightning

Lightning gathers myths. Whether it’s Zeus throwing thunderbolts from the ancient Greek sky, or the moronic misconception that victims become untouchables because they retain an electric charge, these bolts spark the imagination.

But lightning can change your life, as Steven Marshburn, Sr., of Jacksonville, N.C., told us in 2001. Marshburn was struck in 1969 while working in a bank. Although the sky was blue and no storm was in sight, a bolt entered through a wire from the drive-up window.

Afterwards, Marshburn “suffered from severe headaches, chronic daily pain, grand mal [epileptic] seizures, dizziness, problems with my eyes going blurry. Many health problems persist. I have had 20 lightning-related surgeries…”

In 1989, in response to his brush with death, he formed Lightning Strike & Electric Shock Survivors International to investigate the medical aspects of lightning and to support victims and families. In 2001, he told us that members had talked 13 fellow survivors out of suicide.

A shock to the nervous system

Lightning usually kills by attacking the heart, which runs on electrical impulses. While high-voltage electrical injuries often cause severe burns, they are rare with lightning, likely because the bolts — lasting only 0.1 to 1 millisecond –- are too brief to cause severe burns.

Although burns may result if clothing ignites or sweat boils and steam is trapped under clothing, wet, sweaty clothing may actually conduct a heavy current outside the body and reduce the damage.

Raphael Lee, a professor of surgery and medicine at the University of Chicago, and an expert on the effects of lightning strike, told us that most of the initial current in a lightning strike does not pass through the body. However, two electromagnetic phenomena can produce a strong voltage drop across the body:

Strong electric fields are a problem for nerves and muscles, Lee says, because they “have been structured through evolution to be very sensitive to tiny electric fields.” That, combined with their physical length, which spans a large electrical gradient, “makes them very sensitive to lightning.”

Nerve cells can be a meter long, and by extending into different parts of an electric field, they are exposed to high voltages, Lee says. One focus of concern is the cell membrane which can die if strong voltages poke holes in it. Voltage can also wreak havoc in the pores in the membrane, which regulate the cell’s physiology by controlling how ions enter and leave the cell. Normally, for example, the potassium concentration is 1,000 times higher inside a cell, and damage to the pores can result in malfunction or cell death.

Lightning = thunder in the brain?

Although electricity is the natural focus of lightning damage, Lee suspects that an acoustic pulse, or shock wave, plays a major role, and perhaps a dominant one. A lightning bolt is surrounded by hot, ionized gas that arises in nanoseconds or microseconds and whose temperature may exceed 10,000 ° C. “When you heat something in a small area in such a short period, there are going to be shock waves,” he says.

The power of this acoustic wave is obvious when lightning hits and splits a tree, Lee adds. But inside the brain, the shock can trigger traumatic injuries similar to those caused by a roadside bomb or artillery shell.

Neurological injury: no passing matter

Lightning injury can be severe, long-lasting, and hard to treat, and it “may affect any or all parts of the nervous system,” according to Mary Ann Cooper, an emerita professor of emergency medicine at the University of Illinois-Chicago.

In a 2009 study of survivors of lightning and other electric shocks, 78 percent of the survivors had at least one psychiatric diagnosis; many of the troubles related to learning, memory and executive function.

In 2001, Cooper told The Why Files that confusion, caused by slowed information processing, is a hallmark of lightning injury. Symptoms include “difficulty in short-term memory, coding new information and accessing old information, multitasking, distractibility, irritability and personality change.”

Damage to the frontal lobe, the site of much higher thinking, is common, according to Cooper. “Many suffer personality changes because of frontal lobe damage and become quite irritable and easy to anger. The person who ‘wakes up’ after the injury often does not have the ability to express what is wrong with them…and cannot carry on a conversation, work at their previous job, or do the same activities that they used to handle. As a result, many self-isolate, withdrawing from church, friends, family and other activities.”

Cooper said some cell types continue suffering for weeks after the injury, and that nerve cells seem to “spend a long period trying to heal themselves, until finally the cell body is exhausted” and the cell dies. That process accounts for a delayed disability syndrome among survivors.

Help at hand?

Long-term neurological consequences are a major research area, Lee says, because they also occur in traumatic brain injury. “People are trying to sort out what is the best treatment, and understand why some people are more susceptible to delayed neurological problems. The body is very complicated and … the weight of evidence suggests there are genetic predispositions to complications after a blast causes traumatic injury to the brain, and lightning injury may be no different. Many people recover, but some don’t. What is different about the people who don’t?”

– David J. Tenenbaum

How did galaxies form? It’s a cardinal mystery of the early universe. Microwave radiation created 380,000 years after the Big Bang shows a smooth array of molecules, spread out like a fog. The contrast to the situation one billion years later is complete: by then, matter was concentrated in stars and galaxies, separated by empty space.

Nowadays, most galaxies hide at least one super-dense black hole, whose gravitation prevents even light from escaping. Until now, nobody knew about black holes in the earliest galaxies.

Yesterday, Ezequiel Treister of the University of Hawaii and colleagues reported that most or all of the earliest galaxies also had black holes.

A problem of roots

The data illuminates the ultimate roots question – how our universe formed its present structure, and in particular, what happened during the billion years after the Big Bang banged about 13.7 billion years ago.

For 380,000 years, “During the embryonic universe, the fluctuations in density were about one-one thousandths of a percent, but over a billion years, structures developed,” Alexey Vikhlinin, author of a commentary in Nature, told The Why Files. “These galaxies are essentially the same type of objects in the present universe,” says Vikhlinin, an expert in X-ray astronomy at the Harvard-Smithsonian Center for Astrophysics.

How did we go from the primordial fog to a universe with ultra-dense galaxies, neutron stars and black holes separated by a vast nothingness where each cubic centimeter has about one lonely atom?

The vast epoch of ignorance, Vikhlinin says, “is called the dark age because little has been observed, and one of the major questions in astrophysics is how this transformation took place.” The new observations show that roughly the same proportion of matter (excluding the enigmatic dark matter and dark energy) was concentrated in galaxies and black holes then as now.

“These results show that pretty much every galaxy must have contained a substantial black hole, similar to today,” says Vikhlinin, “but this is the first observation that the relationship between galaxies and black holes that exists today, existed 1 billion years after the Big Bang.”

An extraordinary step

In the study, Treister and colleagues correlated long exposures from

Hubble Space Telescope, which can see extraordinarily distant (and ancient) galaxies, and

Chandra X-ray observatory, which picked up X-rays from distant, unidentifiable sources.

By pinpointing the source of Chandra’s X-rays on Hubble’s galactic snapshots, the scientists located ancient black holes inside some of the first galaxies.

The study benefited from three features, says Vikhlinin. “The necessary Chandra and Hubble data were taken only recently, and the observations were immediately made available to every interested scientist,” along with some money for their interpretation.

Treister also looked at the highest energy range that Chandra can detect, Vikhlinin adds. Because Chandra’s mirrors are more sensitive to lower-energy X-rays, “most people work in this region.”

The newly detected black holes produced a surprising result – that the basic structure of the universe has not changed terribly much in the 12.7 billion years since that ancient light embarked toward a planet that did not yet exist.

The “so-what?” part

Although the study shines some light on the presence of black holes and galaxies during the dark age, it does not provide a complete answer, says Vikhlinin. “It definitely seems as if galaxies and black holes have evolved in parallel. The growth of one controls the growth of the other, and vice versa, but the nature of the process and why they evolve in parallel is not entirely clear.”

Logically, a black hole would require a galaxy to provide the cold gas that it inhales. (This gas heats up as it enters the hole, creating the black hole’s X-ray signature; it also supplies material for the stars in the galaxy.)

But why a galaxy would need a black hole is less clear, Vikhlinin says. “We don’t know if galaxies can form in regions that initially don’t have the right conditions for the growth of a black hole. Maybe whenever a galaxy starts to grow actively, it makes a black hole in the center.”

Although the new evidence for an unchanging relationship between galaxies and black holes narrows the possible explanations, the formation of the first galaxies and black holes “remains one of the biggest unsolved problems in astrophysics,” Vikhlinin says.

– David J. Tenenbaum

The death toll from the May 22, 2011 tornado in Joplin – now 122 — is the latest tragedy of a horrific year for tornadoes. On April 27, twisters in Alabama and nearby states killed 314, the fourth highest in U.S. history. The 480 deaths in 2011 are already the highest number since 1953, and tornado season continues through mid-August.

The Why Files asked Jonathan Martin, an expert on the large atmospheric disturbances that form tornadoes, some questions about tornado prediction. We edited the answers of Martin, a professor of atmospheric and oceanic sciences at the University of Wisconsin-Madison, after the interview.

The Why Files: What must we know to make a good tornado prediction?

The Why Files: Are predictions getting more accurate?

The Why Files: Why so much damage and death this year? Is this a result of climate change?

For decades, scientists have thought that the pre-historic Antarctic climate was governed by events at the other end of the planet — in the Arctic. That’s because variations in solar radiation in the northern summer tracked nicely with the temperature record from sediment cores and ice cores taken on or around Antarctica.

Our record of temperatures in the deep south is carried in the ratios of oxygen and hydrogen isotopes (atoms with different masses) contained in ice cores. But Thomas Laepple, of the Alfred Wegener Institute for Polar and Marine Research in Germany, has just published an article maintaining that because the Antarctic ice cores did not accumulate at a steady pace, they have not been interpreted correctly.

Today, more snow (the source of ice), gathers in winter. Because that likely also happened in the past, ice cores from Antarctic tell us more about winter than summer, says Laepple.

And God created winter!

Photo 1: Hans Oerter, Alfred Wegener Institute, Germany, Photo 2: Eric Cravens, National Ice Core Lab

This 150,000-year-old piece of Antarctic ice is 10 centimeters in diameter, and was taken from a depth of 2,250 meters. After researchers clean, measure and catalog this core, it may be stored in a giant freezer like the one in the next image (rollover).

When Laepple and his colleagues factored in this seasonal effect, the level of sunlight in the southern hemisphere suddenly began to explain Antarctic temperatures. Although the orbital cycles still globally affect solar radiation, there was no longer a need to look at the other end of the Earth to explain rhythms in Antarctic temperatures.

The orbital cycles in question are named for Serbian engineer Milutin Milankovitch, who, about a century ago, sought to understand how three slow shifts in Earth’s orbit would affect the amount of sunshine in different regions, different seasons and years.

These orbital variations, which are influenced by gravity of the moon, sun, Jupiter and Saturn, are the basis of the “Milankovitch cycle:”

As scientists examined ocean sediments and then ice cores, the Milankovitch influence on solar radiation in the Northern hemisphere became the accepted explanation for the changing global climate. But when Laepple factored in the seasonal nature of Antarctic snowfall, he found that Milankovitch could explain the climate on the southern continent more directly. “I don’t question that the Milankovitch cycle has an influence on climate,” says Laepple, “but I question that its influence on the Antarctic is coming through the Artic.”

The adjustment was needed because more ice accumulates during winter and does not affect the overall climate record, Laepple says, “but it completely changes the recording of the signal stemming from the precession of the earth axis, which was the evidence for the remote North-South connection.”

Photo 1: Steven Profaizer, Photo 2: Sepp Kipfstuhl, Alfred Wegener Institute, Germany

Scientists use massive drills to uncover the stories about past climates told in ice cores (roll over for to see a core from a depth of 2,668 meters).

How would you explain it?

Climate is never simple, notes Richard Alley, a climate expert and professor of earth science at Penn State, who was not involved in the research. The Milankovitch cycle, he says, “shifts sunshine around on the planet, with more in some places and less in others, changing the length of seasons, the total sunshine during seasons … so it is not surprising that multiple hypotheses can be advanced to explain a given climate record. Ultimately, the mere fact of correlation is not the answer; we seek understanding of the physical linkages. … The new paper provides a clever new idea for a physical linkage, and I anticipate it will get people discussing and studying.”

Any new study concerning climate processes could get sucked into the political vortex enmiring global warming, so we asked if Laepple’s study of Antarctic conditions should lead us to question the widely-accepted theory that burning fossil fuels and changing land use have altered the climate.

Laepple reminded us that he’s studying changes that occur over periods of 10,000 years. He also insists that the new analysis “will not change the basic record of glacial and interglacial periods — the march of ice ages over the past million years. We are focusing on the precession cycle [the 21,000-year cycle affecting the location of Earth's axis], as this provides the evidence showing where and how the climate is affected by radiation changes, and might hold the key to the mechanism of slow climate change.”

Years ago, scientists began to revise their interpretation of Greenland ice to account for the seasonality in snowfall, Laepple says. “This new study is part of a long discussion. As we interpret the climate record, we have to focus more on how the climate signal gets recorded in the climate record.”