Space Ring Could Shade Earth and Stop Global Warming

A wild idea to combat global warming suggests creating an artificial ring of small particles or spacecrafts around Earth to shade the tropics and moderate climate extremes.

There would be side effects, proponents admit. An effective sunlight-scattering particle ring would illuminate our night sky as much as the full Moon, for example.

And the price tag would knock the socks off even a big-budget agency like NASA: $6 trillion to $200 trillion for the particle approach. Deploying tiny spacecraft would come at a relative bargain: a mere $500 billion tops.

But the idea, detailed today in the online version of the journal Acta Astronautica, illustrates that climate change can be battled with new technologies, according to one scientist not involved in the new work.

Mimic a volcano

All scientists agree that Earth gets warmer and colder across the eons. A delicate and ever-changing balance between solar radiation, cloud cover, and heat-trapping greenhouse gases controls long-term swings from ice ages to warmer conditions like today.

Earth's Atmosphere An illustration of the ring of particles or spacecraft casting a shadow on equatorial Earth. To keep the particles in place, gravitationally significant shepherding spacecraft might be employed. They would herd the particle much like small moons keep Saturns rings in place. Credit: Star Technology and Research, Inc.

Those who are often called experts admit to glaring gaps in their knowledge of how all this works. A study last month revealed that scientists can't pin down one of the most critical keys: how much sunlight our planet absorbs versus how much is reflected back into space.

Nonetheless, most scientists think our climate has warmed significantly over the past century and will grow warmer over the next hundred years. Various studies claim the planet is destined to warm by anywhere from 1 to 20 degrees Fahrenheit over the next few centuries. Seas will rise dramatically, the scenario goes, inundating coastal cities. But another group of scientists argue that the temperature data supporting a warming planet is not firm and that projections, based on computer modeling, might be wildly off the mark.

Either way, perhaps our fate is more in our hands than we might have imagined.

"Reducing solar insolation by 1.6 percent should overcome a 1.75 K [3 degrees Fahrenheit] temperature rise," contends a group led by Jerome Pearson, president of Star Technology and Research, Inc. "This might be accomplished by a variety of terrestrial or space systems."

The power of scattering sunlight has been illustrated naturally, the scientists note. Volcanic eruptions, such as that of Mt. Pinatubo in 1991, pumped aerosols into the atmosphere and cooled the global climate by about a degree. Other researchers have suggested such schemes as adding metallic dust to smoke stacks, to flood the atmosphere and reflect more sunlight back into space.

In the newly outlined approach, reflective particles might come from the mining of Earth, the Moon or asteroids. They'd be put into orbit around the equator. Alternately, tiny micro-spacecraft could be deployed with reflective umbrellas.

A ring created by a batch of either "shades the tropics primarily, providing maximum effectiveness in cooling the warmest parts of our planet," the scientists write. An early version of their idea was presented but not widely noticed in 2002.

Eccentric but reassuring

Those researchers who don't buy the argument that global warming is occurring at any significant rate nor that humans are largely to blame may warm up quickly to the new idea.

Benny Peiser, a social anthropologist at Liverpool John Moores University in the UK, tracks climate research and the resulting media coverage. He's among the small but vocal group that goes against mainstream thought on the topic of global warming.

"I don't think that the modest warming trend we are currently experiencing poses any significant or long-term threat," Peiser told LiveScience. "Nevertheless, what the paper does show quite impressively is that our hyper-complex civilization is theoretically and technologically capable of dealing with any significant climate change we may potentially face in the future."

Peiser also notes that the Kyoto Protocol, a global agreement to reduce greenhouse gas emissions, is estimated to cost the world economy some $150 billion a year. He also sees a broader rationale for supporting the seemingly bizarre manner of managing Earth's temperature budget.

"I believe that this mindset, despite its apparent eccentricity, is actually rather reassuring," Peiser said. "It provides concerned people with ample evidence of the extraordinary human ingenuity that, as so often in the past, has helped to overcome many predicaments that were regarded as impenetrable in previous times."

He also sees an ultimate big-picture reasoning to look favorably on the notion of controlling Earth's climate.

"Whatever the cost and regardless of whether there is any major risk due to global warming," Peiser said, "it would appear to me that such a space-based infrastructure will evolve sooner or later, thus forming additional stepping stones of our emerging migration towards outer space."

Stop coal, stop global warming, says architect

"The only fossil fuel that can fuel global warming is coal. If you stop coal, you stop global warming. End of story," he said. Architecture 2030 is a non-profit that encourages builders, suppliers and architects to move toward making carbon neutral buildings by 2030.

The problem with coal is two fold: it spews a lot of carbon dioxide, among other materials into the air, and the world has a lot of it, making it tempting to use. In the U.S. alone, there are 151 coal plants in the planning and construction phase.

The emissions from a single coal-fired power plant for one month will negate the efforts Wal-Mart is putting forth to curb its emissions. Wal-Mart wants to reduce its greenhouse gas emissions by 20 percent in seven years, he said.

Home Depot has announced it will plant 300,000 trees to offset is carbon dioxide. Unfortunately, those 300,000 trees will have to live 100 years before they offset the fumes from ten days from a coal-fired plant, he said. Replace every incandescent bulb in America with compact fluorescents? The benefits are eradicated by the carbon dioxide from two coal-fired plants over a year, he said.

"The silver bullet is no more coal," he said.

The coal question is the big question in the green industry. Coal plants do put a lot of carbon dioxide into the atmosphere, but getting rid of them rapidly, say many, is economically unfeasible. Some have begun to advocate erecting more nuclear power plants to offset coal use. Several companies have also put forward ideas for cleaning up coal.

Of course, that won't be easy, but there are technologies and ideas that can help right now, said Mazria. Designing buildings to take advantage of passive cooling and natural lighting will cut energy use. Solar panels will reduce fossil fuels, he said. Architecture 2030's goal is to make the building sector carbon neutral by that year. According to stats from Oak Ridge National Laboratories, buildings consume approximately 48 percent of the energy in the U.S. (43 percent goes to operations, 8 percent goes to construction) and account for 43 percent of the greenhouse gases. 76 percent of the electricity generated in the U.S. goes to operating buildings.

And the U.S. has conserved before. Energy use between 1973 and 1983 stayed relatively flat, according to stats from the Energy Information Agency, he said. But in that time period, 35 million new cars got on the road.

Mazria also showed off some very scary simulations of what will happen if sea levels rise to a meter or more. A lot of coastal Florida will vanish at 1 meter. Galveston, Texas goes under at 1.5 meters.

Climate change may become irreversible if the atmosphere hits 450 parts per million of carbon dioxide, he said, citing studies. Right now, the earth is at 385 parts per million and the figure is currently rising at 2.2 parts every year. Without changes, we will hit the 450 level by 2035, he asserted.

How Will Climate Refugees Impact National Security?

BHOMRA, Bangladesh – A high, heavily reinforced barbed wire fence cuts a jagged line through an otherwise empty field of tall grass and tamarind plants here. Climate change didn't bring this fence, but it is providing a fresh reason for its existence and ongoing expansion.

On this side of the fence, rising sea levels caused by climate change are beginning to inundate low-lying Bangladesh. Scientists estimate that by midcentury as many as 15 million people could be displaced.

On the other side of the fence, India isn't taking any chances. Already alarmed about illegal immigration, it is nearing completion of about 2,100 miles worth of high-tech fencing along its long and porous border with Bangladesh.

"Bangladesh is a country that could provide more climate refugees than anywhere else on earth," said Isabel Hilton, an environmental commentator whose London-based nonprofit promotes climate change dialogue in China and throughout Asia.

"What that fence says to me is, wherever those people are going to go, they're not going to India," Hilton said.

The prospect of international migration is a touchy subject in Bangladesh. But for national security experts, it's the most feared global consequence of climate change. As warming temperatures deplete water supplies and alter land use, military analysts warn, already-vulnerable communities in Asia and Africa could descend into conflicts and even wars as more people clamor for increasingly scarce resources.

A distant issue, or today's problem?

Research on how climate change might spark conflict is still in its infancy, and it often tends to be thin and speculative. Indeed, a growing body of international conflict experts say the threat is greatly overblown. Nevertheless, the international security argument has become a sharp weapon in the arsenal of climate change activists who want a global emissions treaty.

Just last month, Lord Nicholas Stern, the eminent climate change economist, warned that failing to reduce greenhouse gas emissions could bring "an extended world war."

But in Bangladesh, where most of the country is less than 20 feet above sea level, many analysts say leaders appear caught between wanting to ring alarm bells about climate change and a desire to avoid the touchy and seemingly unresolvable issue of migration.

India claims that about 5 million Bangladeshis already are living there illegally, while Bangladesh officials say the numbers are wildly exaggerated. The issue is a constant source of tension between the nations. Climate change isn't helping.

"This question of migration to India is one of the topics that is a heated debate in our country, because we believe people are not moving to India," said Abdul Kalam Azad, a senior research fellow at the Bangladesh Institute of International and Strategic Studies. He and others describe climate migration as a distant issue earning an inordinate amount of media hype.

Rabab Fatima, South Asia representative for the International Organization for Migration, said the political sensitivity has led to a dearth of studies on what climate change will mean for migration patterns in Bangladesh.

"The country is not yet prepared to know how to deal with it," she said. The prevailing attitude, she said, is that "climate change is a big problem. Migration is a big problem. Let's not link it. Let it happen in the next generation."

'We are in trouble here'

In the border village of Harinagar, on the other hand, cross-border climate migration is an everyday cause of stress and concern. Almost every person in this cluster of mud and thatch homes has a relative who has illegally crossed the Ichamati River to find work in India.

Reef Warns Of Sea Level Rise

A fossil coral reef, lying several metres above today’s high tide mark at Foul Bay near Margaret River, points to the high point of the last major sea level rise.

Investigators from the ARC Centre of Excellence for Coral Reef Studies (CoECRS) consider the reef – the most southerly coral reef yet known – is a harbinger of what could happen again as global CO2 levels and temperatures rise during the 21st century.

“We’ve dated the reef to about 128-125,000 years ago, right in the middle of the last interglacial, or the last period of global warming before our most recent ice age,” says Professor Malcolm McCulloch, deputy director of CoECRS and an earth scientist at The Australian National University.

“The reef lies about 2.5 metres above the current high tide zone, which means that for it to survive and grow, sea levels would have had to be at least 3 to 4 metres higher than at present.

“There is some evidence – still controversial – that sea levels may briefly have been as much as 6 metres higher.”

The coastline of WA, being geologically stable, has a number of both living and fossil coral reefs along it, the results of the Leeuwin current bringing coral larvae down from Indonesia and northern Australia over many tens of thousands of years. Together these reefs indicate what occurred during the last big sea level rise.

“At the time when this reef grew we know that atmospheric CO2 levels were high, climate had warmed, that the northern icesheets had melted significantly and that sea levels rose - before dropping by around 130 metres again as the ice-age returned and locked up water,” Prof. McCulloch says.

“Water temperatures off Margaret River would then have been more like water temperatures off Geraldton today, allowing the corals to flourish and reefs to form. The discovery is of particular importance as it shows that sea levels rose not only because of the expansion of the oceans due to warming, which can account for ~1/2 metre of sea level rise, but also because it indicates that relatively large scale melting of landbased icesheets occurred in Greenland or the Antarctic. It is the very rapid rise in sea level from catastrophic melting of landbased icesheets where there the greatest uncertainty and concern lies. Now from the Margaret River corals we have evidence of not only unusually warm ocean temperatures, but that that this was associated with rapid melting of icesheets contributing to an additional 3 to 4 metres of sea level rise. ”

The cause of the sudden global warming leading to the end of the ice-ages is thought to be due to changes in the elliptical nature of the Earth’s orbit combining with other factors, such as variations in its tilt or wobble. During the ice ages atmospheric CO2 was around 180 parts per million, compared to 280 parts per million during interglacials. We don’t know quite why CO2 levels rose so much during the last interglacial, but it may have been partly due to a reduction in the ocean’s ability to take up atmospheric carbon, as the seas warmed.

Today CO2 levels are even higher, at 380 parts per million with the additional 100 ppm being mainly due to human activities. Prof. McCulloch says the oceans currently removed around 40 per cent of the anthropogenic CO2 from the atmosphere and it would be a matter of concern if their ability to do this decreased under global warming. If levels continue to increase, to above 500 – 600 parts per million as many scientists expect to be the case by 2050, then the climate shifts and warming effects and will become even more dramatic and surpass those of the Last Interglacial warm period”

“Sea level rises and falls have occurred throughout geological history and are all slightly different from one another. However what took place in the last period of global warming 125,000 years ago gives us an idea of what to expect under the current phase,” he said.

“We should certainly be paying attention to what the corals are telling us.”

Climate Uncertainty With CO2 Rise Due To Uncertainty About Aerosols

In a paper to be published in the November issue of the Journal of the Air and Waste Management Association, Stephen Schwartz, an atmospheric scientist at the U.S. Department of Energy’s Brookhaven National Laboratory, argues that much of the reason for the present uncertainty in the climatic effect of increased CO2 arises from uncertainty about the influence of atmospheric aerosols, tiny particles in the air. Schwartz, who is also chief scientist of the Department of Energy’s Atmospheric Science Program, points out that aerosols scatter and absorb light and modify the properties of clouds, making them brighter and thus able to reflect more incoming solar radiation before it reaches Earth’s surface.

“Because these aerosol particles, like CO2, are introduced into the atmosphere as a consequence of industrial processes such as fossil fuel combustion,” says Schwartz, “they have been exerting an influence on climate over the same period of time as the increase in CO2, and could thus very well be masking much of the influence of that greenhouse gas.” However, he emphasizes, the influence of aerosols is not nearly so well understood as the influence of greenhouse gases.

As Schwartz documents, the uncertainty in the climate influence of atmospheric aerosols limits any inference that can be drawn about future climate sensitivity — how much the temperature would rise due to CO2 doubling alone — from the increase in global mean temperature already observed over the industrial period.

The global warming of 0.5 degrees Celsius (0.9 degrees Fahrenheit) that has taken place since 1900 suggests that, if there were no aerosol influence, the effect of CO2 doubling on mean global temperature would be rather low — a rise of 0.9 degrees Celsius (1.6 degrees Fahrenheit). But, the likelihood that aerosols have been offsetting some of the warming caused by CO2 all along, says Schwartz, means that the observed 0.5-degree-Celsius temperature rise is just the part of the CO2 effect we can “see” — the tip of the greenhouse “iceberg.” So the effect of doubling CO2, holding everything else constant, he says, might be three or more times as great.

“Knowledge of Earth’s climate sensitivity is central to informed decision-making regarding future carbon dioxide emissions and developing strategies to cope with a greenhouse-warmed world,” Schwartz says. However, as he points out, not knowing how much aerosols offset greenhouse warming makes it impossible to refine estimates of climate sensitivity. Right now, climate models with low sensitivity to CO2 and those with high sensitivity are able to reproduce the temperature change observed over the industrial period equally well by using different values of the aerosol influence, all of which lie within the uncertainty of present estimates.

“In order to appreciably reduce uncertainty in Earth’s climate sensitivity the uncertainty in aerosol influences on climate must be reduced at least threefold,” Schwartz concludes. He acknowledges that such a reduction in uncertainty presents an enormous challenge to the aerosol research community.

An editorial accompanying the paper credits Schwartz with presenting “a unique argument challenging the research community to reduce the uncertainty in aerosol forcing of climate change in order to reduce the uncertainty in climate sensitivity to an extent that would be more useful to decision makers.” The editorial also suggests that, “Schwartz’s calculations are not only of interest for the issue of climate change but may serve as a paradigm for environmental issues in general.”

This research was funded by the Office of Biological and Environmental Research within the U.S. Department of Energy’s Office of Science.

Researchers Improve Predictions Of Cloud Formation For Better Global Climate Modeling

The National Science Foundation (NSF)-funded researchers, led by scientists at the Georgia Institute of Technology, also have developed a new instrument for measuring the conditions and time needed for a particle to become a cloud droplet. This will help scientists determine how various types of emissions affect cloud formation.

Georgia Tech scientist Athanasios Nenes will present a lecture on the work at the American Geophysical Union’s fall meeting in San Francisco on Dec. 17. The session is titled “Tropospheric Aerosol Processes: The Physical and Chemical Aging of Aerosol Particles and Their Impacts.”

Clouds play a critical role in climate, Nenes explained. Low, thick clouds cool the earth by reflecting solar radiation whereas high, thin clouds have warming properties by trapping infrared radiation emitted by the earth.

Scientists have learned that human activities influence cloud formation. Airborne particles released by smokestacks, charcoal grills and car exhaust restrict the growth of cloud droplets, causing condensing water to spread out among a larger number of smaller droplets. Known as the “indirect aerosol effect,” it gives clouds more surface area and reflectivity, which translates into greater cooling power. The clouds may also have less chance of forming rain, which allows cloud to remain longer for cooling.

“Of all the components of climate change, the aerosol indirect effect has the greatest potential cooling effect, yet quantitative estimates are highly uncertain,” said Nenes. “We need to get more rigorous and accurate representation of how particles modify cloud properties. Until the aerosol indirect effect is well understood, society is incapable of assessing its impact on future climate.”

Current computer climate models can’t accurately predict cloud formation, which, in turn, hinders their ability to forecast climate change from human activities. “Because of their coarse resolution, computer models produce values on large spatial scales (hundreds of kilometers) and can only represent large cloud systems,” Nenes said.

Aerosol particles, however, are extremely small and measured in micrometers. This means predictive models must address processes taking place on a very broad range of scale. “Equations that describe cloud formation simply cannot be implemented in climate models,” Nenes said. “We don’t have enough computing power -- and probably won’t for another 50 years. Yet somehow we still need to describe cloud formation accurately if we want to understand how humans are affecting climate.”

To address the lack of computer power and shortcomings of existing parameterization, Nenes and his research team have developed simple, physics-based equations that link aerosol particles and cloud droplets. Then these equations can be scaled up to a global level, providing accurate predictions thousands of times faster than more detailed models.

This modeling method has proven successful in two field tests. Data was collected from aircraft flying through from cumulus clouds off the coast of Key West, Fla., in 2002, and from stratocumulus clouds near Monterey, Calif., in 2003. Compared with this real-world data, predictions from Nenes’ model were accurate within 10 to 20 percent.

“We never expected to capture the physics to that degree,” Nenes explained. “We were hoping for a 50 percent accuracy rate.”

Another challenge in predicting climate change is to understand how aerosols’ chemistry affects cloud formation. Each particle has a different potential for forming a cloud droplet, which depends on its composition, location and how long it has been in the atmosphere. Until now, people have measured and averaged properties over long periods of time. “Yet particles are mixing and changing quickly,” Nenes said. “If you don’t factor in the chemical aging of the aerosol, you can easily have a large error when predicting cloud droplet number.”

Working with Gregory Roberts at the Scripps Institution of Oceanography, Nenes developed a new type of cloud condensation nuclei (CCN) counter. This instrument exposes different aerosol particles to supersaturation, which enables researchers to determine: 1) how many droplets form and 2) how long they take to form.

Providing fast, reliable measurements, the CCN counter can be used on the ground or in an aircraft. “It gives us a much needed link for determining how different types of emissions will affect clouds formation,” Nenes explained.

Nenes and Roberts have patented the CCN instrument, and a paper describing the technology will be published in an upcoming issue of the journal Aerosol Science and Technology.

The new modeling method and CCN instrument have far-reaching applications for predicting climate change and precipitation patterns, the scientists believe.

The indirect aerosol effect is counteracting greenhouse warming now, but will stop at some point, Nenes explained. “One of our goals is to figure out how long we’ll have this cooling effect so we can respond to changes.”

NASA Studies How Airborne Particles Affect Climate Change

"The majority of aerosols form a layer of haze near the Earth's surface, which can cause either a cooling or warming effect, depending on aerosol type and location," said Jens Redemann, lead author of the science paper at NASA Ames Research Center, Moffett Field, Calif.

Different types of aerosol particles can influence visible light and other kinds of radiation, affecting climate and temperatures, the scientists reported. "Changing the flow of radiation – including light – above and within the atmosphere changes the energy available for driving Earth's climate," said Phil Russell, also a NASA Ames scientist.

"Our study measured how aerosols change the flow of solar energy," Russell said. This solar energy includes visible light and also radiation at shorter and longer wavelengths in the ultraviolet and infrared ranges.

To find out the extent to which tiny particles in the air could affect climate, NASA scientists flew in a low-flying aircraft over the dark waters of the Gulf of Maine. Two types of instruments on the aircraft measured radiation from the sun.

Radiometers – devices that measure the intensity of radiant energy – measured total solar energy coming from all directions. At the same time, a sun photometer – an instrument that measures the intensity of the sun’s light – measured sunlight coming directly, straight from the sun through the atmosphere. The quantity of aerosols in the atmosphere between the sun photometer and the sun is proportional to the difference between the light intensity measured by the sun photometer and the amount of light that would pass through an aerosol-free atmosphere.

Combining measurements of total solar light intensity from all directions, solar light intensity directly, straight from the sun, and the amount of aerosols in the atmospheric column, scientists can estimate how much of the sun’s energy is scattered (redirected) and absorbed (causes heating) by atmospheric aerosols. These measurements are useful to climate scientists as a reality check for computer climate models.

Role Of Solar Radiation In Climate Change

Special instruments have been recording the solar radiation that reaches the Earth’s surface since 1923. However, it wasn’t until the International Geophysical Year in 1957/58 that a global measurement network began to take shape. The data thus obtained reveal that the energy provided by the sun at the Earth’s surface has undergone considerable variations over the past decades, with associated impacts on climate.

Investigating which factors reduce or intensify solar radiation and thus cause “global dimming” or “global brightening” is still very much a nascent field of research. The American Geophysical Union (AGU) has now published a special volume on the subject which presents the current state of knowledge in detail and makes a considerable contribution to climate science. “Only now, especially with the help of this volume, is research in this field really taking off”, stresses Martin Wild, senior scientist at the Institute for Atmospheric and Climate Science of ETH Zurich, who is a specialist on the subject.

Decrease in solar radiation discovered

The initial findings, which revealed that solar radiation at the Earth’s surface is not constant over time but rather varies considerably over decades, were published in the late 1980s and early 1990s for specific regions of the Earth. Atsumu Ohmura, emeritus professor at ETH Zurich, for example, discovered at the time that the amount of solar radiation over Europe decreased considerably between the 1950s and the 1980s. It wasn’t until 1998 that the first global study was conducted for larger areas, like the continents Africa, Asia, North America and Europe for instance. The results showed that on average the surface solar radiation decreased by two percent per decade between the 1950s and 1990.

In analyzing more recently compiled data, however, Wild and his team discovered that solar radiation has gradually been increasing again since 1985. In a paper published in “Science” in 2005, they coined the phrase “global brightening” to describe this new trend and to oppose to the term “global dimming” used since 2001 for the previously established decrease in solar radiation.

Only recently, an article in the journal Nature, which Wild was also involved in, brought additional attention to the topic of global dimming/brightening.

Air pollution favors photosynthesis

In this study, for the first time, the scientists examined the connection between global dimming/brightening and the carbon cycle. They demonstrated that more scattered light is present during periods of global dimming due to the increased aerosol- and cloud-amounts, enabling plants to absorb CO₂ more efficiently than when the air is cleaner and thus clearer. According to the scientists, this is because scattered light penetrates deeper into the vegetation canopy than direct sunlight, which means the plants can use the light more effectively for photosynthesis. Consequently, there was around 10 percent more carbon stored in the terrestrial biosphere between 1960 and 1999.

The special volume, which appears in the AGU’s Journal of Geophysical Research, provides an overview of the current state of knowledge. Almost half of the publications in the volume were either completely or partially written by ETH Zurich scientists. Wild is the guest editor, and author or co-author of ten of these articles.

The articles provide the first indication of the magnitude of these effects, how they vary in terms of time and space and what the possible consequences might be for climate change. They also discuss in detail the underlying causes and mechanisms, which are still under debate.

Many questions left open

It is particularly unclear as to whether it is the clouds or the aerosols that trigger global dimming/brightening, or even interactions between clouds and aerosols, as aerosols can influence the “brightness” and lifetime of the clouds. The investigation of these relations is complicated by the fact that insufficient – if any – observational data are available on how clouds and aerosol loadings have been changing over the past decades. The recently launched satellite measurement programs should help to close this gap for the future from space, however.

“There is still an enormous amount of research to be done as many questions are still open”, explains Wild. This includes the magnitude of the dimming and brightening effects on a global level and how greatly the effects differ between urban and rural areas, where fewer aerosols are released into the atmosphere. Another unresolved question is what happens over the oceans, as barely any measurement data are available from these areas.

A further challenge for the researchers is to incorporate the effects of global dimming/brightening more effectively in climate models, to understand their impact on climate change better. After all, studies indicate that global dimming masked the actual temperature rise – and therefore climate change – until well into the 1980s. Moreover, the studies published also show that the models used in the Intergovernmental Panel on Climate Change’s (IPCC) fourth Assessment Report do not reproduce global dimming/brightening adequately: neither the dimming nor the subsequent brightening is simulated realistically by the models. According to the scientists, this is probably due to the fact that the processes causing global dimming/brightening were not taken into account adequately and that the historical anthropogenic emissions used as model input are afflicted with considerable uncertainties.

“This is why at ETH Zurich we are working with a research version of a global climate model, which contains much more detailed aerosol and cloud microphysics and can reproduce global dimming/brightening more effectively”, says Wild. For him, the studies so far constitute “initial” estimates that need to be followed up with further research.

Signs From Earth: Now What?

"One. Two. Three. Lift!" barks Cathy Whitlock, a fossil pollen expert and paleoclimatologist at the University of Oregon. She and the three of us—two of her students and I—tighten our grips on the cold metal tube of a lake-bed drilling rig and heave. "Again," she commands. Slowly, inch by inch and groan by groan, the coring barrel that Whitlock and her students had manhandled into the marshy shore of Little Lake, a blue jewel of water in Oregon's central Coast Range, emerges from the mud.

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"Once more," orders Whitlock. We bend to the task and at last free the barrel from the muck. Whitlock has extracted a couple hundred similar cores from the deep sediments of this lake, but she beams like a kid getting her first bike as she slides her latest sample of old mud, five centimeters (two inches) thick and a meter (3.3 feet) long, out of the barrel.

"Oh, that's a lovely core," she says. To me it looks about as interesting as a Tootsie Roll. But to Whitlock's trained eye even the chocolate hue of the mud holds a story. "That rich brown color tells you it's full of organic matter—especially pollen," she says, slicing the core in half lengthwise with her pocketknife. "You can't see the pollen without a microscope, but it's there."

And in that pollen lie clues to one of the greatest puzzles facing researchers like Whitlock: What has caused—and will cause again—the sudden climate changes that our Earth periodically undergoes? Not the 100,000-year fluctuations between a glaciated and a warmer Earth that have occurred for the past million years or so, but the more rapid shifts that scientists have recently identified when the Earth switched suddenly from frozen ice age to picnic-warm and back again. How often and how quickly have such dramatic changes happened? Perhaps most important, what do these past abrupt reversals tell us about the direction of Earth's climate today and in the future?

To answer such questions, scientists are busy unearthing signs of ancient climate in a surprising array of sources: glacial ice and moraines, stalagmites from caverns, tree rings and corals, dust and sand dunes, and the microscopic shells of organisms buried in deep-ocean sediments. Others, hoping to piece together the climate of the more recent past, turn to human records, using archaeological inscriptions, vintner and gardening diaries, and ship captains' logs. "We need both human and natural records," explains Ohio State University glaciologist Lonnie Thompson, who specializes in retrieving ice cores from the dwindling glaciers on tropical mountains. "We want to understand how the climate worked before and after people appeared. That's the only way we'll figure out what impact people have on climate, how much we're responsible for the way it's changing now."

Just how swiftly climate changes can occur is clear from Whitlock's study of her Little Lake cores. Those like the ones we drilled are stored at her university lab. Each meter (3.3 feet) of mud contains about 2,300 years of pollen grains from trees, grasses, and flowering plants. To find the pollen in the mud, Whitlock takes smudges from every core at set intervals, then puts the mud in a chemical bath that eats away everything but the thousands of previously invisible pollen grains. She places a droplet of the pollen residue on a slide and then "reads" about 300 grains, identifying the species of each one—a process that allows her to trace how the vegetation in the Coast Range changed during the climatic variations of the past.

"You hit bedrock at the lake at about 18.25 (59.9 feet) meters," Whitlock says, placing a sample slide beneath her microscope. "The pollen at that level dates to about 42,000 years ago."

Very few mountain lakes have such a continuous record, she adds, since they are often formed when glaciers retreat. But a landslide that blocked a small stream before the last ice age made Little Lake. The pollen in its muddy sediments "tells us what the coastal Oregon environment was like before and at the height of that ice age and how it changed as the climate warmed about 13,000 years ago," says Whitlock.

"It was a big change," she continues. "Here's what the forest looked like 21,000 years ago at the height of the last ice age. And, oh man, was it a different world."

I take her place at the scope, and she guides me from grain to grain. It's a surprisingly easy tour, since there are really only two types of pollen on this slide: the large, kidney-shaped grains of Engelmann spruce trees, and the smaller grains of mountain hemlock, which look like ovals with two small ears.

"Now think about this," Whitlock says. "Engelmann spruce doesn't grow in the Coast Range today. Instead, you find Douglas fir; that's the dominant conifer. But there isn't any Doug fir pollen on that slide. Doug fir doesn't show up until close to the end of the last ice age, and then—suddenly boom!—it's there and the spruce forest is gone. And that happens in 200 to 500 years: A whole forest vanishes and another one takes its place."

Whitlock pauses. "So we want to know how that happened and why. What caused the forest and the climate to change so dramatically and abruptly? And what happens if the climate shifts in the other direction, toward an ice age again or toward even warmer conditions? How are we—people—going to respond?"

Ice cores from Greenland, first obtained and analyzed in the 1960s, gave scientists early clues to rapid climate change. Because the ice there has accumulated undisturbed for over 100,000 years, it holds some of the best records for such things as past temperatures, amount of precipitation, and atmospheric conditions.

The Greenland cores, combined with even older ice cores from Antarctica's Vostok Station, showed the expected long periods of gradually increasing cold followed by shorter warm periods. But the Greenland ice also revealed that within the long, cold stretches there were short periods of warming and cooling. These shorter changes came in bursts, causing the climate to jump from cold to hot to cold again, sometimes in mere decades. The past climate had behaved like "an impish three-year-old" flicking a light switch, as Richard B. Alley, one of the scientists on the early 1990s Greenland drilling project, wrote in his book The Two-Mile Time Machine. And that raised a new question, one that remains unsolved: What caused—and may cause again—all those flickerings?

Sudden climate flips occurred throughout the last ice age—from about 70,000 to 11,500 years ago. At the height of this glaciation, vast ice sheets blanketed much of North America, Europe, parts of Russia, and Antarctica. Periodically the ice melted, then advanced again, until the final melting—an event that marks the beginning of the modern warm (and more climatically stable) epoch known as the Holocene.

But getting to the Holocene was a start-stop affair. It began with an abrupt warming—probably the cause of Whitlock's suddenly altered forest. Then there was another switch, back to cold times, and yet another warming at 11,500 years. In that jump, Greenland's surface temperature increased by 15 degrees Fahrenheit (8.4 degrees Celsius) in a single decade. England warmed suddenly too, becoming a haven for certain beetles that can only live in balmier climes. And on both sides of the North Atlantic, the sudden warmth melted terrestrial glaciers thousands of years old in just a few hundred years.

"All those events happened essentially overnight," says Oregon State University's Peter Clark, who is tracking climate changes in Ireland's glacial geology. "We'd like to understand why the sudden retreats happened—what triggered them and if something like that could happen today," says Clark. "But to get those answers, we first need to know as precisely as possible when the ice melted."

In an effort to answer that question, Clark and fellow geologist Marshall McCabe from Ireland's University of Ulster don their rain gear and knee-high rubber boots, grab shovels and plastic bags, and make their way to a muddy cliff in a farmer's pasture above Ireland's Atlantic coast. Along the way, McCabe points his shovel at a small palm tree planted outside the farmer's house. "You know, we're at the same latitude here as southern Alaska. And that palm shows that our friend, the North Atlantic Ocean conveyor, is working," he says, referring to the ocean currents that pull warm water from the tropics to the Irish coast, keeping its temperature mild. "Otherwise, the palm would be dead."

From their studies of coral reefs and marine sediments, paleoclimatologists have shown just how important this ocean circulation system—the North Atlantic conveyor—is to the climate of the entire planet. During the ice ages it weakened and even occasionally stopped, triggering a cascade of events that ultimately led to warmer temperatures in the Southern Hemisphere and colder temperatures in the north.

"That conveyor sits right offshore," McCabe adds, this time aiming his shovel toward the sea. "So Ireland is particularly sensitive to any big changes in what it's doing; they're felt here immediately."

In the last ice age, with the conveyor slowed down, Ireland was much more like Alaska. Glaciers covered its mountains and pushed across the land and into the sea. But whenever the climate switch was flipped and the deep freeze momentarily ended, Ireland's glaciers began to retreat—rapidly. Meltwater coursed over the land, cutting deep river-size channels and pouring a slurry of mud into the sea. "These were high-energy events," says McCabe.

As the mud settled, tiny organisms called zooplankton were buried in the sediments. Today, with relative sea level far lower than in the past because the land is no longer weighted with ice, those muddy deposits are up to several hundred feet above the ocean, and a geologist who knows where to look can find in them the fossils of the shell-covered zooplankton called foraminifera (forams for short). Forams are an integral part of paleoclimatological research because their calcareous shells can be dated. And that's why McCabe and Clark have come to this pasture: to dig about 50 pounds (23 kilograms) of foram-filled mud for dating. With precise dates for the rapid retreat of the ice in hand, the two will be able to link Ireland's glacial history with that of North America and Scandinavia.

By dating forams from mud on the Irish Sea coast, McCabe and Clark found evidence for a rapid 35-foot (10-meter) rise in global sea level about 19,000 years ago. "That was a Northern Hemisphere melting, a pulling back of the entire ice margin," says Clark. "It wasn't just a little local event. We figure that the equivalent of two ice sheets the size of Greenland's today must have melted within a few hundred years."

What could have triggered such a large-scale event? McCabe and Clark argue that it could have been the weight of the ice itself. As the ice sheets grew, their increasing weight pushed down on the underlying land. Where the glaciers sank far enough to reach sea level, the ice began to float, breaking up into icebergs. "That would have added more fresh water to the ocean, changing its salinity and deepwater currents," says Clark.

More fresh water in the North Atlantic would have slowed the conveyor and decreased the amount of warm water pulled from the tropics, changing ocean circulation dynamics and temperatures as far south as Antarctica. Computer models that simulate the Earth's climate show that what happens in the North Atlantic very quickly affects the rest of the planet. "As the water gets cooler here, the ocean gets warmer in the Southern Hemisphere," says Clark. "It's a seesaw effect. That warming could have caused an ice sheet in Antarctica to melt."

And that additional cold fresh water from Antarctica would, in turn, have caused the tropical warm currents to flow back toward the north, starting up the North Atlantic conveyor. Once again the Northern Hemisphere ice sheets would have begun to melt.

"You essentially would have ended up with ice sheets melting at both ends of the Earth at slightly different times," says Clark. "Today we have two big ice sheets: Greenland and Antarctica. And the climate is changing because of the high amount of carbon dioxide we've put in the atmosphere. How will it affect those ice sheets? If they melt, how will that affect us?"

Not everyone is convinced that the North Atlantic Ocean conveyor is the only switch for the Earth's sudden climate changes. "Maybe that's true for the higher latitudes, but it's not for the tropics," says Lonnie Thompson, whom many credit with retrieving the best paleoclimate records from the torrid zone—the latitudes between the Tropic of Cancer and Tropic of Capricorn. Indeed, until research by Thompson and others showed something different, most scientists regarded the tropics as a place where little climate change had ever taken place—not even during the ice ages.

"There's a bias in our view of climate change that sees events in the Northern Hemisphere as the most important," Thompson explains as we gear up to enter his ice-core storage room in the basement of Scott Hall on the Ohio State University campus. "But it's a data-collecting bias: That's where we have the most records from."

Behind a nondescript, beige door marked 089-B lie 6,000 meters (6,562 yards) of ice cores that give Thompson the data to challenge that interpretation. The cores come from glaciers crowning summits in the Andes, the Himalaya, and Alaska, and from Mount Kilimanjaro. I'm glad for the down-filled parka, gloves, and snow boots when the first blast of arctic-cold air from Thompson's ice room hits my face.

The cores are kept in silvery, cardboard cylinders and lie in stacks on frost-covered shelves. A temperature gauge reads minus 30 degrees Celsius (minus 22 degrees Fahrenheit), and I shiver in spite of the down. But the numbing cold is necessary to preserve what has or will soon disappear: the climatic history of the tropics. "The sources for these records—the glaciers on the highest mountains—are melting because of the increasing greenhouse gases in the atmosphere," Thompson says. "Some of the ice we've collected and have here is already gone from the mountains."

Greenhouse gases, such as carbon dioxide and methane, are released by a variety of human activities. Over the past 150 years, the amount of these gases has increased enormously in the Earth's atmosphere, trapping more heat and causing temperatures to rise—and glaciers worldwide to melt. And as the ice melts away so do the records that Thompson and other scientists deem vital to a better understanding of Earth's climate.

Thompson pulls down one of the cardboard containers and carries it to a table, handling it as carefully as if it were a tome from a library's rare-book room. "We forget that the Earth is a globe and that 50 percent of the surface of the planet is in the tropics. That's a major heat source, and I think it has a much bigger role in driving climate change than we've realized."

Thompson opens the cylinder and pulls out a meter-long (3.3-foot-long) ice core that's wrapped in plastic.

"This is a core we drilled on Sajama mountain in Bolivia," he says. It is dense and white, yet as Thompson points out, it also has slight variations, the faintest ringlike bands, indicating the annual accumulations of snowfall. By counting the bands, he can estimate the age of a core. And this one, Sajama's final core, the last one Thompson pulled from the mountain's ice before hitting rock, dates to 25,000 years ago, making it the oldest core Thompson has found in his high-altitude work in the tropics.

"This core shows that there actually were climate shifts in the tropics of the same magnitude that Greenland experienced during the ice ages," he says. Near the Equator, Earth's climate had switched rapidly back and forth from cold to warm just as it had in Greenland. And that makes Thompson think that the North Atlantic isn't the only driving mechanism for these abrupt changes. There may be a second driver in the Pacific Ocean.

Other anomalies in this high-mountain ice suggest that the past 10,000 years, which is often characterized as a stable climate period, was in fact also given to climate swings. Thompson opens another cylinder and produces a core from the ancient snows of Mount Kilimanjaro. Like the Sajama core, it is dense and white—except for a two-centimeter-thick (one-inch-thick) band, which is black.

"That's dust," says Thompson. "It dates to 4,200 years ago when there was a terrible 200-year drought in North and East Africa. The upper atmosphere must have been full of sand, dirt, and dust, all of which mixed with the snow as it fell on Kilimanjaro."

Hieroglyphic inscriptions from the period describe how the annual Nile flood failed for about 50 years. The Egyptians suffered in a drought, and people died from famine. At about this time Egypt's Old Kingdom ended, and a period of social and political upheaval began. Thompson believes that the dry spell contributed to the collapse of the Old Kingdom. Some archaeologists also think that the drought extended north into the eastern Mediterranean and contributed to the decline of the Akkadian empire in Mesopotamia.

"It shows what climate change can do," says Thompson. "That was an abrupt, but natural, occurrence, when there were only 250 million people on the planet. Now there are 6.3 billion of us, and we're changing the climate."

Every paleoclimatologist I'd spoken to had said much the same thing. Some were certain that we had already succeeded in flipping one of Earth's climate switches and had triggered a new abrupt change. Others were more cautious, saying only that given the steady emission of carbon dioxide and other gases, the climate was bound to be different. All were alarmed by our collective refusal to slow down our use of fossil fuels. One wryly summed up our behavior as a "remarkable experiment," a quip I pass on to Thompson as we leave his ice-core room.

"He forgot one word," Thompson says, ready as ever to add to the record what is missing. "It's a remarkable, uncontrolled experiment."

"The climate of the past is our anchor for looking at the future," Cathy Whitlock told me when explaining the importance of her fossil pollen studies. "If we can understand the past linkages between the ocean, atmosphere, and biosphere, and determine which parts were the really big players in past sudden change, then maybe we can better deal with future surprises."

That's the dream, the goal of paleoclimatology. And although all the connections among the disparate parts of the Earth's climate have yet to be fully untangled, computer modelers have made big steps in predicting what the weather will be in the near future. One of the best models runs on a supercomputer at the United Kingdom's Hadley Centre for Climate Prediction and Research. Simon Tett, a Hadley Centre climate specialist, sets up his laptop at my London hotel and calls up a map of the world. Superimposed on it are swirls and colors representing ocean and atmospheric currents—essentially a model of Earth's climate. Plug in different factors, like a big spike in CO₂ and methane levels, and you can sit back and watch the weather change.

"Right. So here is what the world's climate could be in 2080," Tett says. A red hue settles over most of North America and Europe, indicating higher temperatures, while the Arctic turns from white to blue as the summer ice cap melts.

"People don't realize how dramatic these changes will be," says Tett. "But we expect to see a two- to five-degree [Celsius] (three- to nine-degree Fahrenheit) warming over the next hundred years. It will be higher over land, but the oceans will also warm."

The warming doesn't mean that every place will suddenly become like Miami. Some areas, like the interior of the United States, are likely to grow hotter and drier. Others, like China, Southeast Asia, and the western U.S., may get more precipitation but less snowfall, jeopardizing the drinking water of people in cities like Los Angeles. Sea levels around the world are projected to rise as the last of the glaciers melt and the warmer oceans expand. Intense hurricanes may occur more frequently, and storm surges coupled with the higher sea level could severely damage cities like New York. Heat waves, like the one Europe experienced in the summer of last year, may become the summer norm.

Can we do anything to stop the change?

"No," says Tett. "We'd need to get to zero emissions to stabilize the CO₂ that's already in the atmosphere. And that's not the path we, as societies, have chosen. Even if we were to stop CO₂ emissions now, we are committed to warming.

"Ultimately there will be an effect on the ocean's thermohaline circulation—the conveyor belt," he continues. "Climate models show that circulation will slow, but it's possible that it could collapse. One result of that would be cooler winter temperatures in Europe."

Tett turns off his laptop. "We'll have a better idea of the actual changes in 30 years, because some of us will have lived through them. But it's going to be a very different world."

Outside, the light of a cold winter sun spills over the London streets. It's a week before Christmas and shoppers bustle by. There's the whoosh and honking of traffic, and the smell of diesel and gasoline fumes rising in the air. I hail a cab and set off for the airport.

"The weather's going to change," the cabbie tells me. "It's fine now, but that's the end of it; it's turning rough tomorrow."

I nod in agreement. He is more right than he knows.

Signs From Earth: The Big Thaw

"If we don't have it, we don't need it," pronounces Daniel Fagre as we throw on our backpacks. We're armed with crampons, ice axes, rope, GPS receivers, and bear spray to ward off grizzlies, and we're trudging toward Sperry Glacier in Glacier National Park, Montana. I fall in step with Fagre and two other research scientists from the U.S. Geological Survey Global Change Research Program. They're doing what they've been doing for more than a decade: measuring how the park's storied glaciers are melting.

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So far, the results have been positively chilling. When President Taft created Glacier National Park in 1910, it was home to an estimated 150 glaciers. Since then the number has decreased to fewer than 30, and most of those remaining have shrunk in area by two-thirds. Fagre predicts that within 30 years most if not all of the park's namesake glaciers will disappear.

"Things that normally happen in geologic time are happening during the span of a human lifetime," says Fagre. "It's like watching the Statue of Liberty melt."

Scientists who assess the planet's health see indisputable evidence that Earth has been getting warmer, in some cases rapidly. Most believe that human activity, in particular the burning of fossil fuels and the resulting buildup of greenhouse gases in the atmosphere, have influenced this warming trend. In the past decade scientists have documented record-high average annual surface temperatures and have been observing other signs of change all over the planet: in the distribution of ice, and in the salinity, levels, and temperatures of the oceans.

"This glacier used to be closer," Fagre declares as we crest a steep section, his glasses fogged from exertion. He's only half joking. A trailside sign notes that since 1901, Sperry Glacier has shrunk from more than 800 acres (320 hectares) to 300 acres (120 hectares). "That's out of date," Fagre says, stopping to catch his breath. "It's now less than 250 acres (100 hectares)."

Everywhere on Earth ice is changing. The famed snows of Kilimanjaro have melted more than 80 percent since 1912. Glaciers in the Garhwal Himalaya in India are retreating so fast that researchers believe that most central and eastern Himalayan glaciers could virtually disappear by 2035. Arctic sea ice has thinned significantly over the past half century, and its extent has declined by about 10 percent in the past 30 years. NASA's repeated laser altimeter readings show the edges of Greenland's ice sheet shrinking. Spring freshwater ice breakup in the Northern Hemisphere now occurs nine days earlier than it did 150 years ago, and autumn freeze-up ten days later. Thawing permafrost has caused the ground to subside more than 15 feet (4.6 meters) in parts of Alaska. From the Arctic to Peru, from Switzerland to the equatorial glaciers of Man Jaya in Indonesia, massive ice fields, monstrous glaciers, and sea ice are disappearing, fast.

When temperatures rise and ice melts, more water flows to the seas from glaciers and ice caps, and ocean water warms and expands in volume. This combination of effects has played the major role in raising average global sea level between four and eight inches (10 and 20 centimeters) in the past hundred years, according to the Intergovernmental Panel on Climate Change (IPCC).

Scientists point out that sea levels have risen and fallen substantially over Earth's 4.6-billion-year history. But the recent rate of global sea level rise has departed from the average rate of the past two to three thousand years and is rising more rapidly—about one-tenth of an inch a year. A continuation or acceleration of that trend has the potential to cause striking changes in the world's coastlines.

Driving around Louisiana's Gulf Coast, Windell Curole can see the future, and it looks pretty wet. In southern Louisiana coasts are literally sinking by about three feet (a meter) a century, a process called subsidence. A sinking coastline and a rising ocean combine to yield powerful effects. It's like taking the global sea-level-rise problem and moving it along at fast-forward.

The seventh-generation Cajun and manager of the South Lafourche Levee District navigates his truck down an unpaved mound of dirt that separates civilization from inundation, dry land from a swampy horizon. With his French-tinged lilt, Curole points to places where these bayous, swamps, and fishing villages portend a warmer world: his high school girlfriend's house partly submerged, a cemetery with water lapping against the white tombs, his grandfather's former hunting camp now afloat in a stand of skeleton oak snags. "We live in a place of almost land, almost water," says the 52-year-old Curole.

Rising sea level, sinking land, eroding coasts, and temperamental storms are a fact of life for Curole. Even relatively small storm surges in the past two decades have overwhelmed the system of dikes, levees, and pump stations that he manages, upgraded in the 1990s to forestall the Gulf of Mexico's relentless creep. "I've probably ordered more evacuations than any other person in the country," Curole says.

The current trend is consequential not only in coastal Louisiana but around the world. Never before have so many humans lived so close to the coasts: More than a hundred million people worldwide live within three feet (a meter) of mean sea level. Vulnerable to sea-level rise, Tuvalu, a small country in the South Pacific, has already begun formulating evacuation plans. Megacities where human populations have concentrated near coastal plains or river deltas—Shanghai, Bangkok, Jakarta, Tokyo, and New York—are at risk. The projected economic and humanitarian impacts on low-lying, densely populated, and desperately poor countries like Bangladesh are potentially catastrophic. The scenarios are disturbing even in wealthy countries like the Netherlands, with nearly half its landmass already at or below sea level.

Rising sea level produces a cascade of effects. Bruce Douglas, a coastal researcher at Florida International University, calculates that every inch (2.5 centimeters) of sea-level rise could result in eight feet (2.4 meters) of horizontal retreat of sandy beach shorelines due to erosion. Furthermore, when salt water intrudes into freshwater aquifers, it threatens sources of drinking water and makes raising crops problematic. In the Nile Delta, where many of Egypt's crops are cultivated, widespread erosion and saltwater intrusion would be disastrous since the country contains little other arable land.

In some places marvels of human engineering worsen effects from rising seas in a warming world. The system of channels and levees along the Mississippi effectively stopped the millennia-old natural process of rebuilding the river delta with rich sediment deposits. In the 1930s oil and gas companies began to dredge shipping and exploratory canals, tearing up the marshland buffers that helped dissipate tidal surges. Energy drilling removed vast quantities of subsurface liquid, which studies suggest increased the rate at which the land is sinking. Now Louisiana is losing approximately 25 square miles (65 square kilometers) of wetlands every year, and the state is lobbying for federal money to help replace the upstream sediments that are the delta's lifeblood.

Local projects like that might not do much good in the very long run, though, depending on the course of change elsewhere on the planet. Part of Antarctica's Larsen Ice Shelf broke apart in early 2002. Although floating ice does not change sea level when it melts (any more than a glass of water will overflow when the ice cubes in it melt), scientists became concerned that the collapse could foreshadow the breakup of other ice shelves in Antarctica and allow increased glacial discharge into the sea from ice sheets on the continent. If the West Antarctic ice sheet were to break up, which scientists consider very unlikely this century, it alone contains enough ice to raise sea level by nearly 20 feet (6 meters).

Even without such a major event, the IPCC projected in its 2001 report that sea level will rise anywhere between 4 and 35 inches (10 and 89 centimeters) by the end of the century. The high end of that projection—nearly three feet (a meter)—would be "an unmitigated disaster," according to Douglas.

Down on the bayou, all of those predictions make Windell Curole shudder. "We're the guinea pigs," he says, surveying his aqueous world from the relatively lofty vantage point of a 12-foot-high (3.7-meter) earthen berm. "I don't think anybody down here looks at the sea-level-rise problem and puts their heads in the sand." That's because soon there may not be much sand left.

Rising sea level is not the only change Earth's oceans are undergoing. The ten-year-long World Ocean Circulation Experiment, launched in 1990, has helped researchers to better understand what is now called the ocean conveyor belt.

Oceans, in effect, mimic some functions of the human circulatory system. Just as arteries carry oxygenated blood from the heart to the extremities, and veins return blood to be replenished with oxygen, oceans provide life-sustaining circulation to the planet. Propelled mainly by prevailing winds and differences in water density, which changes with the temperature and salinity of the seawater, ocean currents are critical in cooling, warming, and watering the planet's terrestrial surfaces—and in transferring heat from the Equator to the Poles.

The engine running the conveyor belt is the density-driven thermohaline circulation ("thermo" for heat and "haline" for salt). Warm, salty water flows from the tropical Atlantic north toward the Pole in surface currents like the Gulf Stream. This saline water loses heat to the air as it is carried to the far reaches of the North Atlantic. The coldness and high salinity together make the water more dense, and it sinks deep into the ocean. Surface water moves in to replace it. The deep, cold water flows into the South Atlantic, Indian, and Pacific Oceans, eventually mixing again with warm water and rising back to the surface.

Changes in water temperature and salinity, depending on how drastic they are, might have considerable effects on the ocean conveyor belt. Ocean temperatures are rising in all ocean basins and at much deeper depths than previously thought, say scientists at the National Oceanic and Atmospheric Administration (NOAA). Arguably, the largest oceanic change ever measured in the era of modern instruments is in the declining salinity of the subpolar seas bordering the North Atlantic.

Robert Gagosian, president and director of the Woods Hole Oceanographic Institution, believes that oceans hold the key to potential dramatic shifts in the Earth's climate. He warns that too much change in ocean temperature and salinity could disrupt the North Atlantic thermohaline circulation enough to slow down or possibly halt the conveyor belt—causing drastic climate changes in time spans as short as a decade.

The future breakdown of the thermohaline circulation remains a disturbing, if remote, possibility. But the link between changing atmospheric chemistry and the changing oceans is indisputable, says Nicholas Bates, a principal investigator for the Bermuda Atlantic Time-series Study station, which monitors the temperature, chemical composition, and salinity of deep-ocean water in the Sargasso Sea southeast of the Bermuda Triangle.

Oceans are important sinks, or absorption centers, for carbon dioxide, and take up about a third of human-generated CO2. Data from the Bermuda monitoring programs show that CO2 levels at the ocean surface are rising at about the same rate as atmospheric CO2. But it is in the deeper levels where Bates has observed even greater change. In the waters between 820 and 1,476 feet (250 and 450 meters) deep, CO2 levels are rising at nearly twice the rate as in the surface waters. "It's not a belief system; it's an observable scientific fact," Bates says. "And it shouldn't be doing that unless something fundamental has changed in this part of the ocean."

While scientists like Bates monitor changes in the oceans, others evaluate CO2 levels in the atmosphere. In Vestmannaeyjar, Iceland, a lighthouse attendant opens a large silver suitcase that looks like something out of a James Bond movie, telescopes out an attached 15-foot (4.5-meter) rod, and flips a switch, activating a computer that controls several motors, valves, and stopcocks. Two two-and-a-half liter (about 26 quarts) flasks in the suitcase fill with ambient air. In North Africa, an Algerian monk at Assekrem does the same. Around the world, collectors like these are monitoring the cocoon of gases that compose our atmosphere and permit life as we know it to persist.

When the weekly collection is done, all the flasks are sent to Boulder, Colorado. There, Pieter Tans, a Dutch-born atmospheric scientist with NOAA's Climate Monitoring and Diagnostics Laboratory, oversees a slew of sensitive instruments that test the air in the flasks for its chemical composition. In this way Tans helps assess the state of the world's atmosphere.

By all accounts it has changed significantly in the past 150 years.

Walking through the various labs filled with cylinders of standardized gas mixtures, absolute manometers, and gas chromatographs, Tans offers up a short history of atmospheric monitoring. In the late 1950s a researcher named Charles Keeling began measuring CO2 in the atmosphere above Hawaii's 13,679-foot (4,169-meter) Mauna Loa. The first thing that caught Keeling's eye was how CO2 level rose and fell seasonally. That made sense since, during spring and summer, plants take in CO2 during photosynthesis and produce oxygen in the atmosphere. In the fall and winter, when plants decay, they release greater quantities of CO2 through respiration and decay. Keeling's vacillating seasonal curve became famous as a visual representation of the Earth "breathing."

Something else about the way the Earth was breathing attracted Keeling's attention. He watched as CO2 level not only fluctuated seasonally, but also rose year after year. Carbon dioxide level has climbed from about 315 parts per million (ppm) from Keeling's first readings in 1958 to more than 375 ppm today. A primary source for this rise is indisputable: humans' prodigious burning of carbon-laden fossil fuels for their factories, homes, and cars.

Tans shows me a graph depicting levels of three key greenhouse gases—CO2, methane, and nitrous oxide—from the year 1000 to the present. The three gases together help keep Earth, which would otherwise be an inhospitably cold orbiting rock, temperate by orchestrating an intricate dance between the radiation of heat from Earth back to space (cooling the planet) and the absorption of radiation in the atmosphere (trapping it near the surface and thus warming the planet).

Tans and most other scientists believe that greenhouse gases are at the root of our changing climate. "These gases are a climate-change driver," says Tans, poking his graph definitively with his index finger. The three lines on the graph follow almost identical patterns: basically flat until the mid-1800s, then all three move upward in a trend that turns even more sharply upward after 1950. "This is what we did," says Tans, pointing to the parallel spikes. "We have very significantly changed the atmospheric concentration of these gases. We know their radiative properties," he says. "It is inconceivable to me that the increase would not have a significant effect on climate."

Exactly how large that effect might be on the planet's health and respiratory system will continue to be a subject of great scientific and political debate—especially if the lines on the graph continue their upward trajectory.

Eugene Brower, an Inupiat Eskimo and president of the Barrow Whaling Captains' Association, doesn't need fancy parts-per-million measurements of CO2 concentrations or long-term sea-level gauges to tell him that his world is changing.

"It's happening as we speak," the 56-year-old Brower says as we drive around his home in Barrow, Alaska—the United States' northernmost city—on a late August day. In his fire chief's truck, Brower takes me to his family's traditional ice cellars, painstakingly dug into the permafrost, and points out how his stores of muktuk—whale skin and blubber recently began spoiling in the fall because melting water drips down to his food stores. Our next stop is the old Bureau of Indian Affairs school building. The once impenetrable permafrost that kept the foundation solid has bucked and heaved so much that walking through the school is almost like walking down the halls of an amusement park fun house. We head to the eroding beach and gaze out over open water. "Normally by now the ice would be coming in," Brower says, scrunching up his eyes and scanning the blue horizon.

We continue our tour. Barrow looks like a coastal community under siege. The ramshackle conglomeration of weather-beaten houses along the seaside gravel road stands protected from fall storm surges by miles-long berms of gravel and mud that block views of migrating gray whales. Yellow bulldozers and graders patrol the coast like sentries.

The Inupiat language has words that describe many kinds of ice. Piqaluyak is salt-free multiyear sea ice. Ivuniq is a pressure ridge. Sarri is the word for pack ice, tuvaqtaq is bottom-fast ice, and shore-fast ice is tuvaq. For Brower, these words are the currency of hunters who must know and follow ice patterns to track bearded seals, walruses, and bowhead whales.

There are no words, though, to describe how much, and how fast, the ice is changing. Researchers long ago predicted that the most visible impacts from a globally warmer world would occur first at high latitudes: rising air and sea temperatures, earlier snowmelt, later ice freeze-up, reductions in sea ice, thawing permafrost, more erosion, increases in storm intensity. Now all those impacts have been documented in Alaska. "The changes observed here provide an early warning system for the rest of the planet," says Amanda Lynch, an Australian researcher who is the principal investigator on a project that works with Barrow's residents to help them incorporate scientific data into management decisions for the city's threatened infrastructure.

Before leaving the Arctic, I drive to Point Barrow alone. There, at the tip of Alaska, roughshod hunting shacks dot the spit of land that marks the dividing line between the Chukchi and Beaufort Seas. Next to one shack someone has planted three eight-foot (2.4-meter) sticks of white driftwood in the sand, then crisscrossed their tops with whale baleen, a horny substance that whales of the same name use to filter life-sustaining plankton out of seawater. The baleen, curiously, looks like palm fronds.

So there, on the North Slope of Alaska, stand three makeshift palm trees. Perhaps they are no more than an elaborate Inupiat joke, but these Arctic palms seem an enigmatic metaphor for the Earth's future.

Al Gore and Friends Create Climate of McCarthyism

DISCUSSIONS about global warming are marked by an increasing desire to stamp out "impure" thinking, to the point of questioning the value of democratic debate. But shutting down discussion simply means the disappearance of reason from public policy.

In March, Al Gore's science adviser and prominent climate researcher Jim Hansen proclaimed that when it comes to dealing with global warming, the "democratic process isn't working". Although science has demonstrated that CO2 from fossil fuels is heating the planet, politicians are unwilling to follow his advice and stop building coal-fired power plants.

Hansen argues that "the first action that people should take is to use the democratic process. What is frustrating people, me included, is that democratic action affects elections, but what we get then from political leaders is greenwash."

Although he doesn't tell us what the second or third action is, he has turned up in a British court to defend six activists who damaged a coal-fired power station. He argues that we need "more people chaining themselves to coal plants", a point repeated by Gore.

The Nobel laureate in economics Paul Krugman goes further. After the narrow passage of the Waxman-Markey climate change bill in the US House of Representatives, Krugman said that there was no justification for a vote against it. He called virtually all of the members who voted against it "climate deniers" who were committing "treason against the planet".

Krugman said that the "irresponsibility and immorality" of the representatives' democratic viewpoints were "unforgivable" and a "betrayal". He thus accused almost half of the democratically elected members of the house, from both parties, of treason for holding the views that they do, thereby essentially negating democracy.

Less well-known pundits make similar points, suggesting that people with "incorrect" views on global warming should face Nuremberg-style trials or be tried for crimes against humanity. There is clearly a trend. The climate threat is so great -- and democracies are doing so little about it -- that people conclude that maybe democracy is part of the problem, and that perhaps people ought not be allowed to express heterodox opinions on such an important topic.

This is scary, although not without historical precedent. Much of the American McCarthyism of the 1940s and 50s was driven by the same burning faith in the righteousness of the mission: a faith that saw fundamental rights abrogated. We would be well served to go down a different path.

Gore and others often argue that if the science of climate change concludes that CO2 emissions are harmful, it follows that we should stop those harmful emissions, and that we are morally obliged to do so. But this misses half the story.

We could just as well point out that since science tells us that speeding cars kill many people, we should cut speed limits to almost nothing. We do no such thing, because we recognise that the costs of high-speed cars must be weighed against the benefits of a mobile society.

Indeed, nobody emits CO2 for fun. CO2 emissions result from other, generally beneficial acts, such as burning coal to keep warm, burning kerosene to cook, or burning petrol to transport people. The benefits of fossil fuels must be weighed against the costs of global warming.

Gore and Hansen want a moratorium on coal-fired power plants, but neglect the fact that the hundreds of new power plants that will be opened in China and India in the coming years could lift a billion people out of poverty. Negating this outcome through a moratorium is clearly no unmitigated good.

Likewise, reasonable people can differ on their interpretation of the Waxman-Markey bill. Even if we set aside its masses of pork-barrel spending, and analyses that show it may allow more emissions in the US for the first decades, there are more fundamental problems with this legislation.

At a cost of hundreds of billions of dollars annually, it will have virtually no impact on climate change. If all of the bill's many provisions were entirely fulfilled, economic models show that it would reduce the temperature by the end of the century by 0.11C, reducing warming by less than 4 per cent.

Even if every Kyoto-obligated country passed its own, duplicate Waxman-Markey bills -- which is implausible and would incur significantly higher costs -- the global reduction would amount to just 0.22C by the end of this century. The reduction in global temperature would not be measurable in 100 years, yet the cost would be significant and payable now.

Is it really treason against the planet to express some scepticism about whether this is the right way forward? Is it treason to question throwing huge sums of money at a policy that will do virtually no good in 100 years? Is it unreasonable to point out that the inevitable creation of trade barriers that will ensue from Waxman-Markey could eventually cost the world 10 times more than the damage climate change could ever have wrought?

Today's focus on ineffective and costly climate policies shows poor judgment. But I would never want to shut down discussion about these issues, whether it is with Gore, Hansen, or Krugman.

Everybody involved in this discussion should spend more time building and acknowledging good arguments, and less time telling others what they cannot say. Wanting to shut down the discussion is simply treason against reason.

Bjorn Lomborg, the director of the Copenhagen Consensus Centre, is an adjunct professor at the Copenhagen Business School, and author of The Skeptical Environmentalist and Cool It: The Skeptical Environmentalist's Guide to Global Warming.

A Real Choice on Climate Change: Do Nothing

Global efforts to mitigate climate change are resulting in the most ineffectual diplomacy since U.S. Secretary of State Frank Kellogg and French Foreign Minister Aristide Briand tried to end all war with international law-eleven years before Hitler launched World War II.

The fecklessness of climate diplomacy was on full display last week at the Group of Eight summit of industrialized countries in Italy, where the international community simultaneously vowed to limit global warming and disavowed the necessary action to do so.

During the summit, U.S. President Barack Obama convened a Major Economies Meeting of 17 countries responsible for 80 percent of global greenhouse gas emissions. Together, these countries agreed that they "ought" to limit global warming to 2 degrees Celsius. British Prime Minister Gordon Brown labeled this "historic" and German Chancellor Angela Merkel called it an "important step." A more apt description of the temperature target is "impossible." Here's why.

As a recent study in the scientific journal Nature notes, global greenhouse gas emissions must fall more than 50 percent below 1990 levels by 2050 in order to have a 75 percent chance of limiting warming to 2 degrees Celsius. According to research compiled by the United States Climate Change Science Program (now the Global Change Research Program), a clearinghouse for global warming science conducted by federal agencies, reducing global emissions by 50 percent below 2000 levels by 2050 would require developing countries to reduce per capita greenhouse gas emissions by 62 percent below business as usual, even if developed countries somehow cut greenhouse gases by 100 percent.

Yet the G8 pledged to reduce emissions "only" 80 percent-from an undefined baseline-by 2050. And before the ink was dry on the summit's climate communiqué, Russian and Canadian officials publically questioned the feasibility of the 80 percent emissions cuts for their countries. Developing countries rejected any limits altogether, refusing to commit to expensive emissions cuts that could jeopardize their number-one priority: poverty reduction.

Clearly, the emissions calculus to reach the 2 degree Celsius target doesn't add up. There are three possible scenarios to bridge this gap between rhetoric and reality.

The first is for everyone to quit. Developing countries have a sovereign right not to act on climate change, and their rapidly growing economies will account for the preponderance of future growth in global emissions, which gives developed countries little reason to limit emissions themselves. As Italian Prime Minister Silvio Berlusconi told The New York Times, it makes little sense for the G8 to commit to stringent emissions reductions if "five billion people continue to behave as they have always behaved."

The second scenario is for developed countries to pay trillions of dollars to finance a green energy revolution in developing countries. But this is politically unthinkable: Can anyone sanely imagine the U.S. Congress appropriating hundreds of billions of dollars for China, an economic competitor?

The final possibility is for developed countries to compel developing countries to reduce emissions by taxing the carbon content of their exports. Countries like China depend on export-driven economic growth, so a carbon tariff would surely get their attention, but in a very bad way-retaliation in kind would be almost assured. That would launch a global trade tariff war of the sort that exacerbated the Great Depression. That is the last thing the ailing global economy needs.

Of all three prospects, the smart money is on global inaction. "Doing something" about global warming doesn't come cheap-the International Energy Agency estimates it would cost $45 trillion to halve emissions by 2050-and there is no precedent for international burden sharing of this magnitude for anything short of a world war. Thus, history implies that a global response to global warming is impossible. Current climate diplomacy certainly suggests as much.

That's not a cause for despair. There is ample evidence that the benefits of economic growth unhindered by costly emissions controls surpass the deleterious effects of global warming. According to World Bank estimates, nearly 2 billion people in developing countries rely on dung, wood and charcoal to heat their homes and cook their food. For the impoverished, a coal-fired power plant giving them access to affordable energy would be a blessing. We can afford to let the climate be.

Global Warming 101: Solutions

Global warming may or may not be a problem. Man may or may not be driving it. Given the uncertainties, a significant amount of global regret may apply if we divert too much of our global wealth to solving what may be a non-existent or trivial problem, especially if that diversion mires billions in poverty. On the other hand, we may also regret not doing anything if man-made global warming does turn out to be a problem. It is therefore prudent to examine what steps we can take that would prove beneficial whether or not anthropogenic global warming turns out to be a problem. These steps can be termed “no regrets” policies.

What makes a No Regrets Global Warming Policy? A global warming policy can be termed “no regrets” as long as it:

• Reduces the amount of greenhouse gases emitted into the atmosphere, or
• Mitigates, prevents or reduces a harm associated with global warming, or
• Provides greater capacity for dealing with problems associated with global warming
• Without imposing significant cost or diverting economic activity.

Top Five “No Regrets” Policies

1.) Eliminate all subsidies to fuel use.
Subsidies to energy R&D cost taxpayers millions of dollars while producing minimal benefits. While these programs may be relatively small given the size of domestic energy markets, they serve little, if any, useful purpose while subsidizing large corporations at taxpayer expense. The potential threat of global warming, whether it is real or not, is simply one more reason to eliminate these subsidy programs. An international agreement aimed at ending energy subsidy with binding targets would be a significant victory for emissions reduction. Unlike Kyoto, which forces an energy starvation diet on its participants, such a treaty would be a move to combat energy obesity.

2.) Repeal the Federal Flood Insurance Program.
Much of the concern over global warming’s potential for harm in the US relates to sea level rise and the flooding that will result. However, much of the investment in potentially vulnerable areas is a result of the Federal flood Insurance Program. This program encourages building in vulnerable areas by acting as a moral hazard: people take greater risks because the government has said it will help bear that risk. Reform would reduce the moral hazard connected with building on vulnerable land, transferring the risk from the taxpayer to the private sector, which is likely to take a more realistic view of the issue.

3.) Reform Air Traffic Control Systems.
Greater demand for air travel means more flights, which means greater fuel use and increased emissions. Yet, the current government-operated system of air traffic control, based on a 1920s-era system of beacons, may hinder innovations that could reduce fuel use and emissions. As a general rule, the shorter the flight, the less fuel will be consumed. Yet neither airlines nor pilots have the freedom to choose the most direct and economical route. Giving pilots freedom to map their own course is an attractive and desirable change in the eyes of the industry, and the impact on the environment would be tremendous. As well as saving considerable amounts of greenhouse gas emissions, the policy will deliver significant benefits in terms of time and expense to the US economy. By obviating significant reductions in service levels associated with more routine applications of emissions reduction policy, it is to be preferred to that approach.

4.) Facilitate Electricity Competition.
By rejecting the model of central regulation and allowing suppliers to meet their customers’ needs more exactly while relying on distributed generation, energy waste and the associated emissions will reduce considerably. This reduction in waste will prove economically beneficial even if emissions themselves do not cause problems.

5.) Reduce Regulatory Barriers to New Nuclear Build.
There is no other technology than nuclear that is proven to be capable of providing emissions-free energy at the scale required to make significant reductions in carbon emissions. The problem is that thanks to anti-nuclear activism by environmentalists in the 1970s, it takes a very long time to build a nuclear plant. This pushes development and construction costs up to the level where it is not economically competitive with higher-emitting forms of electricity generation like coal and natural gas. According to the nuclear energy institute, it takes 10 years from concept to operation to build a nuclear plant, and only four of those are construction, the rest is permit application development (2 years) and decision-making by the Nuclear Regulatory Commission (4 years).