Mark Clayton

A New Boom in Natural Gas Threatens Drinking Water

After decades of declining US natural-gas production, an advanced drilling system so powerful it fractures rock with high-pressure fluid is opening up vast shale-gas deposits.

Instead of falling, US gas production is rising, with up to 118 years worth of unconventional natural gas reserves in 21 huge shale basins, an industry study in July reported. Such reserves could make the nation more energy self-sufficient and provide more of a cleaner bridge fuel to help meet carbon-reduction goals urged by environmentalists. Shale gas reserves have a powerful economic lure.

Companies, states, and landowners could all reap a windfall in the tens of billions. Some also predict lower heating costs for residential gas users as production increases. Now, scores of natural gas companies are fanning out from Fort Worth, Texas, where hydraulic fracturing of shale has been done for at least five years, to lease shale lands in 19 states, including Pennsylvania and New York.

But some warn that by expanding hydraulic fracturing of shale, America strikes a Faustian bargain: It gains new energy reserves, but it consumes and quite possibly pollutes critical water resources. "People need to understand that these are not your old-fashioned gas wells," says Tracy Carluccio, special projects director for Delaware Riverkeeper, a watchdog group worried about a surge in new gas drilling from New York to Pennsylvania and from Ohio to West Virginia. "This technology produces tremendous amounts of polluted water and uses dangerous chemicals in every single well that s developed."

Traditional gas wells bore straight into porous stone, using a few thousand gallons of water during drilling. But dense shale has gas locked inside. Hydraulic fracturing, or fracking, and horizontal drilling unlock it. Each hydraulically fractured horizontal well can require from 2 million to 7 million gallons of fresh water mixed with sand and thousands of gallons of industrial chemicals to make the water penetrate more easily.

This frac-water mixture is blasted at high pressure into shale deposits up to 10,000 feet deep, fracturing them. The sand lodges in the cracks, propping them open and providing a path for the gas to exit after external pressure is released. Besides using vast amounts of groundwater, scientists and environmentalists worry that toxic frac water 30 percent or more remains underground and may years later pollute freshwater aquifers.

Millions of gallons of frac water come back to the surface. It could be treated, but in Texas it is most often reinjected into the ground. Millions more gallons of produced water flow out later during gas production. This flow, too, is often tainted with radioactivity and poisons from the shale. Often stored in pits, that waste can leak or overflow while awaiting reinjection.

Simply put: "Each of these wells uses millions of gallons of fresh water, and all of it is going to be contaminated," Ms. Carluccio says.

"Industry spokesmen say such fears are overblown. The wells we drill & are insulated with concrete," says Chip Minty, a spokesman for Devon Energy, an Oklahoma City-based gas company that pioneered hydraulic fracturing in the Barnett shale formation beneath Fort Worth, Texas. "The purpose is to protect any kind of aquifer or ground water layer. Those processes are controlled by regulatory agencies, and that keeps us safe from any kind of aquifer pollution."

A pioneer in "best practices," Devon has also developed a way to purify and reuse frac water. But those techniques are costly and not widely used at present. Whether such practices will be required elsewhere is an open question.

Targets for this new kind of drilling

One huge target is the Marcellus shale basin that spans large parts of New York, Pennsylvania, Ohio, and West Virginia. States are eager to get to get new revenues and so are many landowners lining up to sign leases.

"I'll be glad to welcome the crews with open arms," writes Al Czervic in the Catskill Commentator, an online publication. "Drill here, my friends," he writes, "Drill here. And then, drill some more."

But amid this gold-rush-type fever in the Delaware and Susquehanna River Basins, voices warn that environmental safeguards and industry standards need to be beefed up before drill bits hit -- or the great gas boom could exact a steep price in polluted water.

"Decades ago, we weren't careful with coal mining," wrote Bryan Swistock, a water resources specialist with the Penn State Cooperative Extension, in a recent statement. "As a result, we are still paying huge sums to clean up acid mine drainage. We need to be careful and vigilant or we could see lasting damage to our water resources from so many deep gas wells."

State environmental agencies and industry experts say multiple systems will be in place to safeguard water.

"The current balanced management approach works -- allowing for effective state regulatory programs that appropriately protect the environment while providing for the essential development of oil and gas," wrote Stephanie Meadows, a senior policy adviser at the American Petroleum Institute, a Washington trade group, in an e-mail response to Monitor questions on hydraulic fracturing.

Where safeguards failed

Still, one can point to examples where those safeguards did not work. New Mexico and Colorado, which have struggled with leakage from frac-water waste pits involving gas exploration, are now moving forward with legislation.

"There are numerous instances in various states of surface water and drinking water contamination from hydraulic fracturing," says Kate Sinding, a senior attorney with the Natural Resources Defense Council in New York. "Nobody, including the industry, has done any in-depth examination to find out the impact on ground water. We are seeing some bad stuff coming out of individual wells and taps."

The nation s shale-gas guinea pigs reside in 15 counties around Fort Worth, where shale-gas extraction using hydraulic fracturing has been validated in recent years. The results have brought wealth to some, but infuriated others.

Charlotte Harris and her husband signed a mineral lease last year. But she's upset now. She sharply recalls a day last November when her drinking-water well died and a new gas well 100 yards from her Grandview, Texas, home was born. She washed dishes that morning as usual, she says in an phone interview. But after a shower, her skin itched terribly and she realized the water had a sulfurous odor.

Later that day, without warning, her toilet erupted. Water shot out of it like Niagara Falls. About that time, she learned, powerful pump trucks at the nearby well site were sending pulses of water mixed with sand and chemicals thousands of feet down into solid shale to fracture it to increase the flow of gas. She and her husband now believe some of that fluid escaped under pressure much nearer the surface.

After the Harrises complained, the drilling company had the water tested but found no problem. Harris's next-door neighbor, John Sayers, had a lab test his well water. The lab found toluene, a chemical used in explosives, paint stripper and often in drilling fluids. Almost a year later, the Harris family well water, once clear and sweet, is murky and foul-smelling. Ms. Harris's husband, Stevan, trucks in about 1,500 gallons twice a week, at 15 cents a gallon.

"We're not using that [well] water for anything at all," Mr. Sayers says. "I was told not to drink, wash, or anything. Not even water my grass with it. "

Is New York City drinking water at risk?

In July, New York s governor signed a bill to permit shale-gas drilling using fracturing technology, which could bring the state $1 billion in annual revenues. But the state is first requiring an updated environmental assessment and may yet require companies to reveal the type of chemicals they mix with the water they shoot down the wells -- something that Texas does not require.

New York City is one of only four large cities in the nation with unfiltered drinking water. It flows from the northern Catskill region. That's the same basin in which gas companies want to drill.

Drilling "is completely and utterly inconsistent with a drinking water supply," said New York City Councilman James Gennaro at a press conference last month. "This would destroy the New York City watershed, and for what? For short-term gains on natural gas."

But while New York has a drilling freeze pending its environmental review, a gas-drilling rush is on in Pennsylvania s Susquehanna River region. Scores of wells are being drilled, with applications pending to drill hundreds more. In the long run, some say there may be 10,000 new gas wells across the region.

We're hearing various stories... about flow backwater," says Susan Obleski, a spokeswoman for the Susquehanna River Basin Commission, which oversees water usage. "We could eventually be seeing 29 million gallons a day usage by this industry. That sounds like a lot, but golf courses use double that."

The concern, however, is that the most productive gas drilling areas tend to be in remote, forested areas, with forested streams headwaters areas. If water is removed in significant amounts from there, it could damage ecosystems and Susquehanna watershed water quality.

The SBRC has issued two cease-and-desist orders to companies illegally removing water. It has told 23 others to clarify requirements, and found that about 50, in all, are vying for water, leases, and drilling permits in the region. Tiny Nockamixon Township, which has resisted gas drilling, is being sued by natural-gas drillers.

The Pennsylvania Supreme Court has agreed to hear a case in which some towns are seeking to overturn lower court decisions that keep municipalities from having laws regulating gas drilling inside their borders.

Back in Texas, some are fighting the practice of reinjecting frac water into the earth. In Erath County, near Fort Worth, Bill Gordon has successfully protested several new commercial injection wells that, according to him, would have pumped as much as 30,000 barrels a day of untreated frac water underground. A recent lightning strike set one such well on fire, proving to Mr. Gordon that volatile chemicals remain in the fluid.

"Nobody knows what's in this drilling fluid," he says. "I think we need to know."

What s being injected deep underground?

Hydraulic fracturing and horizontal drilling are not new. Both date back decades. But their combined use to get gas from shale formations is new within the past decade.

Hydraulic fracturing has long been used to get gas from coal beds, a process some say is similar to shale-gas fracturing.

An Environmental Protection Agency study in 2004 concluded that hydraulic fracturing to get methane gas from coal beds "poses little or no threat" to drinking water supplies. But several EPA scientists have challenged that finding.

"EPA produced a final report ... that I believe is scientifically unsound and contrary to the purposes of law," Weston Wilson, a 30-year EPA veteran, wrote in a whistle-blower petition in 2004. "Based on the available science and literature, EPA's conclusions are unsupportable."

Today, chemicals used in fracturing are considered by the companies to be trade secrets. The Energy Policy Act of 2005 exempts companies from being forced by the Clean Water Act, Safe Drinking Water Act, and other federal laws to reveal what chemicals are in their fracturing fluids. But some say that it s critical to know what s being injected deep underground.

"We're very concerned about this toxic drilling and hydraulic fracturing," says Gwen Lachelt, director of the Oil and Gas Accountability Project in Durango, Colo. "We need to know what's in what they're putting into the ground. "

Water-rich New England Building a Desalination Plant

Far from the arid US Southwest and its longstanding water woes, or even the Southeast and its new water skirmishes -- attitudes are shifting in lush New England.

That's right. Despite abundant lakes and good rainfall, weak groundwater resources have crimped economic growth in some areas. As a result, the first big New England desalination plant turning brackish (salt water, fresh water mix) into fresh is expected to go online in Massachusetts this month.

That surprises some people, but not Robert Tannenwald, an economist and director of the New England Public Policy Center at the Federal Reserve Bank of Boston. Two years ago he did a study showing that New England -- contrary to public perceptions -- is not at all water-rich region, but one that needs to manage its water supplies more carefully and look for new sources.

"There's still a general mind-set [in New England] that water as a resource is not in scarce supply -- but it is," Mr. Tannenwald says. "We waste a lot of water. There's a lot of leaky pipes around here. So economics has to kick in and water has to be priced accordingly for the waste to stop."

Initially, the Aquaria desalination plant, hard by the Taunton River a few miles from its mouth on Narragansett Bay, will supply 4 million gallons of fresh water each day to the city of Brockton 16 miles away. Using a reverse-osmosis process, it will filter salt and other impurities from brackish water flowing up the river from the ocean during high tide.

But not everyone is happy about what could become a regional trend. "The fact we are building desalination plants in New England is really a tragedy," says Christopher Kilian, clean-water program director for the Boston-based Conservation Law Foundation. "This is a region that gets an immense amount of precipitation and where fresh water is being squandered. Before we start pouring costly desalinated water into the bucket, we should make the most of what we have and plug the leaks in the pipes."

But Brockton has done that already, cutting water demand from around 11 million gallons per day to about 9 million. Now it needs the certainty that a steady supply of fresh water will bring to ensure economic growth, observers say.

Alfredo Andres is general manager of the new $60 million Aquaria desalination plant in Dighton, Mass., owned by Inima USA, the US subsidiary of Inima, itself a division of Madrid-based OHL.

"We're glad to be here and think this plant will do a good service for towns in this area," he says, looking out over the Taunton River beside the intake area and the net that keeps fish out.

Eventually, he says, a half dozen other communities could be served by the same pipeline if the plant one day expands its capacity.

"Obviously, the first thing a community must do is conserve its water and fix the leaks in its pipes," Mr. Andres says. "But Brockton has done that and they still need water to grow. So do some of the other towns. We think this is the future."

He may be right. With the decline in processing cost, desalination plants with a combined capacity of about 42 million cubic meters a day are operating worldwide today. They will surpass the 100 million cubic-meter mark by 2016, according to a 2007 report by the Zurich-based Sustainable Asset Management (SAM) group investment firm.

There are numerous desalination proposals being weighed for California and Florida, where Inima is also competing for work. Worldwide, the market for large-scale reverse-osmosis filtration systems is expected to grow nearly 50 percent over the next four years, according to the McIlvaine Company, a Northfield, Ill., market-research firm. Topping its sales list forecast is the US, followed by Japan, Saudi Arabia, China, and Spain.

"We expect to see the greatest growth in the area of desalination, especially in Asia and the Middle East," Robert McIlvaine, the company president, said in a statement.

Desalination won't do for Maude Barlow. The Canadian water warrior is worried that desalination puts control of clean water in the hands of corporations and undermines what should be strong efforts by government to stop waste and pollution of natural supplies.

In her view, the future could include desalination plants ringing the world's oceans to produce costly water for the masses, while the rich will "drink only bottled water found in the few remaining uncontaminated parts of the world."

But don't tell that to Inima's Mr. Andres.

"We think we're doing something really good here," he says. "People in this area need water -- and we're helping them."

Nuclear Power Surge Coming

With this week's application to build a new nuclear plant - the first such filing in nearly 30 years - the industry says the US is on the verge of a nuclear power renaissance.

With virtually no greenhouse-gas emissions, reactors are touted as part of the solution to global warming. Over the next 15 months, the Nuclear Regulatory Commission expects a tidal wave of similar permit applications for up to 28 new reactors, costing up to $90 billion to build.

But the renaissance may be less robust than it looks. Even if the projects are successful and building proceeds at breakneck speed, the lead times are so long and costs so high that it's unclear that the US can build enough nuclear plants to make a dent in greenhouse-gas emissions by 2050. They're so financially risky, experts say, that the only reason building plans are under way is that the federal government has stepped in to guarantee investors against loan defaults.

"Clearly, [nuclear power companies] are not so confident or they wouldn't want the federal government and taxpayer to be guaranteeing the loans," says David Schlissel a longtime nuclear industry analyst with consulting firm Synapse Energy Economics in Cambridge, Mass.

The industry says it needs the aid to get nuclear power rolling again.

"Yes, we need some help and assistance getting these large projects off the ground," says Paul Genoa of the Nuclear Energy Institute (NEI) in Washington. "This will always be labeled as subsidies. But one person's subsidy is another person's incentive. These are the first nuclear power plants to be built in years and there's a role for government here."

Also, loan guarantees don't affect taxpayers unless those loans are defaulted on, he points out.

Under the Energy Policy Act of 2005, the industry already is getting an estimated $12 billion in tax breaks and other largess. The Price-Anderson Act, a law dating from the 1950s, caps the industry's liability at about $10 billion in the event of an accident, even though studies show that a major nuclear meltdown could easily run 50 times that.

Now, the Senate version of a new energy bill includes a provision that could provide tens of billions of dollars more in federal-loan guarantees. On Tuesday, the Energy Department announced it would provide up to $2 billion in federal risk insurance for the first six new nuclear-plant projects, protecting them against losses from regulatory or legal delays.

"In my view, these kinds of taxpayer subsidies are vital to the industry, and they wouldn't be building any of these new nuclear plants without them," says Doug Koplow, president of Earth Track, a Cambridge, Mass., consulting firm that analyzes subsidies for all forms of energy, including biofuels.

The nuclear industry gets about $9 billion a year in federal subsidies, he calculates, trailing only oil and coal in federal energy aid. That amount could go far higher if companies were to begin defaulting on guaranteed loans, he adds.

The nuclear industry has already put Congress on notice that it could require loan guarantees of at least $20 billion for planned projects - and more later, NEI officials told The New York Times in July.

The reason is that nuclear power plants are far more expensive to build than coal- or gas-fired facilities. For example: On Monday, New Jersey-based NRG Energy Corp. filed its application with the Nuclear Regulatory Commission to build two reactors in Texas at a cost between $5.4 and $6.7 billion.

That huge startup cost might make financial sense, given a reactor's low operating expenses, especially if government begins to charge utilities for the greenhouse gases they produce. Nuclear power is virtually emission-free.

But the last time that the nuclear industry was on a building spree - in the 1980s - roughly half of the power plants proposed were never finished, in part because of fears caused by the accident at Three Mile Island. Those that were finished were delayed for years and cost far more than estimated. A number of power companies went bankrupt. In late 2003, NRG - the company that filed Monday's permit application - emerged from bankruptcy caused by overexpansion in the 1990s.

If defaults occur in the new round, critics worry federal costs will be huge.

"This is the second or third 'nuclear renaissance' I've seen," says Tyson Slocum, director of energy program at Public Citizen, Ralph Nader's consumer-protection group. "When you look at the cost of these plants and the massive financial subsidies by US taxpayers, I think that money would be better invested in cheaper sources of emissions-free power that don't have the fatal flaws nuclear power does."

In 2003, a Congressional Budget Office analysis warned of potential default rates of 50 percent or more on new plants.

Wall Street is also skeptical. In a July letter to the Department of Energy, six investment banks, including Citigroup and Goldman Sachs, made it clear that federal guarantees were required. "We believe many new nuclear construction projects will have difficulty accessing the capital markets during construction and initial operation without the support of a federal government loan guarantee," they wrote.

The risks might be worth the cost if nuclear power can have a substantial impact in slowing global warming. But even some industry experts doubt that's possible. To reduce carbon dioxide emissions by 1 billion tons annually, the level set by some scientists as a goal for nuclear power, the world would need to build 21 new 1,000-megawatt nuclear plants per year - about five of those annually in the US - for the next 50 years, says a Keystone Center report endorsed by the NEI. The US industry reached that level in the 1980s. But even under its most optimistic assessment, the Energy Information Administration recently projected that only about 53 nuclear power plants would be built by 2056. At that rate, this would not even replace the existing nuclear capacity expected to be retired during that time, the Keystone report said.

While such a conclusion would seem to blunt nuclear power's appeal, industry experts predict that climate legislation is likely to boost the cost of carbon-dioxide emissions. When it does, nuclear power construction will be suddenly very competitive with coal power - and that will accelerate growth faster and farther than predicted, they add.

Nuclear power "clearly can't do it all, but will do its share" to mitigate greenhouse-gas emissions, says Mr. Genoa.

How Vermont May Force the Auto Industry and Congress to Address Climate Change

When historians finally take stock, Vermont may look like the mouse that roared -- the tiny state that brought the nation's mighty auto industry to heel by requiring cars that emit fewer greenhouse gases.

This is one scenario that could unfold following a federal judge's ruling Wednesday, which upheld a Vermont law patterned after California's mandate that the carbon-dioxide emissions of cars sold in the state must be slashed 30 percent by 2016.

The judge's finding -- that federal fuel-economy laws are not in conflict with state emissions laws -- is particularly significant, coming on the heels of a US Supreme Court decision in April. That ruling found that the Environmental Protection Agency has the authority to regulate greenhouse-gas emissions, legal experts say.

On the one hand, Wednesday's decision strengthens the hand of states that want to take action against global warming. But in the longer term, the impact from the ruling could lead to one nationwide standard, which is already expected by many.

In addition to the 12 states with California-style laws on the books, another six are close to acting. The ruling this week could start dominoes falling by:

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Earth too Warm? Just Bury the CO2

Under a blazing west Texas sun, with a whiptail lizard and cattle looking on, Rebecca Smyth works with an assistant to lower a measuring line, then a hose, and finally a slender plastic capsule down an old water well 200 feet deep.

She's hoping the water samples she collects will yield clues to what is, arguably, one of mankind's most pressing environmental questions: Can nations bury their greenhouse gases?

If they can, then governments will have bought themselves a decades-long respite as they search for less carbon-intensive energy sources. If they can't, then a significant rise in global temperatures by 2100 looks inevitable, if fossil-fuel consumption continues at its current pace.

And the answer may well lie here, atop an old west Texas oil field known simply as SACROC, where more CO2 has been pumped underground over a longer period of years than anywhere else on Earth. Her efforts -- and those of the rest of a small army of scientists funded by the US Department of Energy -- are being closely watched. Energy companies want to know their options as Congress mulls over legislative options to global warming. Environmentalists are eager to find ways to slow the rise of greenhouse gases.

"If we don't sequester carbon from coal, we won't be able to stabilize the concentration of CO2 in the atmosphere," says John Thompson, director of the coal transition project of the Clean Air Task Force, a Boston-based environmental group. "It's the linchpin."

Admittedly, pumping huge amounts of carbon dioxide into underground caverns sounds audacious. If the US captured just 60 percent of the CO2 emitted by its coal-burning power plants and reduced it to a liquid for injection underground, the daily volume would roughly equal what the US consumes in oil each day -- about 20 million barrels, according to a report by the Massachusetts Institute of Technology in Cambridge. And the risks are substantial.

Inject too much CO2 and the resulting pressure could cause earth tremors or push deep super-salty groundwater up into freshwater aquifers. Once pumped in, the CO2 may not even stay put in the sandstone formations, below layers of shale and other rock.

Nevertheless, researchers sound confident. "I grew up near Love Canal, so I know the problems of putting stuff underground," says Sue Hovorka, a research scientist at the University of Texas at Austin. "But we're cautiously optimistic this is going to work."

She is one of the scientists tracking the movement of carbon dioxide underground in the nation's first deep-sequestration experiment.

Under a torrid midday sun in the old Liberty oil field south of Houston, she is tracking the progress of about 2,000 tons of food-grade CO2 that she had injected into a well in 2004 and again last fall. Unlike SACROC (Scurry Area Canyon Reef Operators Committee), no CO2 had ever been injected here before, so it should be straightforward to track. But at the moment, Dr. Hovorka is not happy.

Nearly a mile below, her sensitive instruments are trapped in a five-inch steel pipe, and the roughnecks on the rig have spent hours trying to pull them out. A colleague opts to use small explosives to dislodge them. An hour later, the instruments are on their way to the surface and water samples are being analyzed from an adjacent well.

So far, the results are positive.

"Right now the CO2 is stored as small bubbles in the pore spaces of the sandstone," Hovorka says. "We believe it's immobilized and will sit there on a 10,000-year time frame and that when we open this well later nothing will happen. We don't expect any geysers of escaping CO2 or any of the things that people worry so much about."

The amount of potential storage is vast. Three of the five US geologic storage possibilities under review -- salt basins a mile or more deep, mature oil and natural-gas reservoirs, and deep unminable coal seams -- could permanently hold at least two centuries' worth of US CO2 emissions -- about 6 billion metric tons a year, researchers estimate.

But many steps lie ahead. These geologic formations must be tested for environmental safety and their ability to retain CO2. New power-generation technologies that can economically capture CO2 emissions must be developed. Finally, pipelines and infrastructure must be built to collect CO2 from emitters to move it to geologic storage.

Perhaps America's best hopes for geologic sequestration lie with the sandstone formations holding super-salty groundwater here on the Texas coast -- as well as the dwindling oil fields across its vast breadth, says Ian Duncan, associate director of the Bureau of Economic Geology at the University of Texas at Austin. Together, these two geological assets could hold all of America's CO2 emissions for at least the next 40 years, he estimates, enough time to help bridge the gap until solar power or other emissions-free sources of energy become common.

"The question will end up being: How much capacity can we find for injecting large amounts of CO2 over decades?" says Ernest Moniz, an MIT professor and coauthor of the March report that criticized the government for not expediting large-scale sequestration research. "Will we, for instance, be able to inject the CO2 output of 50 big power plants in the ground and have it stay there?"

High-volume CO2 injections of 1 million tons or more are expected to begin in Cranfield, Miss., later this year to push out hard-to-reach oil and to test further the feasibility of geologic storage.

Back in Snyder, Smyth keeps a lookout for rattlesnakes from under her broad-brimmed hat as she collects water samples. She'll compare them with other samples from nearby areas where CO2 is not a factor. Slight chemical differences could yield clues about whether the CO2 is staying put or expanding upward.

"We're not sure we're going to see any significant impact from CO2 here," Smyth says. "But if the impacts are going to show up anywhere in the world, they should show up here where CO2 has been injected so long."

A Carbon Cloud Hangs Over Green Fuel

Late last year in Goldfield, Iowa, a refinery began pumping out a stream of ethanol, which supporters call the clean, renewable fuel of the future.

There's just one twist: The plant is burning 300 tons of coal a day to turn corn into ethanol -- the first US plant of its kind to use coal instead of cleaner natural gas.

An hour south of Goldfield, another coal-fired ethanol plant is under construction in Nevada, Iowa. At least three other such refineries are being built in Montana, North Dakota, and Minnesota.

The trend, which is expected to continue, has left even some ethanol boosters scratching their heads. Should coal become a standard for 30 to 40 ethanol plants under construction -- and 150 others on the drawing boards -- it would undermine the environmental reasoning for switching to ethanol in the first place, environmentalists say.

"If the biofuels industry is going to depend on coal, and these conversion plants release their CO2 to the air, it could undo the global warming benefits of using ethanol," says David Hawkins, climate director for the Natural Resources Defense Council in Washington.

The reason for the shift is purely economic. Natural gas has long been the ethanol industry's fuel of choice. But with natural gas prices soaring, talk of coal power for new ethanol plants and retrofitting existing refineries for coal is growing, observers say.

"It just made great economic sense to use coal," says Brad Davis, general manager of the Gold-Eagle Cooperative that manages the Corn LP plant, which is farmer and investor owned. "Clean coal" technology, he adds, helps the Goldfield refinery easily meet pollution limits -- and coal power saves millions in fuel costs.

Yet even the nearly clear vapor from the refinery contains as much as double the carbon emissions of a refinery using natural gas, climate experts say. So if coal-fired ethanol catches on, is it still the "clean, renewable fuel" the state's favorite son, Sen. Tom Harkin likes to call it?

Such questions arrive amid boom times for America's ethanol industry.

With 97 ethanol refineries pumping out some 4 billion gallons of ethanol, the industry expects to double over the next six years by adding another 4.4 billion gallons of capacity per year. Tax breaks as well as concerns about energy security, the environment, and higher gasoline prices are all driving ethanol forward.

The Goldfield refinery, and the other four coal-fired ethanol plants under construction are called "dry mill" operations, because of the process they use. The industry has in the past used coal in a few much larger "wet mill" operations that produce ethanol and a raft of other products. But dry mills are the wave of the future, industry experts say. It's their shift to coal that's causing the concern.

More plants slated for Midwest, West

Scores of these new ethanol refineries are expected to be built across the Midwest and West by the end of the decade, and many could soon be burning coal in some form to turn corn into ethanol, industry analysts say.

"It's very likely that coal will be the fuel of choice for most of these new ethanol plants," says Robert McIlvaine, president of a Northfield, Ill., information services company that has compiled a database of nearly 200 ethanol plants now under construction or in planning and development.

If all 190 plants on Mr. McIlvaine's list were built and used coal, motorists would not reduce America's greenhouse gas emissions, according to an in-depth analysis of the subject to date by scientists at University of California at Berkeley, published in Science magazine in January.

Of course, many coal-fired ethanol plants on the drawing board will not be built, Mr. McIlvaine says. Others in planning for years may still choose natural gas as fuel to meet air pollution requirements in some states.

Other variations on ethanol-coal are emerging in Goodland, Kan., and Underwood, N.D., where ethanol plants are being built next to coal-burning power plants to use waste heat. Efficient, but still coal.

That could spell trouble for ethanol's renewable image.

"If your goal is to reduce costs, then coal is a good idea," says Robert Brown, director of Iowa State University's office of biorenewables. "If the goal is a renewable fuel, coal is a bad idea. When greenhouse-gas emissions go up, environmentalists take note. Then you've got a problem."

Ethanol industry officials say coal-power is just one possibility the industry is pursuing.

"I think some in the environmental community won't be all that warm and fuzzy about [coal-fired ethanol]," says Bob Dinneen, president of the Renewable Fuels Association, the national trade association for the US fuel-ethanol industry. "It's fair to say there's a trend away from natural gas, but coal is just one approach. Other technologies are part of the mix, too."

He cites, for instance, a new ethanol plant in Nebraska strategically located by a feed lot, using methane from cattle waste to fire ethanol boilers. Another new plant in Minnesota uses biomass gasification, using plant material as its fuel.

Coal for now, wood in the future

Coal may end up being merely a transitional fuel in the run-up to cellulosic ethanol, including switch grass and wood, says another RFA spokesman. While ethanol production today primarily uses only the corn kernel, cellulosic will use the whole plant.

Cellulosic ethanol, mentioned by President Bush in his State of the Union speech, could turn the tide on coal, too, by burning plant dregs in the boiler with no need for coal at all.

"It's a fact that ethanol is a renewable fuel today and it will stay that way," says Matt Hartwig, an RFA spokesman. "Any greenhouse-gas emissions that come out the tailpipe are recycled by the corn plant. I don't expect the limited number of coal-fired plants out there to change that."

Still, Hawkins insists that if ethanol is made using coal, the carbon dioxide should be captured and injected into the ground.

"We favor getting ethanol production up," Hawkins says. "But we obviously favor a cleaner process. We need large cuts in global warming emissions from transportation. It's not good enough for ethanol to simply be no worse than gasoline."

Hybrid-Happy?

Actress Cameron Diaz and Roy Jefferson, a retired government accountant from Fargo, N.D., have something in common: They both love their hybrid gas-electric cars that get 50-plus miles per gallon.

"I laugh when I go by the gas stations" without filling up, says Mr. Jefferson, an octogenarian.

The growing enthusiasm for hybrids is rattling the faith of America's automakers, who have long believed that consumers don't care about fuel efficiency. And it has opened the door to a new theory that hybrid cars — long predicted to be a niche market and a way station to future hydrogen autos — are themselves the answer to revolutionize the fleet and trim the nation's surging dependence on foreign oil.

For proponents of energy independence in the United States, the current level of dependency is worrisome. Last year, 56 percent of the nation's oil -- some 11 million barrels a day -- came from abroad. That's far more than the one-third share imported during the first oil crisis of the 1970s. And it's halfway to the two-thirds share projected for 2025, if nothing changes.

To reduce that dependence will require a massive modernization of America's transportation fleet, especially more efficient passenger cars and light trucks. So are hybrids up to the task?

Most auto analysts still say no, since an enormous number of hybrids would have to be sold over more than a decade to have a real impact. Still, demand for hybrids, the Prius in particular, is so strong that customers are waiting weeks to get one. Some used 2004 Priuses are selling for thousands of dollars more than the cost of a new one. On Tuesday, Toyota announced it would begin building its first North American hybrid car in 2006 at its Georgetown, Ky., plant.

The numbers are turning some heads.

"I was a huge skeptic," says Walter McManus, an auto industry researcher at the University of Michigan's Transportation Research Institute in Ann Arbor. "But I've basically crossed over to the dark side. You can't argue with the market reaction." He estimates Toyota, Honda, and others will sell at least 1.2 million hybrid vehicles by 2010 -- about 7 percent of the US market - and possibly much higher.

If all U.S. cars (not including light trucks) were Priuses today, the nation would save 15 percent more oil than it received from the Persian Gulf in 2002, writes energy-efficiency guru Amory Lovins in his recent book Winning the Oil Endgame.

Of course, a sudden switch is virtually impossible, since there are roughly 235 million cars and light trucks on the road in the U.S. today. Less than one-tenth of 1 percent of those — some 200,000 — are hybrids. So the speed of the conversion will determine how much imported oil the nation might save.

"In our view the hybrids represent a long-term trend toward a dramatically more efficient fleet," concluded consulting firm Booz Allen Hamilton in a 2004 report.

For example: If consumers keep snapping up hybrids and automakers begin to integrate the technology throughout their product lines — including pickup trucks — then hybrids might quickly reach 20 percent of new vehicle sales by 2010 and 80 percent by 2015, according to another Booz Allen Hamilton report. That's the most optimistic of three scenarios the management consulting firm laid out. In the "high adoption" scenario, hybrids would save 2 million barrels of gasoline a day by 2015; in the "medium adoption" scenario, 800,000 barrels of gasoline.

Other estimates vary widely. Hybrids could be 10 percent to 15 percent of new vehicle sales by 2012, the Department of Energy's Oak Ridge National Laboratory concluded in a report last summer. Together, hybrids and efficient "clean diesels" could be 40 percent of new car sales by then if the technologies are widely adopted, it said.

But with gasoline use increasing 1.7 percent a year through 2025, hybrids' impact on oil consumption will be small, according to the latest outlook by the US Department of Energy. It predicts only 1.1 million hybrids will be sold in 2025. Even in the most optimistic case, assuming rapid adoption of hybrid and other car technologies, the U.S. would still chop only 172 million barrels of oil a year by 2025 — about 2.5 percent of expected oil imports that year. On the other side, Mr. McManus predicts more hybrids will be sold in 2010 than the DOE's 2025 estimate.

So who's right? Consumers are eager. Last month, 49 percent of new-car buyers, the highest level ever, had changed their mind or were thinking strongly about buying a vehicle they would not have considered because of gas prices, according to a survey by Harris Interactive and Kelley Blue Book.

"We're going to have many, many choices," says Ron Cogan, editor and publisher of Green Car Journal, a monthly magazine devoted to energy-efficient and environmentally friendlier cars. "Hybrids are here right now. They're quite clearly the next big thing. To look off into the future for hydrogen is not giving enough credit to what we have here and now."

Nissan plans to offer a hybrid version of its popular Altima model using Toyota technology next year. Even GM says it will soon offer "mild hybrid" technology that stops a car's motor while stuck in traffic — and automatically restarts it. At least 17 hybrid-electric models will be available in the US market by 2006 with 38 forecast by 2011, market research company J.D. Power and Associates reported in February.

Even so, the company is not bullish about hybrids. "Despite the significant growth in the number of models and annual sales over the next five years, we anticipate hybrid market share to reach a plateau of about 3 percent near the end of the decade," writes Anthony Pratt, a senior manager at J.D. Power, in the report.

Conventional wisdom holds that the long-expected growth of hybrids will be slow. Skeptics abound.

"They make a nice story, but they're not a good business story yet because the value is lower than the cost," said Carlos Ghosn, chief executive of Nissan Motor Co., at the National Automobile Dealers Association convention in New Orleans in January.

Even McManus — the hybrid cynic-turned-believer — has serious doubts about how big an impact even a massive surge in hybrid sales will have on reducing America's oil dependence. His analysis, for instance, shows a "rebound effect." For every 1 percent decline in the cost of fuel, Americans drive 1.85 percent more.

Another factor working against hybrids' overall impact on cutting oil imports is the rising number of vehicles on American roads. The fleet grows about 1 percent a year. "I can't imagine a circumstance where we can reduce it enough to cut a significant portion of what we get from over there," McManus says.

Nevertheless, with gasoline prices at more than $2 a gallon, Detroit auto executives seem to be changing tack. Hybrids could be everywhere in the future, if hybrid is defined broadly as any vehicle that uses more than one method of providing power to the tires, some say.

"If you think about the 15- to 20-year time frame, you could argue that all vehicles are going to be hybrids," Michael Tamor, manager of Ford Motor Co.'s Sustainable Mobility Technologies, reportedly told a conference of the Society of Automotive Engineers in February. Meanwhile, the head of GM, Robert Wagoner, has recently said hybrids are important after all. The company is said to be seeking access to Toyota's hybrid technology.

"All we've been hearing for 15 years is that consumers don't care about fuel efficiency, that they care more about cupholders than fuel economy," says Bradley Berman, editor and publisher of Hybridcars.com. "I would say that fuel economy is the new cupholder."

If hybrids do indeed become the "next big thing," with a bigger impact on U.S. oil consumption than is still today widely believed, it probably won't be because of eco-celebrities like Ms. Diaz, but because of a shift by masses of ordinary Americans, Mr. Cogan says.

Unlike Diaz, who has her own environmental show on television, Mr. Jefferson, is an avowed Republican who doesn't at all mind drilling for more oil in Alaska's wildlife refuge. Still, three years ago he decided he wanted something different in a car. And he liked the idea of cutting pollution a bit - and helping the U.S. rely less on foreign oil, too. So he bought a Toyota Prius.

What does he think of hybrids? Are they the next big thing that will help America get free from imported oil? "I'm no scientist," he says. "But I wouldn't bet against it."

Birds On the Brink

When R. Given Harper set out to understand why North America's migratory birds were declining, he set a unique course. While other researchers zeroed in on habitat loss as a key problem, he decided, on a hunch, to look at an old culprit -- the pesticide DDT -- and its specific effects on songbirds.

The results were intriguing. Traces of DDT and other related chemicals were showing up in the birds. But the real shock came when Dr. Harper, a biology professor at Illinois Wesleyan University in Bloomington, compared his results with DDT levels in nonmigrating songbirds. These year-round residents of North America -- including a who's who of birds like the northern cardinal, black-capped chickadee, and dark-eyed junco -- had more kinds of chemicals and dramatically higher levels of them than the migrating species.

Those are surprising results. Heavily restricted in the United States since 1972 and a declining problem for eagles, osprey, and other predatory birds, DDT continues to show up in alarming levels in nonmigrating songbirds. Does that spell trouble ahead for these still-healthy species? Are humans at risk? No one knows. But one lesson seems clear: Beware of what you put into the environment, because it can be extraordinarily difficult to remove.

"These [findings] are reminders that our decisions are going to affect us for decades," says Greg Butcher, a senior scientist with the Audubon Society and author of a recent "State of the Birds" report that showed many North American species in decline. "There may not be a toxic effect that kills birds at these levels. But it very well could affect their embryonic development."

Harper's findings are puzzling partly because of their geographical specificity. Some 18 species that reside year-round in North America have roughly 1 to 10 parts per million of DDT -- 2 to 10 times the levels of those that migrate to Latin America. Also, all 17 of the organochlorine compounds that Harper tested for -- chemical cousins to DDT -- appear in each of those nonmigrating species. In contrast, one to five of the compounds were found in migrating birds.

Those are preliminary findings from a yet-to-be published study, although they build upon Harper's decade of peer-reviewed research on the same topic. His findings also parallel Canadian and US research that show organochlorines bioaccumulating in other North American bird species, experts say.

"These birds are the canaries in the coal mine, warning us about what's going on in our environment," says Theo Colborn, coauthor of Our Stolen Future, a 1996 book that focused on developmental problems caused by pesticides and other man-made chemicals.

Such conclusions are premature, say spokesmen for the chlorine industry. They note that Harper's research has not been peer-reviewed yet. "It would be a mistake to say, not knowing the levels, how significant his findings are compared to others," says Kip Howlett, executive director of the Chlorine Chemistry Council (CCC), a trade association in Arlington, Va. Since DDT was banned, bald eagles and several other species have been rebounding, he says.

Just why North American songbirds that do not migrate have high levels of metabolized DDT and other organochlorines in their bodies remains a mystery, Harper says in a phone interview.

One hypothesis: The US used far more DDT than Latin America, so there may be a lot still lingering in the soil, he says. About 1.4 billion pounds were used in the US from World War II until 1972, the Environmental Protection Agency says.

Harper's findings suggest that any reintroduction of banned chemicals could have "a more immediate and dramatic toxic effect than we saw the first time around," Dr. Butcher says.

At least 50 countries ban DDT use although it is still legally used for malaria control in 20 nations, experts say. The US and other nations have also banned several related organochlorine pesticides, such as chlordane and dieldrin. Others, such as lindane and endosulfan, are still registered for use.

So far, Harper's research has focused on detecting organochlorine levels in birds, not on their effects. "We're not certain of the specific impacts of these compounds on birds," he says. "We suspect the presence of these pesticides may at least play a part in the decline of neotropical migrants and may cause trouble for some nonmigrants, too."

The DDT and six other organochlorine compounds that Harper found in the birds are related to chemicals banned by international treaty. The treaty, the Stockholm Convention, labels them as "persistent organic pollutants," or POPs, because they remain in animals, humans, and the environment for years. They also tend to evaporate in warm climates and blow on the winds to cold, northern reaches, where they concentrate. Pesticides like DDT and lindane show up in high concentrations in Inuit populations, seals, and polar bears, Dr. Colborn notes.

Early next month in Uruguay, more than 50 nations will discuss rules for adding new chemicals to the POPs ban treaty, which came into force last year.

The US chemical industry and President Bush hailed the treaty, and the US signed it in 2001. Yet legislation to enact it is currently stymied in Congress. Legislators disagree whether to include tough language that would automatically ban new chemicals in the US as they are added to the treaty list.

But until the US ratifies the treaty, it will only be an observer and not permitted to vote on the new mechanism or on any chemicals that may be nominated for addition to the list, observers say.

"We support the treaty itself and its implementation into US law," says Michael Walls, managing director of the American Chemistry Council, an industry association in Arlington, Va. "We've been encouraging the Bush administration and Congress to move quickly.... The unfortunate consequences of not having ratified the treaty is that the US won't have a vote at the first meeting."

One of the first chemicals that some say could be nominated for addition to the list is lindane, which Harper found in most of his songbirds in North America. It's a pesticide used to treat seeds and also an ingredient in shampoo to combat head lice.

In California, where lindane-based shampoo is banned, a state agency reported one rinsing of lindane shampoo could contaminate 6 million gallons of water, notes Kristin Schafer, program coordinator at Pesticide Action Network, an environmental group in San Francisco. New York is also weighing a ban, she says.

A major reason scientists worry about DDT and other organochlorines is that they are powerful "endocrine disruptors," whose effects on humans and wildlife are little known. Colborn and Harper charge that such chemicals can, even in tiny amounts in the body, interfere with embryo development and harm reproduction and survival.

"Every one of these chemicals has an endocrine disruptor effect that can harm the development of the embryo by interfering with hormones," Colborn says. She says there's growing evidence of a link between organochlorines and learning disabilities and human disorders, which have multiplied since such chemicals came into common use.

But the issue is dosage, not detection, counters the American Council on Science and Health, a nonprofit group advised by scientists and others and created to counter activists' claims. "Current levels of environmental chemicals in the general population are well below those considered to be associated with adverse effects and thus do not pose a risk to public health," it concluded in a 2003 book.

And regulation of current pesticides already takes into account bioaccumulation, writes a spokesman for CropLife America, a trade group representing pesticide manufacturers, in an e-mail.

Deeper studies may be needed to settle the issue fully. Although pesticides have been thoroughly tested, the human hormone system is so complex that there are no generally accepted methods to screen chemicals for adverse health effects, the CCC website says.

Glenn Wiser, a senior attorney with the Center for International Environmental Law, disagrees: "The lesson from the songbirds is that DDT and other POPs are still used worldwide and are still a problem."

Life on Tired Earth

For hundreds of years, cod swarmed in waters off Newfoundland's rugged coast. But by 1992, rampant overfishing had crushed the cod. Price tag to people: tens of thousands of jobs lost and billions of dollars spent in job retraining.

Last year, a weather satellite spotted a monster dust cloud over Africa — hard to miss at 5,000 miles wide. Tree-cutting in northern Africa helps nourish such clouds, which cross the Atlantic, settle into U.S. coastal waters, and possibly contribute to toxic algae blooms. Price tag to people: breathing problems for U.S. coastal residents.

Cod depletion and dust clouds seem like pretty different problems. But they each play a role in the overall environmental degradation of the planet — a condition that a new global study says has escalated so quickly over the past 50 years that it outpaces anything experienced by ecosystems in human history. Demands for water, food, fuel, timber, and fiber — all part of global economic expansion -- have driven the change. The result: a big increase in short-term human benefits, less hunger, and more wealth. But this progress has been counterbalanced by a massive loss of diversity of life on Earth.

That's the state of the world, according to the first Millennium Ecosystem Assessment produced by some 1,300 scientists from 95 countries charged with painting a global eco-portrait. The United Nations-sponsored study was funded by the World Bank and several private foundations.

"We've had many reports on environmental degradation, but for the first time we're now able to draw connections between ecosystem services and human well-being," says Cristian Samper, director of the Smithsonian Institution's National Museum of Natural History in Washington and a chief architect of the study.

Northern Africa's drying Sahel region and Newfoundland's emptier coastal waters, he says, are just two examples in an overall conclusion that 60 percent of the world's ecosystems are being degraded or used unsustainably. Ecosystems being drained or degraded largely in the pursuit of human well-being include:

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Assessing the Jet Threat

Gazing into a clear blue Wisconsin sky, David Travis was amazed by what he did not see: not one fluffy airliner contrail. Not that day or in the two days that followed the 9/11 terror attacks, when commercial airliners in the United States were grounded.

For Dr. Travis, a climatologist at the University of Wisconsin at Whitewater, that tragedy had a tiny silver lining. A sky without jet contrails became a once-in-a-lifetime opportunity to see if the skinny, man-made clouds really did affect climate, as he had long suspected.

Little is known about the global climate effects of airliner exhaust. Although jets create far less greenhouse gas than power plants or automobiles, they have an outsize impact because of where they spew it – the delicate upper troposphere and lower stratosphere, five to seven miles up from Earth's surface. And an expected boom in airline travel in coming years is likely to swamp any efficiency gains from the next generation of airliners, such as the just unveiled Airbus A380.

The result: growing scientific concern that jets may be turning the skies into a hazier, heat-trapping place.

"Airliners are special because even though their total emissions are relatively small, compared to other sources, they're putting their emissions directly into the upper troposphere," says Joyce Penner, a University of Michigan professor of atmospheric science and lead author of a landmark report on aviation and the atmosphere. "It's a special location."

When injected together into the icy atmosphere, the mix of exhaust gases – including water vapor, unburned hydrocarbons, particulates, sulfates, nitrogen oxides (NOX), and carbon dioxide – produces clouds and has two to three times the warming effect of carbon dioxide alone, Massachusetts Institute of Technology researchers reported last year.

That finding meshes with what Travis found. Comparing ground temperature readings during the 9/11 flight ban with those after and before it, Travis found that those seemingly inconsequential wisps fanning out miles above the earth were like a blanket, reducing temperature fluctuations nationwide.

Travis's findings heightened scientists earlier suspicions that the cirrus clouds formed from contrails did much more than just suppress temperatures – perhaps playing a bigger role in global climate change than many had suspected. A key 1999 international report had cited airliner exhaust as responsible for 3.5 percent of the climate warming shift.

By 2050, carbon-dioxide emissions from airliners are expected to grow two to 10 times the 1992 level, thanks to increasing air traffic, according to the Intergovernmental Panel on Climate Change report co-authored by Dr. Penner. By then, aircraft emissions will have risen to 5 percent of the cause of global warming, IPCC says.

New research suggests the problem could be even bigger. "Contrails can be called a cause of warming and definitely need to be considered in climate-change models," says Patrick Minnis, an atmospheric scientist at Langley Research Center in Hampton, Va., part of the National Aeronautics and Space Administration.

Hot Under the Contrail

Contrails not only can reduce temperature variations, but also increase surface temperatures – enough to account for the entire warming trend in the U.S. between 1975 and 1994, according to a study Dr. Minnis published last year. Still, he notes, additional research is needed. Just because contrails "could account for all the warming, it's not absolutely certain they did," he says.

Other scientists say neither contrails nor airliner exhaust poses much of a warming threat.

"If you're worried about the planet warming up, airplanes are not the first place to look to reduce the impact," says Andrew Gettleman, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colo. "It's a fairly small piece of the puzzle. ... More than 95 percent of global warming is caused by other things, like power plants."

Much of the concern over contrails' potential impact on climate is coming from the European Community, which, ironically, unveiled the world's largest airliner last month. The four-engine Airbus A380 – far larger than a Boeing 747 – carries up to 840 passengers. Not to be outdone, Boeing is ramping up production of its twin-engine 7E7 Dreamliner, the first carbon-composite airliner that will be lighter and burn far less fuel per passenger mile than older airliners.

Improving fuel efficiency is one of the big environmental success stories in aviation. Better engines, aerodynamics, and other factors have improved airliner fuel efficiency 60 percent in the past 35 years, says Ian Waitz, a professor of aeronautics at the Massachusetts Institute of Technology and an authority on airliner emissions' impact on the atmosphere.

Although the A380 and 7E7 will sport even more fuel-efficient engines, they will add to an already burgeoning global fleet of some 12,000 airliners. Airbus hopes to sell more than 700 of its megaliners; and Boeing, more than 2,500 of its Dreamliners.

"Even with a 40 to 50 percent improvement in fuel efficiency, you're faced with a 3 to 20 factor increase in the amount of travel, so we are going to have to have big increases in emissions with that kind of growth," says David Greene, a co-author of the IPCC report and scientist at the Center for Transportation Analysis at Oak Ridge National Laboratory in Tennessee. Because it will take decades to turn over the global fleet, pollution will moderate only very slowly, he says.

Future contrail scenarios depend much on how much fuel is burned – and at what altitude. One possible solution, noted by researchers in England, would be to fly at lower, warmer altitudes. Contrails require moist yet very cold air to form, prevalent over some regions, such as the American Midwest, or Northern and Western Europe. By flying 6,000 feet lower, aircraft would produce fewer contrails, a team of scientists from Manchester Metropolitan University reported in 2003.

But flying lower in denser air would cut fuel efficiency. Burning more fuel would increase carbon dioxide output, possibly neutralizing benefits, other point out.

Efficiency Problems

Even today's more efficient engines have a downside. The ever higher pressures and internal fuel-combustion temperatures that such engines require tend to increase NOX emissions – a major ingredient in smog. Special combustion-chamber designs and technology can reduce NOX formation. And such "low-NOX" exhaust options have been available for one of today's most popular engines – yet few are purchased because of the extra cost, experts say.

Unless low-NOX engines become more popular, NOX could grow more than fourfold over 1992 levels by 2050, IPCC forecasts.

Even so, the NOX issue is small potatoes, says Professor Waitz in an e-mail. "We should be concerned about all potentially important environmental impacts, but we must also recognize that aviation is a relatively small contributor."

For others, however, contrails pose a threat of growing gradually into a murky blanket that reduces earth's temperature swings and dims the sun – a scenario that would hurt crops and even maple-sap harvests by helping harmful insects survive.

"The jet-contrail problem is not really a pollution problem – it's a cloud problem," notes Dr. Travis back in chilly Wisconsin. "We're disrupting the natural radiation and energy balance of the planet ... trapping outgoing radiation and blocking incoming sunshine. And that makes the world a cloudier, warmer, less enjoyable place."

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