The bulk of the company’s future barrels lie in hard-to-access fields deep beneath seawater, in the Arctic, and in nearly impenetrable geological formations in Colorado and elsewhere, requiring extensive drilling and massive infusions of chemicals and freshwater to flush them out. These reserves are truly the bottom of the barrel in terms of the world’s hydrocarbon supplies, viable only in a regime of high energy prices and lax environmental restraints. Much of Exxon Mobil’s untapped natural gas, for example, is the so-called sour type, laden with toxic chemicals that are expensive to remove. And by far its single-biggest undeveloped deposit is the Canadian tar sands, the hydrocarbon muck found beneath northern Alberta’s vast boreal forest. Exxon Mobil and others are making plans to mine the region’s bitumen sand on an immense scale—with grim ramifications for the environment, near and far. Last year, were it not for newly reported reserves of 1.1 billion oil-equivalent barrels of Canadian bitumen, Exxon Mobil’s proved reserves would have significantly declined.

Separating the bitumen oil from the sand and clay that surrounds it requires a huge influx of energy in the form of heat and steam. Canada is burning vast amounts of natural gas for the job. The result: Every barrel of crude from tar sands releases three to five times as much carbon dioxide into the atmosphere as a barrel of oil produced conventionally. The process also sucks up enormous quantities of fresh­water and spews it out as tailings waste into giant lake beds of toxic sludge.

“We’re exchanging a clean-burning fuel”—natural gas—“for a dirty fuel, and we’re using freshwater to do it,” says Philip Weiss, an energy analyst with Argus Research Co. In a statement, Exxon Mobil disputed that the tar sands projects are environmentally damaging. “The oil-sands industry currently accounts for only 4 percent of Canada’s total emissions,” according to the company.

Inside Exxon Mobil, senior management sees its own “corporate social responsibility,” as Tillerson put it at last year’s annual meeting: satisfying the world’s insatiable appetite for oil and natural gas. Tillerson also frames this mission in moral terms: What right do Western environmentalists have to push basic amenities like electricity and car travel beyond the reach of millions of people just emerging from poverty in the developing world? “Who are we to say, ‘We’ve got ours; you can’t have yours’?” says a recently retired Exxon Mobil executive.

Since taking over for Lee Raymond in 2006, Tillerson has softened his predecessor’s combative stance on global warming, but he certainly hasn’t replaced it. The company acknowledges that temperatures and greenhouse-gas levels are both rising, but Tillerson has said he isn’t convinced that there’s a causal link between the two. Still, recognizing the risks, Exxon Mobil now says it’s willing to entertain greenhouse-gas restrictions, as long as these efforts are on an equal footing with “other important world priorities, such as economic development, poverty eradication, and public health.” Tillerson has recently expressed a preference for a carbon tax over a cap-and-trade system because he says a straight tax would be more efficient.

Such statements only further infuriate the company’s critics, who say Exxon Mobil’s concerns at this juncture amount to posturing. Although an overwhelming consensus may exist among scientists that global warming is real, Exxon Mobil can point to the lack of universal agreement about the prudence of spending hundreds of billions of dollars over several decades on carbon-reduction programs to reverse the trend. The noted physicist Freeman Dyson, for example, who has no quarrel with the warming data, has suggested that it might be a more humane public policy to spend some of that money on addressing immediate problems—eliminating poverty or infectious diseases, for example—while searching for cheaper technological fixes to greenhouse-gas emissions.

Still, after intense pressure from environmental groups and some members of Congress, Exxon Mobil has stopped funding certain high-profile global-warming skeptics such as the Competitive Enterprise Institute. But in the most recently available financial data, the company was still plowing millions of dollars into other conservative groups that stoke doubts about climate change. “Exxon is a purveyor of carbon. We’re not ‘beyond petroleum,’ ” says one of the company’s former lobbyists in Washington. And though the curmudgeon Raymond is gone, the operative who actually built Exxon Mobil’s global-warming-denial machine, Ken Cohen, still heads the company’s large department of public affairs.

Cohen, an Exxon lawyer who emerged as a close confidant of Raymond’s after Exxon purchased Mobil in 1999, followed the tobacco industry’s playbook. According to Greenpeace, Exxon Mobil gave nearly $23 million between 1998 and 2006 to a network of conservative nonprofit groups that propagated doubts about global warming, even as climate scientists were reaching consensus on the clear and present dangers. Several of the same groups and spokespeople on Exxon Mobil’s payroll had previously taken tobacco-industry money to downplay the health dangers associated with cigarette smoke. Cohen funded the drive—regarded as “black ops” by some Exxon Mobil insiders—with special earmarks and budget lines approved from above. The project was a closely held secret within the company. “This was neither legitimate science nor legitimate charity,” says one source familiar with the process.

“It was propaganda.”

More recently, Exxon Mobil has found subtler ways to mold minds on climate change. Between 2004 and 2007, it donated $2.5 million to the American Geological Institute for Faces of Earth, a four-hour TV series on the geologic history of the planet. Though the last part of the series nominally addresses “how humans are shaping Earth,” the 43-minute program skirts the core issues of contemporary climate change. Instead, the documentary, which aired on the Science Channel in 2007 and is being sold to schools, casts man-made warming as part of an 8,000-year process dating back to the advent of the plow. It features several reputable scientists hinting at the imminent dangers of today’s heavy fossil-fuel use but repeatedly cuts away to images of natural forces such as erupting volcanoes, while the narrator’s voice redirects the discussion to geologic time scales. “There’s a lot of talk today about Earth’s changing climate in surprising and alarming tones,” the narrator says, in the film’s only direct reference to global warming. “The geologic record tells us that the climate has always cycled between cold and warm. These conditions are natural to the planet. But the geologic record also reveals that we should be in a cooling cycle. But we’re not.”

Exxon Mobil seems to be getting defter at selecting whom to fund. In one of its largest individual research grants in recent years, the company’s foundation awarded $250,000 to a pair of reputable researchers at the University of British Columbia for a project called Fuel Choices and Human Welfare. The money is being used to study the implications of fuel choices for a range of environmental and health outcomes. Replacing gasoline with diesel fuel, for example, reduces carbon-dioxide emissions but can increase air pollution.

“Anybody that tells you they’ve got this figured out is not being truthful with you,” Tillerson said at the 2008 annual meeting. “There are too many complexities around climate science for anybody to fully understand all of the causes and effects and consequences of what you may choose to do to attempt to affect that.”

Obama’s energy agenda calls for eliminating oil imports from the Middle East and Venezuela—or 27 percent of all U.S. oil imports—by 2018. Such a precipitous drop could devastate Exxon Mobil, which gets nearly 40 percent of its imported crude from the Persian Gulf region, making it the largest importer of Middle Eastern oil to the U.S. The company also sees U.S. energy consumption declining, but much more slowly than Obama wants. Obama also vows to implement an economywide cap-and-trade program to reduce America’s greenhouse-gas emissions by 80 percent by 2050. To seriously reduce greenhouse-gas emissions, carbon prices may need to be set high enough to push effective oil prices above $80 a barrel, which could give alternative fuel sources a big leg up, says Daniel Kammen, a University of California at Berkeley physicist who has advised Obama on energy issues.

“You can’t defeat the incumbent without fundamentally changing the rules of the game,” Kammen says.

seeing exxon mobil at this moment, with its reserves dwindling and its management under assault by shareholders, it’s hard not to compare it to Wall Street, as least with regard to the public mood. Investment banks and old-line oil companies seem equally popular with the current occupant of the White House.

Exxon Mobil “allowed itself to be seen as a villain on climate change, as a company that’s more interested in throwing up roadblocks than finding solutions,” says Elizabeth McGeveran of F&C Asset Management PLC, a London-based fund manager. “For any company in this globalizing world of ours, that type of reputation is a mistake.”