Mr. Carnac said: “Companies see that the trend is inevitable. What you see here is a hardening of that understanding.”

Other companies that are incorporating a carbon price into their strategic planning include Microsoft, General Electric, Walt Disney, ConAgra Foods, Wells Fargo, DuPont, Duke Energy, Google and Delta Air Lines.

During the 2012 election, every Republican presidential candidate but one, Jon Huntsman, questioned or denied the science of climate change and rejected policies to deal with global warming. Opponents of carbon-pricing policies consider them an energy tax that will hurt business and consumers.

Mainstream economists have long agreed that putting a price on carbon pollution is the most effective way to fight global warming. The idea is fairly simple: if industry must pay to spew the carbon pollution that scientists say is the chief cause of global warming, the costs will be passed on to consumers in higher prices for gasoline and electricity. Those high prices are expected to drive the market away from fossil fuels like oil and coal, and toward low-carbon renewable sources of energy.

Past efforts to enact a carbon price in Washington have failed largely because powerful fossil-fuel groups financed campaigns against lawmakers who supported a carbon tax.

In 1994, dozens of Democratic lawmakers lost their jobs after Al Gore, who was vice president at the time, urged them to vote for a climate change bill that would have effectively taxed carbon pollution. In 2009, President Obama urged House Democrats to vote for a cap-and-trade bill that would have required companies whose carbon-dioxide emissions exceeded set levels to buy emissions rights from those who emitted less. The next year, Tea Party groups spent millions to successfully unseat members who voted for the bill.

But Exxon Mobil, which last year was ranked by the Fortune 500 as the nation’s most profitable company, is representative of Big Oil’s slow evolution on climate change policy. A decade ago, the company was known for contributing to research organizations that questioned the science of climate change. In 2010, Exxon Mobil purchased a company that produces natural gas, which creates less carbon pollution than oil or coal.