If quitting cold turkey is not an option, what's the best way to phase out a bad habit?

Steely discipline is admired, though in some cases a little bit of coddling works better. Some people like to create a game that rewards success, while others say punitive measures work best.

Discouraging bad behavior is even more complex when an entire industry is guilty. Telling a company that it must stop pumping a substance into the atmosphere because it is now considered pollution is hugely difficult when billions of dollars are at stake.

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Accountants, economists, attorneys and executives gathered at The Houstonian Hotel recently and debated the best way to persuade energy companies to reduce carbon dioxide emissions. The symposium was sponsored by the University of Houston and the International Fiscal Association, which focuses on international and comparative law in public finance.

On one hand is a carbon tax, notably favored by Exxon Mobil Corp. and other major oil companies, while on the other is a cap-and-trade system, currently used in California, the European Union and China. Both approaches can achieve similar results; the difference is in the journey.

Major oil companies prefer a tax because it's relatively straightforward. Refineries, power plants and natural gas distributors pay a tax on every ton of carbon dioxide that will be released when their products are combusted.

These companies already pay taxes based on volume, and this one could be simply added on. The federal Inter-Agency Working Group determined in 2010 that carbon dioxide emissions have a social cost of about $42 a ton, a good starting point for 2020.

Applying that inflation-adjusted tax would raise $975 billion over 10 years, enough to pay for President Donald Trump's tax cuts or for a good portion of his infrastructure plan. Better yet, it could pay down the federal debt.

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Under a cap-and-trade system, the government sets a limit on carbon dioxide emissions and then auctions off permission to pollute. Companies and brokers can then trade pollution credits.

Economists believe forcing companies to pay to pollute encourages them to emit less CO2. Businesses can also capture CO2, earn credits and then sell the credits to polluters for a profit.

A decade ago, both Republicans and Democrats in Congress supported a price for carbon with a preference for a cap-and-trade system, said Victor Flatt, director of the Environment, Energy and Natural Resources Center at the University of Houston Law Center.

"In 2009, all the powers that be thought there would be no way to pass a carbon tax because the word tax was itself toxic," Flatt said. "The Republican party now prefers to propose taxes rather than cap-and-trade systems."

Flatt said conservatives believe a new tax, coupled with offsetting cuts elsewhere in the tax code, are simpler. Cap-and-trade systems can become quite complex, and the European Union's CO2 cap-and-trade system has turned out to be fundamentally flawed and accomplishes little.

Oil companies prefer the simplicity of a tax and the message it sends, he added.

"A cap says carbon dioxide is harming us, and it must stop here," Flatt said. "A tax says: 'We're helping the country raise revenue. This is the cost of doing business.'"

Nathan Meehan, president of oil and gas consultancy Gafney-Cline and Associates, a Baker Hughes subsidiary, said energy companies also see a chance to profit.

"A tax would encourage carbon capture, use and storage," Meehan said. "The people who do that best are the oil companies, and we'll be cashing that check."

Placing an affordable price on carbon, though, is unlikely to change behavior enough to generate significant decreases in emissions, Meehan said. He pointed to nations with very high fuel taxes and how little impact high prices have had on encouraging alternatives or greater efficiency.

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Encouraging positive behavior, rather than punishing the bad, works better, he said. Tax credits for electric cars and carbon capture systems would do more than a carbon price, Meehan said.

Realistically, though, everything is needed. Consumer data shows that a carbon tax that raises pump prices will encourage people to buy more efficient vehicles. Trade in renewable energy credits prove that cap-and-trade would encourage more carbon capture. And the available tax credits encouraged me to buy an electric car.

Justice is another important social factor often missed by economists. People, companies and nations should pay the full cost of their pollution and not foist them onto others, particularly not future generations. Fair is fair, we need to start taking responsibility for our bad habits.