Visitors who climb aboard the steam trains in the Disneyland resort in southern California need not worry about their carbon footprint. The trains are powered by soy-based cooking oil recycled from the resort's kitchens.

It's a Mickey Mouse gesture, really, when set against the millions of miles that park visitors travel by car and plane to reach Disneyland. But it's driven, in part, by an innovative and forward-thinking tool that Walt Disney, which posted revenues of $42.3bn (£27.8bn) in 2012, uses to regulate its greenhouse gas emissions. A self-imposed carbon tax.

It's not just Disney. Although most of the world's governments have declined to put a price on carbon emissions, a handful of global companies, including Microsoft and Shell, have chosen to act on their own. They have established internal carbon prices in an effort to reduce emissions, promote energy efficiency and encourage the use of cleaner sources of power, just as a government tax or cap-and-trade program would.

"The more you emit, the more you pay. The less you emit, the less you pay," said Beth Stevens, a senior vice-president at Disney. "We want to provide an incentive for the businesses to innovate."

At Disney, the carbon tax seems to be working, by driving incremental efficiency measures that might otherwise have been overlooked and by raising funds to buy carbon offsets. Since 2009, when the tax was imposed, the company's engineers have changed thermostat set points, installed light sensors and efficient bulbs, increased the efficiency of chillers, heat exchangers and pumps, and shut down the lights on park icons like Cinderella's Castle and Spaceship Earth when the parks are closed.

But, and this is a big but, Disney's vacation cruise business has been so successful that the company doubled the number of carbon-spewing ships in its fleet, from two to four. That helped drive a 46% increase in Disney's absolute emissions from 593,416 tons in 2010 to 867,353 tons in 2012, the company has reported.

The good news is that Disney could then turn to what it calls a climate solutions fund, where monies from its carbon tax are deposited. The tax, the price of which depends upon the costs of offsets and the volume needed by Disney to reach its emissions targets, has been set at between $10and $20 a ton and has raised about $35m so far. That has enabled Disney to invest in a variety of certified forest-carbon projects in Inner Mongolia, China, Peru, and the Democratic Republic of the Congo, as well as in Virginia, Mississippi and its home state of California. Taking those carbon offsets into account, Disney's 2012 emissions have been cut in half from a 2006 baseline. The company has set a long-term goal of zero net emissions.

Why bother with these voluntary carbon taxes? Partly to prepare for government regulation of emissions, if and when they arrive. Rob Bernard, Microsoft's chief environmental strategist, explains: "I think it's likely that over time society is going to move in this direction. It's hard work. We should get to it now."

To their credit, Disney, Microsoft and Shell all support US and global policy to regulate global warming pollutants. "Current scientific conclusions indicate that urgent reductions in greenhouse gas emissions are required to avert accelerated climate change," Stevens has said. While Shell says it supports "an international framework that puts a price on CO2."

Shell's carbon price was established "not to deliver major change but to demonstrate the possible" by showing that pricing carbon could drive change in a cost-effective way, according to David Hone, a climate change adviser at Shell. Shell has set the highest carbon price, about $40, but no money actually changes hands inside the company, according to Angus Gillespie, the firm's vice-president for CO2 strategy. Instead, the price is used to guide capital allocation, with the oil industry's long-term investment horizons in mind: "It's based on the level of mitigation that we, Shell, think is necessary to make sure that our products are robust in the long term. This is Shell internally mimicking the system we'd like to see."

Gillespie was vague about specifics but said the price had shaped decision-making. "There have been CO2-intensive opportunities that we have decided not to pursue because the $40 ton makes them unattractive," he said, without naming any. At the same time, Shell has invested in carbon capture and storage projects, notably the Quest carbon capture and storage project in the Canadian tar sands, because of its belief that the technology will make sense, if regulators set a steep carbon price.

For its part, Microsoft has promised to achieve net zero emissions during the current fiscal year, which ends in July, for its data centres, software labs, offices and employee air travel, by increasing efficiency and purchasing renewable energy. The company describes its environmental strategy as "be lean, be green, be accountable," with the internal carbon tax, which is now set at a modest $6 to $7 a ton, serving as a driver of accountability. As Rob Bernard explains: "When you book the flight, it'll show you how much carbon you'll be using. If you stop in Chicago, you'll be using more."

Data centres and offices will be assessed on the tax, which is tracked by software designed by CarbonSystems and paid into a fund administered by the company's chief financial officer. This fiscal year, it is expected to raise about $10m. Microsoft works with a company called Sterling Planet to buy certified renewable energy certificates (RECs) and direct carbon offsets. Interestingly, Microsoft will also use some of the money in its carbon fund to make energy efficiency grants to business units – an idea that percolated from the bottom up.

The tax, Bernard told me, is "accelerating and amplifying conversations around the importance of energy and carbon." That won't solve the climate crisis, but it's a start.

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