How do you count carbon?

Although various governments have already erected carbon accounting and abatement systems, the issue remains unsettled. The easiest plan to administer is a carbon tax tied to the fossil fuels consumed directly by an individual or company. Politically, however, taxes have proven a difficult sell. Cap-and-trade systems, meanwhile, can lead to vague credits with amorphous values.

Manufacturers have also complained that they get saddled disproportionately with the burdens in carbon schemes, while activists have complained that carbon accounting, normalized for revenue, can mask increases in emissions. On the other hand, companies have complained that carbon accounting, if not properly created, can penalize growth. But what about in terms of economic importance? On that scale, ExxonMobil might be the greenest company on the planet.

Autodesk, the design software giant, has decided to step into the breach. It has created its own carbon accounting methodology – the Corporate Finance Approach to Climate-Stabilizing Targets (C-FACT) – that considers carbon emissions (and increases in carbon emissions) adjusted against the "value" or change in value produced by the company.

Value, according to Emma Stewart, senior program lead of the Autodesk Sustainability Initiative, is defined by Autodesk as gross profit, or revenue generated minus costs.

Though it might appear that way at first, this is not just a scheme that favors software companies, which tend to have high gross profits and low carbon emissions. Where you begin is not the important part, she said. The issue is how a company can improve its emissions from a baseline while accommodating growth and increases in profit.

The system also accommodates short-term deviations, forecasting and cost-saving measures.

C-FACT grew out of a company-wide effort to reduce carbon emissions. Autodesk itself does not generate much in the way of carbon emissions directly. Still, the company's output of greenhouse emissions increased from fiscal 2008 to 2009. The increase, though, coincided with a growth surge.

In 2009, the company generated 83,073 tons of greenhouse gases and reported $2.1 billion in gross profit in fiscal 2009, leaving it with 0.04 kilograms per dollar.

Autodesk is now in the process of discussing C-FACT with various organizations and standards bodies.

As part of its overall effort, Autodesk has imposed fairly high carbon emissions standards on itself. The company wants to reduce emissions by 85 percent. Its accounting will include "an unusually high level of indirect emissions," Stewart said. Autodesk, for example, will include carbon emissions generated by customers flying to its conferences, not just the carbon consumed by its own executives to get to the same event.

"We want to err on the side of over-accounting," she said.

The company will also continue to tinker with its tools to reduce emissions. In some ways, most of Autodesk's emissions are twice removed. It emits relatively low amounts of emissions directly and, unlike Samsung or Sony, Autodesk does not sell products that get plugged into walls. They are software applications that sit on other things plugged into walls.

"Our biggest impact comes through influence and building functionality into tools," Stewart said.