CHICAGO — The threat of global warning, by no means unanimously accepted five years ago, has now reached a significant threshold in terms of public awareness: corporate marketing.

As delegates from 190 nations meet in Bali for a crucial climate change summit, an increasing number of American businesses are looking to play off that concern, offering consumers a chance to feel they are participants in the battle to save the planet while generating good will for their own brands.

For example, Megabus.com, the discount bus company with its hub in Chicago, said last week it will give away 100,000 trips in 2008, describing the promotion as a way for travelers to reduce their "carbon footprint."

"Environmentally, it goes without saying that if we can get people out of their cars, we are saving carbon dioxide from going into the environment," said Dale Moser, president of Megabus .com. The company estimates the free rides will cut carbon dioxide emissions by 6.9 million pounds for every 100 miles traveled.

Meanwhile, Orbitz Worldwide Inc., the Chicago-based Internet travel service, is making it simpler for customers to reserve hybrid rental vehicles and to make contributions to offset the greenhouse gases created by their plane flights.

"This is to make it easier for people to find sustainable travel," said Steve Barnhart, CEO of Orbitz. "We are certainly trying to be more friendly to the environment."

Orbitz uses the services of Carbonfund.org for what are commonly called "carbon offsets."

Carbonfund.org partners with other environmental groups to take action that will remove greenhouse gases from the atmosphere, or prevent their creation in the first place.

"Reforestation in Nicaragua is one of our bigger projects," said Russell Simon, spokesman for Carbonfund.org. Trees take up and store carbon dioxide, a greenhouse gas. Reforestation projects also are popular because they provide habitat for wildlife and prevent soil erosion.

Simon said his not-for-profit is undergoing explosive growth. In 2005 Carbonfund.org received $40,000 in donations and offset an estimated 8,000 tons of greenhouse gases from the atmosphere. This year, the group expects to receive $4 million to $5 million and offset 800,000 tons of greenhouse gases.

"Consumers are demanding that companies do meaningful things on behalf of the environment," Simon said. And the businesses that respond are leaders in fighting greenhouse gases and deserve respect for that, he said.

ECO-FRIENDLY PLASTIC?

Even affinity cards are going green.

General Electric's Money Earth Rewards Platinum Mastercard is the first U.S. credit card dedicated to reducing carbon emissions. Up to 1 percent of purchases made with the credit card go to projects like capturing from landfills methane gas, a ferociously powerful greenhouse gas, or developing wind and solar power projects.

The company said that a person charging $750 a month will, over the course of a year, offset an average individual's production of greenhouse gases.

Laurence Minsky, who teaches advertising at Columbia College, said a company that uses its environmental concerns to distinguish itself from its competitors gains an advantage.

"People want to feel good about the products they are buying," Minsky said.

Many people are concerned about global warming and will favor goods and services that benefit the environment.

As for reducing global warming, environmentalists say that some businesses are taking a very good, very small step in the right direction.

"People and businesses are stepping up to help," said Howard Learner, executive director of the Chicago-based Environmental Law and Policy Center.

He said he thinks the corporate efforts to curtail greenhouse gas emissions are sincere.

"But let's not confuse good actions with necessary actions," Learner said.

"The largest sources of greenhouse gases are coal-fired power plants and cars and trucks. Until those problems are fixed, huge amounts of pollution will go into the atmosphere."

AUTO INSURERS, TOO

Northbrook, Ill.-based Allstate Corp. is looking at both large and small ways of cutting greenhouse gas emissions.

The insurer is testing an auto insurance program in Ohio and Colorado that cuts the amount of paper involved in providing insurance. Among its other features, Allstate donates $30 to Carbonfund.org for each customer who signs up.

Allstate spokesman Brad Keena said Allstate will invest $200 million over the next three years in environmentally beneficial projects, including a solar power project.

"It's part of our investment portfolio," Keena said.

That is the kind of action Jonathan Goldman, executive director of the Illinois Environmental Council, thinks is needed to curb global warming.

"Let's not look at global warming as a problem that is going to take a lot of money to solve," Goldman said. "Businesses will see new markets open up to them and it's going to make money and it's going to create jobs."

And if companies want to capitalize on acting and being seen as green, that is fine, too.

"It is simply good business," Goldman said.