The focus of investor groups like the CDP has been on the energy and auto sectors, simply because their exposure is more likely, in the short run, to result in regulation restricting emissions of carbon dioxide.

Cinergy Corp. is one of three electric utilities that last year bowed to investor demands to report on their exposure. John Stowell, the company's vice president for federal affairs, environmental strategy and sustainability, says that the issue was on the boardroom table anyway. "We have evaluated the trend on Capitol Hill, and we've seen that more and more Republican senators are showing concern about the build-up of carbon dioxide in the atmosphere, and are judging that, politically, they need to do something proactive on control."

Stowell doesn't expect to see new regulations introduced by the Bush administration, which has refused to sign the Kyoto treaty and disputes the severity of the issue, but he says that "if you look ahead 10 years, it's hard for us to imagine that there won't be some kind of carbon-regulating program."

CalPERS' Hickox says that Lugar's interest was a result of a steady stream of foreign officials who raised climate change as an issue when visiting the Senate Foreign Relations Committee, which Lugar chairs. "There's a frustration on the part of the international community that we're not willing to be part of the solution, and I think that's starting to take its toll on the administration," says Hickox.

Andrew Logan, a Boston-based program manager with CERES, one of the groups working to bring investors together, says there's no question that the U.S. will introduce some kind of regulation. "The only real questions are what it will look like and what the costs will be," he concludes.

Shareholder success in forcing utilities like Cinergy to adopt a more progressive stance is set to be repeated this year with U.S. oil companies. During the 2004 proxy season, Anadarko Petroleum Corp. and Apache Corp. both faced shareholder resolutions calling for improved disclosure. The Anadarko resolution was backed by 37% of shareholders. In Apache's case, 31% of voters backed the resolution. This year, rather than oppose such a significant minority of shareholders, the two companies have agreed to release climate risk reports. "Since last year, we've seen a marked increase in the willingness of companies to sit down and discuss these issues with shareholder groups," says Nahla Durrani, managing director for social investment research with Rockville, Md.-based Institutional Shareholder Services (ISS), a proxy services firm. "They're looking at what investors are asking for, comparing their own practices with what their peers are doing, and choosing dialogue rather than confrontation."

Investors aren't just worried about how emissions regulation will affect the energy and power sector either. For instance, the Investor Network on Climate Risk has pushed AIG Inc. to talk more openly about its exposure to climate change.

In the auto industry, Ford Motor Co. and General Motors Corp. both faced shareholder resolutions last year. Although neither resolution attracted the level of support seen at the oil firms, Ford announced in March that it would release a full report later this year.

Challenges such as these could soon be experienced by a far wider range of companies. CalPERS' Hickox says that, as a rule of thumb, the corporate carbon emissions pie can be cut into thirds, with energy and power producing one third, transportation producing another, and everyone else jointly producing the rest. Investors may currently be worrying about those first two groups of companies, but they haven't forgotten the final third.