(Reuters) — Public corporations are supposed to warn investors about the risk to their businesses from climate change, but the tone and wording of those disclosures vary widely among big U.S. manufacturing, automotive and energy companies, according to company documents, and legal and corporate governance experts.

Pressure on companies to inform investors about risks associated with climate change was intensifying even before New York state's attorney general disclosed last month that he was investigating ExxonMobil Corp. for its handling of such disclosures.

The U.S. Securities and Exchange Commission in 2010 issued guidance that companies could be required to address climate risks depending on laws, regulations, international treaties, the consequences of business trends or the potential physical impacts of climate events.

Environmentalists say the SEC guidance gives companies too much latitude.

"There's a huge gap between what companies know and what they're disclosing," said Andrew Logan, director of oil and gas and insurance programs for Ceres, a nonprofit group that works with companies and investors to address environmental concerns. A spokeswoman for the SEC declined to comment.

Ceres found that 41% of S&P 500 companies did not include any climate-related disclosure in their 10-K filings — annual reports to the SEC — in 2013.

Some companies that do address climate change do so indirectly.

In its 2014 10-K filing, General Electric Co. did not mention "climate change" but identified regulations, including environmental ones, as a risk factor. GE also wrote that environmental obligations could cut into profits. The company further addressed climate change in a separate sustainability report, a spokesman said.

American Electric Power, one of the largest utility companies in the United States with many coal-fired plants, began disclosing information about climate change risk in at least its 2008 10-K filing, a company spokeswoman said. "Regulation of CO2 emissions could materially increase costs to us and our customers or cause some of our electric generating units to be uneconomical to operate or maintain," the company wrote in a 2014 filing.

Auto giant General Motors Co. did not mention the words "climate change" in its 2014 10-K filing but warned that regulations related to greenhouse gas emissions "may have a significant effect on how we do business."

A spokeswoman for General Motors said the company has been transparent in addressing climate change in a variety of public documents, including 10-K forms, sustainability reports and press releases.

For its part, Exxon has said it worked on climate science in a transparent way for nearly 40 years and has regularly disclosed the business risks of climate change to investors.

The company mentioned climate change and greenhouse gas restrictions as a risk in its 2014 10-K filing.

"These requirements could make our products more expensive, lengthen project implementation times, and reduce demand for hydrocarbons, as well as shift hydrocarbon demand toward relatively lower-carbon sources such as natural gas," the company wrote.