The agreement represents another novel use by Mr. Cuomo of the Martin Act, a powerful tool that allows the attorney general to bring criminal as well as civil charges. Mr. Cuomo’s predecessor, Eliot Spitzer, used the law to vastly expand the office’s investigations of suspected Wall Street malfeasance.

Now Mr. Cuomo has turned it into a de facto form of environmental enforcement, too. For energy companies, including those based far from New York, he is able to claim jurisdiction because they issue securities on Wall Street.

The agreement with Xcel requires the company to analyze the likely effects on its business of current and future legislation or regulations in the states and countries where it operates and to disclose that information in its investor filings with the Securities and Exchange Commission.

Congress and many states are considering global warming legislation. Ten states stretching from Maryland to Maine, including New Jersey, New York and Connecticut, have struck a deal to cap emissions and allow trading of pollution allotments among producers.

Under the agreement with Mr. Cuomo, Xcel will disclose the financial risks of lawsuits and of federal or state court decisions that would affect its business. The company will also analyze and disclosed the “material financial risks” to itself associated with global warming, like drought  coal plants are prodigious users of water  or rising sea levels.In a statement, the chairman of Xcel, Richard C. Kelly, said the company had already voluntarily reduced carbon emissions and planned to continue to do so.

“We previously provided detailed information concerning the expected impact of climate change and greenhouse gas emissions regulations on our operations, and under this agreement we will make even more detailed disclosures,” Mr. Kelly said. “This agreement will enhance our already aggressive efforts to be responsible environmental stewards.”

Xcel officials said their reductions of greenhouse gases had totaled 18 million tons since 2003. They added that the company planned to build an additional 6,000 megawatts of renewable energy generation by the end of the next decade.