New York Attorney General Andrew Cuomo wondered whether investors in coal-burning utilities were being sufficiently well-informed about the risks of where they were parking their money. So he subpoenaed five companies for information -- Xcel Energy, the AES Corporation, Dominion, Dynegy and Peabody Energy.

Were they disclosing the full roster of financial risks -- like the cost of possible future lawsuits or higher operating costs from new regulations that put a price on carbon?

Now a year later, Cuomo has reached a disclosure deal with a first company. Xcel Energy has agreed to give its investors detailed warnings about the risks that global warming poses to its business.

Cuomo, who used the Martin Act to press his case with the companies, explained the importance of the deal in a statement:

Touting US coal as cheap and abundant is a favorite pastime of fans of coal expansion.

Want proof that it’s not true? Just look at this shocking new data from the Energy Information Administration on the costs of Appalachian coal, parsed here by Appalachian Voices.

It’s hard to know where to start: maybe that Central Appalachian coal, which accounts for roughly one-fifth of US coal production, has zoomed suddenly to nearly $140 ton. In 2007, prices were at $40 ton. That represents a jump of 350% in a single year.