Companies are required to calculate the risks to their businesses based on a range of potential threats to their business models, but there is currently no requirement that they calculate the potentially catastrophic costs of climate change. A few U.S. companies do so voluntarily, but most do not.
However, in a letter  to Chrisopher Cox, Chairman of the Securities and Exchange Commission (SEC), 27 institutional investors, including ten state officials with responsibility for overseeing risks to public employee pension funds, called on the SEC to require all publicly-traded companies to disclose the financial risks of global warming in their securities filings:
"Shareholders deserve to know if the companies they own are going down the prudent path ”“ adopting environmental practices that will enable them to thrive in a world of increasing environmental concern and regulation ”“ or whether they are following a path that will damage both our environment and our bottom line," said California State Treasurer Phil Angelides, a trustee of two of the nation’s largest public pension funds, CalPERS and CalSTRS, which collectively manage about $400 billion in assets.
A number of state fiduciaries who signed the letter have also been pushing companies through shareholder resolutions to disclose more on how they plan to respond to the risks of climate change-- a strategy that had led more than a dozen electric power companies, along with a few auto and oil firms, to publish reports on their financial exposure from new regulations and other climate-related risks.
In response to this shareholder pressure and general public education efforts, forty companies, including Boeing, IBM and John Hancock, have joined a business council organized by the Pew Center on Global Climate Change , part of a growing chorus  of the business community that are promoting the need to change business and government practices to deal with the crisis of climate change.
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