A group of investors, including the California Public Employees Retirement System, came out in support Monday of a shareholder resolution asking coal company Massey Energy to explain its response to growing pressure for limits on carbon dioxide emissions, Forbes reports.

Massey’s board of directors, however, is urging shareholders to defeat the measure. “Carbon cannot be removed from coal and Massey cannot provide coal that does not emit carbon dioxide when it is burned,” the company said in its proxy statement sent to shareholders. “Accordingly, we are not in a position to ‘significantly reduce’ carbon dioxide from our ‘products’ as the proposal suggests.”

The move is backed by Ceres, which announced the filing earlier this year.