ExxonMobil's support for a tax on carbon emissions isn't that strong, noted Rep. Fred Upton, R-Mich. In November, Exxon said a carbon tax could be crucial in efforts to address increasing emissions. "I sat down with the Exxon folks a couple of months ago and let it be known that this is not a proposal that, certainly under Speaker Boehner [R-Ohio], is going to be coming through in the House," said Upton, chairman of the House Energy and Commerce Committee.