The president will not propose that a carbon tax be part of this autumn's deal to avoid the so-called fiscal cliff, the head of the Treasury Department's environmental tax division said today. The Obama administration "has not proposed a carbon tax, nor is it planning to," Gilbert Metcalf said today. Instead, he said, the onus would be on Republican lawmakers to show interest in a carbon tax as a way to raise funds to offset any deal to prevent the combination of tax increases and mandatory spending cuts set to take effect at the end of this year.