I am struck by how many liberals insist on reducing carbon emissions immediately, but, on the deficit, say there is no urgency because no interest rates rises are in sight. And I am struck by how many conservatives insist we must reduce the deficit immediately, but, on climate, say there is no urgency because, so far, temperature rise has been slight. (Although 2012 was the hottest year on record in the continental U.S.) One reason interest rates are so low is that they are being suppressed by the Federal Reserve’s quantitative easing. That won’t last. As for the climate, well, “Mother Nature doesn’t do quantitative easing,” said Harvey. Beware of nonlinear moves in both.

We can’t go off coal overnight, and we can’t go into recession by cutting spending overnight, but we need to start tapping on the brakes in both realms by agreeing on spending cuts, tax increases and new investments that would be phased in as the economy improves, as well as higher efficiency standards for power plants, buildings, vehicles and appliances that would be phased in, too.

A carbon tax would reinforce and make both strategies easier. According to a September 2012 study by the Congressional Research Service, a small carbon tax of $20 per ton — escalating by 5.6 percent annually — could cut the projected 10-year deficit by roughly 50 percent (from $2.3 trillion down to $1.1 trillion).