Most people who think about the issue at all probably imagine that achieving a drastic reduction in greenhouse gas emissions would necessarily involve big economic sacrifices. This view is required orthodoxy on the right, where it forms a sort of second line of defense against action, just in case denial of climate science and witch hunts against climate scientists don’t do the trick. For example, in the last Republican debate Marco Rubio — the last, best hope of the G.O.P. establishment — insisted, as he has before, that a cap-and-trade program would be “devastating for our economy.”

To find anything equivalent on the left you have to go far out of the mainstream, to activists who insist that climate change can’t be fought without overthrowing capitalism. Still, my sense is that many Democrats believe that politics as usual isn’t up to the task, that we need a political earthquake to make real action possible. In particular, I keep hearing that the Obama administration’s environmental efforts have been so far short of what’s needed as to be barely worth mentioning.

But things are actually much more hopeful than that, thanks to remarkable technological progress in renewable energy.

The numbers are really stunning. According to a recent report by the investment firm Lazard, the cost of electricity generation using wind power fell 61 percent from 2009 to 2015, while the cost of solar power fell 82 percent. These numbers — which are in line with other estimates — show progress at rates we normally only expect to see for information technology. And they put the cost of renewable energy into a range where it’s competitive with fossil fuels.

Now, there are still some issues special to renewables, in particular problems of intermittency: consumers may want power when the wind doesn’t blow and the sun doesn’t shine. But this issue seems to be of diminishing significance, partly thanks to improving storage technology, partly thanks to the realization that “demand response” — paying consumers to cut energy use during peak periods — can greatly reduce the problem.