Each new climate-change study seems more pessimistic than the last. This May and June, for example, were the hottest ones on record for the planet. Storms and droughts occur with increasing frequency. Glaciers are rapidly retreating, portending rising seas that could eventually displace hundreds of millions of people.

Effective countermeasures now could actually ward off many of these threats at relatively modest cost. Yet despite a robust scientific consensus that greenhouse gas emissions are at the root of the problem, legislation to curb them has gone nowhere in Congress. In response, President Obama has proposed stricter regulations on electric utilities, which some scientists warn may be too little, too late.

Why aren’t we demanding more forceful action? One reason may be the frequent incantation of a motley collection of myths, each one rooted in bad economics:

Myth 1: The enormous uncertainty of climate science argues for a wait-and-see strategy.

The claim here is that reducing greenhouse gases would be a wasted expense if climate change ends up causing only minor problems. But uncertainty cuts two ways. Things might not be as bad as expected, but they could also be much worse.

In other domains, uncertainty doesn’t counsel inaction. Few people, for example, recommend disbanding the military simply because adversaries might not invade. In any event, many scientists now believe that storms and droughts caused by climate change are already causing enormous damage, so all that remains uncertain is how much worse things will get. And as Robert Shiller has written in this space, when the risk is as high as it now seems, economics tells us that insuring against worst-case calamities is prudent.