Still, there’s some rough justice in the conservatives’ cheap shots. In Washington’s blizzards, the greens were hoist by their own petard.

For years, climate-change activists have argued by anecdote to make their case. Gore, in his famous slide shows, ties human-caused global warming to increasing hurricanes, tornadoes, floods, drought and the spread of mosquitoes, pine beetles and disease. It’s not that Gore is wrong about these things. The problem is that his storm stories have conditioned people to expect an endless worldwide heat wave, when in fact the changes so far are subtle.

Other environmentalists have undermined the cause with claims bordering on the outlandish; they’ve blamed global warming for shrinking sheep in Scotland, more shark and cougar attacks, genetic changes in squirrels, an increase in kidney stones and even the crash of Air France Flight 447. When climate activists make the dubious claim, as a Canadian environmental group did, that global warming is to blame for the lack of snow at the Winter Olympics in Vancouver, then they invite similarly specious conclusions about Washington’s snow — such as the Virginia GOP ad urging people to call two Democratic congressmen “and tell them how much global warming you get this weekend.”

Argument-by-anecdote isn’t working.