I went to see "An Inconvenient Truth" recently, but the theater was closed. The power was out because of an overheated transformer. It was Day 9 of our 11-day heat wave here in the San Francisco Bay Area, where Mark Twain once supposedly, but probably apocryphally, compared our foggy summer to the coldest winter he'd ever known.

The fog kept failing to arrive, however, as we sweltered in triple-digit heat. I briefly remembered the single night I'd hated the fog, freezing in extra innings at Candlestick Park. But mostly I recalled the sheer wonder of watching it spill over sun-struck mountains, summer after summer, and I yearned for its return. Where had it gone?

I'd just returned from a week in a Mexican desert to find it several degrees hotter at home, in a marathon that meteorologists have called unprecedented. My 7-year-old's skin was so warm that I took his temperature. A neighbor had to shut down the emergency sprinkler system at his house, which, sensing fire, was about to douse his furniture.

Inland, where incomes are lower and temperatures normally higher, the elderly and infirm have been quietly dying in their overheated apartments and cars, sometimes slumped in front of running fans. Yesterday, state authorities were blaming the heat for more than 130 deaths.

Local meteorologists offered clashing opinions about why the fog stayed away, but they agreed that the culprits included a mass of warm air that shifted northward from the Four Corners and parked over the Great Basin. Part of this high-pressure air mass extended over California's coast, tamping down the cool sea breezes. The days were scorching, the nights sticky and hot.

The San Francisco Chronicle published an article headlined "Scientists Split on Heat Wave Cause," which said some climate experts attributed the heat wave "at least partly" to global climate change. "Others, however, disagree," the article continued, "and say it's still too early to blame the current weather on the planet's changing climate."

This made me wonder: When will it be too late? I get it that you can't blame climate change for any one weather event. But I can also see that there's a pattern emerging — and it sure looks a lot like what mainstream scientists have been predicting for several years. They've been warning of more frequent and severe heat waves and warmer nighttime temperatures that rob you of any relief. You don't really need a climatologist to know which way the wind is blowing.

"Aren't you scared?" I asked my husband. "Sure," he said, and went back to watching the A's.

I know he's mentally healthier than I. Twain, after all, also is supposed to have said that everyone complains about the weather but nobody ever does anything about it. At the time, his comment was pithy and wise. But times have changed: A consensus of leading scientists suggests the world has a chance of stalling climate change if we make deep and immediate reductions in our fossil fuel consumption. This would take some leadership, but I'd put my children in day care and work fulltime for someone with that kind of vision, and I'd bet parents across the country would do the same.

Katherine Ellison is the author of "The Mommy Brain: How Motherhood Makes Us Smarter." She wrote this commentary for The New York Times.