If the planet is really overheating, why are these people using so much money, time, fuel, and water in the fight against frost?

The Good Life: Foothill grape growers fight a cold war - Sacramento Living

He decides to turn on his fans – 32-foot-tall monsters with 15-foot blades – to fight frost there.

These kinds of nights, these early, freezing mornings with frost alarms ringing, are part of the fabric of the wine world. They happen everywhere, every spring, in Napa, Sonoma, the Russian River Valley, the Santa Lucia Highlands of Monterey. Name your region, frost alarms have been sounding this month.

Battles with frost are common to all farmers – and vineyard growers are first of all farmers. The California Farm Bureau Federation gives out constant updates and warnings on frost and ice, and spring is a busy season.
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There are potential problems with all methods, beyond freezing in your truck. The fans, for instance, should not run in snow or sleet because the weight of the ice will wreck the machinery.
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"When we give tours, I ask people to guess what month we use the most water," Bush said. "Everyone says July or August. But it's really April for frost control."