The federal government has ratcheted down its estimates for oil production from the Monterey Shale twice in less than a year. This latest, dramatically lower estimate leaves no doubt that California needs to focus on developing and advancing clean fuels and renewable energy. ("U.S. officials cut estimate of recoverable Monterey Shale oil by 96%," May 20)

Relying on oil will lead only to an economic dead end.

The more we come to know about the Monterey Shale formation, the clearer it is how little anyone really understands it and the extreme extraction methods that the oil industry is now using — intensely — in California to exploit it. We need a time out from these extreme methods, like fracking, to assess what's really going on. We need a moratorium.

Kathryn Phillips

Sacramento

The writer is the director of Sierra Club California.

Gov. Jerry Brown has displayed cognitive dissonance by supporting both climate change mitigation and fracking in California.

Fracking not only perpetuates our dependency on fossil fuels, it also releases methane all along the supply chain, which is a greenhouse gas less prevalent in the atmosphere than carbon dioxide but roughly 30 times more potent as a heat-trapping gas.

Brown is trying to be slick like the streets of Atwater Village after the 10,000-gallon oil spill last week by appealing to both sides of the aisle. But like those streets, he is finding himself mired in a sticky situation, where he will need to fully commit to a side.

Californians are noticing that the governor's position on the issue of climate change is about as stable as the ground upon which Big Oil is fracking.

Amanda Grossi

Los Angeles

The writer is a field manager for Environment California.

I don't know why companies are even looking for oil anymore. What oil is left will be used up at some point. Meanwhile, extracting it gets more costly, and that doesn't include the hidden costs of the damage to the environment, including its contribution to global warming.

The sun produces energy; it has done so for billions of years, and when it stops, so will our planet. We should not build another house without solar panels. There should also be small wind turbines for our home patios that can help out when it is windy.

We don't need oil, and we really don't need shale oil.

Jenny Wilder

Apple Valley