by Michael Shellenberger

A growing number of independent and industry experts agree that carbon emissions would rise from increased natural gas use were Diablo Canyon nuclear power plant to close.

This may come as a surprise to those who think that California's cap on carbon emissions would prevent an increase in emissions, and so I contacted UC-Berkeley economist Severin Borenstein, a former advisor to the California Air Resources Board (CARB) on California's cap and trade program, to get his opinion.

"California's current emissions cap is very unlikely to be binding," Borenstein told me, "so losing Diablo Canyon would raise emissions.”

Borenstein is the latest energy expert to conclude that closing Diablo Canyon would result in higher emissions from electrical generation from natural gas.

The energy market research firm PIRA Energy Group found natural gas use would likely rise 34 percent between 2023 and 2026 in northern California. “[PG&E] would actually increase their dependence on gas-fired generation over a short time frame because that’s really the only option that’s available to them,” a PIRA analyst told KQED.

Two analysts at Bloomberg Intelligence agreed, saying “Gas-power plants will probably be needed for backup when wind and solar plants aren’t available." They noted that "Greater use of natural gas may make California’s emission goals more challenging to meet.”

The CEO of PG&E, Tony Earley, claimed the utility would replace Diablo Canyon's electrical generation with renewables, but Revis James, an experienced electricity markets analyst at the industry association to which PG&E belongs, the Nuclear Energy Institute, contradicted PG&E's claim, calling the proposed deal "risky, complex and expensive":

The proposal does not even pretend to find enough carbon-free replacements. It says that 2,000 gigawatt-hours will come from carbon-free resources and 2,000 gigawatt-hours will come from efficiency. That’s ambitious. However, last year the Diablo Canyon reactors produced 18,500 gigawatt-hours, four and a half times more than the specified replacements. That’s a very big gamble.

James' statement was unusual because the nuclear industry group is usually careful to avoid contradicting claims made by its member organizations. PG&E's Earley, formerly NEI's board chair, continues to serve on NEI's board, and his bio continues to boast that he "worked to revitalize the U.S. nuclear industry."

And James is one of the country's leading experts on carbon emissions and the electricity sector. Before joining NEI, James directed the Electric Power Research Institute's Energy Technology Assessment Center that modeled various potential impacts of climate policies on the electricity sector.

The only experts claiming the proposal to close Diablo won't increase emissions hail from groups that either negotiated the deal or have long sought to shut down nuclear power plants.

“We’re determined to avoid” increasing emissions, Ralph Cavanagh of the Natural Resources Defense Council, which negotiated the deal for his organization, told KQED. “We’re all going to work together to ensure that the fears of our adversaries are not realized: that anytime you lose a nuclear plant you automatically get an uptick in fossil fuels and pollution."

But even some experts at anti-nuclear organizations admitted that natural gas generation could increase.

“We could be at risk of running the gas fleet higher than we would otherwise run it,” Laura Wisland of the Union of Concerned Scientists said.