Bartel, who spoke this week at a council study session, said CalPERS' projections that investments will earn 7.75% annually were overly optimistic.
The equities markets, he said, are too volatile for Costa Mesa to count on its debt with the statewide retirement fund shrinking any time soon.
Costa Mesa's payments to CalPERS cover the annual costs for the city's already retired workers and payments to cover its future retirees.
The fund's investments are supposed to help, but the recession, which was followed by market volatility, sapped years of gains in short order, which left cities statewide to cover the losses.
Add Costa Mesa's substantial reliance on sales-tax revenue — also bruised in the recession — and the city found itself in a hole hard to climb out of without using its reserves.
"Pensions are not the problem," Bartel told council members at the study session Tuesday. "They're exacerbating the problem."
The problem, at least according to four of the five members of the council, is that Costa Mesa's pension payments are taking up an increasing amount of the city's budget.
An estimated $18 million of Costa Mesa's $114-million budget will fund pensions this year.
The council majority wants to reduce those costs — through outsourcing, mostly — and increase city spending on maintenance and capital improvements.
Councilwoman Wendy Leece, the lone dissenting voice, wanted to negotiate with employees before trying to outsource their jobs.
Bartel suggested the city pay more on top of what CalPERS requests from it annually, a move that would limit the peaks and valleys in its annual costs, but be more expensive in the short term.
The biggest change, though — one that non-public safety employees agreed to last year — would be to create a second pension tier for new hires, Bartel said.