San Diego continues to tout greenhouse-gas reductions that never happened

The office of newly minted Mayor Todd Gloria released a climate report this week that claimed the city of San Diego has cut greenhouse-gas emissions by a whopping 25 percent over the last decade.

That’d be an incredible feat and reason to celebrate for any city in California — if it were true.

Since former-Mayor Kevin Faulconer adopted the city’s climate plan in 2015, the city has relied on faulty data that massively exaggerates cuts to its largest source of climate pollution: tailpipe emission from cars and trucks.

In fact, according to the flawed calculations, the city met its 2020 target for slashing greenhouse gases before the climate blueprint was even approved.

City officials have acknowledged the issue — first reported by the Union-Tribune in 2017 — but continued to trumpet progress based in large part on vehicle-emission reductions that never occurred.

The issue stems from the use of outdated data provided by regional transportation and planning experts.

When the city drafted its climate plan five years ago, it chose 2010 as the baseline year against which all emission reductions would be calculated. A key component of the process was establishing the amount of driving that occurred at that seemingly arbitrary starting point.

Rather than conducting a new traffic analysis for the 2010 baseline year, the city relied on old modeling projections. The problem was that the data was generated before the Great Recession hit in 2008 and didn’t account for the major decline in driving that resulted from job loss during the economic collapse.

As a result, the climate plan greatly overestimated the amount of people on the road for its baseline year. By 2016, it appeared on paper as if the city had taken hundreds of thousands of cars off the road — from an inflated 13.7 billion miles driven in 2010 down to 12.7 billion miles traveled just half a decade later.

Such a dramatic drop in driving would have to be accounted for with either a huge exodus of jobs or a massive move toward public transit, said Ethan Elkind, director of the climate program at UC Berkeley’s Center for Law, Energy and the Environment.

“Unless they can point to something that has changed on the ground, these numbers do look suspect to me,” he said.

Neither happened. Rather, the economy slowly improved over that time and transit use was flat, according to census data.

Faulconer’s and now Gloria’s teams have repeatedly said the city relied on the “best available data” when it calculated its baseline year. But both have baulked at making any substantial changes to address the discrepancy.

“We want to be thorough and thoughtful before we decide to touch that baseline and make sure we fully understand what the results are going to be,” Ashley Rosia-Tremonti, sustainability manager at the city of San Diego, said in an interview Tuesday.

“We’ve been very clear in the reporting that those reductions in the baseline year are … not a result of any specific actions that either the state, our region or the city has taken to reduce (vehicle miles traveled),” she added.

The city has reduced climate pollution from driving in the years following the adoption of its climate plan. Between 2016 and 2019, it slashed tailpipe emissions by about 4 percent.

“San Diego has taken significant steps toward meeting our Climate Action Plan goals …,” Gloria said in a press statement Monday.

But that 4 percent is dwarfed by the supposed 22 percent cut in vehicle pollution the city has taken credit for between 2010 and 2015 prior to the plan’s implementation.

The reductions to driving based on the faulty data account for nearly half of the city’s overall emissions cuts from 2010 to 2019 — roughly 1.5 million metric tons of greenhouse gas out of a total reduction of 3.3 million tons.