AQMD’s Smog Predictions: How Clear Is the Vision?
Fast forward to an August afternoon in Los Angeles, a decade into the 21st century. Do the skyline and mountains sparkle in a sea of blue, or is the region still cloaked by a filthy, lung-stinging layer of smog?
The ability of the South Coast Air Quality Management District to accurately predict the future has become a focal point in the controversy over a new plan that will guide Southern California’s effort to combat pollution.
The AQMD’s latest clean-air plan relies upon computer-generated scenarios of what smog will be like in the year 2010 that entail as much speculation as fact. The scenarios have triggered the suspicions of scientists, environmentalists and other critics because the AQMD switched to much rosier predictions without having its methods scrutinized by independent experts or its own advisory council.
The new forecast is such a dramatic departure from predictions made in a 1994 plan that some critics are questioning whether the AQMD engineered its computer modeling in order to appease politicians and businesses that want smog rules eased. Because the new models found that fewer emissions must be eliminated to achieve healthful air, future clean-air remedies can be less painful and less expensive.
“Because I’m a modeler, I know how uncertain the exercise is,” said Akula Venkatram, a UC Riverside engineer who was one of nine members of the AQMD’s scientific advisory council who resigned Aug. 8 in protest. “In science, one assumes the modeling practices are bad unless there is proof they are good.”
The computer modeling is the compass navigating the tortuous path toward cleaner air. It directs the range and scope of all future smog rules in Los Angeles, Orange, Riverside and San Bernardino counties, an area of 13 million people. The AQMD’s new, more optimistic predictions could save businesses millions of dollars annually in an anti-smog bill estimated in 1994 to exceed $5 billion per year.
The Environmental Protection Agency and the state are reviewing the new computer modeling to see if it was technically sound, but AQMD executives say their analytical team is sheltered from the political fray and followed the latest, scientifically sound practices.
“There has been political pressure, but that did not influence any decisions on the modeling,” said AQMD Executive Officer James Lents. “We stand by the work.”
After a series of public workshops to detail the plan’s methods beginning next week, the agency’s governing board expects to vote on the new air quality plan--based on the more optimistic computer models--on Nov. 8.
In predicting smog into the 21st century, the AQMD has factored in hundreds of assumptions about the future--from the miles driven by cars to the wind flow on summer days, the reactivity of various chemicals and the volume of manure excreted by dairy cows.
The modeling process is so complex that only a handful of people outside the agency understand it. Yet if a single factor is off, it can skew the entire outcome, forecasting skies that are cleaner or dirtier than reality and yielding an attack on smog too weak or too vigorous.
In their resignation letter, the AQMD’s advisors from USC, UCLA and other institutions said the agency “is embarked on a course that will not lead to attainment” of federal health standards. They cited as a major reason the “large uncertainties in the models, data and assumptions used to predict air quality” and a lack of external review.
“The model they are relying on is extremely sensitive to changes in information, and there is a lack of confidence about their predictions,” said Jane Hall, a Cal State Fullerton economist who quit the advisory council.
“Various members of the council have worked with staff and have not been able to effect change as far as how the databases were assembled,” she said. “The district is not looking for external advise.”
Mel Zeldin and Henry Hogo, the AQMD managers who led the analysis, said they reached the more optimistic predictions after a two-year, $1.4-million overhaul of the data plugged into the model. The study provided more reliable and updated estimates of the volumes and sources of particulate pollution, especially in Riverside and San Bernardino counties, they said.
“The 1994 data was a crude approximation at best,” said Zeldin, project manager for the clean air plan. “We have a much better way now of simulating it.”
The AQMD has been renowned for its technical expertise, and the analysts for the plan collectively have 200 years experience in modeling air quality, said AQMD deputy executive officer Barry Wallerstein. The models were checked for accuracy by seeing how well they would have predicted past years’ smog, and they performed well, Zeldin said.
Still, the AQMD analysts concede that some assumptions they plugged in are arguable, and that approximating such a complex chemical and meteorological process 14 years into the future is precarious. The plan is scheduled to be revised again in 2000.
“There is significant uncertainty with these models,” Wallerstein said. “But uncertainty runs in both directions. What we’ve seen in the past couple years is that air quality improved faster than what we predicted.”
Lents said the modeling “is better than a guess. It’s just a question of how much better. It gives us some idea of where we’re going, but it’s a mistake to treat it like a precise instrument.”
Adding to doubts about the AQMD work, district officials last month told The Times that two leading Caltech air quality scientists, Glen Cass and John Seinfeld, assisted in the new analysis. That was erroneous due to a miscommunication, the district staff said. Cass and Seinfeld, who are creating sophisticated models for the AQMD to improve future planning, were not contacted to assist with the latest plan. “The model was devised by staff in-house at the AQMD,” Cass said. “I have not provided them information because I haven’t been asked.”
Los Angeles Mayor Richard Riordan’s staff has hired consultants to test the AQMD’s conclusions. City officials say they want to ensure the smog problem is neither overstated nor understated, resulting in too many regulations or so few that stricter measures would need to be imposed.
Similar independent analysis by Riordan two years ago prompted the AQMD board to delay adoption of its 1994 plan. At his request, the board dropped some controversial proposals for cutting particulates, especially provisions aimed at the city’s harbor and airport.
Also, Riverside Mayor Ron Loveridge and Riverside County Supervisor Roy Wilson--both AQMD board members--have created a special panel to explore whether the new plan does enough to reduce particulates. Its accuracy is especially critical to their county, which has the nation’s worst levels of particulates.
State air quality experts and the U.S. Environmental Protection Agency also are reviewing the findings and the data used in the computer models. The EPA has the authority to freeze the Los Angeles region’s federal highway funds and to impose other penalties if the state fails to adopt an effective plan.
The goal of the AQMD’s anti-smog plan has remained the same: to reach the federally established limits for particulates in the air of the four-county region by 2006 and for ozone by 2010. Ozone, a powerful lung irritant formed when fumes react in sunlight, and particulates--fine pieces of nitrates, carbon and other substances--are the area’s most pervasive and hazardous air pollutants.
What has changed substantially in the plans, though, is the AQMD’s conclusions on the air’s “carrying capacity”--the tons of emissions the atmosphere can hold and still achieve the two federal limits. The new models say it will be necessary to reduce nitrogen oxides and hydrocarbons in the air from the current 2,600 tons per day to 1,017 tons--compared with a 587-ton target set two years ago.
As a result, the AQMD staff revised its plan to recommend adopting 61 new rules but dropping or shelving 36 other proposals. Also, it is no longer considered necessary to enact separate, more stringent measures for combating particulates--especially fumes from heavy-duty diesel engines.
“Our message,” Lents said, “is the same: We’ve got to adopt some significant rules that clean up emissions over the next few years. The fact that it’s a little easier than we thought shouldn’t be interpreted as we think it will be easy.”
Wallerstein said people will be less skeptical and suspicious once the staff explains the rationale for its new predictions in next week’s workshops. “There is nothing magical in there,” he said.
The main factors include:
* Particulates and ozone dropped 20%--more than expected--between 1990 and 1993, due to the recession, as well as controls on cars and industry being more effective than anticipated.
* The AQMD based its worst-case smog scenario on weather conditions in 1987, discarding its use of a June 1985 day when severely stagnant air was more conducive to smog.
* Road dust and the Chino area’s dairy farms turned out to be a much smaller source of particulates than estimated in 1994. Measuring fumes from cows and roads, the staff concluded that dust is half as voluminous and the dairies’ ammonia emissions are 70% lower than estimated.
* The region is expected to grow slower--totaling 16.8 million residents in 2010, 600,000 fewer than projections from two years ago, according to the Southern California Assn. of Governments.
Lents said no experts outside the agency reviewed the data or read the draft due to time constraints in adopting the plan. But he said his staff sought more public input than they did with earlier plans, providing monthly updates to a business and community task force that included some engineers and scientists.
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Hazy Forecast
The AQMD’s new anti-smog plan revises thinking on the volumes of key pollutants that can be carried safely in the air.
Source: South Coast AQMD
