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New California Almanac of Emissions and Air Quality

Staff of the California Air Resources Board have just published the 2005 edition of The California Almanac of Emissions and Air Quality. It is data- and chart-rich, with extremely clear explanations about the different types of pollutants and methods for analyzing the different data. The landing page for the report is here.

The entire report can be downloaded as well as an Excel version of all the tables.


The Almanac, which also forecasts emissions through 2020, reveals several things:

  • First, the tremendous progress that has been made over the last few decades.

  • Second, the magnitude of the challenge in the future.

Vehicles contribute some 67% of California’s air pollution—and while the state’s population continues to grow rapidly, the Vehicle Miles Travelled (VMT) grows even faster.

The Almanac forecasts the following changes in population and VMT for the different regions of California:

% Growth in Population and VMT, 2005–2020
Air Basin RegionPopulationVMT
Statewide 22.3% 27.1%
South Coast 20.0% 20.6%
San Francisco Bay 12.7% 23.9%
San Joaquin Valley 35.3% 44.0%
San Diego 22.7% 18.0%
Sacramento Valley 27.5% 34.2%

This forecast takes California in fifteen years from a state that in 2005 will have a population of 37.5 million driving 872.9 million miles per day to one that in 2020 will have a population of 45.8 million that drives 1.1 billion miles per day.

In other words, not only is California adding population—and motor vehicles—at a rapid rate, that population and those new cars are driving more than ever.

Progress has been made—but more will be required.


Joe Deely

I'm a bit confused by your - "the magnitude of the challenge in the future." What is this big challenge you are talking about and how did you extrapolate this from the new state report?

This report shows both the tremendous progress that has been made in reducing air pollution in California over the last 30 years and it shows that the trend of reduction will continue.
See table 3-1 in article or data below.

A lot of these improvements in coming years are already built into current model cars... as the car population changes over time these improvements will come automatically. No further changes needed. I do not see much of a challenge there.

One more point... for some reason this report by CARB uses population figures from a California Department of Finance 2000 data versus 2004 data. The 2004 data has population for 2020 at 43,851,741 versus the 45.8 million noted in this report. This means that pollution should be even lower than predicted!

California Air Resources Board 2005 Almanac (web)
Chapter 3 Statewide Table 3-1
Statewide Emissions (tons/day, annual average)
Pollutant 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
NOX 4811 4982 4945 4871 4128 3629 3026 2499 2059 1811
ROG 7131 6739 6180 4748 3691 3013 2402 2145 2031 1993
PM10 1901 1931 2004 2144 2047 2061 2113 2177 2234 2298
PM25 803 785 778 816 758 767 779 796 811 829
CO 41295 37609 35588 29603 22182 16906 13204 10848 9213 8248


Simply that with more vehicles driving more miles, the aggregate output is the challenge. We’ll need additional emissions controls to offset that future growth—which CARB is planning on.

Even with the unarguably impressive progress made to date, for example, maximum measured ozone contributions still exceed the State standard in 10 of the 15 air basins.

Joe Deely

Thanks for the response. However, I think you missed what I was saying.

My point is that we will not need any additional emission controls to offset more vehicles driving more miles. Emissions are already dropping much faster per year than total miles driven is increasing. All that needs to happen is for people to continue buying new less polluting cars to replace their older higher polluting cars.

Therefore.. no challenge.

One other point... the comment made by the Chairman of the CARB which you quoted,

"...motor vehicles contribute about 67% of our pollution."

is really a classic example of the poor use of statistics. Yes vehicles are responsible for 67% of the total weight of pollutants. However, the main reason for the 67% is because vehicles are the primary emitters of CO. As can be be seen in the chart above the total emissions of CO outweighs the emissions for the other four major pollutants combined. But guess what? we are already in compliance with CO standards. So why worry about CO? Shouldn't we be more worried about the other four pollutants. Look at the data for these pollutants and you will find that vehicles -and especially cars-are responsible for far less than 67%.


Well, I see what you’re saying...but I don’t have as sanguine a view. :-).

First, the ongoing decrease in forecast emissions is not only based on ongoing turnover of the fleet, it’s also based on the presumption of increasing stringency on the regulation side.

The report factors in new clean fuel regulations, tougher mobile source regulations, and even the existence of the California CO2 law, which, by also reducing fuel consumption, helps on a number of fronts. None of those are a slam dunk, as the current lawsuit against the CO2 regulation shows.

However, even with these assumptions, if you look at the projected results on a per average vehicle basis, I think it looks a bit more difficult than it sounds.

I took a look at three specific emissions dealt with in the report: CO, NOx, and PM10.

I also only looked at on-road mobile source emissions—i.e., only gasoline and diesel vehicles, as listed in the almanac. That way we keep this discussion just focused on the vehicles, and not on broader area sources.

CO. In 2005, mobile sources are projected to produce 7,629 tons/day of CO, dropping 65% to 2,661 tons per day in 2020. Converting that to grams, and applying the estimates of vehicle miles traveled, that results in a fleet average 7.9 grams/mile in 2005, dropping to 2.2 grams per mile in 2020, or a drop of 73%. The current ULEV status for CO emissions for passenger vehicles in CA is 1.7 g/mi up to 50k miles, then 2.1 g/mi at 120k. In other words, to meet the projections in the almanac, the average CO emission rate for the entire fleet—large and small vehicles—will have to be at approximately the passenger car ULEV levels of today.

NOx. On-road mobile source NOx emissions drop from 1,518 tons/day in 2005 to 532 tons/day in 2020, or 65%. Performing the grams and vmt conversions yields 1.58 g/mi in 2005, dropping 72% to 0.435 g/mi in 2020. ULEV passenger car standards for today are 0.05 g/mi to 50k, and 0.07 g/mi at 120K.

PM10. PM10 mobile emissions are projected to increase 8% from 50 tons/day to 54 tons per day. Yet with the increase in mileage, that works out to a drop in PM10 emissions from 0.05 g/mile in 2005 to 0.04 g/mile in 2020—all of which exceed coming EPA and California standards.

And none of that address CO2 emissions.

So, a couple of thoughts. First, in the area of CO, getting the entire fleet average to that of a current passenger ULEV is an enormous task.

Second, even in areas where the is incredible progress (70+% reductions are great)...the total average result is still higher than expected today in low-emissions vehicles.

I really am a technology optimist. Solutions exist today, better solutions will exist tomorrow. The difficulty—and magnitude—of the challenge, from my point of view, is on the policy and consumer sides. We’ll achieve the results, as you say, if people keep buying more fuel-efficient and lower-emitting cars, switching to biofuels, using alternative fuels, using electric vehicles and so on. But we need the larger buying populace to embrace that, and we need the ongoing toughening of the regulations. Not easy. :-)

Joe Deely

Thanks for taking the time for your detailed response. I really like the calculations you did – they put things in better perspective. Like you, I am also a technology optimist, perhaps a little more so. :)

I also like to focus on making sure that time and money is spent on the right problems and even more importantly the right solutions. I want to see us improve air pollution in California as much as we can for as cheap as we can. In order to do this we must have our priorities straight.

Here’s my (very different) take on the three pollutants you analyzed (CO2, NOx and
PM10. Your calculations inspired me to research the emissions standards a little further.

CO – Your calculations show that the average for all cars will have to match the current ULEV standards. You think this will be hard to do… my answer, not that hard. I think that almost all new vehicles will actually be SULEV compliant by 2020 and the older vehicles that they will be replacing will be ULEV compliant.
However, this is really a mute point because we(Californians) should not even be focusing on CO. We already meet CO standards, so let’s concentrate our limited time and resources on more important pollutants. I’m not saying that just because we have met the standard we shouldn’t keep lowering CO emissions. However, it will continue to drop because of fleet turnover anyway, so its not worth worrying if the drop is 20,30 or 40%.
We have to focus on the real problems.

PM10 – This is really an example of making sure we are applying our resources efficiently and getting the most bang for our buck. You, worry about whether the increase in mobile emissions from 50 to 54 tons is really accurate. Even if it goes to 60 tons, who cares? This will still be less than 3% of total PM 10 emissions. Any money or effort in reducing PM10 emissions should be invested in more important programs. For instance, here is some information from a LA’s AQMD board meeting – see

“Under AQMD’s Rule 1186, originally adopted in February 1997, cities must purchase, lease or contract for sweepers certified as PM10-efficient after Jan. 1, 2000, whenever they replace existing sweepers or sweeping services…. These sweeper standards help implement a Best Available Control Measure for entrained road dust, which is projected to reduce PM10 emissions by 13.1 tons per day by the year 2006.”
If new sweet sweepers in LA will reduce PM10 emissions by 13.1 tons, then let’s make sure the whole state has new street sweepers before we worry about vehicular emissions of PM10.

NOx – Now this is a pollutant that we should be worrying about. It is a contributor to ozone, in which, unlike CO, we fail to meet current standards. Also, unlike PM10, vehicles are a primary contributor to NOx- currently just over 50%.
However, this one has me a little confused. I did the same calculations as you and came up with the same numbers, 1.58gms/mile currently, dropping to 0.435gms/mile by 2020.
With the current standard for ULEV at 0.07 gms/mile and since I think most cars purchased in California over the next fifteen years will be ULEV compliant we should have much lower numbers for emissions in 2020! I’m guessing that vehicular emissions of NOx will be down to less than 300 tons/day by 2020 not the 532 shown by CARB. So not only am I saying that this will not be a challenge, I’m saying that CARB has underestimated NOx reduction. I am going to try and check with them on this.

So, a couple of thoughts. We must have our priorities straight in attacking air pollution in California. That means that we should not be worrying about spending more effort on reducing either CO emissions or PM10 emissions from vehicles. There are much better was to spend our resources.
You have goaded me into doing a little more research on this matter and I am now even more firmly convinced that reductions in pollution from vehicles is basically on auto-pilot over the next fifteen years. Money and effort in fighting air pollution needs to move away from vehicles and into other sources.


I am wondering how much hummers pollute. Can you say something about that?


if you want lower emissions quit using gasoline. unfourtunately we really cant to keep being mobile. hopefully someone in the government will definately change this and make it to where we wont have to worry about pollutants increasing, not due to just cars, but everything. more people equal more pollutants, we the people need to really look into alternative fuels at an extremely fast rate. by then 2020 who knows california might be terrible to live in. even if the laws get strickter and less pollutants are out the more cars on the road there are they are still going to be going into our air. say if you cut it in half, say there is 500 people which is unrealistic of course, your making 250 peoples worth of pollution now. Say 1000 people are there... you're still making 500 peoples worth of pollution... sure the number might be cut in half... but the pollution is still there. sure i drive a car, sure i hate how it pollutes, and say if bush made everything start to run on say hydrogen id get rid of my car in an instant to save our world. im not a tree hugger but i would want my kids and grand kids to live in something they aint going to die from and everything else around em.

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