Part of the Bay Area News Group

cars and SUVs only 28 percent of greenhouse gases?

By enelson
Wednesday, December 12th, 2007 at 11:58 pm in air travel, driving, Environment, rail, trucks.

tailpipe.gifI hesitate to call attention to someone else’s correction, particularly because I’ve had two of my own in short order. For a journalist, that’s enough to keep you up at night.

Still, we learn from our mistakes, and even fatal mistakes can teach others, to paraphrase Al Franken.

Gov. Arnold Schwarzenegger’s spokespeople provided a teachable moment for me when they quoted their boss saying:

“With motor vehicles contributing to roughly 40 percent of the state’s greenhouse gas emissions, it is imperative that we be granted the fuel waiver from the federal government.”

The occasion was today’s decision in Fresno by U.S. District Court Judge Anthony Ishii that California has the power to regulate tailpipe emissions for cars and light trucks, a category that includes SUV’s.

The governor has championed the state’s global warming fight on the world stage, so this was a good opportunity to cheer for a home-team touchdown.

About four hours later, the press release comes again, this time corrected to say that motor vehicles are contributing “roughly 28 percent” of California’s CO2 emissions.

As a journalist, I have to marvel that quotes can just be edited to make them more accurate. But that’s not the point here.

The point is, who knew?

Thinking back through the whirwind of discussions of how the Bay Area is going to fight global warming, I remember hearing, over and over, that our personal vehicles contribute the bulk of greenhouse gases. Some people standing at various podiums said things like “nearly half” to make the point that getting people out of their cars will make a big difference in the global warming battle.

I’m just as keen to cut back on tailpipe emissions as the next commuter, but this little correction made me scratch my head. To test my theory, I asked a co-worker what she thought cars and light trucks contributed to greenhouse gas emissions.

“Nearly half” was the answer. The answer had sunk into our subconscious.

After I found out where the mistake came from, everything made sense.

The 40 percent figure represents all transportation sources. That includes planes, trucks and ships. What California whipped the automakers in court about was tailpipe emissions standards for cars and light trucks only, that is, what contributes 28 percent of all of the state’s greenhouse gas emissions.

I’m not saying that there’s been this great campaign to decieve people or that global warming is a hoax. It’s just that when we’re passionate about a cause, the facts tend to get obscured.

Thinking back, I do remember more circumspect officials using the words “transportation sources” in connnection with the higher numbers for the state and Bay Area’s greenhouse gas contributions.

Still, I think many people have assumed, as whoever crafted the governor’s quote did, that our personal vehicles were a much bigger part of the equation than they actually are.

 The number makes sense, too. While there are clearly a lot of cars and SUVs out there, and while tailpipe standards haven’t been increased in  decades, emission controls on them are still head-and-shoulders above the rest of transportation.

Devices to improve truck and train emissions are a fairly new phenomenon, while marine and aviation emissions have been ignored up until about 10 minutes ago. Just as that old 1970s muscle car puts out enough smog for a whole fleet of modern cars, the rest of transportation pollutes disproportionately more than cars and light trucks.

Local update (12/13/07, 11:35 a.m.): Karen Schkolnick, the Bay Area Air Quality Managment District’s helpful public information person, pointed me toward some local stats: 2008 projection for all transportation sources: 52 percent of C02 emissions.  Cars and light trucks: 29.5 percent. She noted that being as this is a major transportation hub, one might intuit that we’d get hit a bit more than other areas with transportation generally.

As was quickly pointed out, 28, 29 percent is a sizeable chunk, just not what a lot of people thought. On this list passenger cars (not counting light trucks) is the largest sub-category, with 18.2 million tons of CO2 projected. That’s about 19 percent of the total. The next highest emitter with its own category is combustion at landfills, at 12.4 million tons, or nearly 13 percent.

Illustration from

[You can leave a response, or trackback from your own site.]

15 Responses to “cars and SUVs only 28 percent of greenhouse gases?”

  1. V Smoothe Says:

    28% is a lot!

  2. South Bay Resident Says:

    You’re only sort-of right when you say that devices to improve truck and train emissions are new. This is correct when you talk about smog-forming emissions and particulate emissions, but CO2 emissions (which are directly tied to fuel economy) are of deep concern to railroads and truckers. In fact, freight railroads have cut their CO2 emissions for moving a ton of freight one mile by 50% since 1977. Heavy trucks now use about 20% less energy (and thus emit 20% less CO2) to move a ton of freight one mile than they did in 1977. It is worth noting that moving a ton of freight on truck for a given distance takes about 60 times as much fuel as moving the same ton of freight for a mile on a train. This suggests that one of the best policies that CA could pursue to reduce global warming would be to encourage shifting freight from road to rail. Unfortunately, one of the effects of the state’s heavy investment in commuter rail has been to reduce rail freight capacity.

    Los Angeles has done a better job improving its freight railroads than the Bay Area. Specifically, some public-private partnerships such as the Alameda Corridor and the Alameda Corridor East have improved freight movement and reduced pollution. Additional projects are planned, including adding additional track near the Tehachapi loop, which is the main freight bottleneck going out of LA.

  3. david vartanoff Says:

    No, commuter train increases have not caused freight constraints. Example it was the Capitol Corridor which paid Union Pacific to restore double track between Davis and Sacremento eliminating a bottleneck created by previous Souther Pacific bean counters. Closer to home Union Pacific owned two parallel mainlines from downtown Oakland to Fremont. Rather than link them north of Fruitvale where they were very close together, one was torn up and abandoned decreasing throughput.

  4. Reedman Says:

    The largest source of greenhouse gases on a worldwide basis is
    livestock, not transportation.
    (Reference: United Nations report, November 2006,
    “Livestock’s Long Shadow–Environmental Issues and Options”).
    Regulating the CO2 from US automobile tailpipes will
    give a lot of people a sense of self-righteousness, but
    from a climate science viewpoint it’s “arguing the gnat and swallowing the camel”.

  5. Bruce De Benedictis Says:

    Livestock do not increase the amount of carbon-based compounds available to become greenhouse gases, they merely convert its form. The same thing is true of forests and forest fires, bacteria, and all the other natural recyclers of carbon compounds. They do not dig up or eat fossilized carbon to increase the amount available to become greenhouse gases. It takes human intervention to do that.

  6. John Miller Says:


    Unfortunately, the number Reedman refers to us equivalent green house effect not CO2. Livestock emit CH4 that in huge quantities ant it is equivalent to several times the amount of C02 in terms of its ability to trap heat in the atmosphere. While the carbon is not being added to the system, attaching those pesky Hydrogen atoms to them makes them just as bad.

  7. Bruce De Benedictis Says:

    I was referring to all carbon compounds. If livestock (which includes humans, by the way) do not do the conversion, other plants and animals will. In fact, it is not the livestock that makes methane, it is the flora in the livestock, as well as similar flora that exist pretty much everywhere which do the actual conversion of carbon compounds into methane. That is where swamp gas comes from, just as one example.

    The livestock were doing the conversions before the extra carbon became a problem. They are not the reason the icecaps are melting. After all, we have wiped out so much of the large animal population that there could be less now than when the bison covered the continent.

  8. South Bay Resident Says:

    david vartanoff,

    The Yolo Causeway (the former single track section near Davis that was recently restored) is a perfect example of rail freight being harmed by passenger rail. UP had decided to remove one of the two tracks quite some time ago because a single track was sufficient for the 40 daily trains that they moved on that route. It was the addition of the 24 daily Capitol Corridor trains (now 36) that made the additional track necessary. In fact, the impact of the passenger trains on that section of track was particularly severe because while the freights all moved at more or less the same speed, the passenger trains move significantly faster, requiring more passing sidings and so on. Actually, the double tracking wasn’t enough to relieve the congestion created by the addition of passenger trains, and additional crossovers are being added to that section of track to better handle the speed differentials between the freight ans passenger service.

    It is very difficult to optimize a rail network for both freight and passengers. With freight railroading, you want to run long, heavy, slow trains, fuel and labor efficient trains, which is something that the North American rail network does very well. For passenger trains, you’re more interested in running fast, frequent trains, which Europe does very well, but the U.S. does poorly. However, Europe’s success with passenger rail has led to a moribund and inefficient freight system.

    There are several reasons why freight and passenger trains don’t play well together. The first is the speed differential. Freight railroads compete pretty much exclusively on being able to move stuff that isn’t very time sensitive very cheaply. Moving it cheaply means three things – slow, heavy and long trains. All three of these things lead to reduced operating costs (and greater fuel efficiency). Passenger trains need to be fast and frequent. This means you want light, fast and short trains. Not only do passenger trains have to frequently pass freight trains (which requires more switches and sidings), but they also require different things out of the track on which they run. One example is curves. For a fast train, you want the curves to be banked (called superelevation by railroad folks), for a slow train, you want the corners to be nearly flat. This means that if you optimize for freight trains, you restrict the speed (and reduce the attractiveness) of passenger trains and if you optimize for passenger trains then you require freight trains to move faster around your curves, which increases the fuel costs, leads to shorter trains and increases track maintenance costs.

    It wouldn’t take that much money to dramatically improve rail freight movement around the Bay Area, and doing so would reduce CO2 emissions and congestion more than many competing investments.

  9. Reedman Says:

    Another issue of freight/passenger rail mix is that the Feds essentially require
    any passenger train on rails that are freight connected/compatible to meet
    severe crash test standards. That is why Caltrain cars have to be far
    bigger and heavier than needed for moving people. This is
    one of the distinctions with “light rail” – it legally can’t go onto the rest
    of the rail network.

  10. Reedman Says:

    Methane is has about 20 times more “greenhouse heat
    trapping effect” as carbon dioxide. Humans don’t generate
    much directly (we don’t have the special gut bacteria), but besides
    livestock, rice farming is a large contributor (feeding 1/3 of the world),
    because methane is formed during low-oxygen plant decomposition,
    which occurs in flooded rice paddies.

  11. South Bay Resident Says:


    You’re right about the FRA’s deeply stupid regulations on passenger trains. American passenger trains are designed with a focus on the vehicle surviving an accident rather than collision avoidance and energy management (the European approach). This further handicaps American passenger railroading because the cars have to be much heavier, slower and more expensive than their European counterparts. In the case of light rail, there are some examples of shared track between freight and light rail trains. The first to come to mind is a stretch of track in San Diego which allows light rail trains during the day and freight trains at night.

  12. Bruce De Benedictis Says:

    If you want to blame global warming on ruminants and wetlands like rice paddies, you will need to show that there are significantly more than there were before the changes started, and that is a dubious proposition.

    A summer of 120° weather will kill lots of people, no matter what the cause.

  13. Guy Span Says:

    South Bay Resident:

    The FRA has standards to protect your life. It became clear at the turn of the previous century that light wooden superstructure passenger rail cars were demolished in a collision with heavier steel passenger cars, with a resulting loss in life.

    Restricting light rail, whether DMUs or LRVs from interacting with 10,000 ton freight trains keeps people alive. Most of Europe’s and all of Japan’s high speed rail do not interact with heavy rail except at slow speed choke points where they use an historic station in the center of town.

    It’s not fancy collision avoidance systems (although they have that to keep the light weight HSR from colliding with another), it is the separation of HSR from the inefficient freight and heavy rail that promotes safety. This is similar to US practice.

  14. Tailspin Says:

    Aviation have been ignored largely because they contribute only 3% of CO2 emissions, and on a passenger-mile basis it’s the cleanest petroleum based transportation you’ll find. Which, of course, is not to say that solar powered airliners wouldn’t be cool.

  15. Tailspin Says:

    Disregard my last. The 3% is correct according to the EPA, but the rest is simply wrong. Dunno what I was thinking.

Leave a Reply