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One of the claims in "SuperFreakonomics" is, that reducing CO2 emissions produced by cars have very little practical impact on global warming. Their arguments are:

  • human activity is responsible for only 2% of CO2 emissions, with the reminder generated by natural processes;
  • greenhouse effect of methane is 70 times more than of CO2 (per molecule);
  • ruminants (mainly cows) are responsible for greenhouse gases affecting 50 times more than entire transport sector;
  • even if humanity would reduce CO2 to zero, it wouldn't significantly affect global warming within next few hundred years;

Does CO2 emitted by cars have significant impact on global warming?

matt_black
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vartec
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  • I have an exam to study, but [this](http://epa.gov/climatechange/emissions/usinventoryreport.html) will probably help someone answer the first part of the question. – Borror0 Feb 21 '12 at 15:01
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    I moved to a bigger city last year, and jogging here causes me to have breathing problems afterwards, which I didn't have where I come from. I can smell the gasses from cars when going to work as well. So it's not futile when you try to enjoy life. – Terry Feb 21 '12 at 15:22
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    @djerry: you can smell CO2? interesting... – vartec Feb 21 '12 at 15:30
  • @djerry that might have been smog, also I firmly believe it's the use of fossil fuels that has been dooming the atmosphere. if we can find a way to remove our need for it and use the CO2 in the air in a way that won't just release it again later (i.e. not using it for fuel but for building materials) we'll be fine – ratchet freak Feb 21 '12 at 15:47
  • @djerry - The air pollution from industry, commerce, and residential uses far outperform the transportation sector. So it is no surprise that you have more air pollution where you have a higher density of population. Another factor that contributes is geography. If you live in a valley that pollution can not disperse as effectively as someone living in the plains. – Chad Feb 21 '12 at 19:21
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    @djerry what you smell is not CO2 but the soot, sulfer and other gasses. CO2 is odorless – ratchet freak Feb 21 '12 at 19:21
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    Transport is clearly about 30% of CO2 emissions and I don't recall Superfreakonomics claiming otherwise (or arguing based on the first two bullets at all). I think their argument depends more on the second two. – matt_black Feb 21 '12 at 23:54
  • @matt_black: you're right, actually they say not transport, but "human activity". – vartec Feb 22 '12 at 09:21
  • It would be helpful if you could focus the question a bit more, are you only asking about whether emissions from cars represent a significant part of total greenhouse gas emissions? Several of your bullet point are only tangentially related, and pretty much every one of those would qualify for a separate question. – Mad Scientist Feb 22 '12 at 11:18
  • @Fabian: ok, good point, removed one bullet, made question more straight-forward. – vartec Feb 22 '12 at 11:40
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    The hoary old 'human acitivity is responsible for only 2% of CO2..." often serves as a springboard for erroneous arguments. Without human input, CO2 would be present in the atmosphere at some seady state level. The same holds for a constant human input of CO2. However, that steady state number is not obliged to be only 2% higher than the value w no human input. Absorption and emission are nonliner. Look at atmosphere CO2 for the past few decades. The effect of human additions is far more than 2%. We're up by more than 2% in the last 4 years alone: http://www.esrl.noaa.gov/gmd/ccgg/trends/ –  Feb 22 '12 at 17:24
  • Is futile the word you are looking for? Futile would indicate that any attempt to reduce carbon emmissions from cars would fail... i dont think that is accurate. But if you actually mean inconsequential... that is another story. – Chad Feb 22 '12 at 17:32
  • @Chad: futile, as a measure to reduce global warming. – vartec Feb 22 '12 at 18:14
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    @Wayfaring: do you have any scientific proof, that CO2 would be steady? after all, regardless of human activity in inter-glacial period oceans' temperature would rise anyhow releasing CO2 into atmosphere. – vartec Feb 22 '12 at 18:19
  • No, not over any specific time period. You'd have to measure all the volcanic and biospheric inputs and outputs of the system to get good values. That's not currently possible. However, no one has described a plausible oscillator to drive the changes we're seeing in atmospheric CO2 either. The simpler hypothesis, a static-steady state value for atmospheric CO2, rules until proven otherwise. Steady state: http://en.wikipedia.org/wiki/Steady_state does not follow the sort of shopkeeper-mathematics implied in Freakanomics, it requires p-chem level math. –  Feb 22 '12 at 18:28
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    @Wayfaring: solubility of CO2 in seawater is inversely proportional to it's temperature, it's a science fact that even the most zealous of the warmists don't deny. – vartec Feb 22 '12 at 18:54
  • @Vartec - You have to prove that reducing carbon emmissions period would do that. I don't think that has been proven. But what you really mean is doing so would be ineffective... – Chad Feb 22 '12 at 20:14
  • @matt_black "Transport is clearly about 30% of CO2 emissions" incorrect. That number doesn't take into account CO2 emitted by plants and animals (including humans directly and farm animals), nor other natural sources, only CO2 produced by vehicles and machines/industry. – jwenting Feb 23 '12 at 08:24
  • @jwenting fair point. I meant 30% of *human* emissions. – matt_black Feb 23 '12 at 09:45
  • ah, but that's still ambiguous. Farm animals and the breathing of humans themselves aren't counted toward the total by the warmists, in order to come at that 30%. Neither are emissions by ground being cleared for farming and construction by burning, or accidental fires doing property damage. And of course there's the futility of using CO2 as the sole (or largesT) measure of "climate change" in the first place, but that's another discussion entirely, however relevant to the original question as posed. – jwenting Feb 23 '12 at 10:44
  • @jwenting - I also do not see how it will matter if the earth warms up if we continue to poison the water, land, and air. Damage from pollution has already practically destroyed the natural ecology of China and India. We have many areas in the US, as well as Europe where the pollutants are known to cause health problems, and detectable levels of perscription drugs are prevalent in most of our rivers. But we need to reduce carbon... – Chad Feb 24 '12 at 21:22
  • well said, Chad. And the heart of the problem. "Climate change" is just the latest easy to market scare, and CO2 the boogyman, of the anti-western/industrialist/capitalist crowd (and those who make money off of the scare of course). It's no different from the asbestos scare (which started only after all dangerous asbestos variants had been removed from production for decades), all the food scares, or the "ice age now" scare of the 1970s (yes kids, in the 1970s the same "scientists" predicting imminent overheating were predicting imminent deep freeze based on exactly the same historical data). – jwenting Mar 01 '12 at 06:37

1 Answers1

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tl;dr: No, reducing carbon emissions from cars is not futile.

See also Does a car with a hybrid engine and Lithium batteries pollute more than a car with conventional technology? which directly relates to the global-warming potential of fossil-fuel powered cars.

To determine the question of whether reducing carbon emissions from cars is futile or not, we can investigate three linked questions, each of which gets answered in whole volumes of text, and at the very least each could be a separate question here:

  • Are anthropogenic greenhouse gas emissions causing global warming?
  • Are cars a significant source of anthropogenic greenhouse gases?
  • Would reducing anthropogenic emissions reduce global warming?

If the answer to all those is yes, then it is not futile to reduce carbon emissions from cars. Let's look at each in turn.

Are anthropogenic greenhouse gas emissions causing global warming?

Yes.

Previous questions have covered some of the science; see: Is CO₂ the cause for Global Warming? , the accepted answer to which explicitly addresses the issue of anthropogenic greenhouse gases; and Do human activities contribute to climate change?

From that basis, we know that anthropogenic emissions of greenhouse gases are major contributors to global warming, and that cars are one source.

Are cars a significant source of anthropogenic greenhouse gases?

Yes.

According to the World Resources Institute, road transport accounts for 10% of global emissions.

In the UK, using the figures from the Government's advisory body, the Committee on Climate Change (CCC), surface transport accounts for 22% of national emissions, and of that, 60% is from cars: hence 13% (60% x 22%) of national emissions are from cars. The CCC identifies surface transport as a significant area for attention for two reasons: firstly, its non-negligible 22% contribution to the total; and secondly, that it is a sector where some rapid decarbonisation is possible. In their words, from the source linked at the start of this paragraph:

a 26% reduction in surface transport emissions from 2008 levels is possible by 2020, with a reduction of 44% by 2030

The figures for greenhouse gas emissions include different weightings to reflect the different global warming potential of, for example, methane relative to carbon dioxide. They also include the emissions from livestock.

Would reducing anthropogenic emissions reduce global warming?

Yes.

There are many different emissions scenarios available in the peer-reviewed literature. The IPCC4 summary in 2007 brought together the best available research at the time, and one summary of their different scenarios is available here. The gist reflects that basic underlying physics: higher anthropogenic emissions (scenario A2) means higher temperatures; measures that reduce anthropogenic emissions (scenario B1) will mitigate that, leading to lower temperatures than would otherwise be the case.

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410 gone
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    Also, http://skeptics.stackexchange.com/questions/3435/is-co2-the-cause-for-global-warming does not address whether CO2 is anthopogenic, and references answer links to talk about "greenhouse gases" in general, not CO2 specifically. – vartec Feb 23 '12 at 12:31
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    @vartec Thanks for the comment. I've edited to cover your concern re anthropogenic - hope this helps. Sounds like you've got a lot of related questions here: perhaps you'd like to post them as separate questions: e.g. each of your four bullet points might be a candidate for its own question. See also http://www.skepticalscience.com/argument.php - you might find some of them already addressed, and well-referenced, there, to your satisfaction. – 410 gone Feb 23 '12 at 17:50
  • *"anthropogenic greenhouse gas emissions causing global warming"* AFAIK, **scientist** don't claim that anthropogenic are the **only** ones causing global warming. *"Contributing to"* isn't quite the same claim. Note, that the claim from the question is not of "no effect at all", but rather effect so limited, that not significant. – vartec Feb 24 '12 at 13:20
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    @vartec happy to take it over to chat to discuss further. I don't see anyone claiming that anthropogenic GHGs are the only ones. My answer covers, with referenced sources, the issue of the scale of the effect. "significant" might be subjective. My referenced sources show it's around 10-12%, and that substantial mitigation is possible. So yes, greenhouse gases emitted by cars have a measurable impact on global warming, and no, reducing their emissions is not futile. Whether **you** consider 10-12% to be significant or not is a subjective opinion that's outside the scope of this site. – 410 gone Feb 24 '12 at 15:24
  • @EnergyNumbers many in the political side of the AGW movement claim just that, or make claims so vague that their meaning is readily interpreted as such (playing on the general population's unfamiliarity with chemistry, thus not knowing that they themselves breathe out the stuff. See also DHMO...). – jwenting Mar 01 '12 at 06:40