Quote:
Originally Posted by jamesqf
Wrong way of looking at it. That steel &c produced in the long-ago past already exists, and will continue to exist even if the old vehicle rusts away in a junkyard, or indeed, if it is crushed and recycled. But by driving it instead of buying a new car, you are avoiding the production of steel for the new car.
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I see 3 potential different reference frames.
#1> Vehicle net life time pollution.
What I was referring to in the quote you referenced ... was the vehicle life cycle net pollution ... and for that ... the production cost in the past is 100% valid part of the net life time pollution of that vehicle ... which is how one would compare the life time net pollution of two vehicles.
#2> Individual net life time pollution.
If you are only concerned about your own net life time contribution to pollution ... then the person who bought a new car , any new car is the one who takes the new car production pollution hit ... and if you buy it used ... that production pollution isn't yours ... just the pollution of operation / repairs... this would absolve the person buying the 2012 used vehicle just as much as the 1970s used vehicle ... and thus a Used PZEV Prius can get it's production pollution absolved as well.
#3> Global net pollution
This seems to be the option you are describing ... The globe takes the hit for the net life time vehicle operation including the initial production pollution ... The hit from the new vehicle's production pollution would be a second production hit ... It just comes back to the question of how many miles of running cleaner per mile of operation is a net benefit ... it is not an automatic win for the old dirtier per mile.
Quote:
Originally Posted by jamesqf
But mpg (and its direct connection to CO2 emissions) is what really matters in the context of the world today. Those other emissions are only important when you have a large number of vehicles operating in a small area, such as a city, since they degrade fairly quickly, whereas CO2 is effectively permanent on the scale of a human lifetime.
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I disagree ... for several reasons:
#A>
Our current laws ... and just about any medical doctor you ask ... about the comparative harm from the various toxins.... CO2 vs all the other regulated tail pipe pollutants.
CO2 has a far weaker pound for pound impact than the other tail pipe regulated emissions ... As long as I have enough % of O2 in the Air I breath the CO2 doesn't directly hurt me ... but those other regulated tail pipe emissions are a very different story ... The CO , NOx , etc ... even with the % of O2 in the air I breath those other things can still kill you ... or hurt you ... or animals ... or plants ... etc.
If we are talking about pollution ... there are good reasons why we have tighter regulations about those other toxic emissions.
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#B>
Also if we were to adopt this MPG is what really matters philosophy ... not only would it undo the good that has been done by the other more toxic emissions controls ... see #1 above ... but it would also mean that Bio-Fuels are more polluting than fossil fuels ... because they lower the MPG with their lower energy content per gallon ... and thus put out more CO2 from the tail pipe per mile.
If you are concerned about AGW than this byproduct of , MPG is what matters , is not helping.
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#C>
If You say CO2 is what matters more than those other toxins ... than the byproduct of that ... is that you would be encouraging vehicle engineers to intentionally design vehicles to produce more CO , NOx , etc ... in order to reduce the amount of CO2 that comes out the tail pipe ... and that would be VERY BAD.
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#D>
A much greater total % of the human population lives in the areas concentrated enough for those other tail pipe toxins be able to cause harm.
Even if you aren't in a area of high concentration of those other pollutants ... diluting those toxins over a larger area ... does not in any way reduce the amount of those toxins that the vehicle in question is putting out ... The less toxin emitting vehicle emits less ... less in concentrated areas ... and less in remote distant areas.