Yesterday there was some discussion over the value of hybrids and electrics (EVs) in solving whatever climatological problems are being caused by greenhouse gas production. Some of the remarks were pretty angry or sarcastic so I thought I’d try to put more light than heat into the discussion. I’m going to be a bad storyteller and jump to the conclusion first: the effect of hybrids and EVs is negligible and will be for the foreseeable future.
First, let’s look at where emissions are coming from:
As you can see vehicle emissions from all vehicles account for a little over 25% of all greenhouse gas emissions.
Now, let’s look at what sort of vehicles are on the road:
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Passenger cars account for a little over a third of all vehicles. Both of those charts come from the Department of Transportation.
The U. S. “fleet”, all of the passenger cars in the country, takes more than 20 years to turn over. That length of time is actually increasing as vehicles become more reliable. There are about 250 million cars in the United States, hybrids and EVs account for less than 2% of them, and 2012 sales of hybrids and EVs accounted for less than 3% of all passenger car sales.
Let’s start crunching numbers. First, at that rate how long will it take before all passenger cars are hybrids or EVs? Answer: at the present rate of replacement hybrids and EVs will never be more than 3% of all passenger cars in the fleet. Well, at the present rate of increase in sales how long will it take? Answer: sales of hybrids and EVs in the U. S. peaked in 2009 and have declined since then. Even if the decline in sales as a percentage of the total stops, sales of hybrids and EVs will never exceed 3%.
Okay, okay. Let’s assume that a) the lifetime savings in emissions of an EV or hybrid is 24% (the number in the article), b) the percentage of hybrids and EVs rises to 10% of all passenger vehicles (which, barring some dramatic change in purchasing behavior will never happen), and c) the size of the fleet remains the same. How much will that result in decline in greenhouse gas emissions?
That would be
24% (the savings over conventional vehicles) X 28% (the percentage of emissions due to vehicles) X 34% (the proportion of the total represented by passenger vehicles) X 10% (the assumed proportion of hybrids and EVs)
or .22%, 22 parts per ten thousand. Or, said another way, a very, very small amount. Probably too small to measure with any real confidence. That doesn’t accomplish what would need to be accomplished to reduce (or reverse) whatever global warming is occurring as a result of greenhouse gases. It isn’t even a start.
I could go on by demonstrating that the amount by which China is increasing its production of greenhouse gases exceeds that tiny amount of savings but I think I’ve made my point.
I repeat the hypothesis I stated in my previous post on this subject: emphasis on hybrids and EVs is no practical solution. It’s more credibly explained as a symbolic action with the intent of moving the Overton window.
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Although that does remind me of one of my favorite jokes.
I was hoping sam might appreciate the Plato allusion. I think he brings up an important issue about how we demarcate the role of policy and the role of science and technology in our country.
One place we do that is in the D.C. Circuit court, where non-scientifically trained judges review regulations s to determine whether administrative agencies are behaving in a “scientific fashion.” Like sam, I think that there is a lot a non-scientist can do in this area through the skills of close-reading, logic and rhetoric to evaluate “a science,” but it only goes so far. Unlike sam, I guess I don’t find the actions and temperament of those engaged in the actual research and those actually engaged in skepticism of client science to be presenting themselves in a manner that gives me confidence. So, I remain agnostic.
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