Wednesday, December 28, 2011

Carbon footprints and mathematics

Over the holidays I read How Bad Are Bananas?, a book talking about various services, goods and habits that we have and how much CO2 they pump into the air.  It was well written and fun to read, especially considering the fact that it was pretty much designed to be a list of things with associated numbers; a hard sort of baseline from which to create a compelling narrative!  Most of what I found in the book was fairly unsurprising but there was still a fair bit to learn.  The broad summary is fairly simple:  Anything that requires a ton of heat or long distance flight is really bad.  Certainly giant gas guzzling vehicles on the roads with only one person in them are terrible but nobody needs to be told that, the important thing to know is that getting local produce out of season is often terrible because of the incredible energy required to keep it heated in northern climes.  Just as much it is disastrous to airlift food from far off countries so that we can have asparagus from the Southern Hemisphere in winter.

It turns out that having a dishwasher is a fine thing as long as it is reasonably efficient, run only when full and used for a long time.  Same goes for vehicles, interestingly enough.  If you buy an efficient car, drive it only when you have several people to carry and use it a long time it is just as efficient as many forms of public transit.  There are lots of good bits of information in the book talking about these sorts of issues and I found it really useful to have a bit of a guide as to when it is worth buying a new, more efficient device and when it is better to just run the old one into the ground.  Some devices are such brutal energy hogs or such big polluters that replacing them is necessary but in most cases there is so much CO2 tied up in manufacturing a device that it is far better to simply use it as long as possible and then buy a much more efficient one once the old one finally dies.

The book talks mostly about personal habits and purchases to help give the average person an idea of what their decisions mean but it does cover government subsidies of clean power sources too and it does not paint a pretty picture.  There are some things individuals and governments can do to reduce emissions that are tremendous wins all around like adding insulation to buildings and swapping from coal to gas as a heat source but many of the current things governments are trying are terrible from a cost:benefit perspective.  Generating power from solar cells and windmills certainly reduces emissions but the cost to do so is prohibitive and isn't the cheapest way to tackle the problem.  The author shows a real concern for understanding and lowering our CO2 emissions but makes it clear that many of the current ways governments are approaching it are very inefficient.

One thing I did find that seemed utterly wrong was the author's estimate of the costs of pumping CO2 into the air.  He estimated that for every 150 tons of CO2 sent skyward that one person would die and made some calculations about the cost of saving lives based on this number.  Unfortunately I can't see how that number can be possible since on average each person in the world puts 7 tons of CO2 into the air per year; this would imply that after ~21 years everyone on the planet would be killed by climate change. Clearly the function of CO2 to deaths is not linear but I still can't see how 150 tons / death could possibly be right.  My best guess is that he is off on this figure by at least one order of magnitude and more likely off by two.  I still think that the rest of the numbers in the book are useful guidelines but any time he talks about impact I think his figures can be safely ignored.

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