Apples to Apples

We seem to have this need to constantly compare and judge everything, make everything into a competition. We compare ourselves to others — based on style, clothes, body, money, car — we compare the latest technologies and movies… everything. And in the 21st century there are many ways to judge and compare these things, most easily by using the internet: thumbs up/down, karma, likes, +1, stars, or the more qualitative (and more often than not, rude and/or irrelevant) comment.

I’m not saying we shouldn’t compare things or dismiss healthy competition, it’s just that it seems that we have taken it to extremes, giving stats to everything. For example, there is a stat that Lebron James was the first to achieve “six straight 30-point games on 60 percent or better shooting in each outing”. For the most part stats are very useful in helping us make decisions, but we can be misled by the people who created the stats, due to biases or misrepresentation. For a stat to be useful to everyone, we need to make sure that it has a proper reference frame and that if we are comparing multiple items, that we are comparing apples to apples.

In order for informed decisions we need to have a proper reference frame, and we need to compare apples to apples.

We tend to think that numbers and stats are somehow more objective than qualitative statments. In reality numbers can be highly manipulative when they are poorly presented. The worst offenders for misrepresenting numbers and facts is the mainstream media. Sometimes they may just be reporting someone else’s data and are just passing on the information, not realizing that there is something wrong, other times there is a blatant act to misrepresent the facts, like this graph that Fox created showing the number of people having signed up for Obama’s Health Care program.

6 million is obviously not a third of 7 million, but many people may be watching the news while they prepare dinner — only half paying attention — might hear that a million people less than expected had signed up for the program and glance up at the graph and think ‘Wow, there are a lot of people who have not signed up for Obamacare’. A graph like this may not fool everyone or even most people, but it may still influence enough people to make a difference on some level. It is the media’s job to report news with as little bias as possible, so that citizens can make informed decisions but their own bias and will to increase viewership can often greatly affect the way they report the facts. In the case of this Obamacare graph, it was so blatant that enough people complained and Fox was forced to fix the graph.

Although the media is renowned for this, this type of behavior can be seen everywhere: in advertising, in industry and even among scientists. Though in this case they are often much less obvious, there will always be some bias, even if it is very small and unintentional. A good contemporary example of this that is currently a hot topic in the news is the electric car.

Proponents of the electric car say something like: “the electric car is a far superior option to cars that run on fossil fuels.” Probably. They also say: “electric cars produce no CO2.” That is not true. Though they may not produce any tailpipe emissions, there was most likely much CO2 created along the way during the production of the electricity which was then stored in the batteries of the electric car. Even in california, one of the states with a good share of renewable energy sources, the average CO2 emissions created for the amount of electricity needed to charge a Tesla Model S, is 61.2 kg. This is actually a tiny bit more than the 59.10 kg of CO2 produced by a Mercedes E 350 4matic to travel 360 km (the range of the Model S on a full charge). These numbers were calculated using carbon emissions numbers from the EPA and the Mercedes model was used because it is the same power and very similar size and weight as the Tesla Model S.

These numbers show that the Tesla Model S can actually be worse than an moderately efficient gasoline car of the same power. As much as these numbers are true, this is still not an adequate comparison, this is not comparing apples to apples. For a true comparison the emissions must be compared on a well-to-wheel basis. This means taking into account all the CO2 created in the oil extraction, transportation, refining, more transportation, etc.

Every step along the way accounted for.

This is needs to be done for the gasoline in the Mercedes, as well as for the natural gas, or coal, or hydro power that went into the production of the electricity for the Tesla, as well as including transmission losses in the power lines (which can be significant). Now if the Tesla uses power from solar or wind, then they do truly create no CO2, but unless you have you own solar panels on your roof — which Solar City, with the help of Tesla, is making more available for California residents — it will be hard to tell where the electricity comes from.

And what about the CO2 created in the manufacturing of the materials for the cars? The Model S and many other electric cars are made to be as light as possible because of the extreme weight of the battery packs. Aluminum is a material with a very high strength to weight ratio and it is used extensively in the Model S, but it is also extremely energy intensive and creates a lot of pollution in its mining and manufacturing. If there is a lot of aluminum and other intensive materials used in electric cars compared to gasoline cars, it may take a while before the total CO2 emissions of the electric car actually becomes lower than the gasoline car’s.

The CO2 created in the manufacturing of the infrastructure for both vehicles could also be considered and how the vehicles are recycled. The list could go on, but the point is that there are a lot of hidden factors that contribute to the emissions of vehicles. For a proper and fair comparison, a whole lifecycle analysis of each vehicle should be considered, though this is often very difficult and time consuming, so at least the same stages of the lifecycle should be compared. Since electric and gasoline vehicles are so different, tailpipe emissions for the gas car should be compared to the emissions at the power station for the Tesla since the rechargeable Li-ion battery is only an energy storage medium, not a power source.

Now that we already know that in California both these cars make about 60 kg of CO2 per 360km, but what does that mean? It is obvious that it is worse than producing only 50kg of CO2, but what is its effect on the environment? Or even more basic, how much is 60 kg of CO2? This is where the importance of having a reference scale comes in.

To put this in perspective, 60 kg of CO2 at sea level on a warm day (25 degrees C), would fill 8100, 4L milk jugs. Or about the size of a small bedroom.

Although the mass of CO2 is a much better parameter because it is not variable with temperature or pressure like volume is, it is difficult to picture the weight of a gas. Without some sort of reference that the reader understands, an absolute number is often extremely useless. For example most people would have trouble visualizing the scale of 8100 milk jugs, but a bedroom is easy.

The size of a bedroom provides an accessible way to understand the scale of the emissions of a car, but it is not always so easy to understand scale. An example of this is the model of the solar system. The planets on these models are usually to scale, but the distance between them is not. It’s not because astronomers are being biased about the positions of the planets, it is simply because it would be highly impractical to draw the models to scale. It would require meters upon meters of paper to space the planets out correctly, and the majority of the paper would be blank. A website here (http://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html) does a great job of showing the solar system to scale, and it is really quite amazing just how far apart the planets are. So although many times people try to adjust their data to benefit their cause, it is also possible that it is just impractical or impossible to display the data more accurately.

Statistics, graphs and other data are very useful in helping us make all kinds of decisions, and the internet goes a long way to enabling access this kind of statistical content from anywhere. But just because it is easily accessible does not mean that it is necessarily useful or even an accurate representation. The next time someone says “this one is the best” or “this one is the most environmentally friendly”, it is important that we check the source of the information to consider any bias that the author may have, that we have a good scale/frame of reference for some context and most importantly that they are actually comparing apples to apples.

This post was partially inspire by this post on XKCD (http://blog.xkcd.com/2013/05/15/dictionary-of-numbers/) , which talks about the importance of context for numbers.

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This post was written by L.D, a Master’s student currently working in clean energy technology.

If you would be interested in writing a guest post for Thought Infection please contact me at thought.infected@gmail.com

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One thought on “Apples to Apples

  1. There is a saying: statistically if one man ate a chicken and another man ate nothing they had half a chicken each.

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