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Attribution Metaphor

By: Dr. Ricky Rood, 3:30 PM GMT on March 25, 2009

Attribution Metaphor:

Last week I was at a meeting of the Friendship Collaborative which is an organization dedicated to “Building bridges between science and faith.” The premise at the foundation of Friendship Collaborative is that there is common concern about maintaining a sustainable environment, and that faith and science have much in common. Related to the Friendship Collaborative is an emerging group Creation Care for Pastors.

During the meeting there was much discussion about the communication of climate change. There are a number of metaphors that are used to describe the greenhouse effect. A common one is the example of a greenhouse or, equivalently, a car left in the sunlight. In this example the visible radiation of the Sun goes through the glass, and it heats the dashboard, the carpet, and the upholstery. The hot surfaces in the car then emit infrared (or thermal) radiation at a wavelength that does not propagate so easily through the glass. The car gets very hot. A small crack in the window allows heat to escape through the motion of air. This is both a relevant and imperfect analogy of the greenhouse effect in the Earth’s climate. (An aside … please do not leave children and pets in the sun heated car. It’s dangerous and far too common! Unattended Children and Cars).

Another useful metaphor of the greenhouse effect is that of a blanket. In some ways I like this metaphor better. The basic idea is that a greenhouse gas like carbon dioxide acts like a blanket; it holds heat near the surface of the Earth. We all have an intuitive feeling that if we are cold and put on more clothes or a blanket then we will get warmer. This assumes that we, humans, are a source of heat. The blanket then holds the heat closer to our bodies for a while.

These metaphors for the greenhouse effect are often accepted in conversation. When we think about the attribution of warming of the Earth’s climate to greenhouse gases we generally don’t have as easy a metaphor. Generally our metaphor relies on “fingerprinting;” that is, the “shape” of the warming is different if the warming is caused by the Sun changing as compared with warming by more carbon dioxide. (I wrote a series on attribution about a year ago. Here is one on Fingerprinting: An Introduction). This metaphor remains complex, and I think it safe to say that some rely on “just having faith that the complex science has been done correctly.”

The following metaphor occurs to me. To my knowledge it is novel, but before I claim it, I’d like to know if any others have heard this metaphor … and, of course, does it make sense?

Imagine that you are a healthy person in a room and you are cold. You have multiple choices on how to get warm. You can put on a sweater or a blanket. You can turn up the heat. You can exercise. There are other more complex strategies.

Consider the two most straightforward approaches. Turning up the heat or putting on a blanket. It seems intuitive that it is straightforward to measure which strategy the person in the room chooses. If the heat is turned up, then the temperature goes up everywhere. (Plus there would be other changes in, for example, air flow.) If the person uses the blanket the temperature only goes up near the person. Plus, in fact, if you could measure it, the temperature outside of the blanket would go down a little because the person’s heat would not get into the room. For the most part, however, if the person uses the blanket the temperature in the room will not change. The possibility of attribution of why the person gets warmer is, in fact, relatively easy to determine in these two cases. The mechanism could be posted as a hypothesis and checked.

Make sense? Improve it?


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