Friday, February 15, 2013
The injuries and property damage from this meteor are sad, indeed, and the victims warrant our concern. The event, however, should not cause the rest of us to live in fear of death from the sky. Understanding the actual hazard from such events is the business of the field of risk assessment. Adler's book, above, was the first thing I had read on the subject. The earliest copyright date I've found is 1973, but my sense is I read it even earlier. Maybe not. Its subtitle, Death from Falling Watermelons, succinctly summarizes the essence of risk. The diagram below explains:
We never walk down a street scanning nearby rooftops for watermelons because it simply doesn't happen. Yes, if one did fall on our head it would really ruin our day, but the risk is so low that it doesn't occur to us to be concerned. But there is a difference between perceived risk and actual risk. Sometimes we grow so accustomed to an action that carries significant risk that our perception of that risk is numbed. Consider riding in an automobile and not using the seat belts. Consider continuing to burn fossil fuels despite the evidence of global warming and it's impacts. Sometimes our perceptions of risk are heightened by the newness of a technology. Consider choosing coal over nuclear for electricity generation, when the cumulative impacts of coal are much greater than the nuclear fuel cycle. I once saw a cartoon of a bumper sticker on a coal truck that proclaimed, "There's no fuel like an old fuel."
Every action we take has risks, even breathing, and we all unconsciously do risk assessments on a continuing basis. But are we dealing with actual risk or simply perceived risk?