Guest Post by Geoff Russell. Geoff recently released the popular book “Greenjacked! The derailing of environmental action on climate change“.
Even if they don’t own one, most readers will have seen a Satnav, those miracles of modern technology which will direct you across town to a suburb and street you’ve never been to before. After you enter your destination, there’s a little pause and perhaps the screen displays a message like: “Calculating…”, and then the instructions start.
Okay, so why the pause?
Once it’s located its required satellites and knows where you are, the Satnav runs some form of shortest path algorithm to work out how to get to the destination. If you are interested, here’s a walk through of one popular algorithm in action.
Really impatient people might be annoyed by the pause. For such people, there’s a much faster way of proceeding which would make that pause so short as to be imperceptible. Here’s the algorithm for a no-pause Satnav. First make a list of each road passing through your current location. After all, you have to travel down one of these. Then consider some point a small distance (say 30 meters) away on each of the roads. It’s high school maths to determine if this point is closer to your destination than your current location. If it is, then off you go. Then at the next intersection of any kind, do the same thing again. The algorithm would be lightning fast, the pause would vanish, and it always takes you in the direction of the destination.
At this point you should get out a piece of paper and start doodling. Might the algorithm use dead end roads? Ah … yes. If you go down one, can you ever get out? Ah … no. Consider roads slightly less than tangential to a circle around your destination. Might the algorithm take them? Ah … I guess so. Could you end up driving backwards and forwards along such a road forever? Ah … yes, theoretically.
Obviously, the algorithm sucks; even though at each point it always chooses a road that takes you toward the destination. But it can suck even it doesn’t make any of the mistakes I mentioned. It can suck by simply taking a hopelessly circuitous route.
If you think about it, this algorithm is pretty close to the current international approach to tackling climate change. Of course, a Satnav is just for one person, but the climate change mitigation process is highly parallel, so it’s like everybody involved is using this same sucky algorithm.
How often have you seen news stories about some so-called climate friendly project; they all have a prominent claim somewhere like: “This project will deliver clean energy to Y thousand homes!” or, “This project will save X tonnes of CO2″? All such claims tell you is that the project is taking you somewhere closer to zero-carbon nirvana. They tell you nothing about whether you will ever get there or how long it might take.
Consider as an example: the on-going global roll out of biofuels.