There are a few things that I want you to hold in your mind for a second.

• In mathematical notation ? stands in for 'tends to'.
• In 'optimisation' the focus is on the approach to optimum, and therefore a much better description is 'improvement'.

Now on with the meat of this story.

There was a recent day for academics at Cardiff University organised by the RIBA. It’s planned objective was to integrate carbon neutrality into design briefs. However, from the reports I’ve had, the event was somewhat hijacked by the inability to decide on what ‘zero carbon’ really means.

Hearing about this gave me some of those strange wavy flashbacks, the kind of thing that you’d get in a program like Happy Days when Richy Cunninham was explaining why he just isn’t as cool as The Fonze. It reminded me of all the tedious discussions we were all having about optimisation about 4 years ago, about all the meaningless crap that was pumped out about finding the ‘optimum solution’. Finally we all (or at least the people I still talk to realised that our lives were too short to find optimum solutions to anything non-trivial, and what we really needed was_ improvement_.

In optimisation the solution landscape was usually a pretty funny shape, nobody could really tell you what direction to search in, or what you’d find there, but with ‘zero carbon’-ness things are a bit more black and white. We know that all we need to do is to keep reducing the carbon footprint of whatever it is that we want to talk about and we’re onto a winner, right?

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Well this is where we run into a bit of a sticky point. Zero is a funny number, other than ? it is just about the most controversial number out there. This is all explained in Nothing: A Very Short Introduction, and The Book of Nothing amongst others. (Not to be confused with The story of O.)

So in our current context, what does 0 mean? This seems so simple until you think even a little bit hard about it.

“So my dinner is totally zero carbon dude!
I rode my recycled fixed wheel bike to the vegan grocery store, smoked an organic american spirit cigarette, and then got my veggies and rode home”

What’s up here? Our hero has cycled (no emissions), he’s bought vegan food (carbon positive probably, as the plants have taken up CO₂ while they were growing, and then ridden home. The hero’s cigarette could easily be thought of as carbon neutral, as the same amount of CO₂ was released by burning it as by growing it. Winner!

Ok, so this is a pretty dumb example, but it makes the cracks appear pretty quickly. The store had lights most likely, they will be using electricity, the veg needs to be tended and taken to the shop, probably using a fair bit of diesel. The cigarettes will have a whole load of associated things, think about the electricity used to light the adverts on billboards etc. This is one of those infinite regress situations, and sooner or later we need to find out if the person who sold you the cigarettes has ever bought fireworks, or had a coal fire at christmas. This can be taken to absurd levels, but it illustrates the point quite nicely.

This is the classic asymptote graph (the positive half). The right hand side is the part where we are talking about the shopkeepers shoe laces, and the left is where cycling to the shop instead of driving makes a big difference.

It would be very easy to throw up our hands and say that as we will probably never achieve we should follow the hedonistic route and do nothing, but as secretly we are motivated by glory and laziness (well at least I am!) we should do stuff now as we get the biggest effect for the least input - or more accurately we get more effect per unit of effort input.

So to tie this all up, lets not talk about aiming towards carbon zero, or how close we are to it, but rather how far we are from the baseline (lets be lazy and use the standard 1990 emissions level). How big are our reductions, how much have we improved by, not how close we are to an ambiguous target.

You can unload those thoughts now.