I've long been a proponent of the core Viridian argument that "making the invisible visible" (MTIV) -- illuminating the processes and systems that are normally too subtle, complex or elusive to apprehend -- is a fundamental tool for enabling behavioral change. When you can see the results of your actions, you're better able to change your actions to achieve the results you'd prefer. I've come to understand, however, that it's not enough to make the invisible visible; you also have to make it meaningful.

The canonical example of how MTIV works is the mileage readout standard in hybrid cars. Almost invariably, hybrid owners see a gradual but noticeable improvement in miles-per-gallon over the first month or so of hybrid vehicle ownership. This isn't so much the car being "broken in," but the driver: because of the mileage readout, the hybrid driver can see what driving patterns achieve the best results.

A growing number of non-hybrid cars now include miles-per-gallon readouts; will we see similar improvements in driver behavior as a result?

Possibly, but not likely. The hybrid miles-per-gallon readout comes in two forms: an average mileage, whether calculated for the current tank or the total vehicle miles; and a real-time, current mileage display, which will fluctuate significantly while one drives. As far as I have found, the non-hybrids with mileage readouts only include the average mileage display, not the real-time display. (Update: Howard notes in the comments a few makes of non-hybrid cars that do have both the average and real-time displays. I would be very interested in an examination of driver behavior -- and possible changes in behavior -- for those cars.)

This is useful information, to be sure; it's good to know what kind of mileage a vehicle gets in real-world use. But as a means of MTIV, it's not terribly helpful, because it breaks the connection between the action and the result. After the first few dozen miles of a given tank of gas, the average mileage readout changes very slowly, and only with sustained greater-than-average or less-than-average mileage driving. Small variations get lost in the noise. This means that minor changes in driving behavior can't be mapped to minor changes in miles-per-gallon. Without that connection between "I did this" and "I got that," drivers can't as easily learn to drive in a more efficient way. The driver needs to be able to compare behaviors and results to learn what works best. Both forms of display are necessary. The average mileage is the context for the momentary changes, and it's the comparison between the two that provides meaning.

This dilemma isn't just an issue for cars.

Late last month, the UK's environment secretary, David Milbrand, proposed putting ecological impact labels on all food products sold in UK stores. These labels would focus on the amount of carbon emitted as the result of the production of the food item. In this, the UK government is playing catch-up with some of its businesses, as the grocery chain Tesco announced in late January that it would be adding carbon labels to the products it sold. And now the Carbon Trust, a UK non-profit that works with businesses to reduce their greenhouse impacts, has embarked on an effort to build a labeling standard for adoption across industries. (It should come as no surprise that I'm very much in favor of this sort of labeling!)

So let's say this works out, and soon every bag of crisps you buy has a little label on it showing how many grams of carbon resulted from that bag's production. Now you can compare it to other snacks, and try to eat only the goodies with smaller numbers in the label. But while that level of comparison is helpful, it doesn't offer the larger context necessary to make the comparison meaningful. You still don't know whether both the (e.g.) 100g of carbon resulting from the production of a bag of crisps and the (e.g.) 50g of carbon resulting from the production of a bag of carrots are outrageously high, ridiculously low, or vanishingly irrelevant.

In order for any carbon labeling endeavor to work -- in order for it to usefully make the invisible visible -- it needs to offer a way for people to understand the impact of their choices. This could be as simple as a "recommended daily allowance" of food-related carbon, a target amount that a good green consumer should try to treat as a ceiling. This daily allowance doesn't need to be a mandatory quota, just a point of comparison, making individual food choices more meaningful.

The food carbon labels without the recommended amounts is roughly like the real-time mileage readout on a hybrid: useful data about one's immediate actions, but without any way of measuring overall results. Similarly, the recommended allowances without abundant carbon labels is akin to the average mileage display: a way of seeing overall goals, without any way of directly connecting action and result. Both the individual data and the broader context are necessary.

This is a pattern we're likely to see again and again as we move into the new world of carbon footprint awareness. We'll need to know the granular results of actions, in as immediate a form as possible, as well as our own broader, longer-term targets and averages. This is certainly not a surprising observation. We're still early enough in the carbon awareness era, however, that even the obvious steps are useful to note.