In all of these posts about urban development, there is an underlying idea that I should probably spell out explicitly more often. My concern here is not so much that the urbanists are wrong, but that this and many other public policy discussions are being conducted under extremely dangerous conditions.
This is a hugely complicated issue but the major points that worry me can be broken down to four or five basic categories (depending on how you split them):
The overwhelming majority of the people conducting this discussion come from a remarkably homogeneous group (economically, geographically, educationally, and culturally). Furthermore, this group lands on the far end of the spectrum on any number of relevant dimensions. This invariably leads to distortions and blind spots;
This discussion has come to be dominated by a simple and elegant narrative with notable utopian elements. Not coincidentally, this narrative is remarkably appealing to the group conducting the discussion;
Much, if not most, of the supporting evidence for the narrative comes from a handful of outliers such as the Bay Area. What's more, the great success of some of these outliers may have more to do with having been in the right place at the right time for various industry booms than with the cities having pursued any particular policy.;
There is also a morality play at work here. This is often unavoidable in public policy debates but it becomes very dangerous when the judging is done by a homogeneous and insular group and the focus is on the sins of those on the outside.
Which brings us to our case in point. The worker who lives 25 miles outside of St. Louis, Missouri and commutes to work is seen as engaging in wasteful and environmentally costly behavior, but the Manhattan-based executive who flies once or twice a month to cities on the West Coast is not, despite the trip being roughly one hundred times longer and the mode or travel not being by any stretch of the imagination green.
The new paper, published in the journal Environmental Science and Technology, finally pins some numbers on all this theory by examining the impact over different time periods of various different modes of transport. The results are illuminating.According to the paper, if we focus just on the impact over the next five years, then planes currently account for more global warming than all the cars on the world's roads – a stark reversal of the usual comparison. Per passenger mile, things are even more marked: flying turns out to be on average 50 times worse than driving in terms of a five-year warming impact.If we shift to a 20-year time frame, things look completely different. The short-term impacts have largely died down and the plane looks considerably better – helped along by a quirk of atmospheric chemistry which sees nitrous oxide pollution from the aircraft engines causing cooling during this period by destroying methane in the air. The paper even suggests that for any time frame longer than 20 years, flying is typically greener per kilometre than driving (although when I phoned to check this, one of the authors of the report confirmed my suspicion that this isn't true in Europe, where fuel-efficient cars are more popular).
If we compare by miles traveled and we assume the average automobile fuel efficiency remains constant, air travel is much worse than auto travel in the short term and slightly better in the long term, but both of those assumptions are questionable.
In an age of hybrids, plug-ins and increasingly viable electrics, it should just take time or a good regulatory push to get us to where Europe is. On the question of miles traveled... As we mentioned in a previous discussion of drunk driving, using per-mile comparisons when discussing modes of transportation with wildly different ranges is problematic at best. The decision to travel long distances and the decision to go by air are closely related and the causality goes both ways.
It would be easy to get mired in the details, but we can be fairly sure that a sharp reduction of air travel would encourage people to look for closer substitute destinations or to eliminate trips entirely (in the 21st Century, there is little reason for insisting that people be physically present for a meeting). Cutting back on air travel would certainly seem to be the environmentally sensible thing to do, but for this post, I'm less interested in going green than in going meta.Is the larger discussion healthy and productive.
Homogeneity is not always a bad thing. Sometimes a group of people of like backgrounds and similar minds can converge on a common vision and produce something wonderful and innovative. In these cases, isolation and even insularity can help get things started. (Chicago was a theatrical backwater before the Post-War renaissance.) At some point, though, there has to be cross-fertilization. Otherwise conjectures become implausible, judgements become biased and ideas become stale.
Following the debate on urban renewal, food stamps, tax policy, education reform, etc. I constantly notice, not only that a plurality and possibly a majority of stories seem to come from the same perspective (top quartile, Ivy League, upscale neighborhood in a high-density city), but that the writers have no idea how unrepresentative their experiences (including bicoastal living)can be.