"Most people agree climate change should be understood through robust scientific evidence. Such a standard should also apply to measures to reduce the climate impact of our cities."

Okay, provide some 'robust scientific evidence' that anthropogenic climate change is occurring, and then you can take it from there. Till then you're simply debating about whose fantasy is going to fool the public the longest.

The thinking on such matters can be greatly simplified with the premise that energy consumption is directly related to cost. That premise is easily verified at the level of a national economy. There will be some variation as one takes smaller and smaller slices of an economy but the default assumption should always be that 'energy follows the money'. So the conclusions of a study on the energy costs of dense urban life should have been immediately apparent from the simple fact that it costs more to live downtown than in the 'burbs. And inner city dwellers tend to be richer and to spend more. Hence their lifestyles mean they account for more energy consumption.

Of course there is an ultimate need for rigorous full life cycle analysis of embodied energy and the like. But such analysis is always subject to uncertainty because of the major problem of setting boundaries to its components. And it's always complicated. So look at costs first. If something costs more it's likely to use more energy. End of story, unless there are clear mitigating factors.

Two issues which can easily be overlooked:

(1) surveys of energy use versus density - do these include the use of energy in transport? And the reductions in this use of energy that come with medium/high density are only realised when the decent public transport (which can be supported by medium/high density) is actually provided, and when city design changes to the point where shops are within walking distance, and so forth

(2) simply measuring average density of cities is useless - I've seen (overseas) small medium density residential areas separated by green fields - the public transport works well because of the number of people living within 5-10 minutes walk of each tram stop, not because of the density of the city as a whole