Machka 

Except that they keep discovering that these models have errors.

tandempower

While I don't dismiss the issues of carbon emissions and fossil-fuel non-renewability is significant, the more overlooked (or ignored) issue is that of sprawl. While carbon and fuel scarcity may take a few generations to become dire for the more privileged in the world, the kinds of cities and economic practices they develop and maintain in the mean time will set up future generations for success or misery in failing to adapt to eventual resource-shifts.

All that is really needed is for a significant-enough number of people in each locality to live comfortably enough car-free for the lifestyle to serve as a viable choice for anyone and everyone who gets economically pressured to relinquish driving at some point in the future. Logically, the transition away from fossil-fuels can take place gradually as long as the economy is growing less instead of more dependent on them. What's more is these fuels will deplete slower and carbon emissions will grow less threatening as the amount of people living car-free increases. This will only benefit those who continue to drive by rendering greater stability of economic growth.

Bicycle production, like the production of motor-vehicles, is basically renewable as long as the energy-demand of these industries doesn't exceed the sustainability of responsible energy-sources. What isn't responsible is to continue replacing green space with pavement and buildings. Both paved-areas and buildings should be designed to leave trees and watersheds intact and functioning. Basically we need to re-forest cities as much as possible and develop existing natural lands without disturbing natural habitats much, such as by only building bike roads and a few narrow service roads for service vehicles and deliveries. Combining this with sustainable agriculture adds another dimension to the challenge.