In the first two posts in this series (1 and 2), I discussed the requirements and challenges of transitioning our global economy to renewable sources of energy. My interim conclusion was that there are serious doubts about our ability to affect any significant transition from fossil fuels to renewable energy. Much of this uncertainty is the result of uncertain systemic energy return on energy invested. In other words, when all inputs are taken into account—as must be done where we’re talking about shifting energy sources on a civilizational level—can a world powered by solar and wind power itself the way it has on oil, gas, and coal?

The key take away is precisely this uncertainty: we simply don’t know if renewables—either current or potential future technology—will be up for the job. Where does that leave us? This discussion—and many others related to Peak Oil—is really a matter of what is known as the “Precautionary Principle,” or what degree of consensus is required before we embark on a course of action that may result in irreversible harm. Because the Precautionary Principle has such broad application in discussions of Peak Oil, I’ve modeled this post as a discussion of the principle itself, using the issue of renewables transition as but one example of its application.