Vaclav Smil's "sobering thoughts" of the 21st century seem to follow the perspective of technological sustainability over ecological sustainability. He proposes five major drawbacks of the transition to new energy sources, all of them concerning the shortcomings of technical sustainability to adopt a certain standard of strategies which are environmentally conscientious. Smil acknowledges that current technologies have not been developed which will make the shift from fossil fuels to renewable resources easy and seamless. Current technologies are incapable of managing the energy density of renewable energy which would be necessary to meet the energy density of the fossil fuels that we are currently relying on. Smil approaches the concept of sustainability by exposing the technical limitations of both the natural world's ability to generate energy and the limitations of technologies which humans have created to harness natural energy. Smil does not mention a transition of public attitude as the necessary element of a sustainable future, but rather focuses on a transition of improved technologies and policy.
If we do not meet our energy needs by 2112, it is due to the fact that the supply of fossil fuels is adequate for generations to come, new energy technologies are not developed enough for us to fully rely on them yet and their production and dissemination will not be economically feasible or distributed evenly enough for successful results. Therefore, meeting our energy needs by 2112 is most likely unattainable given the current status of sustainable technological improvement and appetite for unsustainable energies.
A more optimistic story would be concluded with the attainment of our energy goals by 2112. In this case, society at large is able to collectively acknowledge a more environmentally conscious mentality. Economic growth and development is also able to occur in areas which it was previously lacking, giving way for updated, more expensive technologies. To be sustainably successful is to be able to achieve the enormity of technical and infrastructural requirements that will be necessary to make a difference on a global scale.