I know, odd title right? Let me begin this article with a brief explanation on what a TI civilization is. Type I, or T1, is part of the Kardashev scale. The Kardashev scale refers to how much power a civilization can harness or produce, going from Type I to Type III. Type I is a civilization that can harness all of the power available on a given planet, Type II all the power produced by a star, and Type III all the power produced by all the stars in a galaxy. Some scientists have placed Humanity at less than Type I currently (specifically around .72), and have coined us as T0.
This may sound rather heavy on the Science Fiction side, and in many ways it is, tho the scale is rarely mentioned in Sci-Fi works. It does, however, have relevance. The amount of energy production is usually directly proportional to the total energy consumption. Energy consumption is directly proportional to current population. Therefore, if technology growth cannot keep up with the energy demands of the population, then both will fail. Worst case scenario; technological advancement stagnates, energy production then lags behind population growth, which in turn causes a feedback loop on technological advancement, eventually leading to a population crash. Basically this means no new energy technology advancements with continued population growth could lead to a decent back into the middle ages or worse. (Of course best case scenarios can lead to a technology singularity, but I won't get into that because that is very close to Sci-Fi.)
There are a few ways to avoid this worse case scenario, one of which being further advancements in Nuclear Fusion technologies. Now I know what you are thinking, Fusion is always going to be 30 years away, but that might not be the case. Currently the ITER is working on a prototype reactor. Another option is Solar energy. Now technically to produce all of the power available on Earth using Solar power we would have to cover the entire surface of the planet with solar collectors, but the technology still has its own benefits. There is also Breeder technology, which is a more efficient form of Fission. For a Fission reactor to be considered a Breeder reactor it basically must be designed to created more fissile (what maintains the nuclear reaction) material than it consumes. Lastly, to keep the feedback loop from occurring we can research more efficient ways of using our current energy, which is likely the most immediate thing that we can do as a civilization. All of these have their own pros and cons, but all of them share either reduced or zero carbon footprints.
Here are some links to organizations currently working on some of these technologies.