First off, whether our energy economy at the end of this century is primarily fusion or thorium is a valid debate. Both are viable options but I agree with you that it will take a long time to perfect. That is why solar will be used as a bridge (or maybe it will be used permanently). The number of solar cells that can fit on a panel is doubling every year and cells that can retain and store solar for long periods of no sunlight (and also systems that can distribute energy from regions with more sunlight) are already in existence.
Listen, I agree with you that climate change is the biggest problem for our civilization. That is why we must transition from our current energy economy onto a sustainable one. If we don't transition then we are in massive trouble. But we will change because that is the nature of our species. We built the foundations of our global energy infrastructure in the 18th and 19th centuries. We didn't know what the repercussions of burning fossils fuels were. We know now. There are entrenched industries that will fight the transition, but it won't matter. Once one country (my guess is Germany at the moment because they are world leaders in solar energy) transitions to a predominantly solar economy (probably the 2020s - because that is when solar will be able to produce more energy than oil for a lower coast (i.e., grid parity)) other countries will adopt the new system or fall behind (way behind).
New economies and industries emerge in a natural selection type fashion. Because solar companies know that they could be making the types money that oil is currently making there is now extremely intense competition to produce the most efficient and least expensive solar grids that can power cities and vehicles. Check out Elon Musk's Solar City.
By 2050 the nightmare that was the fossil fuel era will seem distant and archaic. Scientists that warn us of global warming are not wrong. They are right. However, the narratives they create for the future are functional in that they will motivate industry to change. Change will be slow (slower than we would all like) but it will come. Once it does come it will spread quickly (probably as quickly as the internet from 1995-2000).
Again, if we don't then we die. But we aren't going to die. We are going to change. And we will be better for it.