There's an old curse that seems relevant: "May you live in interesting times." Times are certainly interesting. At this point, it seems like some sort of full-scale war between NATO and Russia is more likely now than it has been any time since the 1980s (granted then it would have been NATO against the USSR but the basic point is the same). Worse, at least historically the military and diplomats spent much of their time making sure that things didn't spiral out of control. Without the Cold War feeling, people may feel less of a need to guard against such issues. Worse, Russian military doctrine currently describes a limited nuclear strike on conventional military targets as a de-escalation http://thebulletin.org/why-russia-calls-limited-nuclear-strike-de-escalation . While in official documents they reserve that terminology for using nuclear weapons to handle direct conventional military attacks on Russia itself, one finds very worrying the level of doublethink where one describes being the first to use nukes as de-escalating a situation.
During the Cold War, one popular explanation for the Fermi paradox https://en.wikipedia.org/wiki/Fermi_paradox, the apparent lack of highly advanced civilizations in the universe, was that species end up blowing themselves up. For most of my life, this belief looked almost quaint but it is not looking disturbingly likely. At this point, the evidence for some sort of serious barrier to civilizations emerging substantially is much stronger than it was a few decades ago. The apparent lack of K3 or K2.5 civilizations is at this point substantially robust https://en.wikipedia.org/wiki/Kardashev_scale with around 100,000 galaxies searched and almost no sign of any civilization using a substantial fraction of its galactic energy output http://www.scientificamerican.com/article/alien-supercivilizations-absent-from-100-000-nearby-galaxies/. With this return to Cold War norms, it looks like we need to not only take seriously that there's a Great Filter, but that the Filter might be nuclear war. That's especially the case because a nuclear war does not need to kill every member of the civilization to completely destroy any hope of a technologically advanced civilization. If not enough natural resources have been consumed by the civilization (e.g. the easily accessible coal and oil) then even if the species survives it may not have the ability to reboot itself to a high tech level since getting to a high tech level may actually require access to these resources (in which case one gets essentially one chance to get to be a high tech civilization).
In the case of natural gas power plants. . . For now, they're much better than coal. For the future, solar power and nuclear fusion will eventually kill them off.
If we ever get fusion to work effectively it might end up killing everything off. But in the moderate term, solar isn't going to be the only one. A combination of nuclear fission, solar, wind, geothermal and hydroelectric is much more viable and solves many of the problems. Fusion is a very long way off and it is likely that we'll stop having susbstantial fossil fuel use well before fusion is a common power source.
Use the Force, Luke.