..glowing embers ... brought about by similar egos
There is hardly anything man can do to seriously damage this planet. Honestly, there isn't. We can do unpleasant things to our environment and we can make the planet uncomfortable for a little while. If we go insane and blast off all of our nuclear weapons some day we can do a decent bit of damage, but nothing like what nature has in store for us. In fact, let's assume someone could detonate all the nuclear weapons on earth at the same time, it would be like a firecracker compared to the K-T Extinction Impact. Since nuclear weapons would be detonated in an all-out war, it is unlikely that more than half would actually explode (the rest being rendered useless by actions of war). Detonating all nuclear weapons would come nowhere near what the K-T Extinction Impact was, and that isn't even that big of an explosion in nature.
Don't believe the 1950s propaganda. An all-out nuclear war will not kill everybody on the planet, probably not even half of the humans on it. It will not cause decades or centuries of unlivable conditions on the earth. Human kind would recover at a reasonable rate and probably thrive in a moderate amount of time. Some places would probably not be seriously affected at all.
Here is a funny factoid to think about - Hiroshima took a direct hit by a nuclear weapon. How long did it take before it was perfectly save to live in Hiroshima after the nuke hit? Answer: a couple of months. It was reasonably safe in the days after the explosion. No serious radiation damage was done to humans in the days and weeks following the explosion. Fetuses in the womb of their mothers during the explosion were adversely affected by radiation, but few or no noticeable radiation damages are known from babies conceived in the time after the bomb dropped.
If you want to imagine a big explosion, think of a Gamma Ray burst in our neighborhood. A decent sized star would release many times more energy in less than a second than our sun will release in its entire lifetime of about 10 billion years.
Compared to "mother nature" the most insane murderous human being ever lived was positively a nice guy/gal.