I think the end - end of human life on earth - is inevitable. But I don't see any evidence that a God will have anything to do with it. The majority of all species that have ever lived are now extinct. It should not be surprizing that humanity will eventually have the same fate.
But I honestly don't see humanity going extinct as a result of climate change. I think we could see a period of adversity with more frequent and more deadly weather related events that would take a toll on human population growth. We might even see the human population start to decline as a result of famines, wars and disease pandemics. But there will come a certain point when the population gets so low that humans are no longer able to have a measurably negative effect on the climate. At that time the earth will slowly restore itself.
As a side point I think I should mention that Watchtower's application of Revelation 11:18's "ruining the earth" to pollution of the earth, is quite disingenous. Let's look at the whole verse:
"But the nations became wrathful, and your own wrath came, and the appointed time for the dead to be judged, and to give [their] reward to your slaves the prophets and to the holy ones and to those fearing your name, the small and the great, and to bring to ruin those ruining the earth.”
Let's consider the context. The first part of the verse seems to be emphasizing that all righteous people great and small will be rewarded by him. The natural contrast to this is to say that all the wicked great and small will be destroyed. How can it instead, mention only those who are damaging the environment? That doesn't fit the context. What about the murderers, theives, fornicators, spiritists? All of these are ignored to mention those who are littering? That makes no sense. Reasonably, the expression "those ruining the earth" must have a broad meaning that encompasses all practising sinners and isn't speaking only or especially of those damaging the environment. So why use the expression "those ruining the earth"?
One of the interesting things about the book of Revelation is its regular rehashing of OT imagery. There are references to Balam (Revelation 2:14; Numbers 22), Jezebel (Revelation 2:20; 1 Kings 16:31), Gog of Magog (Revelation 20:8; Ezekiel 38:2), the temple guard found asleep being stripped of his clothes (Revelation 16:15), Babylong the Great, etc. The same is true of the expression "ruining the earth". It is actually a rehashing of the idea found at Genesis 6:11,12:
"And the earth came to be ruined in the sight of the [true] God and the earth became filled with violence. So God saw the earth and, look! it was ruined, because all flesh had ruined its way on the earth."
So this is where the writer of revelation got his expression about those ruining the earth. He was borrowing a similar expression as used in Genesis to implicitly compare the future destruction of the wicked to the situation that happened back in Noah's day. Just as God had to destroy those who ruined the earth in Noah's day, so too he will once again destroy those ruining the earth. So what does ruining the earth actually refer to? Well, what does Genesis 6:12 say? "[the earth] was ruined because all flesh had ruined its way". Yes, it's actually referring to people's sinful way of life. So the earth that is being referred to is not the literal physical planet but human society. Sinful conduct of every kind contributes to the ruination or breakdown of human society. So the expression "those ruining the earth" thus encompasses all willful sinners great and small as they contribute to the ruination of the societal fabric of the world of mankind. So revelation 11:18's reference to "those ruining the earth" is really a reference to all willful sinners who contribute to making the world a decadent place. It is not referring only or especially to those polluting the planet.
http://meletivivlon.com/2012/12/11/ruining-the-earth-how/
