The points about ice-ages ought make us consider that the world is relatively cool at present. Although we are in (probably) a warm interglacial, just be glad none of us will ever see the results of the end of the Ice-Age completely.
The arguments really revolve around human activity disturbing a natural event that, albeit with small perturbations lasting no more than a few centuries at a time, would otherwise be a long-term, fairly stable conditions in human-historical terms.
In other words, the Earth would be expected to warm further – the previous interglacial brought sea-level some 10 metres or more above present – but much more slowly. Wildlife was able to adjust to this, and so were our ancestors when their drift Northwards was blocked by Arctic conditions. The South of England was not glaciated, but was Arctic tundra.
Our far-descendants faced with whatever happens, will find it far harder to adjust to a changing climate, especially if changing at an artificially-rapid rate, than our Palaeolithic ancestors and their Neanderthal cousins would have done. (Though we don't exactly know just what did happen to bring about the entire demise of the latter species, beyond hypothesised absorption into our own by breeding.)
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Mars? 
Regarding colonising Mars, I still think that of science-fiction and Musk bank-balance realms – delete the less-credible. The planet cannot support life, especially our own. Who on Earth would want to live on Mars?
It is a cold desert under a very thin atmosphere of mainly carbon-dioxide; and even if colonised in something like Antarctic-research scale and purposes the attempts would be faced with gigantic problems starting with the sheer travelling-time and isolation of the trip each way.
Let alone of support there and for the return trip
Even assuming it would be possible to return from a planet of similar mass to Earth, so a trip there is not just a one-way ride to Eternity with a stop at Mars Services……..