What conclusion would change if the graph started at an earlier, warmer period?
As far as I know, three crucial things would still hold true:
Earth has not been as warm as today since humans existed, in the past 200’000 years. We don’t know if we can thrive in these conditions. Chances are, we can’t. We’re optimized for another climate. We have no precedent wether future Earth is habitable for us.
Earth has never warmed this rapidly, never. Speed matters a lot, as lack of time makes the difference between adaption and extinction.
Whatever the cause, and however normal it may be, the current development, and rate thereof, causes substantial issues on many fronts.
What conclusion would change if the graph started at an earlier, warmer period?
As far as I know, three crucial things would still hold true: