The joy of living in an interglacial period is much akin to living in "interesting times".

Ultimately it is the amount of energy coming from our sun that keeps the planet habitable - for now at least, cosmically speaking. But we have:
1 an atmosphere that moderates solar radiation,
2 a tilt & wobble of the planitary axis that causes irregular heating of the surface that reflects or absorbs radiation/heat differently based on surface material,
3 a sun that does NOT produce solar radiation at a uniform, never changing rate,
4 volcanic activity and now human activity that changes the makeup of said atmosphere,
5 whatever I left off but can still be a factor :).

Try balancing that all out ... you make models based on observations and best guesses on current trends... cross your fingers and then keep refining your work. And put up with the second guessing and denial of those who just do not want their comfortable ideas or vested interests to be disturbed.

Where is the "tipping point"? Hopefully we aren't there yet or likely to be soon, because we are having a hard enough time supporting the current population - which is still increasing- and major climatic change may screw our ability to raise adequate food for those hungry mouths.

The geek likes to try and stay optimistic... but sometimes it's just hard.