[pale-hands]

This is your claim, right?

> The conditions required for the amount of land-based ice to melt [in order for coastal cities to flood] will have meant that the extinction of most (if not all) life on this planet would have occurred long ago.

I suppose your calculations are simply the energy required to melt the additional volume of water required to raise sea level by x meters, and that the increased rate of heat retention due to AGW could not supply the heat required in y years, for some reasonable values of x and y. I'm prepared to stipulate that that is so. (I would set x=2 to flood some major cities, and y = 2100 - 2017 = 83).

Well, melting all that ice is not the concern, although no doubt it will happen in a few thousand years. The concern is that ice which is currently above sea level will slide into the sea, as the NY Times article discusses. Calculating that would require a whole lot of modelling and detailed knowledge, well beyond a fifth grader (whatever that is in your country), or even a lone genius with superb arithmetical skills.