Climatologist James Hansen emphatically argues that cumulative emissions are what really matter – how much warming the planet experiences depends on what proportion of the world’s fossil fuels get burned.
One reason for this is the long lifetime of CO2 in the atmosphere, with much of it remaining after thousands of years. That being said, the model simulation I have seen shows concentrations dropping sharply, and then tapering off with time:
It seems like it would be helpful to put together that chart with this one, showing historical and expected CO2 concentration increases:
A combined chart on the same scale would illustrate what would happen to CO2 concentrations if we stopped emitting at some point soon, specifically what the next few decades would look like.
It seems at least logically possible that timing of emissions could matter. Imagine, for instance, that having emissions cross a certain concentration threshold would really matter. If so, spreading out human emissions so that absorption of CO2 by the oceans would keep the concentration below that cap could be quite beneficial.
It seems an important question to sort out, given how the whole BuryCoal project is focused on limiting total human emissions, rather than trying to space them out.