Pre-industrial levels when we were still coming out of significant cooling period. In every other period of human history, increased average temperatures have coincided with golden ages. Depending on where you peg your baseline for what "normal" temperatures are, the projections can look more or less scary.
I'm suspicious of anyone attempting to boil down the operations of such a dynamic, chaotic system as climate into simple cause and effect. There's so damn many things that feed back on each other, and that's just the tip of the iceberg that we think we understand. Much more research needs to be done.
https://en.wikipedia.org/wiki/Roman_Warm_Period
https://en.wikipedia.org/wiki/Medieval_Warm_Period
I'm suspicious of anyone attempting to boil down the operations of such a dynamic, chaotic system as climate into simple cause and effect. There's so damn many things that feed back on each other, and that's just the tip of the iceberg that we think we understand. Much more research needs to be done.