The smoothing coefficient (or data resolution, however you want to look at it) on that chart is vastly different over different periods of time, leading to a misleading hockey stick type visualization.

So what you're saying is, even though it may have went high in the past, you believe that we have the possibility of dropping cool again in a short (decadal) period of time?

What I'm saying is, the human heartbeat looks very spiky when you sample it 250 times per second. When you collect data in minute-long periods though, it looks like a flat line.

We do not have daily, yearly or even decadal temperature data for the time period 15,000 BC the way we do for the modern day. There is a lot of historical variability that is not shown on the graph. That variability could easily reach today's levels or higher, for moments.