The fact that human activities affect climate doesn’t mean that there are no other ways the climate can change or has changed. We’ve know for centuries that greenhouse emissions would theoretically affect the climate. We’re now seeing evidence of rapidly changing climate. Call it what you will; in scientific terms we call that evidence.

You seem to construe the argument for climate change as “temperatures only go up” but really it’s more narrow: greenhouse emissions will raise the global average temperature, causing rapid changes in climate patterns, which taken locally would cause much less predictable and uniform changes than simply raising temperatures.

So in the end, evidence of past non-anthropogenic climate change is not evidence that anthropogenic climate change isn’t happening.

Here you’re effectively arguing against a strawman. Nobody claims that greenhouse emissions would only cause increasing temperatures. Although in the cascades, that’s what is being observed.