Ask HN: Most compelling evidence of climate change?

I'm asking this here not because this is a climate change forum but because I think a lot of smart, introspective and skeptic individuals frequent HN.

The question is simple, what is the most compelling evidence that climate change is happening?

Alternatively if you have good evidence to believe that climate change is not happening please share it.

In any case please link to the source so we can validate your statement and let's keep the conversation friendly.