Ask HN: What are some good sources of climate data to analyze?

I've noticed that articles mentioning climate and climate change that make it to the front page end up being flagged.

I think this is probably fair, because discussions about such articles invariably end up being political and don't end up contributing very positively to HN.

I certainly have thoughts and opinions on this topic, but upon reflection I realize they're not especially well informed. They're mainly based on what I've read in popular media, and I'm hoping I can do better than that.

So I'd like to approach it from another direction. If I want to get some raw climate data for myself, and analyze it using R or Python, what would be a good starting point?

Are there specific data sets that I should focus on? Are there any well known papers that I should read?