Need help finding peer reviewed Articles on global warming.?

I need help finding a peer reviewed article on the contributions humans have to global warming. i need to find this online. i also need a peer reviewed article on studies saying that global warming is the cause of the earth natural climate cycle and not so much human contribution. this is for a bio paper and i am... show more I need help finding a peer reviewed article on the contributions humans have to global warming. i need to find this online. i also need a peer reviewed article on studies saying that global warming is the cause of the earth natural climate cycle and not so much human contribution. this is for a bio paper and i am struggling to find peer reviewed articles. please post the links thank you
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