[Telepathic Intruder]

"Humans have mass so they do cause gravity."

Yes, but the mass that make up humans was already present in the Earth prior to humans, so we did not create the mass that creates the gravity. Double touché

But seriously, I'll admit humans effect the environment, but to what degree? A single volcano can produce more CO₂ than humans have ever produced. And who's to say how harmful CO₂ actually is? There would be no life on Earth without it. Those little seemingly unnecessary details are not even addressed.

[palmer]

A single volcano can produce more CO2 than humans have ever produced.

Often repeated but definitely incorrect. A single large volcano (Pinatubo) produced about 42 Mt of CO2. see http://pubs.usgs.gov/pinatubo/gerlach/ In contrast man produces 82 Mt a day (about 30Gt a year)