Point #1 - Yes, climate change is a natural phenomenon. In general, those changes have taken place v e r y s l o w l y allowing plants and animals to adapt. In the rare times when a big event like a meteor strike or a giant volcano blows and the temperature changes rapidly, there are mass die-offs. We are currently causing a HUGE number of animal extinctions every single day all over the planet.

Addressing point #2 - Mercury cannot be used as a comparison, because Mercury has no atmosphere. Therefore, heat can readily escape. That's not the case with our atmosphere. The more CO2 that goes into it, the more heat it holds. That has been true of the Earth since its formation.