1) Climate Change due to human influence on the environment
This one's pretty easy. Lets begin an experiment by opening our eyes. Perhaps we can see asphalt, dams, buildings, agricultural land? Roads? Houses? That's all due to humans. Now adjust the "climate control" knob and notice the effect in your room.. so I think you will agree, humans can affect our climate.
The interesting questions are in the details. How fast are our species becoming extinct and what does it mean for our survival? What is all this extra CO2 in the air going to do? How much longer can we visit Venice? By what date will middle USA be a desert? Could we reverse that trend? What changes will occur in the oceans that will affect us now that we have killed off almost all the large fish?
2) Evolution of life on Earth due to long term natural selection
You gotta love people who claim they don't believe in evolution. Literally this means you don't believe that time passes. Actually things move, the Earth rotates, things change, and it's called evolution. Life changes, it can be observed on short time scales in the lab or the greenhouse or on large time scales by looking at the fossil record.
There are certainly many puzzing questions and mysteries about biological evolution, but I feel this is a rant already