"As long as the baseball I hit is moving upward, there is no air resistance. Air resistance only slows it down when it is falling downward."

Air resistance is always in play so it always has air resitance no matter what.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide