What I don't get is:
The Earth for all practical purposes is a closed system, meaning nothing gained or lost by any actors ON the surface. We take stuff from underground, put it on top of the ground, change the form of materials by burning them (combined with Oxygen - part of our atmosphere) and take things from one part of the globe to another part. The net change (for practicality's sake) is still zero.
As far as matter goes, it's true that we don't gain or lose much. It's practically a zero sum game.
However, we don't have a matter problem, we have an energy problem. As far as energy goes, the planet is
not a closed system. We get a very large amount of energy from the sun. Maintaining the relative equilibrium that we've come to over the ages requires that a certain amount of that energy is released back out into space.
The problem that we're facing now is that we're keeping more of that energy, due to the increasing greenhouse effect of the environment, and this is heating the planet.
Humans aren't creating the energy, but we are contributing towards changes in the atmosphere that are keeping the energy in our system instead of letting it be released back into space.