Climate change is not simply polluting our air, water, or land. It is adding chemicals into the air that are changing the way heat transfer occurs. It is true that this generally heats up the entire planet and the data have showed this trend not only occurring, but accelerating as human industrialization expanded.
This effect is outside the natural cycle because the chemistry has altered the natural heat transfer properties in our atmosphere. This is most easily observed that ice which has not melted in 600,000 years, is melting!
To those that can not conceive humans can affect the planet need look no farther than CFCs causing holes in the ozone layer. The level of atmospheric CFCs has dropped because of regulations and the ozone layer is slowly reverting to normal and full recovery is expected in a few more decades.
The problem with global warming is the tipping point, the arctic. The arctic has always been a net greenhouse gas sink, that is the environment there uses more greenhouse gasses than it omits. The melting of the arctic is uncovering bogs, vast areas of bogs. These bogs will within the next 5–10 years have the exposed frozen plants begin decomposition and that will be a new, vast source of greenhouse gas emissions turning the arctic from a greenhouse gas sink into a greenhouse gas emitter. That change is the tipping point, the point of no return, at least with the technology we currently have.