Disruptions to the cycles were most likely responsible for the warming and cooling trends of the past whether they were man-made or "natural", such as global instability, including volcanic eruptions, etc.
"Remedies" with the sheer number of humans currently inhabiting the globe and expected to double in 25 years, does not seem feasible. Any answer includes a massive die off... that includes humans. Perhaps "natural" disasters will take care of that for us.