There have been reports of Global Warming on Mars that is in line with the rise experienced by the earth.
This tends to suggest Global Warming is a phenomenon that is outside our control.
In science we do 2 experiments to indicate whether something is cause. In this case we have Mars with no people on it and Earth with people on it and the same effect is occurring. My first guess would be people are not the cause of the effect. The effect is there surely, but we are not its cause.
Since the effect is occurring on both Earth and Mars the likely cause is the Sun. Either it is burning more brightly or the region of space we are moving through has less 'dust' to absorb the sunlight.
Whatever the truth I think this information is very important for the global warming debate and should be brought to more people's attention.