The 3% of carbon emissions idea is idiotic...

The climate remains in equilibrium if there are only natural causes of carbon dioxide emissions. Other natural processes will compensate for these. When humans start producing some more carbon dioxide, there is nothing to compensate for it, so the effect builds up.

Think of it as a tank with 97 inlets open and 97 drains open. The water level in the tank does not change. However, if we add 3 more inlets (which will comprise only 3% of the total water flowing into the tank), the water level will start rising.