In case it's not: particulates do indeed cool the Earth. This mitigates the warming effect of CO2 emissions to an extent. The problem is that particulates don't last very long in the atmosphere, whereas CO2 lasts centuries.
To maintain a constant level of cooling, you have to keep burning more coal, which steadily increases the atmospheric concentration of CO2, which steadily increases warming. Before long you'll have overcome the cooling effect entirely and will be on a steady path to increased warmth.