At this point, the only evidence that would change my mind is that we discover and quantify some natural process that will cool the Earth and offset the impact of our CO2 emissions over long periods of time.
For example, we are about to experience a solar mininum. This might offset global warming for a decade or two, but if we keep pumping CO2 then, as soon as it ends, the warming will ramp up. This natural event simply delays the impact. So to prove to me that global warming isn't something we need to tackle, I need evidence that some long term cooling factor exists. What is it, how long will it last, how much will it offset warming?