A better example would be coasting down a hill, then hitting the gas as the road flattened out. As I explained way back on page 2, the relative contributions towards the average global temperature by solar irradiance, volcanic activity, and greenhouse gases is fairly well charted. Probably about 60% of temperature increase up to 1940 was likely due to the sun, But then wavered some until about 1960 where it largely plateaued. A series of decent volcanic eruptions through the latter half of the 20th century then muted the effects that would have been apparent–namely that the temperature increase due to greenhouse gasses was climbing.
http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch06.pdf (PDF - Page 477)
http://www.mri-jma.go.jp/Dep/cl/cl4/IPCC-AR4/volcano_hist.html