Australia's Senator Malcolm Roberts about human influence on CO2 in atmosphere

Senator Malcolm Roberts, an Australian politician, points out that two, natural experiments have occurred recently.
Fossil fuel use reduced greatly for a period in 2008/9 & again in 2020. In both cases. Atmospheric CO2 concentrations continued their steady March upwards.

Aside from the question of how much CO2 contributes to raising surface temperatures, the rate of increase should have moderated if human activity was an important driver. It seems it isn’t.