Carbon dioxide in the atmosphere is continuously measured by several observatories such as that at Mauna Loa, Hawaii. So far, the reduction of emissions due to the pandemic-induced economic slowdown has not resulted in a lower carbon dioxide content of the atmosphere.
As explained by Dr. Roy Spencer: “Atmospheric levels of carbon dioxide (CO2) continue to increase with no sign of the global economic slowdown in response to the spread of COVID-19. This is because the estimated reductions in CO2 emissions (around -11% globally during 2020) is too small a reduction to be noticed against a background of large natural variability. The reduction in economic activity would have to be 4 times larger than 11% to halt the rise in atmospheric CO2.” (Source) This means that carbon dioxide is an insignificant driver of global warming. It also shows that reducing carbon dioxide emissions will have very little effect on global temperature.
See also: A Review of the state of Climate Science