Nope. Human deforestation and fossil fuel is primarily responsible for the rise from 280 ppm to 420 ppm (and rising). There's simple no other explanation. Not volcanoes (have not changed), not ocean warming (only a small portion of the CO2 rise is from ocean warming).
Oh, there are!
E.g. One is that warming rises CO2 level. Warmer Earth releases Co2 from the soil and water.
In this theory it is not that Earth is warming because the Co2, but that CO2 is rising, because Earth is warming.
Chicken or egg.
BTW 400 ppm is still a lot less than Earth average. There are hundred of published research papers which evaluate plant growth as a function of CO2 concentration in Atmosphere. (Very easy scientific experiment) Depending on plant, the optimal concentration is between 1000 and 2000 ppm. All plant grow better in more Co2
e.g.
https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-018-1243-3
This one is even from the alarmist:
https://climate.nasa.gov/news/2436/co2-is-making-earth-greenerfor-now/
420 ppm = 0.04%.
Go back to teabagging Geroge Soros and leave us alone.