For a long time, the role of carbon dioxide in the atmosphere has both pros and cons: on the one hand, the increase in its concentration can promote the accumulation of photosynthetic products in terrestrial ecosystems, increase soil carbon storage, and form a soil carbon sequestration effect, which is a positive effect. On the other hand, It will increase the emission of greenhouse gases such as methane and nitrous oxide in terrestrial ecosystems and exacerbate the greenhouse effect, which is a negative effect. 
carbon dioxide still has the majority of negative effects in the atmosphere.
Whether the increase in carbon dioxide concentration is good or bad depends on how humans use it.