Unfortunately, it's not just CO2 that has an effect on climate... there's also other gases, particularly methane, that are relevant for climate change. And with the current warming going on, there will be not "just" the methane emissions from fermentation, cow farms and leaking natural gas pipelines, but also a ton of methane from currently thawing Russian permafrost, or methane clathrate deposits (which alone are estimated to hold more carbon than all other sources of fossil fuels combined).