[palmer]

The beer needs to be warm enough for the yeast enzymes to work. If too cold, they become dormant and the fermentation ceases.

That definitely is one of the most interesting CO2 generation analogies I have heard. But manmade CO2, including beer emissions, is about twice the observed atmospheric rise.

Remove man from the equation and there would still be a rise in CO2 from natural warming. But the rise would be much less.

[Chaguito]

Your statement that CO₂ would be rising "much" less without human beings is in reality is a hypothesis, not a conclusion.

It could be relatively easily tested by measuring the ratio of C¹⁴O₂ to C¹²O₂ in the atmosphere, vs. the same ratio in, say, wood of an exactly known age from, say, the 18th century. By reversing the known decay rate of C¹⁴, the ratio in the pre-industrial 18th century could be calculated.

Since all the fossil fuel that has been burned since the 19th century has had 0.000% C¹⁴, the current ratio of C¹⁴O₂ to C¹²O₂, all things being equal, should be "much" lower, if your hypothesis is correct.