The biosphere has literally billions of tons of carbon already. Limiting excess carbon is not a bad idea, especially when it throws the whole system into balance.
Nearly no scientists are making doomsday predictions either, and that's a bad thing. Even most scientists tend to underestimate the present danger of the current situation.
To be fair, there's a non-zero chance of a CJD outbreak, and same for wasting disease that originates from deer. If or when they cross over to humans, it's going to be nasty.