JFYI this "tree" technology of which you speak, can only be deployed at the earth's surface. AFAICT, OP was asking about upper atmosphere, which doesn't mix muc

JFYI this "tree" technology of which you speak, can only be deployed at the earth's surface. AFAICT, OP was asking about upper atmosphere, which doesn't mix much with the lower atmosphere. Perhaps trees plus some way to mix the atmosphere? Also, I believe we were talking about methane - and while these nifty "tree" things appear to sequester CO2, I believe these produce some amount of methane. Again, perhaps pair Trees(tm) with something to address the methane? For example, I've heard about "fire" but unsure if it can be deployed in the upper atmosphere, requires unrealistic concentrations of methane, or whether its outputs and side effects are acceptable. :-)