Mankind will be the death of planet Earth; but not from AGW. In mankind’s headlong rush into things it knows nothing about, nature will be messed up so much that, if left to its own devices, will leave the planet a scorched ball of - nothing.
Their goal is to reduce CO2 to some “acceptable” level. That decrease, however, means that fewer plants will survive to produce O2. Less O2 = people die. Less CO2 also means ozone layer breaks down, allowing radiation to get through. More temperature increase ......
Ozone is broken down mainly by solar ultraviolet which increased greatly in the 20th century causing the ozone hole. The recovery is basically because solar activity has decreased a lot since the 90's. The CFC's are also a factor but catalytic. They will affect the rate of breakdown.
Well, I'll go another direction and express great concern about... genetic engineering.
I suspect it has a greater potential for widespread disruption of life from (as occurs from so much of our brainiacs' efforts) unintended consequences.