Sure, a medicine may be lethal (but after many trials, errors, cases etc - people developed efficient drugs and medical procedures). But there are many people;

Sure, a medicine may be lethal (but after many trials, errors, cases etc - people developed efficient drugs and medical procedures). But there are many people; it's a big difference if one dies or everyone dies. "Even more experimenting" is a bad idea. The current situation is bad and we should change its causes. (Otherwise it's like healing tooth with painkillers.) Here I would guess that the average value of risk is highly negative (as in any case with dealing with complex systems). And there are many imaginable consequences, which are far worse than the current pace of global worming. E.g. poisoning biosphere, accelerating global warming, etc. And, no, global warming is not an asteroid impact (i.e. killing everyone and everything), so "all or nothing" is a poor mentality (and deadly dangerous!).