I'd say you've gone wrong twice, here. You have included problems (with unusual "solutions") with probabilities on hugely different magnitudes on the same list

I'd say you've gone wrong twice, here. You have included problems (with unusual "solutions") with probabilities on hugely different magnitudes on the same list, and presumed that every problem is equally soluble. Global warming has a reasonable probability distribution and a very feasible solution. Compare that to hostile aliens with the ability to travel from the far reaches of undetectability to Earth- the technology gulf would be impossible to overcome.