Is the sixth extinction preventable. Why or why not?

Answer 1

I assume you believe there have already been five.

No, the sixth extinction is not preventable.

If Al Gore is wrong, global warming won't happen or will be harmless. If Al Gore is right, and if mankind succeeds in stopping or reversing it, then we dodged the bullet and averted a calamity. In either case, whenever the next extinction comes, for whatever reason, it will be the sixth. If not before, it will probably happen when the sun enters its red giant or white dwarf stage.

Answer 2

there are many ways that life could be annihilated on earth.

an asteroid could cause mass extinctions (and have in previous history). but if detected early enough in its trajectory, an asteroid could be knocked off it's path enough to keep it away from earth.

climate change has been depicted as a doomsday crisis. this probably isn't the case. while there is some increase in temperature, it isn't enough to wipe out life on earth. temperatures rise, water levels rise due to melting glaciers, thus we'll have to move away from the coasts. climate change will cause us to make adaptations but it won't eliminate us. to see an example of greenhouse effect that could kill us, see Venus.

other things like pollution or lack of resources could cause extinction as well.

many things are preventable if identified and treated early enough. but there are things that could come out of nowhere, in which case hope would be slim.