>>(How do people make these estimates? A journalist here invented the "National Guesswork Authority", and it seems to me it's working overtime - globally...)<<
Probably by fishing last nights dinner out of the loo and using that as their information. Lots of senationalism out there, but then that's what sells. Who cares if the ship is going to take 400 years to turn into iron ore on the seabed? But if it's going to happen within a couple of decades, we just...just...just gotta do something!
(Exactly what that something we gotta do happens to be, remains ill defined.)