Climate change: time for the sceptics to put up or shut up | Comment is free | The Observer
Say I were to ask you to prove that the dinosaurs were wiped out when
an asteroid collided with the Earth 66m years ago, in what is now
snappily called the Cretaceous-Paleogene extinction event.
If you
were as weirdly obsessed by these catastrophes as I am, you would maybe
start by citing the worldwide layer of sediment known as K-Pg boundary,
which was first discovered near Gubbio, in Italy, and is thought to be
the fallout from a massive explosion. You would mention the soot that is
associated with this layer, the site of a huge impact in the Yucatán
region of Mexico 66m years ago and, finally, you'd ask what else could
have caused the dinosaurs to die out more or less overnight. A sceptic
might respond that this is all supposition, evidence tenuously linked to
fit a very recent theory: none of it constitutes proof and no one can
ever know why the dinosaurs vanished to allow the rise of mammals and
the eventual evolution of man.
So you would quote more evidence,
such as the presence in the K-Pg layer of iridium, an element rare on
Earth but not in asteroids, as well as the altered state of quartz,
which can only be made under extremely high pressure, such as is caused
by a huge impact of a 10km asteroid. You would mention the long darkness
when only ferns grew and the fact that the seas were emptied of all but
the most tenacious species.
A slogan is projected
by Greenpeace activists on a cooling tower of Belchatow power station in
Poland. Photograph: Kacper Pempel/REUTERS
