When the astroid struck earth 60 MYBP most of us think of the dinos
becoming extinct. However, what isn't looked at is the massive
global biosphere loss and how that impacted climate for many years
afterward--resulting in first a layer indicated ash and burns and
then a layer indicating glaciations in the geo record. The astroid
resulted in massive marine loss in the microbial biosphere,
upsetting living earth ELECTRICAL patterns.
No one in the biological community disputes that we are currently in
the midst of a human induced extinction event.