The global environmental cooling seen in the…
540 CE
The global environmental cooling seen in the year 540 is probably due to a comet impact, evidenced by global tree ring growth diminution.
(Baillie, M.G.L.
(2007).
Tree-Rings Indicate Global Environmental Downturns that could have been Caused by Comet Debris, Chap.
5 in Bobrowsky, Peter T. and Hans Rickman (eds.
), Comet/Asteroid Impacts and Human Society: An Interdisciplinary Approach, Springer-Verlag, Berlin.
ISBN 3-540-32709-6, pp.
105–122.)