It happened before.
Will it happen again?
commondreams.org/news/2015/04/10/oceans-facing-carbon-rates-which-spurred-mass-die-250-million-years-ago
Will it happen again?
commondreams.org/news/2015/04/10/oceans-facing-carbon-rates-which-spurred-mass-die-250-million-years-ago