Levels of atmospheric carbon dioxide of around 400 parts per million (similar to 2000s) had increased temperature by over 2–3 °C (3.6–5.4 °F) around three million years ago. This temperature increase eventually melted one third of Antarctica's ice sheet, causing sea levels to rise 20 meters above the preindustrial levels.[71]
the current version of the gbr is around 8000yrs old...you should google ancient reefs ...pretty interesting...shame the white shoe nupties dont appreciate it