Although the Earth’s been decidedly blue for 600 million years, rising populations of phytoplankton caused by rising temperatures are once again causing the world’s oceans to turn green.

Today, the world's oceans appear deep blue, contrasting with the light blue color of the sky ... which meant it would have given the ocean water a green hue because iron hydroxide absorbs blue ...

But hundreds of millions of years ago, most of the ocean was literally green, more so than it is today. And it’s possible that color could eventually ... a compound that absorbs blue light.

Irish nationalist groups active in the U.S. – the Fenians, Clan na Gael and, later, Irish Northern Aid – participated in ...