Carbon dioxide in Earth's atmosphere just reached a major milestone
September 29, 2016, 9:36 a.m. by Russell McLendon
CO2 data from Mauna Loa in Hawaii suggest 400 ppm is the new normal.
As U.N. makes history on Earth Day, Leonardo DiCaprio reminds us not to rest on laurels
April 22, 2016, 2:31 p.m. by Russell McLendon
More than 170 world leaders signed the Paris Agreement on Earth Day 2016, but that's just the beginning.
The Pliocene called. It wants its CO2 levels back.
May 8, 2015, 11:24 a.m. by Russell McLendon
Earth just averaged 400 parts per million of carbon dioxide for a month, which hasn't happened in human history — and possibly not since the Pliocene Epoch about 3 million years ago.