Settled science: CO2 stays in the atmosphere for 100 years, or thousands of years, or five years

[Warmist Seth Borenstein]:  Warming gas levels hit 'troubling milestone' - Boston.com

WASHINGTON—The world's air has reached what scientists call a troubling new milestone for carbon dioxide, the main global warming pollutant.

..."The fact that it's 400 is significant," said Jim Butler, global monitoring director at the National Oceanic and Atmospheric Administration's Earth System Research Lab in Boulder, Colo. "It's just a reminder to everybody that we haven't fixed this and we're still in trouble."

Carbon dioxide is the chief greenhouse gas and stays in the atmosphere for 100 years. Some [what percentage of yearly emissions?] carbon dioxide is natural, mainly from decomposing dead plants and animals. Before the Industrial Age, levels were around 275 parts per million.

...Tans called reaching the 400 number "depressing," and Butler said it was "a troubling milestone."

..."The news today, that some stations have measured concentrations above 400 ppm in the atmosphere, is further evidence that the world's political leaders -- with a few honorable exceptions -- are failing catastrophically to address the climate crisis," former Vice President Al Gore, the highest-profile campaigner against global warming, said in an email. "History will not understand or forgive them."

..."These milestones are always worth noting," said economist Myron Ebell at the conservative Competitive Enterprise Institute. "As carbon dioxide levels have continued to increase, global temperatures flattened out, contrary to the models" used by climate scientists and the United Nations.

He contends temperatures have not risen since 1998, which was unusually hot.

Temperature records contradict that claim. Both 2005 and 2010 were warmer than 1998, and the entire decade of 2000 to 2009 was the warmest on record, according to NOAA.

When it comes to greenhouse gases carbon dioxide isn't the only culprit

[Andrew Glikson] CO₂ remains in the atmosphere for thousands of years.

CO2 Science

He finds that the RT for bulk atmospheric CO2, the molecule ¹²CO2, is ~5 years, in good agreement with other cited sources (Segalstad, 1998), while the RT for the trace molecule ¹⁴CO2 is ~16 years.