CO2 Crash: Atmospheric CO2 down Sunday to 399.54 ppm from Friday high of 399.88 ppm Friday was a new high. Read more at Keeling_Curve’s Twitter feed. Share this: Email a link to a friend (Opens in new window) Email Print (Opens in new window) Print Share on X (Opens in new window) X Share on Facebook (Opens in new window) Facebook More Share on LinkedIn (Opens in new window) LinkedIn Share on Pinterest (Opens in new window) Pinterest Share on Tumblr (Opens in new window) Tumblr Share on Reddit (Opens in new window) Reddit