HMM: No Rise of Atmospheric Carbon Dioxide Fraction in Past 160 Years, New Research Finds. You could still get ocean acidification, but this means that global warming, if any, can’t be because of increased atmospheric carbon dioxide, if there isn’t any.

UPDATE: Looking at the abstract in Geophysical Research Letters, I think I’m wrong, above — I believe the “fraction” that’s constant isn’t the fraction of CO2 in the air, but the fraction of emitted CO2 that remains in the air. So atmospheric carbon dioxide levels could still be rising, just not as rapidly as models predict. Sorry — the news story was confusing, at least to me.