The dinosaur media are—yet again—reporting the death of climate skeptics because of the latest, greatest paper published by Nature magazine. Increases of dreaded carbon dioxide appear to have preceded the warming that initiated human civilization.
For years, my less-green friends have pointed to the long ice cores in Antarctica, where annual striations go back hundreds of thousands of years. The temperature can be inferred from the relative abundance of common oxygen (16O) and its rarer isotope with two additional neutrons, 18O. In most cases, temperature changes before carbon dioxide does, seemingly inverting the normal cause and effect for the current climate rage.
Not so, say Jeremy Shakun, from Harvard, and his eight colleagues from around the world. They gathered up 80 so-called “proxy” indicators of local temperature (including the Antarctic ice cores), and compared them to the amount of carbon dioxide trapped in the ice. It appears that—after a little non-CO2 temperature rise of speculative origin—carbon dioxide increases indeed preceded the massive deglaciation that began about 20,000 years ago.
Shakun et al. argue that the Antarctic ice cores are a special case, where through a very complicated (and hard to verify) chain of causation, temperature will in fact increase before carbon dioxide.
Enter the internet, one of the greatest things that has ever happened to science. Because of requirement for increased data transparency (pushed, in no small part, by the Climategate gang’s reluctance to release theirs), the numbers behind important papers are now available online.