Centennial-Scale Jumps in CO2 Driven by Earth’s Tilt
By Katherine Kornei, Eos/AGU.
Excerpt: Human activity is pumping carbon dioxide into Earth’s atmosphere at an unprecedented rate. But centennial-scale increases in atmospheric carbon dioxide—albeit significantly smaller—also persisted in the past. These so-called carbon dioxide jumps are tied to the tilt of Earth’s axis, new research suggests. ...The concentration of atmospheric carbon dioxide, [at a] level of 315 parts per million was measured in 1958, when modern records began. Today the value is 420 parts per million. On average, the concentration of atmospheric carbon dioxide has been increasing by roughly 1–3 parts per million per year since the late 1950s. ... Etienne Legrain, a paleoclimatologist at the Institut des Géosciences de l’Environnement in Grenoble, France, and his colleagues... analyzed 203 measurements of carbon dioxide concentration ranging in age from 260,000 to 190,000 years before present. ...they spotted seven unusual events in which the carbon dioxide concentration increased by more than 5 parts per million from one data point to the next. ...the researchers noted that 18 of the 22 known carbon dioxide jumps in the past 500,000 years occurred when the tilt of Earth’s axis of rotation—known as the planet’s obliquity—exceeded the average value of 23.3°. Earth’s tilt varies over a roughly 41,000-year timescale, primarily because of our planet’s gravitational interactions with the Sun and Jupiter. ...During periods of higher-than-normal obliquity, higher latitudes receive more solar energy. That change allows more vegetation to grow at higher latitudes....