Quantum mechanics of the greenhouse effect

Light is made up of packets of energy called photons. Molecules like CO ₂ they can only absorb them when the packets have exactly the right amount of energy to move the molecule into another quantum mechanical state. Carbon dioxide is usually found in its "ground state," where its three atoms form a line with the carbon atom in the center, equidistant from the others. A molecule also has "excited" states in which its atoms wave or wobble. A photon of 15-micron light contains the exact energy needed to spin a carbon atom around a central point in a kind of hula-hoop motion. Climate scientists have long blamed this hula-hoop condition on the greenhouse effect, but — as Ångström hypothesized — the effect requires too precise an amount of energy, Wordsworth and his team found. The hula-hoop condition cannot explain the relatively slow decline in photon absorption rates beyond 15 microns, so it cannot explain climate change by itself. (JOSEPH HOWLETT, more at wired.com)