This week we learned that there has been a “precipitous” fall in Antarctic sea ice since 2014. That won’t increase sea levels, but it’s still bad because white ice reflects more of the sun’s heat back away from Earth than dark water. As the ice melts, more heat will be absorbed, which will melt more ice. This vicious feedback is known as the “albedo effect”.

The term comes from the Latin albus, meaning white, from which we also get “albino” and “album” (which in ancient Rome could mean a blank tablet). In English it is first recorded, meaning “pure whiteness”, in a letter by the astronomer royal John Flamsteed, complaining about Isaac Newton’s Optics: “He calls the colour of that representation of the sun which is made by the collection of his rays … whiteness … but ’tis far from albedo.”

From then on “albedo” could be used medically (for an unusual whiteness of bodily fluids) or botanically (a fruit’s pith). The modern astronomical use dates from 1860, and denotes the reflectivity of a planet or other object in space. Some experts suggest that we could nudge Earth’s albedo back up again by painting all roofs white, which has to be worth a try.