Since the polar regions act as a barometer for climate change, there is much talk about ice at the COP21 climate conference in Paris, France. So, to get an idea of how much sea ice there is in the Arctic Ocean a small calculation can be made in terms of Eiffel Towers.

It would take 0.005 cubic kilometre of ice to encase one Eiffel Tower, 1 cubic kilometre of ice would encase 192 Eiffel Towers and, hence, 8000 cubic kilometres of ice to encase 1.7 million towers. This is roughly about the same volume of ice that was floating in the Arctic Ocean at the beginning of November 2015.

Every year, the Arctic Ocean experiences the formation and then melting of vast amounts of sea ice. An area roughly the size of Europe melts every summer and then freezes again the following winter, reaching its minimum around September and maximum around March. While satellites have been able to observe the seasonal change in ice extent for some time, it is thanks to CryoSat that scientists have been able measure the thickness of the ice, which is needed to work out the volume and understand the real changes taking place.