The seas cover 71 per cent of our “blue planet,” and so they might also seem too vast to be altered by humanity. But the world’s diameter is close to 13,000km, and the ocean is never more than a few kilometres deep. So if you scooped all the world’s water into a sphere, its circumference would barely cover France.
Even modest rises in average temperatures raise the sea level, through the melting of polar ice and glaciers, and the expansion of liquid water. Indeed, past changes have been dramatic: the sea has risen over 120 meters since the end of the last ice age, when temperatures were 4-5°C lower. Even if the world can fulfil the stretching ambitions of the Paris agreement, climate change will push the mercury up by another 1.5°C over-and-above the pre-industrial age.
While the rise in average sea levels in the industrial era has thus far been modest—a little under a foot—in some times and places it climbs by far more, and now does so at an accelerating rate. Is it, for example, just a coincidence that all five of the costliest storms in American history have occurred in the years since 2005?