Picture a world where some of the world's largest and most important cities are underwater.
New York, Mumbai, and Osaka. London, San Francisco, and Amsterdam. All flooded.
This reality is may be much, much closer than we think.
A study published today in the journal Nature suggests that seas will rise at least 3 feet over the next century, which is much faster than previously expected.
Before, scientists of the Intergovernmental Panel on Climate Change (IPCC) had projected at least 1 foot of sea-level rise for most locations and 3 feet as a general upper limit. (Though the IPCC did acknowledge levels could be higher in some places.)
The new research, however, says we're probably locked into at least 3 feet over the next century if greenhouse gas emissions continue at their current rate.
The new estimate is so different because researchers accounted for new factors in their models, such as ocean warming that could accelerate the collapse of the West Antarctic ice sheet — and fill up oceans with an unimaginable amount of water.
The authors also say that in some parts of the world, coastlines could vanish under 5 or even 6 feet of water.
The upper boundary, by the year 2500, is nearly 50 feet of sea-level rise. If that sounds shocking, we're with you: It could inundate significant parts of low-lying coastal cities and disappear entire islands.
According to a 2014 IPCC report, roughly 95% of the area of the ocean will rise.
Climate-change deniers will say that global average temperatures have been higher in past geological epochs, and that's true. Greenland, for example — where an ice sheet is also disappearing at a frightening pace — was once ice-free in the summer. The West Antarctic Ice sheet was also considerably less extensive than it is today.
But sea levels were 20 to 30 feet higher back then — and that was long before millions of human beings, countless of whom are economically insecure, inhabited the coasts.
The planet is passing troubling milestones more quickly than expected.
The Arctic Circle has reached a new low for sea ice volume and area. Then, for at least one day March, average surface temperature surged past the 3.6 degrees of warming climatologists said would have disastrous effects.
As Elon Musk pointed out yesterday, it's exactly these kinds of anomalies we should be paying attention: They signal the leading edge of the world's climate-to-come.
Whether or not you reject the scientifically established root cause of rising seas (human activity), that world is looking pretty grim.
