According to a new paper out by James Hansen, human warming could force glaciers to melt so fast that seas rise by as much as ten feet in as few as fifty years. Ten feet in fifty years of business as usual fossil fuel burning. It’s enough to change the face of human civilization. To render many of our vast cities waterlogged wastelands as a tide of migrants flood inland to flee the all-too-real rise of the waters.
It’s a situation we really need to get a handle on. One we should be monitoring with increasing concern. One we should absolutely be trying to prevent by ramping down fossil fuel burning as swiftly as possible.
Over the past Century, global sea level rise has been following a steadily sloping curve. At the beginning of the 20th Century, rates of global sea level rise were a mere 0.8 millimeters each year. By mid Century, the rate had increased to around 1.9 millimeters. And by the first decade of the 21st Century, the rate had again jumped — hitting 3.3 millimeters. As of 2014, satellites above the Earth had sniffed out another jump in the rate of sea level increase. A surge in the pace of rising water spiking well above the 3.3 millimeter per year trend line. A potential warning sign that basal melt of ice sheets in Antarctica and Greenland was starting to have an ever-greater impact.
(Largest spike in sea level rise since 1993 is now being observed in the AVISO satellite monitor. Image source: AVISO.)
For as of this past month sea levels had spiked to nearly one centimeter above the annual trend line. A record spike that, as yet, shows little sign of abating.
Other than glacial melt and thermal expansion of the oceans due to a continued accumulation of heat, there are a few other ocean and atmospheric features with the potential to wag the overall trend line. One of these is El Nino. And this year is likely to feature one of the strongest El Ninos on record. But the current spike is also the highest upward variance we’ve seen in the entire satellite record dating back to 1993. It’s a severe wag to the upside that’s worth at least a couple of raised eyebrows.
To hit Hansen’s 10 foot in fifty year mark, what we’d end up seeing is a doubling in the rate of glacial melt from Greenland and West Antarctica every 5-10 years. It’s an extraordinary pace of melting. A signal that should show up in the GRACE satellite sensors measuring gravity loss from the great ice sheets. This signal, however, would also start to show up in the global sea level rise monitors as a continued ramping up of the pace at which oceans are surging. And we can’t entirely rule out that we’re observing some of that quickening in the spike we see now.