Documenting the Train Wreck: Sea Level Rise by 2050

New, more accurate topographic mapping shows that sea level rise could cause Southern Vietnam to disappear by 2050 (source)

by Thomas Neuburger

Most people in power now acknowledge that global warming will drastically remake the planet if it's not addressed in time, if fossil fuels aren't eliminated in time, if preventive measures aren't put it place in time.

"In time" in these constructions usually means "not now, but soon, trust us." Thus we get mainstream plans to reduce carbon emissions to zero (or "net zero," an even vaguer formulation) by 2050, leaving a full generation for people in power to mess around with how to do it and when to start.

How to do it? Let's discuss. When to start? Sometime. All while climate change clips right along at a speed that astonishes even the pessimistic.

New Estimates of the Effect of Sea Level Rise

A new paper (PDF here) has re-estimated the amount of land vulnerable to the most likely sea-level rise based on the most recent projections under a moderate emissions-mitigation scenario, the IPCC's RCP 4.5 scenario. They did this by using neural net technology to correct for errors in previous estimates of land elevation.

As Denise Lu and Christopher Flavelle put it in the New York Times, "Standard elevation measurements using satellites struggle to differentiate the true ground level from the tops of trees or buildings, said Scott A. Kulp, a researcher at Climate Central and one of the paper’s authors. So he and Benjamin Strauss, Climate Central’s chief executive, used artificial intelligence to determine the error rate and correct for it."

For a number of reasons, primarily cost, these inaccuracies are most prevalent in less wealthy regions of the world, such as Asia and Africa.

The results of this new modeling are striking. For example, the estimate for Thailand of the number of people likely to be affected by sea level rise by 2050 increased to 10% under the corrected topography mapping, up from just 1% under the old one.

Figure 1 from the paper shows four well-populated regions, with the old estimated area colored in blue and the added new area in pink.

Note that it's not the estimated amount of sea level rise that has changed; it's the accuracy of topological mapping that shows who would be affected by the current estimates. In addition, these new estimates don't take into account the effect of land erosion caused by the influx of water. Once the sea has risen and land inundated, the damage doesn't stop there. Next the new shoreline erodes, causing further damage, something not accounted for in the projections.

Millions More Affected Than Previously Estimated

This new data suggests that hundreds of millions more people will be displaced by sea level rise than previously thought. Here's Chart 1 of the paper with the top six affected nations (column 2 uses the old topography data; column 3 uses the new):

The global total by their estimates is 300 million people, more than 220 million more than previously thought.

Climate Central has a good interactive tool (here) for projecting sea level rise under differing scenarios using the new topological dataset. For example, you could change the assumption that we're going to modestly reduce carbon emissions to something more pessimistic (or as some would say, more realistic). You could also look at the outcome for different years —2100, say — or even manipulate the "Luck" slider to modify the sensitivity of our climate system to the increasing increase in CO2 and other greenhouse gases (the "Luck" setting for these projections is Medium).

The Luck setting doesn't take into account the various tipping points that could occur on the way from here to there, such as the sudden collapse of the Antarctic ice sheets. The tool would need a Didn't See That Coming setting to account for those.

As retired Marine Lieutenant General John Castellaw, who served with the U.S. Central Command during the Iraq War said of the coming inundation of Basra, Iraq's second largest city, "So this is far more than an environmental problem. It’s a humanitarian, security and possibly military problem too."

He could just as well be speaking, not just of Basra, but of the entire rest of the world.