You’ve all heard about the horrible tragedy in Bangladesh, still unfolding. Not to distract from that event, or diminish its importance, I thought it would be interesting to have a look at that low lying country in relation to long term sea level rise caused by climate change. I am making no claim here about the maximum rate of sea level rise or about the timing of sea level rise. But the truth is, there have been times in the past when there was virtually no year round ice (glaciers) anywhere on this planet, and sea levels were much higher than they are now. During a time period not too different from the present (probably not as warm, or just about the same) sea levels were several meters (maybe about 6 meters) higher than they are now, suggesting that even under current conditions a lot of the ice in Greenland and Antarctica could melt. In other words, there is an argument that even if we curtail global warming now and keep things at their current somewhat warmed up level ice may continue to melt enough to raise the sea by meters. If we continue to warm the atmosphere and the oceans, the total sea level rise could be much, much higher.
Using the interactive map here, let’s look at Dhaka, the site of the recent and ongoing tragedy in Bangladesh. This is appropriate because it is the first world thirst for goods and luxury that produces both sweat shops like the one that just collapsed, killing hundreds of workers, and that produces global warming that will also produce catastrophic sea level rise.
Here’s a map of the area now, showing the local terrain:
If the entire Greenland Ice Sheet melted (but nothing else), or if a bunch of Greenland and a bunch of Antarctica melted, to produce about 7 meters of sea level rise, this is what the map would look like:
This is not what the region would look like, actually. The sediment here is all soft delta material what would be eroded away horizontally in no time. Another way to think about this is that if the sea went up just a meter or two, this entire region would probably be eaten away by horizontal erosion very quickly. Anyway, let’s add some more water and see what this first approximation would look like. Imagine if the West Antarctic and Greenland ice sheets both contributed maximally to sea level rise. This would be the minimal result:
If all the glacial ice in the world melted, and sea levels rose to the maximum height they’ve ever been, our closeup look of the region would look like this:
As you probably know, Bangladesh is one of the lowest elevation larger countries in the world. In fact, it seems like Bangladesh is defined almost entirely by its topography; Bangladesh is the delta. If we take the same maximal sea level rise as in the last graph, and step back a ways to see the effect at large scale, this is what we get:
By the way, there’s a cool book coming out on the topic, Rising Seas: Past, Present, Future.