Charleston 2040 Sea Level – Add 1 Foot to 2020 Sea Level!

Like a lot (maybe all) of coastal scientists and researchers out there I am constantly considering how sea level rise (SLR) is going to change the results I am generating in the here and now. Along those lines, I just read an article about how FEMA’s maps are going to be off the mark as climate change continues to drive results from the known probabilistic toward the lesser known but continuing long-term trends. The processes driving SLR have been occurring for decades, but they have recently started to accelerate. That means we are not talking about new processes just quicker change.

An unavoidable fact is that today’s sea level (the average) is different than 40 or 100 years ago, i.e., there is a trend to deal with. This is not game changer, however, and we still move forward with predictions, planning, and engineering to name a few. We don’t need to predict the sea level perfectly – that is not even an option, the variability of the natural world makes certain of it (keep reading).

For example, I am looking to define within about 5 -10 cm (a few inches) what the water levels will be in 2040 for the Charleston, SC area. Many would agree that it depends on what curve you use; I can hear you saying, “go with the lower intermediate”. Anyway, picking from about six curves means it is basically rolling the dice and that means getting emotional (I favor the lower intermediate because …), which I am trying to avoid. I want to use the data we have gone through great lengths to collect and verify to define the near future.

Here are the over-view of results from the local tide data – for more details on process see the white paper.

1. Sea Level will be at least 1.3 feet higher than the present datum in 2040 (it is already like ½ foot)

2. Sea Level could be 1.5 feet higher than the present datum in 2040. That is on the NOAA Intermediate-High curve for Charleston and a good planning level for 2040.

3. Monthly variability (1 standard deviation) in mean sea level is on the order of 0.4 feet.

4. Present sea level is accelerating at 1.0 cm/year; by 2040 that will be 1.5 cm/year.

5. Marshes in the SE have a hard time surviving sea level rise beyond 1.25 cm/year.