I use only real-world data in the creation of these maps. Both the terrain and sea levels were modeled using publicly available raster elevation data.
The original map renderings were done using data from the USGS–this dataset showed an estimated maximum sea level rise of about 260′ (see http://pubs.usgs.gov/fs/fs2-
It was then pointed out to me that the IPCC had more up-to-date and presumably more accurate estimates of sea rise, with the highest sea level being 215′. I decided to go with the more recent estimates, and re-rendered the maps to reflect this data. Now all the maps assume a maximum sea level rise of 215′ or 66m. Sometimes, at the highest level of sea rise, a city is completely underwater. That just doesn’t make an interesting map. In these cases I will render the sea at a lower level, but this will always be called out in the map title.
For LA, I generated the terrain and the sea levels from the National Elevation Dataset (NED). According to the USGS, “The NED provides the best available public domain raster elevation data of the conterminous United States…the data are utilized by the scientific and resource management communities for global change research, hydrologic modeling, resource monitoring, mapping and visualization applications.”
For Portland, I generated the terrain and sea levels from USGS digital elevation model quads. For Seattle, I used high-resolution LiDAR. All the LA data was downloaded from the National Map (http://viewer.nationalmap.
These maps are just the extreme endpoints. The damage from sea level rise to ecosystems and human societies will be immense long before the world gets anywhere near these scenarios. I don’t think that anyone is speculating any sort of precise timeline for all the ice sheets to melt. One estimate I found says anything from 1,000 to 10,000 years (http://www.npr.org/blogs/
There are web sites out there where you can map various levels of sea rise. I have spent hours on end viewing what the world would be like–it’s fascinating–but I also think that these sites have a pretty narrow audience. Adding the puns and humorous names brings it more into the mainstream, and expands the audience. There are people who don’t agree with the way I’ve dealt with the subject of climate change with these maps–they think the funny names and extreme sea levels are a distraction from what will actually happen in the lifetimes of the current generations. I believe that what happens to future generations is also important, and that leavening a serious issue with humor will put it into the minds of more people. Plus, I really have a good time making up the names–it’s fun.