A flood of disinformation

Just a quick note from me.

Regular readers will know that I recently scribbled something about that icon of doomsday, Thwaites Glacier. As part of my perambulations around the digital sewer that we call the internet, searching in the sludge for a nugget or two of gold, I came across Justin Rowlatt’s holiday to Thwaites in the southern summer of 2019-20. His breathless report of the visit is here.

Anyway, Rowlatt in discussing the potential for Thwaites to actually bring about the End of Everything featured a map of London showing “areas at risk of flooding” by 2100. It was supplied by an outfit called Climate Central, who seem to specialise in producing terrifying maps of parts of the world underwater.

The first one of theirs I saw, way back, was Norfolk:

“Shocking global warming map shows swathes of East Anglia under water by 2050”

Huge swathes of East Anglia will be under water in 30 years unless drastic action is taken to halt global warming, according to a global flood-risk map built by US-based researchers at Climate Central.

Here’s an “East Anglia” version:

“East Anglia could be ravaged by flooding and high sea levels by 2050, according to global map“

There’s one for Wales…

“Updated climate change sea level risk map shows large parts of Wales flooded by 2050”

There’s one for Devon… this time with some pushback…

“Study warning swathes of East Devon and Exeter could be under water by 2050 ‘doesn’t realistically predict likelihood of future flooding’”

A study’s stark warning that huge swathes of East Devon and Exeter could be under water by 2050 has been played down by county council chiefs.

I could go on and on, but I won’t. The play seems to be to make maps tailored to local news outlets and fling them about to see what sticks. Many outlets are happy to oblige. A quick cut and paste for a bunch of clicks; in return Climate Central gets its eschatological – or should that be scatological – message out to more punters. (Note: Climate Central might supply a web tool which media outlets can use to produce their own shocking maps. I do not know.)

Emulating the London Map

Here is the terrifying map of London as reproduced by Rowlatt:

Naturally being a curious sort of chap I wondered how much sea level rise was represented in the map. Luckily there is a freely available digital terrain model of the UK. All you need after that is a GIS program and ten minutes to colour it in. The vertical resolution of the free map is 1 metre, so I was a bit worried that the “by 2100” map would all have happened in the first increment. Surely not. Surely London was not as flat as that.

Well, I added a metre to sea level. Then another. By the time I had reached +10 metres I finally had something that looked a lot like the Climate Central map.

My next thought was, well, if the sea level is rising at 3 mm a year, how long would it take to rise 10 metres? That number in years is 10,000 divided by 3. More or less 3000 years. It’s more but hey. Let’s be generous. So the “map of London in 2100” was actually the map of London in 5000.

But no. Wait! Slow down. Back up. They’re not talking about the incremental creep upwards of general sea level – they’re talking about storms, dude. Big frickin’ storms comin’ in and bashin’ everythin’ about. These things kinda surge.

Yes, but the tops of the surges presumably increment in tandem with the slowly creeping general rise in sea level… so what your map is actually showing is a large blob of London which is already “under threat” of flooding, to which you may have added a further half metre to widen the envelope a bit. Except you didn’t label it that way. The map looks very much as if the Thames itself represents the danger zone in 2020,  and the red represents the same in 2100. Disinformation indeed. So I made another version. This map has the last 1 m contour coloured yellow. This region we may describe as “the bits of London under threat of flooding in 2100 that weren’t under threat of flooding in 2020.” The pinkish bits, meanwhile, are “bits of London under threat of flooding in 2020, which will still be under threat of flooding in 2100.”

And that’s with a generous 1 metre of sea level rise.

Are you scared yet? Why not?

Oh, finally, I made my own map of future flooding in Norfolk. As before, I’ve coloured in the 0-10 m contours. It therefore represents, at current rates, 3000 years of sea level rise. Note to the insufficiently alarmed: the blue bits are already at sea level! Yike!