London Thames Barrier update

I recently recreated Sea Level Rise (SLR) and Risk of Flooding (RoF) maps for the lower Thames River near the Thames Barrier (blog) for a WhatsApp Group considering the future of its ageing infrastructure w.r.t. recent climate extremes. There followed a global update affecting Sea Level Rise, by James Hansen who sounded the alarm ~ 35 yrs ago (go to 1981 & 1988 in Medium). First is a paper "Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?" (Columbia). Then its companion seminar "Global Warming Has Accelerated: An Intimate Conversation with Leading Climate Scientists" (YouTube).

I mapped conservatively up to 6 m. SLR pre-Pandemic in my previous blog. But as Extinction Rebellion Scientist in Cambridge UK, I mapped up to 12 m. SLR from increased polar ice melt at the time. The recent AMOC reversal discussed by Hansen above led not only to further upgrade that to 15 m. SLR, but also to shorten IPCC anticipated end-century timeframe to mid-century!

PDF here

Here is the original SLR & RoF map blogged previously based on Ordnance Survey topography; as a reminder, SLR is a simple model intersecting incremental elevations against topography:

click to enlarge (full A0 plot here)

Here is the updated SLR & RoF map with two key differences:

• the topography used here is Climate Central's on a free non-commercial license (75 m. resolution slightly down from 50 m. above): it removes infrastructure and vegetation for better ground-truthing - see the consequence here at a global level of those new calculations in 2019
• and the timeframe is moved up from 2100 to 2050 due to the combined factors discussed above

click to enlarge (full A0 plot here)

If risk of inundation looks more severe here, it's because it is... for two reasons:

• SLR is emulated via incremental elevations against a topography: it has been lowered by an avg. 2m. globally, that vastly increases affected real estate as discussed by Climate Central above
• and SLR increment is raised to 15 m.: accelerated polar ice-melt, lesser cloud albedo and potential AMOC reversal discussed in the opening paper / video caused this upward revision

Here is what the difference looks like, using the same map plotting trick for SLR as for RoF:

• the original RoF opaque blues are now the original SLR opaque rainbow colors
• and the original up-to-6 m. SLR halftones atop are now the up-to-15 m. SLR halftones to show the wider affected areas

click to enlarge

The stark contrast between the original mustard color overlays against the new rainbow color extents, shows the significant range increase due to this update. Even without running statistics, it underscores Climate Central's estimates of increased population impact. An update will be run on CoastalDEM v.3 licensed this year against v.2.1 licensed before and posted here.

To recap, what was a "far-tail" scenario at 12 m. SLR est. 2150, is now been drastically brought forward to 2050, due to newly studied and combined accelerated polar ice melt, decreased albedo and AMOC reversal. The targeted 1.5°C annual increase has already been reached and replaced by possible 4°C annual increase that is not sustainable.