Sea Level Rise in the news

A history of long-term relative sea level change in Friday Harbor, Washington - a pattern that our data suggest is not due to land level change...but rather to the sea rising

Is it just me, or is sea level rise breaking through in our neck of the woods?  This week there were multiple articles making the rounds focused on sea level rise in Washington State including
reporting at the Seattle Times and KIRO7 on Zillow's updated sea level rise vulnerability assessment for real estate (which I will get to later) and Chris Dunagan's reporting for the Encyclopedia of Puget Sound on issues surrounding homeowner decision-making in the era of sea level rise and also his piece on SLR planning on Washington State.

Nuisance flooding like this, in Port Townsend on 10 March 2016, is almost certain to become more common and more of a problem in the future.  Photo courtesy of the Local 20/20 King Tides Team

The concept of climate-driven sea level change is nothing new...its been part of the climate change conversation for decades.  What is evolving is our understanding of the processes that drive sea level change (typically referred to as sea level components) over the community planning time-frames of interest.  The Earth system is complex, though, and the problem of interest here is complicated and multi-part:  How do emissions of greenhouse gases integrate with the natural cycles of those gases, how do the resulting concentrations influence the global heat budget, then how is extra heat distributed around and through the globe, and (finally) what are the process and rates at which that heat starts affect the components that lead to sea level rise (for example, how does that head lead to the break down of large masses of land-grounded ice on Antarctica)? 

Antarctica - a huge mass of land-grounded ice (this is an artists rendering of a cut-away view through the ice).  Its future matters to us.  Photo credit:  National Geographic

The evolving understanding of the processes that drive sea level change has led to an intense focus on this problem amongst the scientific community, as evidenced by the publication rate of papers focusing on sea level rise.  I used Web of Science to search for papers with the topics "sea level rise" and "climate change" and came up with this publication distribution through time:

This intense focus on the processes that drive sea level rise, of course, has led to a community planning problem, though; projections of sea level rise, or how much we can expect, change through time.  This isn't surprising if you think about it.  Projecting anything is hard.  As a society we make projections all the time in any number of fields...and many of them don't play out as expected.  In the case of sea level rise, projections will change as our understanding of processes driving sea level rise evolves, and also as we observe sea level rise happening and can compare those observations against projections.

This brings me back around to Zillow's analysis.  I like this approach that they took, where they used their national scope and data-analytics expertise to look at the possible national implications of sea level rise on their core product - homes.  Using a sea level rise of six feet relative to present, they found (perhaps not surprisingly) that places like Florida have a lot at stake.  It also is a reminder, though, that Washington State is not immune from sea level rise (even though we may be less vulnerable on a national scale) - there is a lot of high value infrastructure exposed.

Zillow has taken some criticism though, for the particular sea level they chose to do their analysis with - six feet relative to present sea level.  The Washington Policy Center published a blog, for example, saying that six feet was out of alignment with the most recently published projections by the IPCC.  An early statement in the article sets the tone, "Their projections are, essentially, made up".

Is six feet of sea level rise made up?  Does it "ignore the science", as the title of the Washington Policy Center piece implies?  No, quite the opposite, and here we simply see this problem associated with a rapidly advancing scientific endeavor.  The Zillow analysis uses a very recent NOAA assessment that attempts to assess the likelihood of different levels of sea level rise across the full range of uncertainty (using a very similar approach to what we are doing with the Washington Coastal Resilience Project).  By contrast, the IPCC projection plot shown in the Washington Policy Center blog only communicates a narrower "likely range", which the Washington Policy Center's blog misinterprets as communicating full range of uncertainty.  Zillow nicely acknowledges the uncertainty that the NOAA assessment is trying to communicate by stating, "if the oceans rise six feet – roughly midway between the high end of what the government says is “very likely” (4.3 feet) and the possibility of an 8-foot or greater rise that cannot be excluded." 

Lets dive a bit deeper here.  The "upper ends" of the probability distribution, where sea level rise exceeds the ~2-3 ft (by 2100) best estimate, are driven by places like Antarctica melting a lot more than was previously assumed in past sea level rise projections (ice sheet uncertainties, and their implications, are also touched on in this fascinating recent article by Forbes).  Science seems to be pointing towards these large masses of ice being more sensitive to climate change than has been previously assumed - a conclusion that, if it holds up, will lead to a greater likelihood of higer sea levels represented in future projections.  Its also worth acknowledging that, while 6 feet of sea level rise by 2100 may be unlikely based on NOAA's current assessment (and ours, for that matter), sea level isn't projected to fall in the coming centuries - and we become much more likely to get to 6 feet by, for example, 2150.

And, of course, Zillow could re-run their analysis with a best estimate of 3 feet, and we would still see vulnerabilities emerge, both around the country and in our own neck of the woods.  Despite changing projections, and uncertainty, we gain by planning now to avoid future costly problems.