John’s Blog/Newsletter: SEA LEVEL RISE NOW

In more than a year of public speaking and consulting about rising sea level, the most frequent question I get is, "How high will it get by 2050?" — or some variation focusing on the year 2100, the person's lifetime, etc. It is asked by corporations, individuals, and community leaders. Though perfectly reasonable, I believe it is the wrong question for two entirely different reasons.

First, we have to recognize that it is the combination of slowly rising sea level, extreme tides, and possible storm surge that all combine to put particular property at risk. The difference is that sea level will not go down for at least a thousand years, so is special in that it takes the land away, effectively permanently. But the slow effect of rising sea level also boosts the impact of extreme high tides and the rather random storm events with which we are familiar. It is the COMBINED effect of storms, tides, and sea level rise that undermines property value. It makes the estimate for "how long do we have" very complex because the three operate on entirely different occurrence patterns, but can coincide for maximum impact as Sandy illustrated.

While those in coastal areas wait for sea level to arrive on a time scale of inches per decade, extreme tides will slosh over their threshold more and more often . "King Tides" are now dreaded regular events at lunar high tide in communities from Florida to Virginia, to Seattle, to Australia — all over the world in fact. Houses and streets are already being elevated at great expense to deal with the recent surge of damage from high tides. Those HIGH, high tides are getting higher due to slowly rising sea level. Plus, it is not just your property that needs to be considered since the effect on the community, the utilities, and transportation access all determine the usability and value of a site. (For more information, see my book, High Tide On Main Street: Rising Sea Level and the Coming Coastal Crisis.

The second reason that asking how high the sea will get this century is misleading is that we can not possibly know for sure how high it will get by a specific year far in the future. We can not know exactly how much ice will melt and how much thermal expansion will occur in the coming decades, because NO ONE KNOWS how much heat we are going to put into the Earth system in the next 87 years. That will be determined by our population levels, energy demand, and how we make our energy. All of those determine the level of heat trapping greenhouse gases, now in the range of 400 parts per million (ppm).

Who can possibly know what the mix will be of solar, wind, coal, tar sands, nuclear, algae-based fuel, etc. even four or five decades from now. That will determine how warm the world gets, how much ice melts, how high the sea rises — and how far inland the shoreline moves. That unknown is the reason that the projections for sea level rise by the end of the century have such a huge spread. And if the higher estimates for warming occur, on the order of eight degrees F, we will no doubt see catastrophic melting of the ice sheets in Greenland and West Antarctica, something not currently included in the cautious predictions of most scientists, governments, and the IPCC — as I pointed out in a recent blog post "Government Sea Level Projection Low and Misleading – AGAIN."

I have come up with a different question that gets around the two problems posed above. We can say for certain that the excess heat now stored in the ocean has locked in sea level rise of at least four feet higher than present, at an absolute minimum. (Many of us would even argue that over the very long term, we have now locked in SLR far higher than four feet.) Let's just look at three feet — roughly a meter — as a good guaranteed standard unit for sea level rise, recognizing that it might take a century to happen in the best case, or that it could occur by the middle of this century in the very worst case. That yields a new way to pose the question.

We should ask: "How soon could we get three feet of sea level rise?"

That question seems similar to the question "How high will sea level rise get by ___" but is different for a few important reasons:

1. It puts the fact that it will reach 3 feet and more, right in front of us.
2. It recognizes that we cannot know exactly when, due to some honest unknowns such as how much excess heat will be trapped in the ocean later this century.
3. Most important, it gets us to think big. Instead of hoping and pretending that it may not be too bad, it confronts us with the new reality that sea level will be MUCH higher than the last few thousand years. Thinking about three feet can challenge and inspire us to do better planning, engineering, and construction. It will help advance our thoughts about the impacts on investments, legal issues, national security and more.

Those familiar with my book or blog know that I believe slowly rising sea level will be the most profound change to the planet this century and that the effect has just started. Few people recognize that each foot of sea level rise moves the shoreline inland by more than 300 feet as a global average — in flat places like South Florida, it will be more than that. And counterintuitively, in many places it is not the land on the coast that is most vulnerable. The beach dunes rise up, but often the low land is further inland. While the beach dunes may protect from storms, higher sea level will penetrate the lowest land miles inland.

Like so many things, how we perceive the world is determined by our perspective or reference point, and often by nuance. Sometimes it can be referred to as a paradigm shift. Changing the variable from how HIGH, to how SOON is a good example of that.

If you like this viewpoint, and my way of reframing the question, please share.