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FL - Commissioner Suarez’ annual report on sea level rise; fourth installment.

Analysis of sea level rise data for Miami and policy implications from Miami Commissioner Xavier Suarez

Sea level rise trends have become substantial drivers for policy makers who are tasked with finding ways to protect the health and viability of coastal populations. There is an array of sea level rise projections from the National Oceanic and Atmospheric Association, NOAA (ranging in risk level) that are designed to steer governments and individuals in the right direction in terms of proper planning and execution of sea level rise prevention, mitigation, and adaptation strategies. Independent of the scenario we adapt as a guideline for policymaking, we cannot ignore the indubitable fact that sea level rise has been trending upwards long-term and unfortunately, is imminent. With that in mind, we should carefully choose how to not only analyze the data, but how to use both the short and long-term trends to our advantage, while taking into account all extraneous factors that affect these trends.

When analyzing sea level rise trends, making a comparison from one year to the next and extrapolating a data set in order to infer a correlation to a long-term trend is not a particularly sound method of analysis. Sea level rise, like most other natural phenomena, is ideally analyzed in a multi-year manner, as there are too many acute influences and variables that can mimic a positive or negative fluctuation and skew the data.

However, as a county that has one of the highest recorded sea level rise rates to date, short-term trends can be useful when monitoring resilience plans, urban planning and building, and emergency preparedness. They can serve as a nice check point to help keep us on track and stay proactive in our approach to natural events such as king tides, hurricanes, storm surge, and sunny day flooding.

Now, let’s take a look at the data and the factors that can influence the data:

Locally, Miami-Dade County is experiencing a long-term trend of approximately .2 inches per year or two inches per decade. From an immediate perspective, what this means is that within the next five years, all other factors being equal, the mean sea level might be an inch or so higher than it is now. However, if we isolate the last five years and extrapolate the data, the trend works out to .28 inches per year, or 6.44 inches in 23 years compared to 5.9 inches for the prior 23 years. This may not seem like a significant difference, but could be crucial in terms of acute policy decisions, mitigation of natural weather events, and emergency preparedness.

The graph below (created by Brian McNoldy, Senior Research Associate at the University of Miami’s Rosentiel School) illustrates the long-term linear trend from 1994-2019: this shows us that over 25 years, we are looking at a trend of approximately .22 inches per year or a little less than two feet per century. The numbers trend slightly higher in the last quarter century, possibly due to the Gulf Stream.

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