By Jim Steele

Climate change drives less than a millimeter a year of sea level rise. Stopping the burning of fossil fuels will never protect coastal cities! If the climate change trend continues, 100 years of absolute sea level will only cause a rise of less than 4 inches.

However, there are other drivers that humans must address to prevent the real dangers from relative sea level rise!

Sea level rise measurements have been based on changes reported by tide gauges. Modern satellite data is also dependent on calibrations with those tide gauges. Sadly, Climate Morons ignore land subsidence and fearmonger that rapidly rising sea levels can only be blamed on rising CO2. (upper panel)

However, when the land sinks (technically subsides) it misinforms about the causes of relative sea level rise. Relative sea level is driven by several factors other than CO2. To measure the absolute effects of climate change, land subsidence must be accounted for, and two major dynamics cause the land subsidence.

First, as the major cities’ populations grow along the world’s coast, they increasingly withdraw underground waters from subsurface aquifers to quench the thirst of their inhabitants. However, such withdrawals have caused the land to contract and sink. Cities like New Orleans that were built on coastal estuary sediments, have built canals to re-direct water away from city centers. That well-intentioned government service caused the city’s sub-surface land to dry, contract and sink. In just the last 20 years New Orleans has sunk an estimated 6 to 20 inches causing half of New Orleans to now be below sea level!

With the advent of GPS instruments that measure changes in the elevation of land surfaces, scientific studies can now determine climate driven absolute sea level rise by subtracting how much the land has sunk vs how much sea level has risen. Using recent GPS measurements to assess land subsidence, Boretti (2020) examined the longest reliable sea level tide gauges of the western Pacific and determined climate-driven absolute sea level rise has been less than one millimeter a year. (middle panel).

The second major factor affecting sea level measurements is glacial isostatic rebound. During the last ice age maximum, Chicago was covered by a glacier 3000 feet (0.57 miles) thick. The glaciers’ weight carved out the Great Lakes. The ice sheet was up to 2 miles thick in places and caused the lands north of the Canadian-USA border, and in Scandinavia to sink while leveraging upwards the USA and European coastal lands to the south. When that weight was removed when the glaciers melted, northern lands began rising (rebounding), causing Scandinavian tide gauges to report “falling sea levels”. In contrast US coastal cities began sinking as leveraging stopped. The illustration in the bottom panel shows where the land is sinking (blue) and where it is rising (red).

Only science morons believe our cities will be drowned by climate change. People who are knowledgeable and truly care, will address land subsidence.