A recent statement by Representative Mo Brooks (R-AL), who happens to be a member of the U.S. House of Representatives Science, Space and Technology Committee, is disturbing at best. He suggested that sea levels are not rising because of climate change but because rocks are falling into the sea.

Science Magazine quoted Representative Brooks in a hearing saying that “the California coastline and the White Cliffs of Dover tumble into the sea every year, and that contributes to sea-level rise.” He also said that silt washing into the ocean from the world’s major rivers, including the Mississippi, the Amazon and the Nile, is contributing to sea-level rise. “Every time you have that soil or rock or whatever it is that is deposited into the seas, that forces the sea levels to rise, because now you have less space in those oceans, because the bottom is moving up.” 

Brooks made the assertion when questioning Philip Duffy, Ph.D., President of the Woods Hole Research Center and a former senior adviser in the White House National Science and Technology Council. Duffy was diplomatic and replied that “I’m pretty sure that on human timescale those are minuscule effects.”

To speak plainly, the suggestion made by Brooks is, well, stupid is the first word that comes to mind.

According to NOAA’s National Ocean Service sea levels have been rising at about an eighth of an inch per year, and the rate is accelerating. That may not seem like a lot at first but as NOAA notes, “disruptive and expensive, nuisance flooding is estimated to be from 300 percent to 900 percent more frequent within U.S. coastal communities than it was just 50 years ago.”

What is causing the sea-level rise? The National Ocean Service estimates that “the two major causes of global sea level rise are thermal expansion caused by warming of the ocean (since water expands as it warms) and increased melting of land-based ice, such as glaciers and ice sheets. The oceans are absorbing more than 90 percent of the increased atmospheric heat associated with emissions from human activity.” 

Not rocks.

But where did Representative Brooks get his crazy idea? Actually, the idea has been around for several years in various forms. 

Back in 2011, someone on the AboveTopSecret right-wing conspiracy blog claimed that sea level rise is not due to global warming but is caused by all the big ships on the ocean. The ships displace water, therefore the sea level has got to rise to accommodate them. For better or worse, the suggestion was repeated many times across the internet. No the same as falling rocks, but the same idea. 

While the idea may have made almost no practical sense, it did raise an interesting question — How much would the sea level fall if every ship were removed all at once from the Earth’s waters? If sea level is rising because of the water is displaced by ships, the corollary is, how much would it fall with no ships afloat?

The question is interesting enough that the calculations were run by a variety of groups and they all came up with more or less the same answer. Drum roll please — the best estimate is around 6 microns, or less than one-twelfth of the thickness of a human hair. 

So yes, while rocks falling into the sea can raise the sea level minimally, but it is probably far too small an amount to be measurable. And while those like Brooks on the U.S. House of Representatives Science, Space and Technology Committee blather on about rocks, almost 40 percent of the population of the United States lives in relatively high-population-density coastal areas threatened by rising sea levels.