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Sea Level Rise Analytic
During his summer election campaign, Trump claimed that the sea level would rise by just “an eighth of an inch in the next 400 years,” equating to roughly 0.31 centimeters over four centuries.
This estimate is a stark reduction from his previous projection of an eighth of an inch over 250 years. In reality, current data reveals that the rate of sea level rise is already more than an eighth of an inch per year, highlighting a significant discrepancy between Trump’s claims and scientific evidence.
“The greatest threat isn’t global warming, which is going to cause sea levels to rise an eighth of an inch over the next 400 years… and there will be more properties on the coast, right?” Trump said in an interview on August 12 on X with Elon Musk, the platform’s owner.
“The greatest threat isn’t that. The greatest threat is nuclear warming because now we have five countries with a significant amount of nuclear energy and we shouldn’t let anything happen with stupid people like [President Joe] Biden.”
Since June, Trump has reiterated these figures at least three more times, using them to minimize and even question the reality of current and projected sea level rise. The most recent instance occurred during a rally on August 17 in Wilkes-Barre, Pennsylvania.
“The oceans will rise an eighth of an inch in the next 400 years, but they don’t talk about a lunatic who is building nuclear missiles right now. That’s the real global warming, not this,” Trump asserted. “Global warming will be about nuclear weapons.
No one talks about that. They never mention it, but they talk about an ocean that’s rising, which, if it happens, will give them a little more coastal property.”
At another rally in Virginia in late June, Trump extended his timeframe to 497 years, further distancing his claims from scientific consensus.
Trump’s latest assertions on sea level rise are even more extreme than his previous claim in 2019 that sea levels would rise an eighth of an inch “in the next 250 years,” a statement that was already fact-checked and found to be inaccurate.
Last year, Trump also cited absurdly low estimates of an eighth of an inch in 300 years and a hundredth of an inch in 350 years.
It remains unclear, as it did in 2019, whether Trump is presenting these figures seriously. His campaign did not respond to requests for clarification.
However, the conclusion is evident: the risks of climate change are either deemed insignificant or even nonexistent, when in fact they are very real.
Sea level rise is one of the most visible and devastating effects of global warming. Contrary to Trump’s suggestion that it could lead to “more coastal properties,” rising sea levels increase coastal flooding, including storm surges, which threaten lives and infrastructure.
Moreover, sea level rise contributes to coastal erosion, meaning less beach area, not more. For every inch of sea level rise, approximately 100 inches of beach are lost, according to NASA oceanographer and climate scientist Josh Willis.
Sea level rise primarily occurs because higher temperatures are melting land ice, adding water to the oceans, and because warmer temperatures are expanding the volume of existing water.
(A much smaller contributor is the movement of water on land, such as in lakes and aquifers, toward the seas, primarily through groundwater depletion.) The planet is already significantly warmer than it used to be and continues to heat up due to past and present emissions of heat-trapping pollutants, mainly from fossil fuel burning.
Current and Projected Sea Level Rise
According to the latest data from NASA, the current global rate of sea level rise is 0.42 centimeters, or 0.17 inches, per year.
This is already slightly more than an eighth of an inch per year and far from Trump’s estimate of that amount over centuries.
Satellite data shows that since December 2019, when Trump claimed that sea levels would rise an eighth of an inch in 250 years, the global sea level has already risen by more than 5/8 of an inch.
Sea level rise has accelerated in recent years, and this trend is expected to continue. For example, during much of the last century, oceans rose at an average of 0.14 centimeters (0.06 inches) per year, according to the National Oceanic and Atmospheric Administration (NOAA). But between 2006 and 2015, the average rate more than doubled to 0.36 centimeters (0.14 inches) per year.
Certain locations may be above or below this average due to a variety of factors, including land subsidence, ocean currents, and erosion.
Future projections for sea level rise further overshadow Trump’s already low figures. According to a 2022 NOAA technical report, global sea levels are projected to rise by 30 centimeters (1 foot) above 2000 levels by 2100, even in the most optimistic scenario.
These projections grow to 1 meter (3.3 feet) in the intermediate scenario and surge to 2 meters (6.6 feet) in the high scenario.
The report states that sea level rise in the next 30 years will equal the total rise of the last hundred years. For example, it indicates that by 2050, sea levels along the U.S. coast are expected to be on average 25 to 30 centimeters (10 to 12 inches) higher than in 2000, with Gulf and East Coast areas experiencing even greater increases.
This will quintuple the risk of “major” flooding and make “moderate” flooding more common than the current “minor” floods.
The latest Intergovernmental Panel on Climate Change (IPCC) report from 2021 offers similar projections: an increase of 18 centimeters (7 inches) in global sea level by 2050 and a rise of 38 centimeters (15 inches) by 2100, assuming low emissions, relative to levels from 1995 to 2014.
These increases rise to 23 and 76 centimeters (9 and 30 inches) for 2050 and 2100, respectively, under high emissions conditions.
These estimates do not account for several very uncertain ice sheet processes but could, in an unlikely but possible high emissions scenario, melt Antarctic and Greenland ice sheets more rapidly and add another meter (3.3 feet) or more of sea level rise by the end of the century.
As one of the FAQ sections of the report explains, past and present emissions have virtually guaranteed a rise of at least a third of a foot in sea level by 2050, regardless of whether the world reduces greenhouse gas emissions.
This is because oceans and ice sheets are still responding to the temperature increase. After 2050, the amount of sea level rise is more difficult to predict and also depends more on total emissions.
However, by 2300, a century before Trump’s 400-year mark, scientists project that, relative to the 1995-2014 period, oceans could be up to 3 meters (10 feet) higher with low emissions and between 1.7 and 6.7 meters (5.6 to 22 feet) higher with high emissions.
This does not account for ice cliff instability, which refers to a self-perpetuating feedback cycle that could radically accelerate ice sheet loss as exposed ends of an ice sheet collapse under significant stress.
If added with high emissions, sea level rise could reach more than 16 meters (52 feet), more than 400 times higher than an eighth of an inch.
A study published in Science Advances on August 21 suggests that the Antarctic ice sheet “may be less vulnerable” to ice cliff instability than previously thought, although there remains considerable uncertainty.
