By Jim Steele
In the 1980s, the media and some scientists warned that the island nations in the tropical Pacific would soon be wiped off the ground by rising sea levels due to rising CO2. The Maldives’ director of environmental affairs warned that a sea level rise of 20 to 40 centimeters in the next 20 to 40 years would be catastrophic. The Guardian headlines were made by islanders who left their homes on the island to become environmental refugees. In 2002, Tuvalu, supported by Greenpeace, threatened to sue the United States and Australia for excessive carbon emissions. Smithsonian magazine asked, “Will Tuvalu go under the sea?” However, the Smithsonian also admitted, “Not all scientists agree that Tuvalu’s future is underwater. Some critics have branded the island leaders as opportunists looking for foreign handouts … while people and organizations who sympathize with Tuvalu are “eco-imperialists” who want to impose their alarming environmental views on the rest of the world. “
In theory, given the onslaught of global warming tales and the fact that the entire atoll nation of Tuvalu averages just 6.6 feet above sea level, the fear of a devastating sea level rise was justified. Of course, Tuvalu’s money-seeking Prime Minister Saufatu Sapo’aga told the United Nations that the global warming threat to his island is no different than “a slow and insidious form of terrorism”. In reality, the latest science released in 2018 combined previous aerial and satellite imagery to report a net increase in Tuvalu’s land area. Built on coral reefs, the atoll’s many islands will change shape as coral debris and foraminifera are added to land on the leeward side while losing area on the windward side. Nonetheless, 74% of the islands increased in size while only 27% decreased. In addition, Tuvalu’s growth across the region is reflected in other islands. A similar study that examined “30 atolls in the Pacific and Indian Oceans, including 709 islands, shows that no atoll has lost land area and that 88.6% of the islands were either stable or had grown in area, while only 11.4% shrank. ”How can coral islands grow in a time of accelerating sea level rise?
The answer, contrary to global warming theories, could be that regional sea levels have neither risen more than 3 millimeters per year, nor has the rise accelerated. Part of the frightening misinformation is due to researchers using short-term sea level records, which cannot accurately measure long-term trends. The Pacific sea level rises and falls over decades (see maps above). A single El Nino event can temporarily raise or lower the island’s sea level by 300 millimeters (mm). For example, a study with only 6.8 years of sea level data in Tuvalu had dropped 8.9 mm / year, in contrast to a study from 2008 with 15.5 years of data that claimed the sea level was around 5.9 mm / year increased.
The climate skeptic Eschenbach reported in Tuvalu Not Experiencing Rise in Sea Level Rise (2004) that climate scientists who recorded an average of 27 regional stations with data of more than 25 years had only found a trend of 0.8 mm / year without acceleration. Eschenbach went on to say that the erosion of Tuvalu and the ingress of salt water into drinking water were not caused by the rapid rise in sea levels. Since over 10% of the island was paved, the underground freshwater reservoir, among other things, was not replenished because rainwater was channeled into the sea instead. Meanwhile, the extraction of sand and reefs for construction had disrupted the natural dynamics that kept the island’s shape.
In “The Scientific Basis” of the 2001 IPCC report, they found using tide meters that “the mean sea level rise during the 20th century ranged from 1.0 to 2.0 mm / year” and no detection of the predicted acceleration. However, to support a theory that is unable to combine rising CO2, warming, and accelerated sea level rise, Vermeer and Rhamstorf (2009) created a climate change model that predicts sea level rise from 2.4 feet to 6.2 feet for the period 1990 projected –2100. In contrast, Australia’s NSW main coast specialist observed a consistent trend of weak decelerations at every gauge location across Australasia from 1940 to 2000 and published in 2011 “Is there still evidence of an acceleration in mean sea level rise around mainland Australia?
There were several conflicting problems. Scripps’ esteemed oceanographer Walter Munk found that the IPCC estimates that the 20th century sea level rise was 1.5-2.0 mm / year too high. In 2013, Gregory et. al wrote: Global Sea Level Rise in the 20th Century: Is the Whole Greater Than the Sum of the Parts? They solved the problem of sea level imbalances by simply increasing the previously estimated contributions from ocean warming and meltwater. In contrast, Mitrovica at Harvard solved the same problem by reducing the mean sea level rise in the 20th century to just 1 mm / year.
Meanwhile, new estimates from satellite time suggested that the long-awaited theoretical acceleration had occurred with sea levels rising 3.5 mm per year from 1994-2002. However, as with Tuvalu, such short measurement periods are usually skewed by natural variability and cannot accurately measure long-term trends. Accordingly, subsequent satellite measurements between 2003 and 2011 showed that the global sea level suddenly slowed to 2.4 mm / year. To resolve this conflict with global warming expectations, Cazenave et al. added the estimated water trapped on land during La Ninas to the observed sea levels and added another isostatic adjustment of 0.3mm / year to account for the extent of the ocean basin. It increased the trend of sea level rise from global warming over the past 20 years to 3.3 mm / year, a rate often quoted today.
In addition to Cazenave’s misguided trending from short-term satellite measurements, the calibration of satellite data on tide gauges can be skewed by the undetected land subsidence that normally skews tide gauges. It is common knowledge that sinking land creates the illusion of sea level rise. China’s Huanghe Delta is sinking 10 inches (254 mm) per year and New Orleans is sinking 1.4 inches (36 mm) per year. South Florida is experiencing localized patches of 1-3 mm / year that undermine condominiums in urban areas built on reclaimed marshland. Likewise, the San Francisco airport is shrinking 0.4 inches a year. Between 1980 and 2014, there was no upward trend to suggest that falling sea levels offset the sea level decline, despite the fact that the San Francisco tide meter recorded large sea level peaks in El Nino.
Alberto Boretti robustly assessed the dangers of rising sea levels for islanders in the Pacific and published 2020 Relative Sea Level Rise and Land Subsidence in Oceania by Tide Meter and Satellite GPS. Using only the 6 regional tide gauges with data from more than 100 years, he found that after subtracting the settlement effects from the average relative sea level rise of +1.3 mm / year, the average absolute rise rate was calculated to be an astonishingly low +0.125 mm / year; with no signs of acceleration or signs of thermal expansion. In addition, Boretti’s special case study Tuvalu, which also takes subsidence into account, showed an absolute rate of increase of only 0.157 mm / year from 1977 onwards. This sea level rise due to increased sea volume will only increase by about 0.6 inches in 100 years. The worrying “sea level rise in Tuvalu is due to the sinking rather than the increasing volume of ocean water” from thermal expansion or glacial melt water. The best approach for Tuvalu’s Prime Minister would be to stop the rash urbanization that is subsiding and threatening freshwater supplies and stop covering his political bum by putting the blame on climate change. It may not be possible to stop the descent any longer. Finally, at the end of the 19th century, Charles Darwin rightly suspected that atolls like Tuvalu were formed by fringing reefs attached to a naturally declining extinct volcano.
Jim Steele is Director Emeritus of the Sierra Nevada Field Campus at San Francisco State University, author of Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism, and a proud member of the Carbon Coalition