Save the Maldives!
Full fathom five thy father lies, His aqualung was undersized*
In October 2009 the government of the Maldives held a cabinet meeting underwater to highlight the imminent threat that global warming presented to the archipelago. According to National Geographic “the Maldives may be the first country on Earth to disappear beneath rising seas”. Yet in March 2024 President Mohamed Muizzu announced that nine new airports were to be built across the islands.
Rising seas are amongst the most tangible features of climate change. CO2 is invisible and rising temperatures may go unnoticed in the short term – but we are hardly likely to overlook islands disappearing beneath the waves. The Maldives has an average elevation of just 1.5 metres, about the same as the rise in sea level predicted this century by some climate scientists. So is President Muizzu merely fiddling whilst the Maldives drown, or is the story slightly more complicated?
The Maldives are a group of coral atolls located about 1000 kilometres south of India. The surrounding ocean is about 2000 metres deep. Coral atolls develop in the shallow water around volcanic islands that rise from the oceanic depths. As the islands sink, or sea level rises, coral must grow upwards to maintain access to sunlight. Fortunately corals are vigorous reef builders and can cope with most natural rates of subsidence or sea level rise. Modern atolls have had to grow upwards by about 120 metres since the last ice age. That’s nearly a centimetre (cm) a year on average. But much higher growth rates were needed during the main phase of melting, from 15,000 to 8,000 years ago. Then, sea level was rising at up to 4 cm per year for centuries, as shown in Figure 1 below. The Maldive corals kept pace with that rise
By 7,000 years ago most of the North American and Eurasian ice caps had melted and sea level rise slowed abruptly. We have been able to measure that slow rise with some precision since the introduction of tide gauges about 200 years ago. The tide gauges indicate a relatively constant rise over that period of about 1.7 millimetres (mm) per year. That is about one twentieth of the maximum rate and equates to a rise of 17 cm (about 7 inches) per century. This rise in sea level was, of course, entirely natural and controlled by insolation changes linked to Earth’s orbit round the Sun.
If the tide gauges are correct, it will take nearly 1000 years to drown the Maldives. Yet the Maldives government thinks their islands may be gone within a century – why? The answer to that question starts with satellite data that NASA has been acquiring for the past 30 years. The first satellite measurements of sea level were taken by NASA’s TOPEX/Poseidon satellite in 1992 - several other satellites have followed since. In less than 30 years climate scientists concluded from these new data that the rate of sea level rise was increasing and is now double the historic average.
Take a look at Figure 2 below (from Nerem et al 2022). This chart purports to show sea level rise increasing from 1960 to 2020. The authors fit a quadratic function to the data and conclude that the curve is steepening towards the present day. This all looks very convincing – high quality satellite data allied with mathematical modelling has revealed what those tide gauges missed. Projecting this curve forward in time indicates a sea level rise of about 10-20 cm by 2050 (2-4 times that suggested by tide gauges).
You don’t really need the maths to see that the curve seems to be steepening upwards. But there are other obvious features of the chart that go unremarked by the authors. For example, what happens before 1960? The orange curve shows a rapid increase in sea level between 1940 and 1960. Why is this not modelled? No prizes for guessing that it would not fit the quadratic function. Remember that this function is not evidence of any kind – it is simply a curve that happens to match the ‘best-fit’ observations from 1960 to 2020. It does though allow the authors to conclude that recent sea level rise is non-linear and that opens the door to an attribute beloved of climate alarmists – acceleration. Acceleration is essential if we are to submerge coral atolls in the next century. Even the doubling of rates claimed for the satellite data will only produce about a half-metre rise by 2100.
Before worrying about that, let’s take a longer view again. Figure 3 shows a reconstruction of sea level back to 1850. Here we can see that there are lots of apparent changes in rate. One of the slowest rates was during the 1960 and 70’s – the period that Nerem et al used to start their modelling exercise. But look further back in time and you will see other sluggish periods followed by rapid rises. None of these rises were sustained.
How accurate is the satellite data upon which claims of accelerating sea level rise are based? The measurements are rated to an accuracy of about 3 cm (30mm). Repeated measurement is supposed to reduce this error to a few mm by cancelling out of random noise. This is fine in theory but as the satellites are trying to measure a property (height of the sea surface) that is in constant motion, so that one can never achieve a true repeat measurement, the claimed accuracy seems rather optimistic. There are also a battery of adjustments (“on-going calibration/validation process”) to be made to the recorded data – for transmission of signal through the ionosphere and troposphere, for ocean tides, for variations in wave height and so on. Yet this data is being used to persuade us that sea level rise has accelerated by about 1.5 mm per year since the 1990’s, despite the fact that the tide gauge data do not support it.
The problem with the satellite analysis, then, is that the period of 30 years is too short to definitively confirm the tiny changes its proponents claim. Yet this has not stopped the United Nations Secretary-General Antonio Guterres from warning that hundreds of millions of people are at risk from rising seas. He has even suggested that this will generate conflict as people fight for the ever-shrinking land. This is the climate establishment equivalent of shouting “fire” in a crowded theatre.
Guterres of course is merely taking the more extreme forecasts of the climate scientists and broadcasting them Under the UN banner. Do the scientists themselves really believe these forecasts? I think they do. Figure 2 shows just what you would expect if you accept that the Earth is warming, sea water is expanding and ice caps are melting. But several of the adjustments mentioned above call for expert judgement rather than mathematical rigour. If you are already convinced that sea level rise must be accelerating, you are more likely to favour an adjustment that supports your conclusion.
Discussion of this “on-going calibration/validation process” reminds me of the craniometry debates of the late 19thCentury. Anatomists and surgeons such as Paul Broca collected a wealth of data on human skulls in an attempt to provide a scientific underpinning for racial and sexual differences in intelligence. Most of the researchers were, of course, white Caucasian males. They naturally assumed that they would be at the top of any measure of innate intelligence. So when raw brain size failed to distinguish them from other racial groups, increasingly sophisticated adjustments and corrections were made until the data supported their pre-conceived conclusions.**
Much of the craniometry work was published in reputable scientific journals and you can still read it today. It is clear that these men believed that they were doing objective science and that their conclusions flowed naturally from their data. They were simply unable to recognize their own unconscious bias. As Richard Feynmann pointed out “You must not fool yourself, and you are the easiest person to fool.”
Let’s go back to the Maldives. Coral atolls are simultaneously the most precarious and the most resilient of environments. Precarious because they cannot rise more than a metre or two above sea level; but resilient because the coral reef will continue to match sea level rise. Half a million people now live on the Maldives archipelago. There are hundreds of holiday resorts and there will soon be more than twenty airports. Top of the agenda at that underwater cabinet meeting should have been over-development of the islands. Left to themselves, the corals will be fine.
*Apologies to June Mercer Langfield and Shakespeare.
Nerem et al 2022 - https://doi.org/10.1029/2021EF002290
Gristead et al 2009 - doi:10.1007/s00382-008-0507-2.
**See Stephen Jay The Mismeasure of Man for a full account of 19th Century craniometry