U. of Southampton: We won’t know whether or not sea level is accelerating until 2020-2030. Mojib Latif: models must first take natural variability much more into account
By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(Translated and edited by P Gosselin)
Forecasts have long since fascinated man. There’s something mystical about looking into the future. The oracle of Delphi, a look into the crystal ball, reading tea leaves: indeed the error rate is high, yet that does not deter people from paying more money for more far-fetched predictions.
The ClimateChangePredictions.org website has taken on the task of putting climate change predictions on the test stand to see whether or not they have anything to do with reality. One nice example is sea level rise. Currently sea level is rising 2 – 3 mm per year, and if the trend remains stable, a sea level rise of 25 cm is expected by the end of the century. However this does not keep some attention-seekers from announcing much higher rises to the public. At the ClimateChangePredictions.org website here you will find a highly interesting list of prognoses.
Australian climate scientist John Church predicted 3 m by 2100. For others that figure is much too low, and we are threatened instead with 7 m – or even 100 m! We almost get the impression that the higher the bid, the better the chances of winning – at least that’s the impression we get from the media.
Serious studies show just how absurd the sea level rise bidding has become. Within the framework of a European research program supported by a total of 10 million euros, a consortium of 24 institutes investigated scenarios for future sea level rise. Participating among them was the Bremerhaven-based Alfred Wegener Institute (AWI). The main aim of the 2009 to 2013 ice2sea program was to quantify the melting of land-based ice masses. In May 2013 the researchers presented their Final Report (pdf here). The consortium of scientists concluded that the most probable scenario for sea level by the end of the century is a rise of only between 16.5 cm and 69 cm. That was a bitter disappointment for the alarmists in the field.
So what purpose do the alarmist prognoses serve? Some originate from government organizations, who use them to prop up their aggressive climate policy aims. In the USA the Obama Administration warned of a rise of a rise of 2.10 m by the end of the century – far remote of the mainstream science.
The most recent IPCC report also appears to have lost all contact to reality, which despite all the careful prognoses found in the scientific literature, claims there is a rising danger from sea level rise. Here people like to look 2000 years into the future, absolute nonsense when one considers the numerous poorly known sea level trends.
Who is finally going to blow the whistle on the shrill alarmists and their predictions of a coming flood? When prognoses are far beyond the fringes of the accepted range, it should cause us to stop, think and cast doubt on apocalypse forecasters. For the press they couldn’t care less and gladly view it as a convenient source of attention-grabbing spectacular climate stories.
Within the scientific community, however, scientists see the predictability of sea level far more critically. In March 2015 a group of scientists lead by Mohammad Bordbar – which also included Mojb Latif – published a study that took the natural variability of sea level into greater account. The abstract of the paper stated that we can no longer continue to ignore these processes. The paper appeared in Nature Climate Change. The abstract reads:
“Effects of long-term variability on projections of twenty-first century dynamic sea level
Sea-level rise1 is one of the most pressing aspects of anthropogenic global warming with far-reaching consequences for coastal societies. However, sea-level rise did2, 3, 4, 5, 6, 7 and will strongly vary from coast to coast8, 9, 10. Here we investigate the long-term internal variability effects on centennial projections of dynamic sea level (DSL), the local departure from the globally averaged sea level. A large ensemble of global warming integrations has been conducted with a climate model, where each realization was forced by identical CO2 increase but started from different atmospheric and oceanic initial conditions. In large parts of the mid- and high latitudes, the ensemble spread of the projected centennial DSL trends is of the same order of magnitude as the globally averaged steric sea-level rise, suggesting that internal variability cannot be ignored when assessing twenty-first-century DSL trends. The ensemble spread is considerably reduced in the mid- to high latitudes when only the atmospheric initial conditions differ while keeping the oceanic initial state identical; indicating that centennial DSL projections are strongly dependent on ocean initial conditions.”
Natural variability currently makes it impossible to determine if the speed of sea level rise is beyond the range of natural variability. The University of Southampton also explicitly reports this in a press release dated 9 May 2014. It is necessary to first understand the natural processes and to account for them in the development of sea level rise before an anthropogenic signal can be identified and quantified. It’s indeed going to take another 5 to 15 years before scientists are able to decide whether or not sea level rise has accelerated in an unusual manner. What follows is the press release in its entirety:
“Back to the future to determine if sea level rise is accelerating
Scientists have developed a new method for revealing how sea levels might rise around the world throughout the 21st century to address the controversial topic of whether the rate of sea level rise is currently increasing.
The international team of researchers, led by the University of Southampton and including scientists from the National Oceanography Centre, the University of Western Australia, the University of South Florida, the Australian National University and the University of Siegen in Germany, analysed data from 10 long-term sea level monitoring stations located around the world. They looked into the future to identify the timing at which sea level accelerations might first be recognised in a significant manner.
Lead author Dr Ivan Haigh, Lecturer in Coastal Oceanography at the University of Southampton, says: “Our results show that by 2020 to 2030, we could have some statistical certainty of what the sea level rise situation will look like for the end of the century. That means we’ll know what to expect and have 70 years to plan. In a subject that has so much uncertainty, this gives us the gift of long-term planning.
“As cities, including London, continue to plan for long-term solutions to sea level rise, we will be in a position to better predict the long-term situation for the UK capital and other coastal areas across the planet. Scientists should continue to update the analysis every 5 to 10 years, creating more certainty in long-term planning — and helping develop solutions for a changing planet.”
The study found that the most important approach to the earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual (occurring between years, or from one year to the next) to multidecadal (involving multiple decades) variability in sea level records.
“The measured sea levels reflect a variety of processes operating at different time scales,” says co-author Dr Francisco Calafat, from the National Oceanography Centre. He adds, “One of the main difficulties in detecting sea level accelerations is the presence of decadal and multi-decadal variations. For example, processes associated with the North Atlantic Oscillation have a strong influence on the sea levels around the UK over multi-decadal periods. Such processes introduce a large amount of ‘noise’ into the record, masking any underlying acceleration in the rate of rise. Our study shows, that by adequately understanding these processes and removing their influence, we can detect accelerations much earlier.”
Co-author Professor Eelco Rohling, from the Australian National University and formerly of the University of Southampton, adds: “By developing a novel method that realistically approximates future sea level rise, we have been able to add new insight to the debate and show that there is substantial evidence for a significant recent acceleration in the sea level rise on a global and regional level. However, due to the large ‘noise’ signals at some local coastal sites, it won’t be until later this decade or early next decade before the accelerations in sea level are detection at these individual tide gauge sites.”
The findings of the study, funded by the Natural Environmental Research Council (iGlass consortium), are published in this months issue of the journal Nature Communications.”