Are sea levels are rising dangerously at a rate that has accelerated with increasing human GHG emissions, thereby threatening small islands and coastal communities?
Expert response by Professor Nils-Axel Mörner
In 1991-2005 Professor Mörner was head of Paleogeophysics & Geodynamics at Stockholm University, in 1999-2003 president of the commission on Sea Level Changes and Coastal Evolution, from 2000 on leader of the Maldives International Sea Level Project, in 1997-2003 coordinator of the INTAS project on Geomagnetism and climate, and in 2008,he was awarded the “Golden Condrite of Merit” from Algarve University “for his irreverence and contribution to our understanding of sea level change”.
Claims of dramatic and dangerous sea level rise submerging small islands and coastal communities are not supported by actual observational data
In 1999, I was expert reviewer of the chapter on Sea Level Changes in the IPCC report. I was struck and shocked by two facts; one was that none of the 22 authors was classified as a true sea level specialist, and the other was the very low quality of the text. Because, I had been just elected president of the International Union for Quaternary Research (INQUA) commission on Sea Level Changes and Coastal Evolution, I took up the main issue in our commission, an organization hosting some 300-400 true sea level specialists from all around the world. We had the question of sea level prediction for year 2100 open for inter-commissional networking and for discussions at five international meetings. Our best estimate was + 10 cm ±10 cm by year 2100 (lNQUA, 2000). This was significantly lower than the estimates by IPCC (2001). Later, I revised it to +5 cm ±15 cm. This implies that there is a wide difference between estimates from models (IPCC, 2001) and estimates from observational facts.
It is now time to review available observational facts, and I will focus on those areas that have been doomed to become flooded in the near future.
In this short review paper, I will highlight the main observational facts and their implications. Appropriate background material and discussions are given in the references.
1. The Maldives
The Maldives in the Indian Ocean consists of some 1200 islands grouped in 20 large atolls. All of the islands are low in elevation, not exceeding 2.5 m. The Maldives are often taken as an example of a nation that is seriously threatened by a sea level rise. They are said to be generally doomed to become flooded in the near future.
We have undertaken a detailed sea level research project in the Maldives. The group was composed of true sea level specialists. Personally, I have visited the area six times. This includes three one month-long expeditions. We were able to reconstruct past sea level changes in great details. In the last 4000 years, we record seven sea level oscillations in the order of 0.6-1.0 m, a 20 cm fall in the 1970s and a quite stable sea level for the last 30 years.
Therefore, we can free the Maldives from the condemnation to become flooded. By year 2100, sea level may, at the most, return to the pre-1970s conditions which implies no problems whatsoever.
As coastal areas, they are, of course, vulnerable to extreme storms and tsunamis.
Tuvalu in the Pacific has often been claimed to be in the mode of becoming flooded. The truth, however, is quite different. There is a tide gauge record going back to 1978. This record shows no rise in sea level, only variability around a zero level and three deep lows due to the periodic El Nino Southern Oscillation (ENSO).
No doubts, observations rule out unfounded claims of a serious sea level rise.
Vanuatu in the Pacific has been claimed to be the “first sea level refugees”. There is a tide gauge going back to 1993. It shows no rise, however. Therefore, the proposed sea level rise becomes unfounded and illusive.
Venice in Italy is a cultural treasure. It is located in the Po delta and subjected to a long-term subsidence. Any acceleration in the last 100-150 years would be easily traceable. The records show no traces of any acceleration. It even shows a significant deceleration after 1970.
Much has been said about the future flooding of Bangladesh with an assumed death toll in the order of tens of thousands of people. The country is very vulnerable to flooding. This is correct. The effect from an assumed sea level rise is quite another thing, however.
I have just returned from a short study of the coastal conditions in the Sundarban delta in Bangladesh.
At Kotka, a city located in the delta, it was possible to document firm evidence of strong coastal erosion with no rise in sea level. This implies that we get the same observational answer as in the Maldives; no present sea level rise. This will, of course, have drastic effects both for our understanding of real sea level conditions and of the future of Bangladesh.
6. Thermal expansion
When water is heated, it expands. Because of the stratification in the oceans, the heating will be confined to the uppermost part; probably the top 300 m or so. This will cause a sea surface rise in the order of a few cm up to 10 cm. In coastal areas of shallow water, the expansion will be less, and at the shore it is zero (because there is no water to expand).
7. Satellite altimetry
Satellite altimetry is a recent technique, which allows us also the measure sea level changes in the open ocean. A rising sea level trend has been inferred from selected tide gauges and subjective (non-observational) evaluations. Removing this “personal correction”, the record becomes a monthly scatter around a flat zero-line.
8. Glacial melting
There are physical limits for how fast ice can melt. The maximum rates recorded were those related to the melting of the glaciers of the Last Ice Age. The corresponding sea level rise amounted to 10 mm/year or 1 m per century. This figure sets the ultimate frame for possible sea level changes. Consequently, all claims of a sea level rise by 2100 exceeding 1 m can directly be discarded as physically impossible. Real changes must be significantly smaller.
The Little Ice Ages and Solar Minima in 1440-1460, 1687-1703 and 1809-1821 had little to insignificant effects on sea level, despite significant expansions of the alpine glaciers and Arctic ice cover, and sea surface cooling.
The claims of the IPCC and related persons with respect to sea level changes is deeply biased and not based on actual observation. A total revision is necessary. Its purpose appears to simply be to scare people in advance of the Copenhagen climate change meeting in December 2009.