If there’s a rival to the polar bear as the poster child of global warming, it’s the island nation of Tuvalu in the southwestern Pacific ocean. For over a decade doomsters of manmade global warming have claimed that greenhouse gas emissions cause warming that causes sea levels to rise (through ice sheet melt and thermal expansion of ocean water), threatening low-lying nations. Indeed, sea level rise is probably the most feared impact of global warming--especially since most of the other alleged devastating impacts have been refuted--and is therefore often trotted out as a rationale for a global climate treaty.
The world’s most famous prophet of global warming doom, Al Gore, has forecast 6 to 7 meters (about 19.5 to 22.75 feet) of sea level rise in this century--an amount that dwarfs that offered by another major alarmist, James Hansen (about 1.5 meters, or 4.9 feet) and the more plausible projections of the UN Intergovernmental Panel on Climate Change (about 12 to 23 inches) and those of the more authoritative sea level commission of the International Union for Quaternary Research (about 0 to 8 inches).
In the midst of all the bickering about just how much sea level is going to rise, tiny Tuvalu has been the center stage for sea level rise (SLR) concerns. Claims have been made again and again that the island nation is disappearing beneath the waves.
But observational evidence suggests otherwise. In an analysis of the SEAFRAME study of sea level on twelve Pacific islands (or groups of islands), New Zealand climate consultant and former IPCC reviewer Vincent Gray writes as follows about Tuvalu, starting with a rehash of the SEAFRAME report’s executive summary and then making his own corrective comments:
2.13.TUVALU
The Executive Summary [of the SEAFRAME study] states:
- A SEAFRAME gauge was installed in Funafuti, Tuvalu, in March 1993.
The sea level trend to date is +6.0 mm/year but the magnitude of the trend continues to vary widely from month to month as the data set grows. Accounting for the precise levelling results and inverted barometric pressure effect, the trend is +5.3 mm/year. A nearby gauge, with a longer record but less precision and datum control, shows a trend of +0.9 mm/year.
- Variations in monthly mean sea level, air and water temperatures are dominated by seasonal cycles and were affected by the 1997/1998 El Niño.
- The seasonal sea level cycle shows a peak early in the year, a time when Funafuti frequently experiences flooding.
- Since installation, at least two cyclones have passed through Tuvalu, but only one, Tropical Cyclone Gavin, was registered as extreme low pressure on the SEAFRAME at Funafuti.
- The SEAFRAME at Funafuti, Tuvalu has recorded 14 separate tsunami events since its installation. The largest tsunami signal of trough-to-peak height 8 cm was recorded after an earthquake of magnitude Mw8.3 that occurred near Kuril Islands on 15th November 200[character missing here]
Figure 13 Monthly sea level record from SEAFRAME for Funafuti, Tuvalu
If the depression of the 1998 cyclone is ignored there was no change [in] sea level at Tuvalu between 1994 and 2008; 14 years, despite 14 separate tsunami events. The claim of a trend of + 6.0mm/yr is without any justification.
It’s worth reading the whole of this (PDF, 1.1MB) to understand more about the tremendous difficulties of measuring sea level over time. In the earlier parts of the paper, before focusing on specific islands (or groups of islands), Gray explains how the SEAFRAME study is flawed by changes in measurement methods and equipment over time, resulting in conclusions of exaggerated sea level rise.
For a much more thorough discussion of sea level in the southwest Pacific, also concluding that there has been little or no SLR there in recent years and certainly nothing above normal rates, see this paper (PDF).
And to get a broader grasp of the general issue of sea level change over time, see this article (PDF), first published in the refereed journal Global and Planetary Change, by Nils-Axel Morner, head of the sea level commission of the International Union for Quaternary Research.
In short, sea level has not risen at Tuvalu for at least 14 years. Even had it done so, that would not be evidence of anthropogenic sea level rise, for sea level has been rising for the entire time since the last ice age, and a simple continuation of that rise is sufficient to explain the observed rise over the last 150 years, including the last 30 years.
But anthropogenicity is a necessary assumption behind the call by Rev. Tafue Lusama, in the December issue of the Evangelical Environmental Network’s e-newsletter, to love our brothers and sisters on Tuvalu by reducing carbon dioxide emissions. Yes, we should love our brothers and sisters on Tuvalu. But that does not entail that we should reduce carbon dioxide emissions, for there is no evidence that our carbon dioxide emissions harm them. Rather, since higher atmospheric carbon dioxide concentration promotes better plant growth (average 35% increase in plant growth efficiency for every doubling of CO2 concentration), if anything it is more likely that our carbon dioxide emissions are helping them by enhancing the growth of vegetation on their islands.
