Pacific Island Nations

The WUWT blog has recently had a spate of posts about Pacific Island Nations and the threat of sea level rise. Their common themes are that the threat is overstated, that the Island Nations are trying to swindle us out of money on false pretenses, and any data which show that there is a problem can’t be right. The level of “scholarship” in these posts is perhaps best illustrated by one about the current president of Kiribati, which had to add an “update” after it was published because when he wrote the post, the author didn’t know who the current president of Kiribati is.

I’d rather know what’s really happening with Pacific Island Nations and sea level rise.


I took tide gauge data from PSMSL (Permanent Service for Mean Sea Level) for stations with longitudes from 140°E to 172°E and latitudes from 12°S to 20°N; there are 32 of them, and they’re shown here in red with a red box around them.

Then I aligned the stations’ data so I could form a composite average, and this is what I got:

In addition to the trend, which I’ve estimated with the smooth curve shown in red, there’s also a lot of fluctuation. Much of it is related to ENSO, the el Niño southern oscillation; when ENSO is high (like in 1997/1998 and 2015/2016) sea level in this region tends to dip low.

These are monthly values; those interested in yearly averages can see them here:

I’ve added both the smooth (in red) and a straight-line fit by least squares regression (in blue). The linear fit, from mid-1946 through the end of 2016, rises at a rate of only 1.4 ± 0.6 mm/yr (95% confidence interval). But the smooth suggests the rate hasn’t been constant throughout, that this region has experienced acceleration of sea level rise.

The smooth indicates that at present, the trend is inreasing at a whopping 4.6 ± 2.6 mm/yr, more than three times the long-term linear rate, but the uncertainty in that estimate is quite a bit larger. The Chow test identifies a significant change in the rate of sea level rise around 1993; the linear trend rate since that time estimates the rate at 3.9 ± 1.9 mm/yr.

So yes, sea level is rising in this region, and yes, it has accelerated, and yes, it’s rising at least as fast as the global average.

Naturally some will criticize the tide gauge data. We can compare what tide gauges say to what the satellite data say for this area. One of the longest records is from Kwajalein (part of the Republic of the Marshall Islands), so I retrieved satellite data for its location from the Sea Level site at the Univ. of Colorado. Of course the satellite data don’t start until 1993, but we can compare data since then, giving this:

The entire Kwajalein record looks like this:

The rate since 1993 at this particular site is 6.9 ± 2.4 mm/yr, but I suspect that’s due to a combination of the uncertainty due to noise and a local but temporary effect which recently amplified it relative to the rest of the region.

The overall result is clear. Pacific Island Nations are endangered by sea level rise which is at least as fast as the global average. At the present rate they will be seriously impacted, but considering that all the best evidence suggests sea level will rise even faster in the coming decades — possibly a lot faster — they really are threatened with the disappearance of their home. The fault isn’t theirs, its ours.

The concerted attempt to dismiss their concerns, even to malign them for seeking help, strikes me as petty and mean-spirited … but that’s just my opinion.


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10 responses to “Pacific Island Nations

    • Methane madness

      Yeah that’s a ripper, those bastards deny in public and snicker in private, plenty of nasty Australians support these wankers, resulting in Australia failing to meet CO2 target.

  1. Good to see this. The general public does not understand that sea level change is not uniform. Unfortunately the NASA site doesn’t seem to maintain a map of sea level change, but one is available from the CU sea level site (http://sealevel.colorado.edu/content/map-sea-level-trends). I couldn’t find the map on NASA’s public sites, but that seems typical–too much news, and too little monitoring.

  2. Sea level rise since 1990 sends me to my metric ruler to view what 2cm would look like … about the width of my thumb

    • RP: Sea level rise since 1990 sends me to my metric ruler to view what 2cm would look like … about the width of my thumb

      BPL: Do you understand the difference between vertical sea level rise and land encroachment? Hint: Is it 1 to 1, or is the ratio different?

    • That would be interesting except that the rise in the first graph is much closer to 20 cm, not two cm. Much more than the width of my thumb. Distances look smaller when you misplace the decimal. The current rate is about 2 cm every 4 years.

      You also have to remember that a 1 meter rise in these atoll countries would flood most of the islands. If you only have one meter to lose and 20 cm has gone already you don’t feel good about the future.

      • He left out multiplying the annual rate that caused the width of his thumb times whatever to 2100. Now the ridiculous is complete.

  3. I understand the thrust of this post, but regard to the situation of small island states in the South Pacific, the generalization that they are threatened with inundation from sea level rise may not be entirely correct. Some are low lying and are indeed threatened by flooding from sea level rise. Others are volcanic mounts that will lose almost no significant area from sea level rise. Some are threatened with loss of their fresh water supply (salinization of the fresh water lens as a result of sea level rise). Coral bleaching due to ocean warming threatens the food supply of some. Strengthened typhoons pose a significant threat to some islands. In other words, the climate change effects can be different on different islands.

    https://thediplomat.com/2017/06/for-pacific-island-states-climate-change-is-an-existential-threat/

    Jon Barnett at the University of Melbourne has done a lot of work with small South Pacific Islands. https://www.amazon.com/Climate-Change-Small-Island-States/dp/1138866962 “This book is the first to apply a critical approach to climate change science and policy processes in the South Pacific region. It shows how groups within politically and scientifically powerful countries appropriate the issue of island vulnerability in ways that do not do justice to the lives of island people. It argues that the ways in which islands and their inhabitants are represented in climate science and politics seldom leads to meaningful responses to assist them to adapt to climate change.”

  4. @fred I will never understand how people in Brisbane, where his electorate is located, think Dutton is a stellar person who should represent them, George Carlin was right, we really do need to ‘blame the voters’

  5. Martin Vermeer

    While study of local sea-level records has its own interest, consequential for the long-term impact of sea-level rise are the *global* numbers, which are much less noisy and very robust. You cannot have a large increase in total ocean volume without it being visited in the end upon *all* coastal locations not close to ice sheets — el Niño and other sources of regional sea-level variability be damned.