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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