Friday, April 24, 2015

Sea Level Rise Not as Bad as Feared

But somehow, they manage to turn that into an even bigger problem

A New Look at Estimates for 20th Century Sea Level Rise
In a story last September I wrote that for much of the 20th Century, sea levels rose by “around 1.7 millimeters a year.” Except, that number may have been off, at least according to a recent report by scientists at Harvard and Rutgers University in New Jersey. In fact, the number I quoted may have been too high by about 30 percent.

The new findings raise an important question that often pops up around studies of sea level rise: why is it so hard to measure changes in the height of the world's oceans? Theoretically, it should be easy -- just wade out into the surf and record how high the water gets. Is it to your ankles or your shins. But in reality, there are a lot of uncertainties about the estimates that scientists draw up for how fast the seas are rising.
. . .
But first, here's a bit about that new study, which addressed the increase of water levels in the near past, as opposed to the increase we can expect to see in the future. For years, most studies that looked at the rates of sea level rise during the bulk of the 20th century -- or from around 1901 to 1990 -- tended to come up with similar numbers: during that era, the seas rose by about 1.6 to 1.9 millimeters per year on average.

In the new study, however, the Harvard and Rutgers scientists used a new type of statistical analysis to reexamine sea level records taken from around the globe. As a result they calculated that the actual rate of sea level rise between 1901 and 1990 might have been closer to 1.2 millimeters per year. I had overshot the mark.
I'm suspicious of any "new statistical techniques" that suddenly take a noisy record and claim to find exactly the trend they would like for find in the results.
This analysis, which was published in the scientific journal Nature in January 2015, doesn't disprove the fact that the seas are rising around the world and rising fast. Instead, it suggests that sea level rise is speeding up from what scientists call a lower "baseline." That means the rate of rise is accelerating faster than previously thought. Current rates of rise are now around 3 millimeters per year worldwide. And they're even higher on the Bay, hitting 4 millimeters per year or even more according to some estimates.
This strikes me as more of the trend monkeying we have seen with global temperatures. Cooling of past temperatures after "re-analysis" of the data has made the increased temperatures in the late 20th century seem much more serious than they would look in their absence.

Are we now into an era when the sea level record is similarly "reanalyzed"? Stay tuned.

As for what is happening currently:

Do you see any increase in the rate of sea level rise post 1990? If you can't see it, statistics used to detect it are dubious. In most case human pattern recognition finds (false) patterns that statistics can't.

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