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Satellite altimetry data showing rate of sea level rise  (Source: University of Colorado, Boulder)
World's oceans rise slower since 2005, fail to display predicted accelerating trend.

Satellite altimetry data indicates that the rate at which the world's oceans are rising has slowed significantly since 2005. Before the decrease, sea level had been rising by more than 3mm/year, which corresponds to an increase of about one foot per century. Since 2005, however, the rate has been closer to 2mm/year.

The decrease is significant as global climate models predict sea level rise to accelerate as atmospheric CO2 continues to increase. In the 1990s, when such acceleration appeared to be occurring, some scientists pointed to it as confirmation the models were operating correctly.

Sea level rise was calculated from altimetry data from the TOPEX/Poseidon and Jason-1 satellite missions, published by the University of Colorado, Boulder.

Dr. James Choe, a research associate with the University of Colorado, says the decrease is temporary. "Interannual variations often cause the rate to rise or fall", he says. Choe believes an accelerating trend will reappear within the next few years. Oceanographer Gary Mitchum of the University of South Florida, says making any judgement from the limited data available is "statistically so uncertain as to be meaningless".

Others disagree. Dr. Vincent Gray, a New Zealand based climatologist and expert reviewer for the IPCC, believes that the accelerated trends seen earlier were simply an artifact of poor measurements. "The satellite system has undoubtedly shown a rise since 1992, but it has leveled off", he tells DailyTech. "They had some bad calibration errors at the beginning."

Gray points to a study done by Flanders University using tide gauges which, he says, measured no perceptible increase in sea level over its entire 15 year period.

Sea level has been rising since the end of the last ice age, some 20,000 years ago. During an episode known as "Meltwater Pulse 1A", the world's oceans rose by more than 5 meters per century, a rate about 20 times faster than the current increase.

TOPEX/Poseidon was launched by NASA in 1992, and collected data until 2005. In 2001, NASA and France's Centre National d'Études Spatiales (CNES) launched its follow-up mission, Jason-1.

Jason-2 was launched in June of this year.

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What's the source for the plot?
By jbartabas on 12/15/2008 3:17:16 PM , Rating: 2

A/ where did you get the plot?
B/ what data set did you use for making it?

I've used one data set from University of Colorado and find differences with your plot. You can also note the differences with the plot they have at their home page at For example, the local maxima roughly on the 1998 and 2006 ticks seem misplaced on your plot. Can you specify which one of their data sets you've used for the raw data?

RE: What's the source for the plot?
By masher2 on 12/15/2008 3:24:31 PM , Rating: 2
I used the set with seasonal signal removed, inverted barometer not applied. I used a running average in place of the linear regression, as obviously a straight line cannot show any acceleration or deceleration of the trend.

If one applies an inverted barometer response, the result is very slightly different.

RE: What's the source for the plot?
By jbartabas on 12/15/2008 3:52:04 PM , Rating: 2
Ok thanks, that's the one I've used. Therefore it seems you may have an x-axis issue. See for example the "peak" reaching 0 mm anomaly at beginning of 1998 in the raw data or their plot, it is around 1996 on your plot. Similarly their peak at ~30 mm, around the beginning of 2006, it is during 2005 on your plot (although that one is trickier as I am not sure where the year starts on your plot).

RE: What's the source for the plot?
By masher2 on 12/15/2008 4:39:51 PM , Rating: 2
Good eyes. I had to compress the font to keep it from clipping. That skewed the axis a bit, especially towards the beginning of the range. The labels on the new version above should track better with the data points.

RE: What's the source for the plot?
By jbartabas on 12/15/2008 5:15:16 PM , Rating: 2
If I read your x-axis properly, it is still off by up to 1 year at some locations (eg. 1998 peak).

Here are the raw data & a 2-year running average:

The raw data have a few temporal gaps, it may explain the x-axis shift.

RE: What's the source for the plot?
By whiskerwill on 12/17/2008 10:26:02 AM , Rating: 2
Just curious, but what software did you both use for graphing?

By jbartabas on 12/17/2008 8:45:09 PM , Rating: 2

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