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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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By masher2 (blog) on 12/18/2008 4:32:18 PM , Rating: 2
I apologize for linking to the wrong study. This one is indeed more recent. However, it points up an even larger objection. From the synopsis:

quote:
In Antarctica, the Antarctic Peninsula and West Antarctica are losing mass and East Antarctica is gaining mass, by amounts similar to those of the 1990's.
Again, a curious omission for CNN. It's only the Arctic which is experiencing any acceleration (or was, a year ago at least), whereas the Southern hemisphere reaffirms the same pattern of loss in the east, and gain in the west.


By jbartabas on 12/18/2008 5:38:38 PM , Rating: 2
You should note that the CNN article reports also results from Luthcke et al., who used data as recent as 2008, contrary to Zwally et al. who stopped in 2007. IMO, they would have done better to leave Antarctica out of the story, as 2008 cannot create a trend on its own, and that's the impression left by the article. Or they should have differentiated between one particular recent result for West Antarctica, that still has to be confirmed as being a trend or not, and the situation in the NH polar regions where a trend appears more likely to occur.


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