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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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RE: Talk about statistically insignificant...
By lukasbradley on 12/15/2008 12:12:32 PM , Rating: 2
I'm assuming you don't include ice core samples going back 740k years as "accurate" data?

By masher2 on 12/15/2008 12:38:48 PM , Rating: 5
They're proxies, which is certainly data. How accurate they are remains to be seen. It is known that ice core proxies cannot capture short-term spikes, as entrainment, subsequent gas diffusion while frozen, and the coring process itself all result in a "smearing" process that will average out any readings below a certain minimum width.

In any case, many temperature proxies (ice cores or otherwise) have established undoubtably that climate often shifts at a much faster pace than that we are now experiencing. In the Younger Dryas event (just 12,000 years ago) temperatures changed by 5C in just a few decades.

By ebakke on 12/15/2008 12:42:51 PM , Rating: 3
The further back you go, the larger the range that that data covers. For example, if we go back 24 hours, we can find the minute by minute temperature, precipitation, pressure, dew point, etc etc. If we go back 100 years, we may find daily high/low temperatures, and precipitation. Go back 10,000 years and you have the deduced average rainfall/temp for a 1,000 year period. Go back 740k years, and you have an ice core sample that spans a 75k year period. We have NO idea if within that 75k year timeframe, there were 50 100-year spans that were identical to the past 100 years, or if there were 0. Or 75!

The point is that we just don't have the data.

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