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Science

NASA Scientists Suggest We've Been Underestimating Sea Level Rise (vice.com) 258

Our current estimate about the global sea level is "way off" according to a new study. The study published in Geophysical Research Letters this month suggests that our historial sea level records have been off by an underestimation of five to 28 percent. From a report on Motherboard: Global sea level, the paper concluded, rose no less than 5.5 inches over the last century, and likely saw an increase of 6.7 inches. The reason for this discrepancy was uncovered by earth scientists at NASA's Jet Propulsion Laboratory and the University of Hawai'i at Manoa. By comparing newer climate models with older sea level measurements, the team discovered that readings from coastal tide gauges may not have been as indicative as we thought. These gauges, located at more than a dozen sites across the Northern Hemisphere, have been a primary data source for estimating sea level changes during the last several decades. "It's not that there's something wrong with the instruments or the data, but for a variety of reasons, sea level does not change at the same pace everywhere at the same time," said Philip Thompson, the study's lead author and associate director of the University of Hawa'i Sea Level Center, in a statement. "As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average."
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NASA Scientists Suggest We've Been Underestimating Sea Level Rise

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  • Tide Gauges (Score:3, Interesting)

    by PPH ( 736903 ) on Monday October 31, 2016 @10:12AM (#53184109)

    "As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average."

    It's most likely that tide gauges were placed at locations where the economic impact of tides (on shipping, etc.) were most significant. So, even if the bias in sea level measurements is real, factoring in this impact cancels out the higher levels. In other words, who cares? If the sea level in the middle of the ocean is rising more than near the coast, most of us live near the coast.

    • "As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average."

      It's most likely that tide gauges were placed at locations where the economic impact of tides (on shipping, etc.) were most significant. So, even if the bias in sea level measurements is real, factoring in this impact cancels out the higher levels. In other words, who cares? If the sea level in the middle of the ocean is rising more than near the coast, most of us live near the coast.

      I don't think that follows. Gauges are placed mostly in and around harbors that have a lot of commercial shipping, yes, but those aren't necessarily the areas that are most prone to damage by rising sea levels. Actually, given their relative wealth they're probably among the coastal areas most capable of adapting to changing levels, and they're the areas that tend to already have sheltered natural harbors or artificial breakwaters (or both) in place, which will reduce the impact of higher storm tides.

    • by dywolf ( 2673597 )

      that's not the point they are making.

      yes the tides in those locations are important to know...for the trade in those locations.

      but that doesn't mean they are the best locations for knowledge of the entire tidal system of an ocean.
      those readings get used because they are available.

      but many things affect tides, from local geography to local gravity to nearby river flow (or lack).
      and this bit of knowledge is about a) finding better sites more representative of the whole system rather than just that locality, a

      • by PPH ( 736903 )

        those readings get used because they are available.

        And they are not wrong for their location. NASA doesn't need to add a fudge factor to the tide gauge readings at the local harbor. On the other hand, if they are only realizing now that harbor tide gauge readings don't apply to what is going on in mid-ocean, they need their ministerial credentials revoked by the Church of Climatology. I mean, this is really basic stuff. If they don't have these effects properly accounted for in their models, then why are we listening to "the science is done" crap?

        • by skids ( 119237 )

          I seriously doubt a low-order error in the sea level throws the models off to the point of them being worthless.

          By that that line of reasoning, we should just throw out all our measuring devices because they all probably have a tiny systematic error built into them, and forget the whole concept of centimeters.

  • by MrKaos ( 858439 ) on Monday October 31, 2016 @10:16AM (#53184131) Journal
    The tip of the iceberg.
  • These gauges, located at more than a dozen sites across the Northern Hemisphere

    That doesn't sound right, surely they can use the data from more stations than that? Canada has 125+ years worth of tide and water level data from thousands of stations [isdm-gdsi.gc.ca], maybe NASA should talk to them? It's free to download per water level station, or you can submit a request for the full dataset. (Disclosure: I worked for a time with the team that processes incoming marine data and digitizes historical log books.)

    • Northern north America is still bouncing back up from the compression caused by the last ice age.

      They are likely 'adjusting' that data, old temperature records style.

  • I continue to see articles explaining why for various plausible sounding reasons we need to adjust our raw data to show more climate change than the raw data contains. Can anyone point out any significant examples where the raw data was adjusted to show less climate change? The statistician in me is curious...

  • Without a doubt, we'll still be debugging our 20th century climate models when the clock strikes 2200.

    Sometime in the 23rd century, there will be a Holospace Science-Officer conference (conducted through a Holoreality subspace linkup) to thrash out a few lingering points of disagreement—adjust six inches here, six inches there and we're all good.

  • "These gauges, located at more than a dozen sites across the Northern Hemisphere..."

    Does anyone else see a problem with this sample size?

  • Nuke the moon. No more moon, no more tide and the water level goes down.
    • by GuB-42 ( 2483988 )

      Probably a good for solution against global warming too. Tides heat up the earth, so does the solar energy reflected back to earth.
      No moon, no problem, let's just build that death star and blow up the moon. What about the debris and all that stuff you say? The Ewoks survived, so why can't we?

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