News24

The puzzle of rising sea levels explained

2012-05-20 22:54

Paris - Massive extraction of groundwater can resolve a puzzle over a rise in sea levels in past decades, scientists in Japan said on Sunday.

Global sea levels rose by an average of 1.8mm per year from 1961-2003, according to data from tide gauges.

But the big question is how much of this can be pinned to global warming.

In its landmark 2007 report, the UN's Nobel-winning Intergovernmental Panel on Climate Change (IPCC) ascribed 1.1mm  per year to thermal expansion of the oceans - water expands when it is heated - and to melt water from glaciers, icecaps and the Greenland and Antarctica icecaps.

That left 0.7mm per year unaccounted for, a mystery that left many scientists wondering if the data were correct or if there were some source that had eluded everyone.

In a study published in the journal Nature Geoscience, a team led by Yadu Pokhrel of the University of Tokyo say the answer lies in water that is extracted from underground aquifers, rivers and lakes for human development but is never replenished.

The water eventually makes it to the ocean through rivers and evaporation in the soil, they note.

Groundwater extraction is the main component of additions that account for the mystery gap, according to their paper, which is based on computer modelling.

"Together, unsustainable groundwater use, artificial reservoir water impounding, climate-driven change in terrestrial water storage and the loss of water from closed basins have contributed a sea-level rise of 0.77mm per year between 1961 and 2003, about 42% of the observed sea-level rise," it says.

Cumulative effect

The probe seeks to fill one of the knowledge gaps in the complex science of climate change.

Researchers admit to many unknowns about how the oceans respond to warming, and one of them is sea-level rise, an important question for hundreds of millions of coastal dwellers.

Just a tiny rise, if repeated year on year, can eventually have a dramatic impact in locations that are vulnerable to storm surges or the influx of salt water into aquifers or coastal fields.

In its 2007 Fourth Assessment Report, the IPCC said the oceans would rise by between 18 and 59cm by the century's end.

But this estimate did not factor in melt water from the mighty Greenland and Antarctic ice sheets.

A study published last year by the Oslo-based Arctic Monitoring and Assessment Project (AMAP) said sea levels would rise, on current melting trends, by 90cm to 1.6m by 2100.

Comments
  • amanda.victor2 - 2012-05-20 23:11

    And today? I don't see the IPCC telling everyone that the sea levels have retreated. It's all to alarm people. The sky is falling stuff! Climate alarmists own sea-side property, but at the same time scare the people about how the levels will wipe out countries. What a load of rubbish.

      zaatheist - 2012-05-21 04:26

      Another dumb comment. "Climate alarmists own sea-side property." And nobody else does, and the majority of sea-side properties in Bangladesh, London, New York, Singapore, Amsterdam and the Maldives are owned by climate scientists and I am a stupid person making stuff up. Yeah, Amanada. "What a load of rubbish."

  • Ted - 2012-05-21 00:54

    The folly of man. Spending all those years struggling to get simple answers that God knows for sure! Getting accolades and Nobel prizes to study 2cm of a rise in sea level! It just shows how little we know about this planet and the Mighty hand that made it. It strengthen my faith daily when man struggles with such trivial matters.

      zaatheist - 2012-05-21 04:22

      Stupid is as stupid does. How can we take seriously the opinion of a person commenting on scientific matters who also believes in a book that has talking animals, wizards, witches, demons, sticks turning into snakes, food falling from the sky, people walking on water, zombies flying through the air and all sorts of magical, absurd and primitive stories?

      Ted - 2012-05-21 07:26

      @zaatheist. If evolutionists believe that we came from some kind of a fish after some kind of an accident after some fortuitous big bang, then walking on water is just a walk in the park. I don't see why a stick can't turn into a snake either if evolution proves correct! That would be a natural order of things under evolution, something coming from nothingness.

      John - 2012-05-21 07:36

      @zaatheist: Jesus LOVES you!

      LindiBleu - 2012-05-21 08:09

      @zaatheist - to quote Karl Marx: religion is the opium of the masses. n you know how hard it is to get anyone off opium and its derivative, heroin...

      zaatheist - 2012-05-21 08:47

      @John He probably loves you too but I am definitely his favourite. It is such a pity that the christian god botherers see us non believers as such a threat to their way of life. This says much about their belief systems and confidence in their invisible friend.

      zaatheist - 2012-05-21 08:49

      @Ted And your doctorate is in what again? You have offered a perfect example of "cargo-cult" science. Simply apeing the words and style of scientists doesn't make what you are doing science any more than putting on a tutu makes you a ballerina.

  • Chumscrubber1 - 2012-05-21 06:55

    Very simple solution would be to keep all developments a reasonable distance from the sea shore? But humans are not sensible creatures, look how we develop in the flood plains of rivers, then cry when there is death and destruction due to a flood. I'll never understand it.

  • Craig - 2012-05-21 07:19

    Another bit of climate alarmism as we approach Rio+20. We were told that CO2 was causing rapid warming after 1950 yet the sea level increase has not accelerated, in fact it has fallen by 5mm over the last two years.

      Douglas - 2012-05-21 08:03

      Sea levels have fallen? Citation please. My sources say they've risen continuously, although having risen slightly slower in the recent past. There are various explanations for this. One is that the sun has been in a solar minimum for a number of years now. Had it not been, the rise would have been quite a bit greater, due to thermal expansion.

      zaatheist - 2012-05-21 08:50

      @Craig And your doctorate is in .......? There will always be those, buoyed up by the false confidence of religion, expressing their ignorance of science as a virtue, thus qualifying them to make fools of themselves in public!

      Mike - 2012-05-21 09:31

      @Douglas, we are currently in a period of solar maximum. The last solar minimum occurred in 2008, however, the magnitude of the current solar maximum is significantly lower than usual and there will no doubt be some lag before we see the effects on sea levels.

      Douglas - 2012-05-21 21:39

      Thanks for pointing me right, Mike.

  • pkheswa - 2012-05-21 08:23

    Conspiracy

      zaatheist - 2012-05-21 08:51

      Religious individuals shouldn’t waste people’s time pointing out that science doesn’t have all the answers, unlike religion it answers something. No gods are observed or required in those answers. Reading the comments about science by the sky daddy believers is like listening to children talk about sex: They know it exists, they have strong opinions about what it might mean, but they don’t have a clue what it’s actually about.

  • Peter - 2012-05-21 09:03

    If the the scientist read the Bible they would have solved this puzzle years ago. The Bible refers to the fountains of the deep in Genesis 7vs11. That caused the world wide flood of Noah. Nobody needs a PhD to know that the earth's crust still contains huge amounts of water, hench the rise of the sea level.

      zaatheist - 2012-05-21 10:20

      BWAHAHAHAHAHAHAHAHAHAHAAHAHAHA! Here is a scientist. Scientists believe that every occurrence, including the affairs of human beings, is due to the laws of nature. Therefore a scientist cannot be inclined to believe that the course of events can be influenced by prayer, that is, by a supernaturally manifested wish. But also, everyone who is seriously involved in the pursuit of science becomes convinced that some spirit is manifest in the laws of the universe, one that is vastly superior to that of man. In this way the pursuit of science leads to a religious feeling of a special sort, which is surely quite different from the religiosity of someone more naive. - Albert Einstein

      Peter - 2012-05-21 12:00

      @zaatheist... Shame bra. You are trying very hard to convince yourself that the great God and my Saviour Jesus Christ does not exist. The complexities of Nature itself glorifies Him

  • Tony Lapson - 2012-05-21 09:20

    I don't understand??? Why dont coastal cities start desalinating water from the sea instead? BECAUSE IT COSTS TOO MUCH 'DIGITAL FIGURES' AND 'INKED PAPER'?

      ClaudsDeLuca - 2012-05-21 12:09

      I'm going to make an uneducated guess here and say that it may cost more water to run the plants than the plants will produce. Just a theory... why else wouldn't they be doing it already? Think its time to do some research...

  • DuToitCoetzee - 2012-05-21 11:18

    I see we have a couple of "clever" people that comment today. Well here is my input. If all is true I need to live for another 5600 years(if not longer) before I can sell my property as a "seafront" one. Hhmm! Will I sell privately or get an agent? Decisions, decisions, decisions!!!!

  • Tony Lapson - 2012-05-21 11:59

    The "big picture" simply doesn't matter to those who believe that everything is out of our control and in the hands of the "almighty".

  • ludlowdj - 2012-05-21 13:27

    Once you accept that this is a repeating cycle, its easier to make the link between the truth and the governments lust for money. no matter how much money we throw at the problem nothing will change, the cycle will continue as it always has.

      Douglas - 2012-05-21 21:52

      A repeating cycle? Well, indeed it is. Except you forgot one thing. What we are experiencing today is well outside the bounds of the natural cycles of the Earth, the Sun or Milankovitch cycles. I refer you to http://www.skepticalscience.com/Could-global-warming-be-caused-by-natural-cycles.html

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