Another hockey stick

Realclimate has already covered this, so I won’t say much, but there is a recent paper (Kopp et al. 2016) that does a sea level reconstruction for the past almost 3000 years. The key figure is below, with the red line being the post-2000 sea level rise that wasn’t included in the paper.

Credit : Kopp et al. (2016)

Credit : Kopp et al. (2016)


An obviously interesting result is just how much this looks like a hockey stick, again. However, as David Appell points out a hockey isn’t a surprising result. Since we expect internally-driven warming to largely average out on multi-decade timescales, the dominant influences on those timescales is likely to be changes in external forcings. Since the largest change in external forcing in the last few thousand years has probably been the anthropogenically-driven change over the last 100 years or so, we would expect the largest change to be over the last century or so; a hockey stick. In fact, if you look at the Realclimate post you’ll see another figure that illustrates that the change in sea level in the last century is much greater than in any century in the last 2000 years.

Given that sea level rise is a proxy for changing energy in the oceans, this is a really nice confirmation of what millenial temperature reconstruction have been illustrating for the last 18 years or so. I guess the one question is; where is the Medieval Warm Period? There’s maybe some suggestion of a slightly warmer period ~1000 years ago, but nothing like what what’s happened in the last 100 years or so. Admittedly, this is apparently the first attempt to do a multi-millenial sea level reconstruction, so one should be careful of jumping to conclusions. However, it’s certainly very interesting and largely confirms what we already know; our current warming is unprecedented when compared to the past few thousand years.

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24 Responses to Another hockey stick

  1. Pete Best says:

    The argument appears to be how much seal level rise the 21st century will bring ?

  2. verytallguy says:

    how much seal level rise the 21st century will bring ?

    I believe the polar bear is the standard measure of the impact of global warming.

    I’m not sure of the conversion for seals to polar bears.

  3. Eli Rabett says:

    Consistent and consilient results build the consensus. Spread the word

  4. John Hartz says:

    I played pick-up hockey as a kid growing up in Wisconsin. My hockey stick had a straight handle and a straight blade which I dutifuly wrapped with black tape. Sorry, but the graph in the OP looks more like a gnarled walking stick from Finnian’s Rainbow than it does a hocky stick. 🙂

  5. frankclimate says:

    A well defined global ( because it’s the global SL) “MWP” up to 1100 with a level just like 2000 and a well defined global LIA. Interesting.

  6. David@Nonesuch says:

    The conversion from seals to polar bears is that the bears eat the seals. The residue from the conversion goes on to become content for the GWPF

  7. Frank,
    I think you may be misreading the graph a little. I guess there’s a chance that it was similar in 1100 to what it was in 2000, but it’s more likely that 2000 was warmer than 1000.

  8. Dan says:

    Eli at Judy’s joint, consilience is in the eye of the beholder

  9. Eli Rabett says:

    So, the blind lead the silly.

  10. Dan says:

    It’s the blonde leading the blind

  11. izen says:

    @-frankclimate
    “A well defined global ( because it’s the global SL) “MWP” up to 1100 with a level just like 2000 and a well defined global LIA.”

    While the sea level may be global, the source and sequestration of the liquid water may not be. More likely it represents local climate variation on the glacier and ice-cap land ice in the N hemisphere.

    @-“Interesting.”

    Yes, the highest past peak is around the year 400, about the time of the fall of the Roman empire. Since then ~4inches of water has been locked into land-based ice and contracted. Until ~1850, the reign of Queen Victoria.
    Since then, at a rate an order of magnitude faster than its fall, all that lost ocean water, and more, has expanded and melted back.
    As interesting as the 1A meltwater pulse.

  12. frankclimate says:

    @izen: “More likely it represents local climate variation on the glacier and ice-cap land ice in the N hemisphere.”
    This is of course one possibility. Should it be useful to make an “educated guess” about the quantities of the percentages of sources to the sealevel variation of about 10cm before 400 (up) and after 1100 to 1900 (down)? I’m not sure about the mass-balance of glaciers in this times and I don’t know if glaciers and northeren landice give enough volume for 10cm global SL-change.

  13. Chubbs says:

    RE: the 21st century mentioned in comment #1. The satellite data indicates that sea level has risen 2.3 inches this century with roughly half of that in just the past 6 years vs. a 6 inch rise in the entire last century – so the sea level hockey stick is continuing to slowly bend upwards.

  14. Pete Best says:

    Richard Alley sounds some kind of warning here. Fascinating presentation but a lot of uncertainty. however although we are talking a long time coming the appears that we are close to committing the WAIS to significant melt and the EAIS to some and Greenland to some as sell.

  15. BBD says:

    @-frankclimate

    A well defined global ( because it’s the global SL) “MWP” up to 1100 with a level just like 2000 and a well defined global LIA.

    That graph shows sea level in 2000CE as 4 cm higher than the peak for 1000CE.

  16. BBD says:

    Before there’s any more creative misreading:

  17. anoilman says:

    Pre industrial sea level rise was 1.1 mm/year, and currently we’re at 3.3? This has been verified in many many different ways.

    Professor Mitrovica had a really novel way of identifying sea level rise. Sea level rise affects the rate of Earth’s spin, so by going back through historical documents and determining ‘when’ astronomical events have occurred. It would occur at a very different time of day with different sea level rise.

    This video helps understand all of this;

  18. Vinny Burgoo says:

    BBD, I dragged your pic onto Google Images in an attempt to find out whether its 20th century sea-level rise bar includes the 10% GIA adjustment that’s sometimes invisibly (and somewhat disgracefully) added to contemporary sea-level rise rates. Mystifyingly, Google’s best guess of what that pic is all about is ‘keep calm and sherlock’.

    Now, I’m no Sherlock but I can keep calm enough to ask you directly whether the GIA adjustment is included in your graphic.

    The same goes for anoilman’s 3.3 mm/yr and the Kopp et al graphic in ATTP’s blogpost. My guess is that anoilman’s guess does include the adjustment and Kopp et al’s doesn’t. Your ‘keep calm’ effort? No idea.

    (No, adding 10% isn’t much but it would still be alarmism. I’m concerned that you lot might be not be aware of any exaggerations – if exaggerations they be. Just trying to help.)

  19. Vinny,
    I’ve no idea what you are talking about. Care to explain?

  20. BBD says:

    Vinny

    The figure uses data from Kopp et al. Of course GIA is not ‘added’ to artificially inflate C20th SLR.

    Leave the paranoid conspiracy rubbish at the door please.

  21. Vinny Burgoo says:

    I had feared as much. See: http://sealevel.colorado.edu/content/what-glacial-isostatic-adjustment-gia-and-why-do-you-correct-it

    Strictly speaking, I think it’s a Glacial Isosostatic Adjustment adjustment – that is, the GIA is what the Earth’s crust is doing and the GIA adjustment is what earth scientists do to the global SLR estimate to better allow them to estimate humankind’s influence on global SLR. (If you can’t be bothered to read the link, the short version is that the bathtub is growing and this means that anthropogenic influences on the volume of water in the world’s bathtub is understated by estimates based on tide gauges, physics, necromancy, etc. So they add a bit. That’s fine for some purposes, but not when talking about actual, tide-gaugey type SLR – the sort that actually affects people.)

    You’ll get there in the end, young man. Keep at it.

  22. Ahh, but if we want to understand SLR in terms of global warming, then it seems as though making this adjustment is correct.

  23. anoilman says:

    Vinny…
    You didn’t in any way watch that video or look up any information. Mitrovica’s papers and discussion are very illuminating, particularly about the non-linearity of sea level rise, and tide gauge measurements. But, you will personally never know, if all you ever do is quote mine and hunt for dribs of info that match your world view.

    For instance, did you know that sea level is 900 feet higher at the north pole because the polar cap affects gravity?

    Lastly… I quoted rough numbers with this thing called a question mark. Its use is to imply that I’m don’t know the exact numbers. I’m open to having that refined. 1.1 and 3.8… I dunno… Don’t care. The undeniable fact is that current sea level rise is way higher than it ever has been in human history, and we know we causing it through global warming.

    In the mean time… please study this;
    https://en.wikipedia.org/wiki/Question_mark

  24. BBD says:

    You’ll get there in the end, young man. Keep at it.

    I know what GIA is Vinny. No need to be inappropriately and unwisely patronising. Especially as you are here peddling a particularly stupid version of the ‘alarmists-adjust-the-data’ conspiracy theory. Aren’t you embarrassed by having to stoop to this level?

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