Another New Term Is Added To The Climate Lexicon: Welcome To Your New ‘Semi-Empirical’ World

As a term, ‘semi-empirical’ has been around since 1935, according to Merriam Webster’s Dictionary. It’s not a term I have come across during my years involved in the climate conversation. It kind of sounds like using your favored assumptions to help you get the answer you want.



adjective semi·em·pir·i·cal \-im-ˈpir-ə-kəl, -em-\

Definition of semiempirical

Popularity: Bottom 20% of words
  1. :  partly empirical; especially :  involving assumptions, approximations, or generalizations designed to simplify calculation or to yield a result in accord with observation

However, that’s what climate activist site Real Climate is using to publicize their paper on 2,500 years of sea level rise. Astonishingly, their graph of sea level rise over the past 2,500 years has the shape of a Hockey Stick.

Sealevel rise

The paper is Kopp et al, found here. The Real Climate co-author of the paper is Stefan Rahmstorff (introduced in greater detail below).

Astonishingly, the paper claims to have charted sea level rise for the past 3,000 years, not the 2,500 claimed by Real Climate. I don’t know if that’s modesty or just an example of semi-empiricism.

Anyhow, here’s how they did what they did: “We present the first, to our knowledge, estimate of global sea-level (GSL) change over the last ∼3,000 years that is based upon statistical synthesis of a global database of regional sea-level reconstructions. …”We assess the relationship between temperature and global sea-level (GSL) variability over the Common Era through a statistical metaanalysis of proxy relative sea-level reconstructions and tide-gauge data.”

Okay… proxies again. I start to see where the term ‘semi-empirical’ is relevant here.

Here’s the money graph:

SLR by century

Why, that’s… that’s… more than 5 inches! It’s 5.1 inches, to be more precise.

They continue: “A significant GSL acceleration began in the 19th century and yielded a 20th century rise that is extremely likely (probability P0.95P≥0.95) faster than during any of the previous 27 centuries. A semiempirical model calibrated against the GSL reconstruction indicates that, in the absence of anthropogenic climate change, it is extremely likely (P=0.95P=0.95) that 20th century GSL would have risen by less than 51% of the observed 13.8±1.513.8±1.5 cm. The new semiempirical model largely reconciles previous differences between semiempirical 21st century GSL projections and the process model-based projections summarized in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.”

Well, we’re all in favor of reconciliation, right? And Real Climate wants to share the wealth–they cite other papers as they begin to talk about future sea level rise:

“This brings us to a second study, also published this week in PNAS (Mengel et al. 2016). In this paper a new method of sea-level projections is developed. It is not based on complex models, but also on simple semi-empirical equations. But not for sea level as a whole but for the individual causes of sea-level changes: thermal expansion of sea water, melting of glaciers and mass loss of the large ice sheets. These equations are calibrated based on data from the past and then extrapolated to a warmer future. It is a kind of hybrid between the semi-empirical and the process-based approach (favored by the IPCC) to sea-level projections. The following table compares the projections of the various methods.

Scenario IPCC 2013 Kopp 2016 Mengel 2016 Horton 2014
RCP 2.6 28–60 24–61 28-56 25–70
RCP 4.5 35–70 33–85 37-77 n.a.
RCP 8.5 53–97 52–131 57-131 50–150

Table 1 Global sea level rise in centimeters over the 21st century according to various studies for different emission scenarios. The first scenario (RCP 2.6) assumes successful climate policies limiting global warming to about 2°C; the last (RCP 8.5), however, unabated emissions and heating by around 5°C. (The ranges indicate the 90 percent confidence intervals except for the IPCC, which only provided a 66 percent confidence interval.)”

Note again the use of the term ‘semi-empirical.’ Perhaps that’s appropriate because using RCPs for this type of forecast is similar to examining the entrails of chickens, as the Representative Concentration Pathways started off with the conclusion and worked backwards to find a plausible scenario for reaching said conclusion.

Update: (I slipped a decimal point. Corrected figures here.) Using empirical observations without the need for a ‘semi’ gives us this. So far during the 21st Century, sea level rise has totaled 6.2 cm. Should sea level rise continue at this breathtaking rate we will reach 10 centimeters of global sea level rise by 2025, nine years from now. That will give us 75 years to achieve the other 120 centimeters Stefan Rahmstorff thinks may befall us by 2100.

You can sort of drive a semi through some of these projections.

However, I must be careful. Stefan Rahmstorff was convicted of libeling a German journalist a few years ago when she dared question some of his more alarmist scribblings. He actually drove her out of the profession, despite his being found guilty of libel. As the German newspaper Der Spiegel noted, “Time and again he has not only gone after journalists, but also after scientists who have openly expressed views that Rahmstorf didn’t like.” Sure would hate to annoy this master of ‘semi-empiricism.’ He might tell some ‘semi-truths’ about me.


24 responses to “Another New Term Is Added To The Climate Lexicon: Welcome To Your New ‘Semi-Empirical’ World

  1. I’ve accumulated some stuff on Rahmstorf here:

    My favorite is Steve McIntyre’s verdict: “It turns out that Rahmstorf has pulled an elaborate practical joke on the Community…”

  2. Re: “So far during the 21st Century, sea level rise has totaled 62.4 mm…”

    And that’s trusting the inflated satellite altimetry figures. If you trust the much more trustworthy coastal tide gauges, it’s about half that.

    • So let’s see, in order to be a card-carrying member of the Consensus you must believe:
      Estimating surface temperature based on measuring buckets of sea water is right, satellites are wrong.
      Estimates of ice sheet mass change based on gravity are right, satellite altimetry is wrong.
      Estimates of sea level from satellite altimetry are right, tide gauges are wrong.
      Do I have that right?

  3. Well done. One correction: “It kind of sounds like using your favored assumptions to help you get the answer you want” should be “It uses your favored assumptions to get the answer you want”.

  4. Well. 5.1 inches in the 20th century? I believe it’s generally accepted that any anthropogenic contribution before about 1950 was negligible. According to a figure cited in “Skeptical” Science,
    sea level rise between 1900 and 1950 was about 70mm, or 2.7 inches. There’s about half of the total right there, with no human help.

    If the 1900-1950 rise continued unchanged to present, you’d have just about the entire 5.1 inches. Apparently we are meant to believe that circa 1950 the natural rate of rise documented well back into the 19th century completely ceased and was replaced by anthropogenic sea level rise coincidentally of about the same magnitude.

  5. “So far during the 21st Century, sea level rise has totaled 62.4 mm. Should sea level rise continue at this breathtaking rate we will reach the first centimeter of global sea level rise by 2025, nine years from now. ”
    Huh? You slipped a decimal place. We’re already at +6 cm. 2025 will see us at +10 or so.
    I share your skepticism about +131, though. For one thing, I find it unlikely that even RCP8.5 would raise temps to +5 K above pre-industrial. But of course, it is implausible that we will experience anything like RCP8.5 anyway.

    • Harold, thanks. I don’t know if I am more prone to losing decimal points on posts that you read or if I’m making this type of mistake more frequently. I must remember to turn on the lights before using a solar powered calculator. Not for the calculator’s benefit–for mine.

      • No stones will be thrown from this glass house. I used to do math instantly in my head without any problems. Now I use Excel (especially the “convert” function) even for the simplest calculations because I’ve made so many mistakes.

  6. “semi-empirical” means when one gets caught fibbing they don’t have to apologize.
    “semi-empirical” is a synonym of “revealed knowledge”.
    The the climate charlatans are bold enough to openly push “semi-empirical” garbage dressed up as science shows how badly the climate social madness has corrupted the public square.
    Please show any credible citations to support the claim that Earth has had over two inches of worldwide slr so far this century.

    • hunter –
      First of all, the 62 mm of SLR this century is Tom’s figure, which I was citing in order to point out a conversion error.

      But you seem to be throwing the baby out with the seawater. Aside from the GIA correction (~0.3 mm/year), I see no reason to dispute the CU analysis of the JASON data. Apparently you find that not credible. Please explain why.

  7. “Semi-empirical” is used by those who favor Motivated Reasoning.

  8. My comment at Paul Homewood’s site this morning:
    “My favorite tidal gauge is the one at the tip of Manhattan Island, The Battery, which started operation in the 1850’s. For 160 years there has been no change in the rate of sea level rise. Mankind’s emissions did not initiate the current sea level rise, and they have not changed (accelerated) the rate.”

    Homewood’s post on sea-levels:

  9. In his classic Climate, History and the Modern World, Hubert H. Lamb reported that the highest sea level in the Holocene happened about 2,000 BC (from memory).

    Lamb was not a semi-scientist.

    • The idea that the highest sea level was about 2,000 BC is consistent with what Lamb wrote about glaciers:

      “It was after 2000-1500 BC that most of the present glaciers in the Rocky Mountains south of 57 o N were formed and that major re-advance of those in the Alaskan Rockies first took place.

      “And at their subsequent advanced positions – probably around 500 BC as well as between 1650 and 1850 AD – the glaciers in the Alps regained an extent, estimated in the Glockner region, at about 5 times their Bronze Age Minimum, when all the smaller ones had disappeared.”

    • Climate, History and the Modern World, second edition, paperback, page 115:

      “Of course, the details are less certain than the overall trend, but there is considerable agreement that the most rapid phases [of sea level rise] were between about 8000 and 5000 BC, also that the rise of general water level was effectively over by about 2000 BC, when it may have stood a metre or two higher than today.”

  10. “Semi-empirical” is “semi-truthful”.

  11. From Definition of empirical from
    2: relying on experience or observation alone often without due regard for system and theory
    3: capable of being verified or disproved by observation or experiment

    Semi-empirical could therefore cover phrenology, tea leaves, or casting rabbit bones on the ground as long as half the effort is devoted to objectively observing the objects in question.

    • So if semi-empirical means partly empirical and partly theoretical, then science is semi-empirical.

      Typically, semi-empirical refers to a theoretical calculation in which some inputs can not be obtained from soundly established theory. So one uses observations, described in some mathematical manner (i.e., a “parameterization”), for those inputs. So all climate models are semi-empirical.

      I suppose this will draw yet another silly, scornful, and pointless comment from Hunter.

      • ‘then science is semi-empirical.’ But couldn’t you say the same of many things other than science?

      • Mike M.,
        There is a difference between using parameterization to cover likely but unknown variables. That is reasonable.
        It is a different matter altogether to skew the parameters and ignore knowable ranges to yield the pre-decided results. That is simply marketing for a sale.
        The inaccurate results of the climate fanatic predictions are good evidence that they have chosen the latter method, not the first.

  12. “Semi-empirical science” can join “false but true” in long list of oxymoronic phrases. We should start a helpful list. Any other ideas?

  13. adjective semi·em·pir·i·cal \-im-ˈpir-ə-kəl, -em-\

    1: partly empirical; especially : involving assumptions, approximations, or generalizations designed to simplify calculation or to yield a result in accord with observation.

    2: Making stuff up AKA lying.

  14. Rahmstorf’s first paper on semi-empirical sea level projection was published nearly ten years ago and has been widely discussed since. I can’t understand how you’ve missed that or why you think they’d be using that idea to “publicize” a new paper.

    The reality is that many results beloved of “skeptics” would be accurately described as coming from semi-empirical methods – for example, Scafetta’s various efforts. Indeed most, if not all, climate sensitivity estimates based on a simple forcing-temperature relationship over the instrumental period are essentially using semi-empirical methods.

  15. Judith Curry weighs in on this semi-empirical work. Pielke, as usual, has an excellent observation.

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