Climate models and the Holocene global temperature conundrum

Posted: February 16, 2023 by oldbrew in Analysis, climate, data, History, modelling, Natural Variation, Temperature

Earth and climate – an ongoing controversy

Here we learn “our review revealed how surprisingly little we know about slow-moving climate variability”. In between unsupported assertions about human-caused modern warming, the authors of the review article ponder the realities of natural climate variability, including a warmer-than-today period in the Holocene, under the headings ‘What we know’, ‘What we don’t know’, and ‘Why it matters’. The closing line: “Our review suggests that climate models are underestimating important climate feedbacks that can amplify global warming.” Is this another way of saying long-term natural variation is being underestimated by the models?
– – –
Accurate climate models play a critical role in climate science and policy, helping to inform policy- and decision-makers throughout the world as they consider ways to slow the deadly effects of a warming planet and to adapt to changes already in progress, says Eurekalert.

To test their accuracy, models are programmed to simulate past climate to see if they agree with the geologic evidence.

The model simulations can conflict with the evidence. How can we know which is correct?

A review article published today in Nature addresses this conflict between models and evidence, known as the Holocene global temperature conundrum.

Lead author Darrell Kaufman, a Regents’ professor in the School of Earth and Sustainability, and University of Arizona postdoctoral researcher Ellie Broadman, a co-author who worked on this study while earning her Ph.D. at NAU, analyzed a broad swath of available data from the last 12,000 years to break down the conundrum.

The study builds on work Kaufman did that was included in the latest major climate report by the Intergovernmental Panel on Climate Change (IPCC) and looks at whether the global average temperature 6,500 years ago was warmer, as indicated by proxy evidence from natural archives of past climate information, or colder, as simulated by models, in comparison to the late 19th century, when the Industrial Revolution led to a significant increase in human-caused warming.

This comprehensive assessment concludes that the global average temperature about 6,500 years ago was likely warmer and was followed by a multi-millennial cooling trend that ended in the 1800s. But, they cautioned, uncertainty still exists despite recent studies that claimed to have resolved the conundrum.

“Quantifying the average temperature of the earth during the past, when some places were warming while others were cooling, is challenging, and more research is needed to firmly resolve the conundrum,” Kaufman said. “But tracing changes in global average temperature is important because it’s the same metric used to gauge the march of human-caused warming and to identify internationally negotiated targets to limit it. In particular, our review revealed how surprisingly little we know about slow-moving climate variability, including forces now set into motion by humans that will play out as sea level rises and permafrost thaws over coming millennia.”

Full article here.

  1. catweazle666 says:

    “Accurate climate models…”

    There is no such thing.

  2. oldbrew says:

    Article above:
    Recent studies on this topic have tried adjusting proxy data to account for their presumed weaknesses, inserting plausible forcings into climate models and blending proxy data with climate-model output, all arriving at different conclusions about the cause of the conundrum.
    – – –
    2014 study — The Holocene temperature conundrum.

    A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198-1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models. [bold added]

    So actual temperature analysis contradicts CO2 theory in that period. Conundrum indeed, for ‘one-variable climate’ believers 🤓

  3. Eric says:

    Reblogged this on Calculus of Decay .

  4. Phoenix44 says:

    Do these people really think its possible their literally impossible to be right models could be more right than physical evidence?

    But if their conclusion is that it was warmer, then got cooler befote now warming again, and the models don’t show that, then why are they not saying Climate Change has a big, big problem?

  5. catweazle666 says:

    “Do these people really think its possible their literally impossible to be right models could be more right than physical evidence?”


    The logic appears to be that, if faced with choosing between the data from £10 thermometers or the output from a £100,000,000 computer game – er sorry, “Climate Model”, it would be insane to believe the thermometers.

  6. oldbrew says:

    Hard to have any confidence in the concept of ‘climate sensitivity’. No value for it works well in models, and no-one knows what it is. Does it even exist?

  7. They can’t model past climates and get proper results, they haven’t modeled current climate and got proper results. Their future climate based on their models will never have proper results. They have never studied natural causes of climate change, they assumed greenhouse control and that is causes by a one in ten thousand change in the atmosphere. That change is 0.01 percent, one hundredths of one percent.

    Ice core records show what caused alternating limited warmer and colder past climates.

    Ice cores recorded more ice accumulations in warmest times when polar oceans were warmest and ice advanced and caused colder later due to the ice advance.

    Ice cores recorded less ice accumulations in coldest times when polar oceans were sea ice covered, ice depleted and ice retreated and caused warmer later due to the ice retreat.

    The Greenland and Antarctica warming and cooling have not proceeded in phase with each other for ten thousand years. Sometimes the Arctic and Antarctic warm and cool together and sometimes they are opposite.

    There is thermostat control of Arctic Climates. Check it out!

    When it is warmer, the sea ice thaws and it snows more until advancing ice causes colder.

    Flowing ice is pushed into the warm tropical currents that removed the sea ice and the ice in turbulent salt water currents is chilled to cause the formation of sea ice. Sea Ice prevents evaporation and snowfall and the land ice flows into the oceans and deplete until the ice is too thin and not heavy enough to flow the ice faster than it is thawing, then the sea ice is removed again and the warm cycle that builds sequestered ice on land repeats. The thermostat setting is the temperature that sea ice forms and thaws and that is not influenced by CO2.

  8. This was written:
    This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases.

    Milankovitch orbit differences warms the North and South with alternating solar into each the North and South. Ten thousand years ago the Sun warmed the North polar region more and now the Sun warms the South Polar Region more. The North has maintained less sequestered ice for cooling now than ten thousand years ago.

    The self correcting polar thermostat and controls promote more evaporation and snowfall as needed.

    Now, more ice is needed in the South and the South is getting the needed more.

    Now, less ice is needed in the North and the North is getting the needed less.

  9. oldbrew says:

    Human artefacts keep turning up where glaciers retreat. An obvious clue that temperatures were warmer at some point(s) in earlier times, pre-industrialisation.

  10. JB says:

    “How can we know which is correct?”

    That anyone but a child could ask such a fatuous question.

  11. catweazle666 says:

    Concerning estimates of “Climate Sensitivity”, oldbrew:

  12. stpaulchuck says:

    “when the Industrial Revolution led to a significant increase in human-caused warming.” <— that right there is a bald faced lie. The Industrial Revolution started at about the end of the Little Ice Age. Now pay close attention. This is very complicated. Ice age = cold. Not the ice age = warm(er). Duh. /snark (aimed at the warmist cult)

    Add to that the Roman Warm Period was warmer than today. In fact they grew grape crops in northern England. Something we cannot do today due to cold weather. Then there's the Middle Ages Warm Period, food was abundant, population increased by some 50%. Followed by the LIA where half the population died, mostly from starvation.

    As for predicting the past, that is the standard test for predictive models, especially for stochastic data like future stock prices, future temperatures, etc. If you knew the exact state of every sub atomic particle in the universe at one moment, it is likely you could predict the future state of other particles… EXCEPT for quantum foam's rather random-like appearance and disappearance. Sub atomic butterfly wings.

    We do not know with any sort of certainty what causes the onset of an ice age, nor do we know with any certainty what causes the end of an ice age. Without that, these models are Play Station climate games, doomed to fail.
    “The climate system is a coupled non-linear chaotic system, and therefore the long-term prediction of future climate states is not possible.” – IPCC TAR WG1, Working Group I: The Scientific Basis

  13. Phoenix44 says:

    So pretty good evidence we’ve had significant climate change in the past not just via natural variability but in the opposite direction to that implied by CO2 concentrations. We have pretty good evidence the models are virtually useless. We have pretty good evidence the world was warmer than now recently – in human recorded history.


  14. […] Related: Climate models and the Holocene global temperature conundrum […]

  15. oldbrew says:

    FEBRUARY 17, 2023
    Elephant seal remains show Antarctic sea was warmer in the mid-to-late Holocene
    — by University of Maine

    “Southern elephant seals today tend to haul out in much warmer areas than the Ross Sea,” Hall says. “We were able to use the presence of their molted skin and hair, as well as some bones and mummies desiccated by the polar wind, to show that these seals had once made the Ross Sea their home.”

  16. oldbrew says:

    Re. comment above…

    6 reasons to cruise the Ross Sea
    April 20th, 2022

    Witness the southernmost active volcano in the world

    The Ross Sea is home to the southernmost active volcano on our planet. Mount Erebus is the 6th tallest mountain on the continent and has been active for well over a million years. If you are lucky then you will see showers of spitting lava contrasting beautifully against the white backdrop.
    – – –
    Scientists found 91 volcanoes under Antarctica. Here’s what they might do
    Science — Aug 25, 2017

    The volcanoes are located in the West Antarctic Rift System, a 2,200-mile valley created by separating tectonic plates. The discovery brings the total number of volcanoes in the area to 138. The heights of the volcanoes range from 300 feet to 12,600 feet, with the tallest as high as Mount Fuji in Japan.

  17. […] looked at some of this recently, here and here. Of course the problem nowadays is that weather news is liable to be subjected to the […]

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