Climate signals from ancient ice and wood 

Posted: February 24, 2023 by oldbrew in climate, History, modelling, Natural Variation, research, Temperature, trees
Tags: ,

Hunger stone at Decin on the River Elbe, with dates back to 1616 or earlier [image credit: Norbert Kaiser @ Wikipedia]

We 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 melodrama treatment by climate obsessives. Re. the European droughts, there’s also the evidence of the ‘hunger stones’, for example.
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The Holocene – the time since the end of the last glaciation – which has witnessed all of humanity’s recorded history and the rise and fall of civilisations – began only 11,700 years ago, says Dr David Whitehouse @ Net Zero Watch.

It is a relatively warm period, but how warm was it at its warmest?

What happened in the past informs current climate models placing the current global warming into perspective.

There have been contrasting views on the warmth of the Holocene. Marcott et al (2013) says 0.8°C higher than the pre-industrial period, Lui et al (2014) says 0.5°C cooler. In general, recent CMIP6 models fail to cast much light on the so-called Holocene temperature conundrum.

In a new review of available data Kaufman and Broadman (2023) find a relatively mild thermal maximum, but say more research is needed to understand slow-moving climate variability. They looked at a large variety of natural processes operating in many settings which the researchers say do not all point in the same direction.

The temperature probably peaked about 6,500 years ago about 0.5°C higher than when compared to 1850 – 1900, the warmth chiefly occurring in middle to high latitudes of the northern hemisphere. This is a curious finding as today’s more rapid warming also occurs predominately at high northern latitudes – Arctic Amplification.

Europe’s Summer Hydroclimate

Looking less farther back Freund et al (2023) use tree ring data to examine the European summer hydroclimate back to 1600 and make some interesting findings.

The current analysis utilises widespread, long-term data sets spread over many centuries. Those familiar with the controversy of the “hockey stick” tree-ring analysis will know that tree-ring widths require statistical detrending, making it difficult to use them to reconstruct some aspects of low-frequency climate variability.

Furthermore, tree-ring width data from European lowlands can display weak and ambiguous climate signals. In contrast, tree-ring stable isotopes are thought to be a more useful proxy as they can require less statistical processing.

There has been much debate about whether the European summer drought (2015–2019) was within the range of natural variability or is due to anthropogenic warming. Looking back at historical records suggests there has not been two consecutive summer droughts in central Europe in the previous 250 years.

Also, an extensive tree-ring isotope record from the Czech Republic indicates that the recent drought was unprecedented in the last two millennia. Others have said that based on tree-ring records and reanalysis products, the recent drought is well within the range of natural variability is thus not unprecedented.

In the new study the researchers reconstructed European hydroclimate based on a network of tree-ring stable isotopes of oxygen and carbon ratios. The network combines up to 400-year long, annually resolved records of deciduous oaks from European lowlands and conifers from boreal and mountainous sites.

This is the first time that stable isotope records from tree rings, with their so far untapped high climate reconstruction potential, are used to obtain a gridded spatial reconstruction of the European summer hydroclimate.

Solar Signature

They find three distinct phases and the possible signature of solar activity. Firstly, the years 1600 – 1652 had a wetter climate most apparent in west-central and north-west Europe. Secondly, shortly after the start of the Maunder Minimum (a period of low solar activity) drier conditions began that lasted two centuries affecting the Mediterranean, East and northern Europe.

By the end of the Little Ice Age, about 1875, another change occurred. Central, northern Europe and the Mediterranean show milder summer conditions that prevailed until the 1950s.

There is a trend towards drier conditions in the second half of the 20th century with 2003 and 2006 being the driest years on record which the researchers say is unusual through not unprecedented.

As for the 2015–2019 drought, most of Europe experienced an unprecedented drought with moisture conditions very much below average and in some parts the lowest on record. At the same time however Scotland and parts of Scandinavia as well as Greece and Turkey experienced unusual wet conditions.

The researchers conclude that whilst it seems that 2015–19 drought was unprecedented there might be evidence of longer and more severe droughts.

Full article here.

  1. Philip Mulholland says:

    I am pleased to see that with the application of stable isotope ratios to tree ring data some people are at last beginning to catch up with the pioneering work of Libby, L.M. and Pandolfi, L.J., 1974. Temperature dependence of isotope ratios in tree rings.

  2. Bill Bedford says:

    >Hunger stone at Decin on the River Elbe, with dates back to 1616 or earlier

    Has no one realised that the inscriptions are written from the top of this rock? ie the writing is upside down so all the dates are from the 20th century. 1919 not 1616

  3. JB says:

    So far I have found the following dates:

    What looks like 1616 on the right side is barely legible and could be mistaken for other numbers. Surely there is a better record than this?

  4. oldbrew says:

    ‘If you can see me, weep’: Drought-hit River Elbe reveals ‘hunger stones’ from 1616
    15 August 2022

    Severe drought has caused water levels of the river Elbe to drop, exposing centuries-old “hunger stones”.

    One stone now visible in Decin, where the Elbe flows from the Czech Republic into Germany, is carved with a warning from 1616 that reads: “If you see me, weep.”

  5. Phoenix44 says:

    What I’m unclear about with these hunger stones is that last summer’s drought had very little effect on agriculture? So why would a similar drought have caused hunger previously? In SW France where I spent last summer, the late frosts were a bigger problem as they killed the blossoms of the stone fruit trees – we had no plums or peaches and a single quince. But the sunflowers were great and I believe wheat was too. So why did 6-8 weeks of low rainfall in July/August have caused hunger previously?

  6. oldbrew says:

    This Guardian article points out another local factor on the Elbe:

    The Elbe stones in particular have appeared more regularly – notably during the central European drought of 2018 – since a dam was built in the 1920s.
    – – –
    Earlier generations had limited land transport so waterways were more important then. But the old-time droughts seem to have lasted for months, hence the poor harvests.

    Parts of Europe are already in a winter drought…

    Italy’s longest river, the Po – which stretches from the Alps in the northwest to the Adriatic – has 61 per cent less water than normal at this time of the year

  7. Jim says:

    Interesting, remember it’s not how much rain that falls as to when it falls for farmers. Rain and drought at the wrong time reduces a viable crop yield. And Europe’s crops are downwind from some of the worlds most prolific volcanos and underwater hot spots, which none of the models account for. Such as a simple question of how does a hot spot, change the circulation patterns?

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