[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/7213\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003ECave rock studies provide window into ancient civilisations\u003C\/h2\u003E\u003Cp\u003EMany people think of speleothems, or cave rocks, as being dull and brown. But they come in a wide palette of colours. \u2018I was recently with a friend in an abandoned mine where there were some rocks that had a bluish, greenish sheen because they had a lot of copper in them,\u2019 said Dr Sebastian Breitenbach. \u2018It\u0027s really rare to see that.\u2019\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EThink of a speleothem and you\u2019re probably imagining stalactites and stalagmites. (To remember which is which, try thinking of stalactites having to hold on tight; they\u2019re the ones that hang from the ceiling.) These rocks are formed as water drips into a cave and the dissolved carbonate it contains gradually precipitates out. You also get flowstones formed from underground streams and thin-walled tubes of rock known as \u2018soda straws\u2019.\u003C\/p\u003E\u003Cp\u003EThese rocks grow achingly slowly: a few tenths of a millimetre per year in the fastest cases. This means stalactites can be tens of thousands of years old. And because cave rock is laid down gradually by individual drops of water, it stores a record of their chemical composition.\u003C\/p\u003E\u003Cp\u003EIt turns out that some of these chemical signatures vary depending on the climate at the time. Take for instance the ratio of two isotopes of oxygen, oxygen-16 and oxygen-18. Rainwater contains a specific ratio of the two and so by grinding down samples from speleothems and analysing the isotope ratio at different points along the length of the rock, geochemists can get a hint of how rainy it was, or where the rain originated from when the rock formed. There are plenty of other proxies besides oxygen too.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAncient\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThis record of ancient climate entombed in stone turns out to be useful in giving us a handle on what life was like for ancient civilisations. It can also tell us about periods such as the mysterious Bronze Age collapse.\u003C\/p\u003E\u003Cp\u003EThis was the 50-year period in which several major civilisations in the Mediterranean, including the Egyptian empire, the Mycenaeans and the Hittites, all collapsed about 3,000 years ago. Some reckon \u003Ca href=\u0022http:\/\/www.pages.unibe.ch\/download\/docs\/magazine\/2016-2\/PAGESmagazine_2016%282%29_62-63_Weiss.pdf\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Ethis might have been to do with a megadrought that hit the region\u003C\/a\u003E. But this is a \u003Ca href=\u0022https:\/\/www.sciencemag.org\/news\/2018\/08\/massive-drought-or-myth-scientists-spar-over-ancient-climate-event-behind-our-new\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Econtroversial idea\u003C\/a\u003E and there are plenty of other theories. Some ancient texts pin the blame on \u003Ca href=\u0022https:\/\/www.newscientist.com\/article\/2087924-world-war-zero-brought-down-mystery-civilisation-of-sea-people\/\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Einvading hordes known as the \u2018sea peoples\u2019\u003C\/a\u003E.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018We are sure that they (ancient cultures in Turkey) must have been heavily influenced by environmental conditions.\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EDr Ezgi Unal-Imer, Middle East Technical University, Ankara, Turkey\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003EData from caves can help illuminate what might have gone on by at least showing when and where there was a drought. But there are gaps in the data, not least when it comes to Turkey.\u003C\/p\u003E\u003Cp\u003E\u2018Turkey has been home to many important ancient human cultures, from some of the world\u0027s earliest farming societies in the Palaeolithic to more modern societies like the Hittites, classical Greeks, Roman, Byzantine and Ottoman empires,\u2019 said Dr Ezgi Unal-Imer at the Middle East Technical University in Ankara, Turkey. \u2018We are sure that they must have been heavily influenced by (changing) environmental conditions.\u2019\u003C\/p\u003E\u003Cp\u003EThat\u2019s why she began the \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/842403\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003ESpeleotolia project\u003C\/a\u003E, with the goal of collecting high resolution paleoclimate data from Turkey. She has been collecting samples from caves over the past few years including 10 stalagmites from western Turkey.\u003C\/p\u003E\u003Cp\u003EFive of these cover the Holocene period and she has one sample that provides a continuous line of growth going back 1,825 years. \u2018This covers almost the entire common era \u2013 it\u2019s a really good sample,\u2019 she said.\u003C\/p\u003E\u003Cp\u003EShe\u2019s currently about halfway through drilling 420 samples, which will help her reconstruct the past climate conditions. Dr Unal-Imer is excited about what they\u2019ll uncover. We just don\u2019t know what we will find, she says.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ERain\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EOne thing her project won\u2019t do, however, is quantify how much rain fell in any given year in the past.\u003C\/p\u003E\u003Cp\u003EAt the moment, most speleothem data can only signal short-term climate trends, says Dr Breitenbach who is based at Northumbria University in Newcastle, UK. In other words, it can tell us a certain period was much rainier than the one before \u2013 but not how many millimetres of rain fell. Why so?\u003C\/p\u003E\u003Cp\u003EWell, let\u2019s take the ratio of oxygen isotopes in a rock again. In truth, though this is influenced by rainfall it is also nudged up and down by other factors like temperature, and the topography and humidity of the particular cave.\u003C\/p\u003E\u003Cp\u003E\u003Cfigure role=\u0022group\u0022 class=\u0022@alignleft@\u0022\u003E\n\u003Cimg alt=\u0022Organo-metallic molecules in cave rock may be able to tell scientists about historical temperatures. Image credit - Adam Hartland\u0022 height=\u0022690\u0022 src=\u0022\/research-and-innovation\/sites\/default\/files\/hm\/IMCEUpload\/cave_-_body_0.jpg\u0022 title=\u0022Organo-metallic molecules in cave rock may be able to tell scientists about historical temperatures. Image credit - Adam Hartland\u0022 width=\u0022860\u0022\u003E\n\u003Cfigcaption class=\u0022tw-italic tw-mb-4\u0022\u003EOrgano-metallic molecules in cave rock may be able to tell scientists about historical temperatures. Image credit - Adam Hartland\u003C\/figcaption\u003E\n\u003C\/figure\u003E\n\u003C\/p\u003E\u003Cp\u003EThe \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/691037\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EQUEST project\u003C\/a\u003E that Breitenbach led is trying to change that uncertainty, using two strategies. The first involves detailed work on one of the Waitomo caves in New Zealand. The plan is to measure many proxies in parallel and see how they all vary over time. Variations in one proxy might be caused by several factors and it\u2019s impossible to know how much each contributed. But look at the variations in 10 or 15 proxies in tandem and there should be only one hypothesis for how the rainfall has changed quantitatively, say, that fits all the facts. \u2018Then it\u2019s like an Agatha Christie crime novel,\u2019 said Dr Breitenbach. \u2018All the facts that we learned from the proxies must fit in the interpretation.\u2019\u003C\/p\u003E\u003Cp\u003EOne minus to this strategy, however, is that it requires a detailed understanding of the cave where the speleothem samples were taken. This means the researchers would have to summon their inner\u0026nbsp;detective afresh with nearly every rock sample.\u003C\/p\u003E\u003Cp\u003EThe second strategy is to discover new proxies that really are only impacted by one variable and so can provide quantitative data directly. Dr Adam Hartland at the University of Waikato in Hamilton, New Zealand has been leading this part of the work.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECalibrate\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EHe\u2019s discovered some molecules known as organo-metallic complexes for which it\u2019s possible to quantify how they change in cave rocks in response to temperature in great detail. The trick will be to calibrate this proxy, so that we can say a measurement of a certain amount of the complex signifies a certain temperature. \u2018We know how to do that \u2013 but we haven\u0027t quite done it yet,\u2019 said Dr Breitenbach.\u003C\/p\u003E\u003Cp\u003EWhat does all this have to do with the future though? Well, harvesting information about the past is crucial for answering questions about what will happen to rainfall and temperature in the face of the climate emergency. Take the El Ni\u00f1o\u2013Southern Oscillation (ENSO), a weather pattern that affects ocean temperatures and shifts rain around in the southern hemisphere with catastrophic effects on fishing and farming.\u003C\/p\u003E\u003Cp\u003EAt the moment, we have a poor grasp of how ENSO was affected by climate change in the past. But with speleothems, we can go back in time and look at a period that was particularly warm. \u2018We can see how often there were El Ni\u00f1os, how strong were they, and where were their strongest impacts? Then we can use the past as a key to the future,\u2019 said Dr Breitenbach.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research in this article was funded by the EU. 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