How do we know what the climate was like hundreds of millions of years ago?

Yesterday I posted an article saying that the Earth has been warmer than today for hundreds of millions of years. A couple of readers asked how scientists know what the temperature would have been back then, and a reader provided this wonderful explanation. I love her final two sentences.

How do we know what the climate was like hundreds of millions of years ago?


There are one-celled creatures called foraminiferas which have lived in the oceans for about 550 million years. When they die they become buried in the ocean sediments. Recent sediments are of course soft but pressure and heat have hardened older sediments into sedimentary rocks. These strata have been analyzed with microscopes and these one-celled creatures indicate what the climate was like at the time they died since they are sensitive to temperature.

There are thousands of varieties of foraminifera and some varieties need warm temperatures and others can tolerate cold temperatures. SoO paleontologists have been able to document a pretty clear picture of ancient climates.

You will notice that paleontologists are NOT interviewed about “global warming”. No point in injecting a few facts into the debate.

26 thoughts on “How do we know what the climate was like hundreds of millions of years ago?”

  1. The most important question to answer with any proxy data is: How accurate are your “cooler climate” and “warmer climate” temperatures. Saying these creatures like it cooler doesn’t really say they can only exist in world where the average global temperature is 10 Deg C or 15 Deg C etc. Today we have data showing temperature records going back 10’s and sometimes 100’s of years. These data aren’t “cooler” or “warmer”, they are numbers. If our reader can put some numbers to these “cooler” or “warmer” temperatures? then I’ll be impressed. Also of course we’ll need proof of how these numbers were arrived at. Its very easy to say it was warmer or cooler thousands of years ago, but how do we really know. As far as I know tree rings don’t have “10 Deg C” written next to them.

    • Dear A R Thur, of course trees rings do not have temperatures marked on, it will be a weird thing. We can compare those ancient ring to the ones grown in our time and ESTIMATE temps of past years. If you need precision you could only date back to 1650, when in Paris they started to record atmospherical data. Of course the data base is too poor to be representative of long term climate.

  2. The AGW cultists also avoid HISTORY. Global cold and warm periods were recorded millennia before the Industrial Era, therefore the recent warming/recovery from the Little Ice Age was not unique at all. GEOLOGY is also avoided. Marine terraces occur at levels almost 100 meters above present sea-level, proving sea-level fluctuations during the Pleistocene. Present sea-level rise measured in mm/year is insignificant.

  3. plate tectonics and continent drift have moved the world land masses Since Pangea times. Bismarck ND was with in 1 degree of the Equator when the last Dinosaur roamed North America.
    Ask the Folks in Bismarck how tropical the Temp feel today.

  4. PRIOR TO the beginning of the Warming Cambrian Explosion of a Multitude of Emergent Life Forms (circa 550 Million Years Ago) – what is referred to as, “SnowBall Earth” (existed for roughly 100+ Million years), evidences suggests: most if not all Earth’s Surfaces were covered in ICE… All of which in turn evidences how LIFE likes WARMTH! …

  5. No one who knows something about earth long term history is interviewed about global warming…
    In addition to foraminifera, oxygen isotopes are used but only for water temperature. For shorter time periods also dendrochronology is used. In few words, growth rings of trees are used to determine not only temperatures but also humidity and solar activity.

    • and people dont realise that cold temps usually means dry when its really cold, therefore temps and low rainfall makes tree rings less than desirable to use
      unless your the mmann who can produce miraculously “science tricked” results

    • Tree rings didn’t work out too well for Michael ‘Hookey Stick’ Mann hence he had to do his ‘nature trick’ and use instrumental records to ‘hide the decline’ in the tree ring record. The rings are closely related to the amount of rainfall.

  6. The known forams are well characterized as to temperature prefences. Their ratio cleanly indicats water temperature.

    There are also pollen types in lake sediments that tell you the trees and other plants around. These match the forams and O2 isotopes. There is a lake in Florida that shows cyclical changes with the ice age glacials. It shows that the Gulf Stream slows down in glacials, so not delivering heat to Europe. Then winters in Florida get more oaks and are more like recent summers as the heat backs up in the Gulf. During times like now, more Pines as they do well in the cooler winters.

    In Europe, other isotopes in cave deposits, stalactites and such, confirm Europe was icy cold then. (So yes, I’m moving to Florida…).

    Similarly, pollens and isotopes show Texas stays warm but gets wetter during glacials. As do the fossils of various plants and animals.

    Between fossils, isotopes, pollen, and erosion deposits, you can make a very clear picture of wamth, cold, precipitation, and more for areas both large and small.

  7. It’s 1984 and people are programmed what to think by watching TV and reading the “news”. People now self censor their thoughts even if they suspect something is not true because they have controlled opposition for example denies global warming who is mocked, ridiculed and laughed at. Same old tribe wreaking havoc and destruction wherever they go.

    • look up “cancel culture” the ignorant mobs all jump in and get anything they dont understand(an awful lot) pulled down/retracted etc
      the fuss over Trumps using the word Lynching
      some tards then dive in and have a fit cos its rayciss…
      they lynched a LOT of white men rustlers and others long before they lynched negros.
      but the dweebs have NO historical knowledge and bugger all day to day education either!!!

  8. What about the English economist William Jevons who in 1876 produced a study demonstrating the correlation between sunspots and the business cycle?
    More sunspots, warmer climate and better harvests.
    I’m old enough to have been taught this at school. Since then education has degenerated into political brainwashing.

  9. How the hell do you pick out one celled creatures from all the background Mush after millions of years of compression ?
    Surely temps would fluctuate many times between hot and cold a huge amount in a million years and this would not show up, in what amount of rock, a few millimetres ? How can you then say so much about them and the climate from so very little Mush.
    Someone really needs to explain the science behind the science,
    so as to educate us mere mortals about your wisdom.

  10. Greta is a wee bit misguided when she only thinks ahead by 12 years.
    The silly frog faced bint is now 16. 16 + 12 = 28.
    Now picture the scene when she has given up her unhealthy vegan diet under doctor’s orders, she is now in her 30’s, probably married with kids, her personal climate campaign a distant memory.
    Sweden is still getting snow 3 feet deep every Xmas and Greta fancies a holiday in North Africa just to escape from the winter. She and her family will just fly to Egypt to see the pyramids.
    Oh and I also predict the pyramids will still be there, and not just Greta, THOUSANDS of tourists will arrive and post selfies to Facebook. Groan !

    • 🙂 somehow I dont think she will marry or have kids
      and Id not be suprised if she decides to go anorexic again or tops herself when it all falls in a steamy pile of crap.

      • Laurel I hope not. I wouldn’t wish that future on anybody.
        That abused child has a medical condition which isn’t helped by the politics of socialist revolutionary parents.
        Although the following words are now widely attributed to Cicero, in fact they originated in the 20th century, with novelist Taylor Caldwell’s 1965 book A Pillar of Iron.
        Even though that work often drew directly from the recorded speeches and letters of Cicero for its dialogue, it was nonetheless a work of fiction, and the warning from Cicero about “treason from within” was an invention of Caldwell’s and not a reproduction of Cicero’s own words.
        A nation can survive its fools, and even the ambitious. But it cannot survive treason from within. An enemy at the gates is less formidable, for he is known and he carries his banners openly against the city. But the traitor moves among those within the gates freely, his sly whispers rustling through all the alleys, heard in the very halls of government itself. For the traitor appears no traitor; he speaks in the accents familiar to his victims, and he wears their face and their garments, and he appeals to the baseness that lies deep in the hearts of all men. He rots the soul of a nation; he works secretly and unknown in the night to undermine the pillars of a city; he infects the body politic so that it can no longer resist. A murderer is less to be feared. The traitor is the carrier of the plague. You have unbarred the gates of Rome to him.

  11. There is a non zero percentage of the population that rejects all info presented on the internet as a matter of principle believing it to be conspiracy theories, lies and pornography. They only believe the government , media the evidence of their eyes or imagination.
    Such people can’t be reasoned with or educated.

    • Majority of South African geologists reject AGW, except those employed by government and on research grants. American geologists seem to be more gullible.

    • I would add to your list thermodynamcists as we see the fallacy of the CO2 molecule causing green house warming in a chaotic atmosphere.

  12. To Chris G; et al. … ” How the hell do you pick out one celled creatures from all the background Mush after millions of years of compression ? ”

    Yes! … And On a related note, such “cells” represent the most complex chemistry in the known universe – and of which bio-sciences admit to only realizing but a sliver of their totality – whereby a legion of unanswered questions multiply as findings come in…. PLUS? .. Although competing and contradictory theories exist, It’s the exacting and elusive HOW? they came to be – which still remains under intensive studies..

  13. If I’m understanding this article I link to below correctly, it appears there wasn’t actually an ice sheet covering the middle of Canada during the Pleistocene after all. I always thought it seemed strange to just assume there was a big ice sheet there with no way to prove it. The whole continent of North American must’ve been covered in lakes and rivers though since there sure were a lot of GIANT beavers that during the Pleistocene.
    “Our radiocarbon data set constrains the extent of LIS. Central Saskatchewan was not covered by LIS throughout the Upper Pleistocene. ”

  14. I was lucky enough to meet with one of THE world experts on foraminifera in the ’70s. It it a fascinating and well qualified method.

    Forams make shells. Microscopic, but hard. These are what is studied. Each species and type makes a unique shell shape, visible under a microscope. The shells deposit in layers in sediments as they die and sink. Resolution can be quite fine down to annual deposit layers.

    There are many varieties living in any body of water, and each has a preferred temperature. So depending on exact temperature you get a different ratio of the different shell shapes from the different varieties.

    So think of diatomaceous earth. It is just a collection of similar microscopic shells from diatoms. Forams can make similar deposits of shells in sediments. All you need is a microscope to see the particular shapes and count each type, then lookup the known temperature for that mix.

    It is like comparing fossils of black bear vs polar bear, but on a microscopic scale and with dozens of types so finer precision.

    The shells can also be quite beautiful.

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