Fossilized raindrops dampen theory of ancient warming

Posted: April 6, 2012 by tallbloke in atmosphere, data

I came across this interesting story on the Institute of Physics website today and thought it worth sharing. More puzzles than answers, but it might jog a few ideas.

A meerkat stands guard over ancient raindrops

A technique that uses fossilized raindrops to work out what the air pressure on Earth was billions of years ago has been used for the first time by scientists in the US. By analysing the shapes and sizes of raindrop imprints in volcanic ash, the team has shown that the atmospheric pressure in the Archaean eon was roughly the same as it is today. This is at odds with a popular theory of how the Earth stayed warm enough for life to exist at the time.

Billions of years ago, the Sun was about 20% dimmer than today because a star burns hydrogen more slowly earlier in its fusion cycle. There would therefore have been less radiation reaching the Earth and the surface should have been frozen. However, there is ample evidence of liquid water at the time as well as very primitive forms of life – a mystery known as the “Faint Young Sun” paradox.

Most scientists agree that the Earth must have been able to retain more heat in the past – but the reason why remains controversial. One explanation, proposed in 2009, is that atmospheric pressure was many times today’s figure

causing pressure-broadening, whereby nitrogen and carbon dioxide become more efficient greenhouse gases at higher pressures. 😉

To test this, astrobiologist Sanjoy Som and colleagues at the University of Washington in Seattle reached back into the history books. In 1851 the British geologist Charles Lyell, proposed that atmospheric pressures of the past could be estimated by analysing the marks made by raindrops that have fallen onto volcanic ash. Some of these marks can still been seen today and Lyell suggested that they would reveal the speed at which the raindrops struck the ground. Raindrops hit the ground at terminal velocity, which is reached when gravity equals air resistance. Because air resistance depends on atmospheric pressure, so does the terminal velocity of a raindrop of a given size.

In the subsequent 150 years, however, nobody has successfully implemented the idea – until now. “The reasons, I think, are that, first of all, raindrop imprints are extremely rare,” explains Som.

Copyright IOP read more here

  1. adolfogiurfa says:

    the Sun was about 20% dimmer than today because a star burns hydrogen more slowly earlier in its fusion cycle.
    Then there is no “fossilized fusion” at all…hmmmm, perhaps, after all, EU proponents of an Electric Sun were, once more time, right:

  2. wayne says:

    So today’s raindrops produced far too large imprints in the lava ash so… WalMart generic hairspray adequately applied fixed the scipt, and in a hurry. Five month’s turnaround, not bad.

    Major expenses… Africa expedition, nanometer laser measurement equipment time but to conserve taxpayer’s wallet, hairspray, $1.29. /sarc

    Swiftly passed through Berkeley for authority. “I think it’s a pretty sound study,” says earth and planetary scientist William Cassata of the University of California, Berkeley.

    You’ve got to laugh!

  3. davidmhoffer says:

    I don’t buy it either. I grew up on the Canadian prairie. Sometimes the rain comes down nice and gentle and sometimes it comes down so hard it hurts. Sometimes is stirs the dust when it hits, and sometimes it is like bullets kicking up the dirt when they hit. The fact that there is a terminal velocity doesn’t mean that all raindrops reach it.


  4. wayne says:

    Or cry. :-{

  5. tchannon says:

    You missed my mention in the infamous start of the flood post which contains most things. I recall there is background to the paper, such as a student pouring water out of an upstairs window, the usual things which are turned into bore in a formal paper. I also seem to recall arriving there from a thesis on Venus and GHG, hence was wondering how what could be an awkward result was going to be handled. The delayed publication was also raising an eyebrow.

    “Missing primary Earth dataset

    There is no paleo barometric pressure dataset for earth.

    This is new and I am watching for publication.

    S. M. Som, D. C. Catling, J. P. Harnmeijer, P. M. Polivka, R. Buick. The maximum air density 2.7 billion years ago determined from fossil raindrop imprints, Nature, accepted for publication, 2011.
    – We use fossil raindrop imprints in 2.7 billion-year-old volcanic ash to determine an upper limit on the air density and hence the barometric pressure at that time. The method uses calibration experiments of drops falling into modern, comparable ash. This is the first determination of barometric pressure of a time prior to the modern instrumented era, following Torricelli’s barometer invention in c. 1643-1644.”

  6. Zeke says:

    Georges Cuvier rightly observed that it was very convenient for philosophers and theorizers of his day to introduce millions and millions of years into their geologic systems, so that they did not have to show their evidence and could make unfettered speculations.

    He won the debates in his day and he stands unanswered. He said that the earth has clearly undergone violent revolutions, and now, today, every one is a catastrophist to some degree or another.

  7. adolfogiurfa says:

    @Zeke: Good observation, however such word “catastrophism” could be replaced, as catastrophes or wrong functioning happen when something is out of order, out of “tune”, by “organicism”, which denotes an “a priori” order, as it is found everywhere in nature.

  8. Also saw the article. Poor science! how did they get this published? In a recent review for a respected international journal I recommended a paper be sent back to the authors for a complete rewrite or rejection for a number of reasons including lack of repeatable experimental data. It seems to me that standards everywhere are slipping. I have come across university graduates who can not work out a 10% price discount without use of a calculator.

  9. Larry Ledwick (hotrod ) says:

    davidmhoffer says:
    April 7, 2012 at 12:37 am

    I don’t buy it either. I grew up on the Canadian prairie. Sometimes the rain comes down nice and gentle and sometimes it comes down so hard it hurts. Sometimes is stirs the dust when it hits, and sometimes it is like bullets kicking up the dirt when they hit. The fact that there is a terminal velocity doesn’t mean that all raindrops reach it.


    They are leaving out one critical assumption that you are indirectly pointing out. The terminal velocity is relative to the air not the ground.

    If the rain drop is falling in a column of descending air (ie down draft, or down burst) you have to add the down draft velocity to the terminal velocity of that size rain drop in still air to estimate its actual impact velocity with the ground.

    Researchers have measured actual down burst descent speeds in excess of 86 mph (38.7 meters/sec).

    Since there is no way they can determine if a down burst condition existed at the time the ancient rain drop hit the volcanic dust their estimate of its impact velocity can only be a lower limit to its velocity with relation to the ground.

    We will ignore the possibility the rain drop was actually a hail stone until shortly before impact and might have had a very different coefficient of drag and sectional density than a free falling drop of water. In those cases you get very large high velocity rain drops that as mentioned above hit so hard they feel like they are drilling holes in you and leave huge splash marks near the size of a U.S. 25 cent piece when they hit the sidewalk.

    Bunk is a charitable expression for this steaming pile of —-


  10. Michael Hart says:

    I can confidently assert that not everybody at The University of Washington thinks that Astrobiology merits status as an academic discipline. I’ll put it no more strongly than that.

    Be that as it may, many times I have been soaked in the mountains by rain travelling UP hill due to the wind conditions.

  11. Michael Hart says:

    I forgot to mention the story about “fossils” that were claimed to be present in meteroites that reached earth from impacts of bodies striking mars. Anyone remember that?

  12. Hans says:

    Well, about 15 years ago I was very actively looking for proxy data showing the evolution of atmospheric pressure on earth. It is indeed an important question to solve. I did find some assumed ones but none that I could accept as very probable. Lately I saw an URL in Tallbloke that I consider far more interesting than this article at
    It contains a number of interesting circumstancial evidense for higher surface pressure in the past.

    The drop hypothesis clearly lack much substance. As far as I know winds affect the surface layer of ash and can modify it. Rain droplets also have different sizes and different speed at impact for that reason. Someone is digging up this “drop impact in ash” article for agenda reasons which is a practise we have seen too much since AGW was invented about 30 years ago.

  13. Hans, thanks for the article written by a Chemical Engineer. Pity more people do not look at the vast amount of research by chemical Engineers on subjects such as heat & mass transfer (eg Prof Hoyt Hottel-heat transfer by radiation), fluid dynamics, reaction kinetics, psychrometry, instrumentation & control etc. Some of the early scientists such as Fourier and Stefan would be called Chemical Engineers today.

  14. tallbloke says:

    So no-one likes the paper because it doesn’t stand up to scrutiny. But were not supposed to look at the methodology or assumptions too hard…. we supposed to be distracted.

    Awww, look at the meerkat, they’re so cute. 🙂

    Perhaps the authors need to have a look around for the impression which would be left by a pterosaur suddenly finding itself flying through a standard atmosphere. That’d leave a bigger crater.

    Although this paper isn’t going to decide the issue, we could consider the possibility that atmospheric mass has suffered radical reductions in the past, followed by a buildup to higher values from volcanic action etc.

    What might the causes of large scale change be? Impacts? Drawdown and sequestration of co2 by busy little shell growing critters? Solar hiccups blasting away big chunks of atmosphere? Venus was described by early Akkadian astronomers as ‘the bearded star’. What’s all that about? Did they witness the loss of some of Venus’ atmosphere due to an impact? I think these astrobiologists have given us the right to wildly speculate on this thread, so bring on your ideas and possibilities. 🙂

  15. Richard111 says:

    I’ve got a photograph of my mother-in-law standing on a large slightly sloping rock surface which is clearly marked with shallow parallel grooves. This made me look up some geology and it seems this area of Southern Rhodesia was very close to the South Pole way back when. Now it’s meerkat country. Makes you think.

  16. vukcevic says:

    In dinosaur epoch air pressure (air density) must have been an order of magnitude greater, otherwise the big monsters wouldn’t be able to fly, they were virtually swimming in the fluid. 🙂

  17. tallbloke says:

    Hans: thanks! I was too busy to follow that link at the time. I’ve put it up as a new post. It’s a lot more convincing than this Burt Bacharach of a paper for sure.

  18. vukcevic says:

    Hi tb, please stick a smiley on my post (still don’t how to do it).

    [Reply] Full colon : followed by closing parenthesis )

  19. Joe Lalonde says:


    Again scientists miss the planetary rotation of the planet being much faster than today.
    Also assumes we have not lost a single drop of moisture to space.

    Another assumption how can a rain drop be fossilized?
    Possibly in a cave but then that is not rain.

    [Reply] Keep thinking Joe. 🙂

  20. LazyBoy says:

    You boys don’t like the paper because it doesn’t comport with your climate theory du jour in my humble opinion. I’m not a fluid mechanics expert (except for maybe if the fluid is beer) so I’m in no real position to judge its merits. They admit it’s tentative. If they pursue it, try to improve their duplication of ancient lava beds and raindrop impressions, find some contemporary lava raindrop imprints where the atmospheric pressure is known for experimental controls then this looks quite promising in what might say about the distant past.

    What I would point out is these guys are at least performing experiments. That’s a vast improvement over a lot of the rest of climate science where their idea of experimental investigation is toy models of the ocean and atmosphere running on a computer. What Phil Jones do if he was the primary investigator? Probably gin up a computer model of lava and raindrops and take the output from the like it was irrefutable truth.

    Credit where credit is due.

    Just sayin’

  21. Doug Proctor says:

    What an idea! That and the 1851 initial epiphany …

    Actually, raindrops are quite common in the appropriate material. What you need is a semi-solidified surface that dried out after a sprinkle, not a good rain, and then was rapidly covered up again by a non-erosive process. Besides ash-falls, which can be very low density affairs unless they have been wetted down and compacted, low-angle tidal mud flats are good surfaces. After a storm, or after a reduction in a freshwater stream entering an estuary that drops the input water, large areas of fine muds are exposed. These semi-dry. If they dry too much, the surface cracks into small and large polygonal shapes which, with more drying, curl up at the edges. This is too dry for our raindrop purposes. First, the raindrops don’t make an impression and second, when the next rains or tidal surge comes in, the hockey puck shale pieces are plucked free, being redeposited as curious “stones” called rip-up clasts. But before this stage of dessication, the muddy surface is soft enough to take the crater-like shapes, but hard enough to hold the shape through the subsequent deposit of protective mud (or ash). I’ve seen them on many surfaces of various ages. What is uncommon about the raindrops in this article is the age. The further back in time you go, the less there is of rock to look at.

    By the way, the reason this works is primarily that tides are of varying heights due to the moon-sun-earth interactions. Tidal flats covered every 28 days are uncovered for most of the preceding days. So for the astronomy buffs at this blog: the moon’s presence is recorded in all tidal deposits and more offshore, in the fine muds that drop out: the cycles in the mud laminae record the different intensities of tidal flow through the year. With the right offshore muds in the right place, you could even figure out the month length by the number of cycles during a year (glacial lakes record summer and winter in their mud laminae, and the intensity of both the same way).

    What’s cool (to those with an imagination) is that the record of very small periods of time, not “geologic” time are what we are often looking at. Hours or just minutes. In the raindrop situation, perhaps a few seconds. In the events of storms, one particular hurricane will replace ten thousand years of “normal” behaviour with its 18-hour signature. In Colorado I saw, beside the road, a catastrophic flow deposit of superheated ash and rock, hot enough to weld particles to each other, covered by rock and sand in a confusion, that told of a sudden glacial/ice/snow melt like Mt. St. Helens or Pelee. A very bad few minutes in southern Colorado 35 million years ago.

    Rocks have stories in them. The rain-drops record a story of one particular afternoon under a hot summer sun on a sweltering ash-covered plain. We can all relate to that.

    I love this stuff.

  22. tchannon says:

    I get the impression there is a knee jerk reaction too and I suspect it hasn’t been followed back even though I gave clues.

    If someone wants to do it consider trying to find out what was changed during the delay at Nature. What I am getting at is Nature is establishment and wouldn’t accept boat rocking.
    Paper itself not seen it, has anyone here?