Mass spectrometry and climate science. Part I: Determining past climates

Reposted from Dr. Judith Curry’s Climate Etc.

Posted on June 16, 2020 by curryja 

by Roland Hirsch

Mass spectrometry is essential for research in climate science.

Understanding climate requires having sufficient knowledge about past climate and about the important factors that are influencing climate today, so that reliable models can be developed to predict future climate.

Analytical chemistry enables measurement of the chemical composition of materials, from the amounts of elements and their isotopes in a sample to the identity and concentrations of substances in the most complex biological organisms.

This two-part series covers the application of a powerful analytical chemistry technology — mass spectrometry — to two important areas in climate science:

  • Obtaining reliable information about past climate
  • Understanding composition and behavior of aerosols, which have a large impact on climate

The examples that are included for each topic were selected out of many published papers on the study of climate using mass spectrometry, partly because they feature a very wide range of types of these instruments. The authors were very helpful in providing me with information on their work.[1]

The technology described in this essay may at times be quite complicated! However, I hope that the results of each study will be understandable.

Part 1: Determining past climate

Information about past climate is quite limited. The atmospheric temperature records obtained using satellites and covering nearly all of the earth start only in 1979. Surface temperature records cover only a small portion of the earth, perhaps 15% going back to about 1900, and much less before that. The Argo buoys were deployed ~15 years ago and cover much of the oceans, which had minimal coverage before then. Information about aspects of past climate other than temperatures is even more limited.

Analytical chemistry is providing improved information about past climate, for example:

  • Temperatures, changes in climate, and extreme weather events
  • Concentrations of CO2 and other atmospheric components
  • Extent of sea ice and glaciers over time
  • Impact of geological events such as volcanic eruptions and earthquakes

The first step in studying a sample that was formed in the past (such as a fossil or a layer of sediment under the ocean materials that is more than a few hundred years old and have no attached information) is to determine its age.

The most common way to do this is using mass spectrometry to measure an elemental isotope ratio that is dependent on age. Carbon is often used for dating once-living samples, such as plants or artifacts made of wood, as its main isotopes, carbon-12 (12C) and carbon-13 (13C), are stable, while carbon-14 (14C) is radioactive, with a half-life of about 5700 years. The supply of 14C in the air is constantly replenished by cosmic rays hitting nitrogen-14, but once an organism dies the 14C fraction will steadily go down. [i]

Mass spectrometry is a preferred technique for measuring ratios of isotopes of elements, and reliably determines the fraction of 14C in the once-living sample and thus the age at the end of its life for up to about 20,000 years ago, and possibly somewhat earlier. For older samples other elements must be used, for the 14C fraction is too small to be reliably measured.

Several other elements have naturally-occurring long-lived radioactive isotopes that could be used to determine the age of an older sample. Potassium, for example, is a widely-distributed element with substantial concentrations throughout the earth. Potassium-40 (40K) is a very long-lived isotope (1.25 billion years) with (unusually) two forms of decay, one to stable argon-40 and the other to stable calcium-40.

Argon in the atmosphere contains the 40Ar produced over the lifetime of the earth. However, if the decay occurs in a solid that did not contain any air when it solidified and does not allow the argon produced by potassium decay to escape, then the amount of 40Ar reflects the date when the solidification took place.[ii]

The reverse also can be measured: the amount of 40Ar in air trapped in ice will reflect the age at which the ice formed. [iii] This mass spectrometric technique has recently been used to determine the age of samples at different depths in an Antarctic ice core (Figure 1).[iv] [v] The authors of these studies then measured the amounts of different atmospheric gases in those samples and plotted them as a function of sample age (Figure 2).

Figure 1: Age of samples taken at indicated depth below surface of ice core

Figure 2: Results for key atmospheric gases as function of ice core age (various techniques were used for measuring the gases)

Mass spectrometry is often used to study past temperatures. The ratio of the trace isotope oxygen-18 (18O) to the most common isotope oxygen-16 (16O) in a once living organism depends on the temperature of the air at the time that the oxygen was incorporated into the organism by metabolism. The ratio is measured using mass spectrometry. The higher the temperature, the lower the fraction of 18O in the once-living organism.

A representative study was carried out on mollusks found in layers of sediments near the northwest shore of Iceland, covering the period 350 B.C. to A.D. 1600. The layers in the shells reflected the year-round temperatures in which the mollusks had lived (Figure 3). From such data on many samples at different layers in the sediments the authors constructed a chart of temperatures over that time period. Notably, they were able to correlate these temperatures with historical records in Iceland from 865 to 1600 (Figure 4). The authors pointed out that “On the basis of δ18O data, reconstructed water temperatures for the Roman Warm Period in Iceland are higher than any temperatures recorded in modern times.”[vi]

Figure 3: Example of temperatures derived from a shell that lived through four summers (S) and three winters (W)

Figure 4: Variation of temperatures from the Roman Warm Period to ~AD 1800.Information from historical documents is at the top on the right side.

Another study using mass spectrometry to determine temperatures using oxygen isotope ratios was carried out over in fjords in Sweden, covering a 2500 year period. One of the fjords is on the north coast of Sweden (Atlantic Ocean) and the other on the southwest (North Sea near Denmark). The authors state:

“The record demonstrates a warming during the Roman Warm Period (~350 BCE – 450 CE), variable BWT [bottom water temperatures] during the Dark Ages (~450 – 850 CE), positive BWT anomalies during the Viking Age/Medieval Climate Anomaly (~850 – 1350 CE) and a long-term cooling with distinct multidecadal variability during the Little Ice Age (~1350 – 1850 CE). The fjord BWT record also picks up the contemporary warming of the 20th century (presented here until 1996), which does not stand out in the 2500-year perspective and is of the same magnitude as the Roman Warm Period and the Medieval Climate Anomaly.[vii]”

The authors of this study include a chart relating their temperature information with others in the North Atlantic (Figure 5).

Figure 5: Bottom water temperatures for different locations in the North Atlantic Ocean going back to about 350 BCE. Abbreviations shown at the top of the chart: RWP represents the Roman Warm Period, DA represents the Dark Ages, VA/MCA represents the Viking Age/Medieval Climate Anomaly and LIA represents the Little Ice Age.

The oxygen ratios thus allow estimating temperatures for once-living organisms. Importantly, they allow doing so year-round. Tree ring diameters, which are sometimes used for estimating past temperatures, primarily reflect temperatures during the growing season, and are also influenced by factors such as rainfall and location (such as above or below the treeline at a given time).

A recent study provides a different use of the oxygen isotope ratios for studying past climate: do volcanos have an impact on major climate factors such as the El Niño – Southern Oscillation (ENSO)? Some studies have suggested that major volcanic eruptions can impact the ENSO cycle, but only a few such events have relevant weather data. Fossil corals in the regions impacted by ENSO dating back centuries have well-defined monthly layers. They were dated by mass spectrometry using U/Th ratios. Then oxygen-18 measurements for these layers allow estimation of temperatures coinciding with major volcanos.

The results were combined with prior studies to produce a temperature record covering from ~1100 to ~2000 CE. Six major volcanos in this time period were charted against the temperatures (Figure 6). No evidence was found that the volcanos had caused an ENSO event. [viii]

Figure 6: Coral δ18O measurements of temperatures for six major volcanic eruptions in the last 900 years, with lines at the bottom showing the degree to which stratospheric aerosols reduced downwelling sunlight during the volcanos

Conclusion for Part One

This completes the first post on applications of mass spectrometry to climate science. The second post will focus on studies of factors that need to be understood to be able to develop reliable models of climate, with emphasis on research on aerosols.

Endnotes

[1] The figures and charts and other information from the papers are the property of the authors and publishers.

[i] https://en.wikipedia.org/wiki/Carbon-14

[ii] https://www.radioactivity.eu.com/site/pages/Potassium_40.htm

[iii] M.L. Bender, et al., “The contemporary degassing rate of 40Ar from the solid Earth”, PNAS (2008) 105, 8232-8237 https://www.pnas.org/content/105/24/8232

[iv] J.A. Higgins, et al., “Atmospheric composition 1 million years ago from blue ice in the Allan Hills, Antarctica”, PNAS (2015) 112, 6887-6891   https://www.pnas.org/content/112/22/6887

[v] Y. Yan , et al., “Two-million-year-old snapshots of atmospheric gases from Antarctic ice”, Nature (2019) 574, 663-663   https://www.nature.com/articles/s41586-019-1692-3   and https://www.nature.com/articles/d41586-019-03199-8

[vi] W.P. Patterson, K.A. Dietrich, C. Holmden and J.T. Andrews, “Two millennia of North Atlantic seasonality and implications for Norse colonies” PNAS (2010) 107, 5306-5310 https://www.pnas.org/content/107/12/5306

[vii] I.P. Asteman, H.L. Filipsson, and K. Nordberg, “Tracing winter temperatures over the last two millennia using a north-east Atlantic coastal record”, Climate of the Past (2018) 14, 1097–1118. https://doi.org/10.5194/cp-14-1097-2018

[viii] S.G. Dee, et al., “No consistent ENSO response to volcanic forcing over the last millennium”  Science (2020), 367, 1477-1481   https://science.sciencemag.org/content/367/6485/1477.full

Biosketch

Roland Hirsch has served the field of analytical chemistry in a 52-year career that spans teaching, research, and leadership at Seton Hall University, and 33 years of government service at the National Institutes of Health and the U.S. Department of Energy.  Roland has been a leader of the ACS Division of Analytical Chemistry, as Councilor for 25 years, as Division Secretary for 4 years, Chair-Elect, Program Chair, and Chair, and as its Web Editor for 22 years. Roland organized the 50th-anniversary celebration of the Division and 25 years later, wrote the definitive history of the first 75 years of the Division, published in Analytical Chemistry in 2013.  Roland has also been active in ACS Governance, including Chair of the Committee on International Activities, Secretary of the Committee on Nominations and Elections, Member of the Committee on Divisional Activities, Senior Chemists Task Force, Committee on Committees, and Liaison to the ACS Committee on Professional Training.

Based on a presentation prepared for the American Chemical Society National Meeting in Philadelphia in March 2020. It was to have been in the Division of Analytical Chemistry’s session “Advances in Mass Spectrometry”. The meeting was canceled, but this presentation was revised and made available on the web site for the meeting: https://www.morressier.com/article/mass-spectrometry-essential-research-climate-science/5e735e33cde2b641284a879e

43 thoughts on “Mass spectrometry and climate science. Part I: Determining past climates

  1. Very interesting, but he Greenies are not concerned with facts.

    Perhaps the need for a means of greater wealth creation following the massive debt resulting from nations fighting the virus, may well need to the politicians no longer chasing the Green vote, and instead concentration on increased efficiency.

    One can but hope.

    VK5ELL MJE

  2. According to the author at 1900 we only have temperatures from 15% of the planet

    But here is real evidence

    ‘A representative study was carried out on mollusks found in layers of sediments near the northwest shore of Iceland, covering the period 350 B.C. to A.D. 1600. The layers in the shells reflected the year-round temperatures in which the mollusks had lived (Figure 3). From such data on many samples at different layers in the sediments the authors constructed a chart of temperatures over that time period. Notably, they were able to correlate these temperatures with historical records in Iceland from 865 to 1600 (Figure 4). The authors pointed out that “On the basis of δ18O data, reconstructed water temperatures for the Roman Warm Period in Iceland are higher than any temperatures recorded in modern times.”[vi]”

    The northwest shore of Iceland is not the globe.

    Here is a clue.

    if 15% of the planet measured with THERMOMETERS is UNCERTAIN, then measure LESS of the planet
    with PROXIES is …

    wait for it…..

    MORE UNCERTAIN.

    • So you admit that we don’t know what the world’s temperature was in 1900, and certainly not to the tenth of a degree as your fellow charlatans have been claiming.

    • “On the basis of δ18O data, reconstructed [b]water[/b] temperatures for the Roman Warm Period in Iceland are higher than any temperatures recorded in modern times.”[vi]”

      Stop reading with bias. “temperatures recorded in modern times” obviously refers to water temps in modern times, not air temps!

  3. “The fjord BWT record also picks up the contemporary warming of the 20th century (presented here until 1996), which does not stand out in the 2500-year perspective and is of the same magnitude as the Roman Warm Period and the Medieval Climate Anomaly.”

    In the text, it says:
    “When studying the Gullmar Fjord bottom water temperature record for the last 2500 years, it is interesting to note that the most recent warming of the 20th century (presented herein until 1996) does not stand out, and it actually appears to be comparable to both the Roman Warm Period and the Medieval Climate Anomaly. However, this observation must be interpreted with caution, as our dataset does not go beyond year 1996 due to a lack of material (see discussion below); hence, it does not cover the most recent part of the 20th century warming, which is widely accepted as having been triggered by growing anthropogenic emissions.

  4. “The Argo buoys were deployed ~15 years ago and cover much of the oceans, ”

    That’s like saying 2 or three temperature stations could cover most of the US.

  5. “north coast of Sweden (Atlantic Ocean)”

    Misprint? It sure doesn’t look like that on a map. Maybe there’s an arm of a fjord that reaches through Norway? Although I couldn’t see that either.

    • Agree. This must be Norway, not Sweden. Sweden does not have fjords and no Atlantic Coast.

      • Thanks for the correction. The Atlantic Coast fiord they cite is in Norway. The main part of the study is the “Gullmar Fjord (Sweden)”, as shown in the maps in the paper.

      • My last reply seems to be lost in moderation. I think the reference to the “Sweden’s Northwest Atlantic” coast probably refers to dating of a sequence of late Pleistocene-Early Holocene marine sediments in the Lake Vanern Basin. Lake Vanern is in Western Sweden North of the modern Atlantic coast. While generally described a being in Southwest Sweden, if one squints at it just right, it could probably be reasonably described as being near Sweden’s Northwest Atlantic coast. The temporary marine incursion was presumably an artifact of glacial depression followed by glacial rebound — similar to that in North America that deposited marine sediments as far inland as the Ottawa River.

        I had a link, but it appears the Internet Gods have hidden it somewhere in a maze of twisty little passages not easily navigable from my browser.

  6. Mosh and Stokes what is it with you two?
    Are you historians or are you hysterical ?
    The three climate optimums since the earth recovered from the last Ice age 12000 years ago were all warmer than present .
    There has been a concerted effort by climate scientists to rewrite history to fit their theories .
    Graham

    • “The three climate optimums since the earth recovered from the last Ice age 12000 years ago were all warmer than present .”

      Not even wrong. There was one optimum “roughly the interval 9,000 to 5,000 years BP, with a thermal maximum around 8000 years BP.”
      https://en.wikipedia.org/wiki/Holocene_climatic_optimum

      You might be referring to the so-called “warm” periods, but they were weak, were not global and not synchronised. Modern warming has be global and abrupt and is now very likely the highest it’s been since the peak of the Eemian 125,000 years ago.

        • Well, from that page there does appear to be a “pronounced” warm period in China circa 950-1250, albeit with a cooler period in the middle of it. But that is about all you could say. I don’t see anything there that refutes what I wrote above.

      • You Warmunists all sing from the same Climate hymn book. Here’s a thought: try reading beyond your usual astro-turfing climate nonsense. Oh wait, you can’t, because it’s an ideology, bordering on religion. My bad.

      • Loydo would you please describe how an IR photon causes CO2 to produce warming? Or what is the emissivity of CO2 at 288 K. Or possibly the updated specific heat of dry air with CO2 ppm of 415.

        • In laymen’s terms, the IR photon gets absorbed by the CO2 molecule, causing it to vibrate. That motion is then transferred to other molecules in the atmosphere. The CO2 molecule is then free to absorb another photon.

        • mkelly June 20, 2020 at 6:50a: I hope this reply to the third of your questions to Loydo is not too dated. I had to go to my lab at the covid-closed university where I am semi-retired to retrieve some calculations. It turns out that 18 months ago I calculated the values of Cp for dry air with CO2 concentrations of 400 ppmv, 800 ppmv, and 4000 ppmv. I used figures for dry air since I wanted to see the effects of changes in the concentrations levels of CO2 alone. Here are the results:
          400 ppmv: Cp=29.08 kJ/(kmole-K)
          800 ppmv: Cp=29.07 kJ/(kmole-K)
          4000 ppmv: Cp=29.0 kJ/(kmole-K)
          All calculations done with a hand calculator with the obvious result that there is NO CHANGE in the molar value of specific heat for this concentration range – there simply aren’t enough CO2 molecules around…

      • Like most of his fellow alarmists, Loydo likes to strain at gnats, in order to avoid actually dealing with the science.

        Technically, the Minoan, Roman and Medieval warm periods are not called optimums, however it is standard practice to generically refer to any warm period as an optimum.

        Loydo also likes to spread the lies he has been taught.
        All three of those warm periods were global and were warmer to much warmer than today.

        • “All three of those warm periods were global and were warmer to much warmer than today.”

          False and false as my link above clearly demonstrates. You call me a liar without any substantiation…then brazenly tell one yourself. Do please go on…

      • The warming has not been global, nor has it been all that abrupt. 0.7C over 150 years is not abrupt.

        Beyond that, the proxies have resolutions in the century to millennial range. Any warming faster than that would not be detected by the proxy. This has been explained to you many times, however like the rest of your ilk, you prefer to spread lies.

      • Loydo the material you have posted from Wikipedia clearly shows that the world was warmer than present and it terminates in 2016 and there has been no warming since the last super El Nino .
        What you and your warmist friends don’t want to accept is that you claim that the world has warmed around 1.5 C since man started burning fossil fuels from 1880 .
        That was the end of the little Ice Age and of course the world warmed up otherwise there would be widespread famine and starvation .
        There is well documented evidence that the MWP a thousand years ago was global and was right across the southern hemisphere .
        20 years ago warmist climate scientists and among them were James Renwick and Jim Salinger from New Zealand admitted that the MWP and the other climate optimums were warmer than present and that these were inconvenient facts that negated their alarmist story .
        Warmist scientists have tried to rewrite history but some things such as how the Vikings farmed in Greenland 800 years ago and many other facts such as tree stumps found under retreating glaciers tell a much different tale.
        The global warming scare is a scam and if it was real the scientists that are shouting the loudest would be able to work out for them selves that our global population rely’s on affordable and plentiful energy .Very few of them advocate for nuclear power .
        If they can;t work that out for them selves it tells us a lot about their power of reasoning .
        World population has surged from less than one billion to over eight billion and if warmist scientists alarmists and politicians get there way and restrict fossil fuel use famine and food shortages will become the norm across the world .
        The best thing that the world could would be to defund all this climate change nonsense and use the money to lift desperate people out of mind less poverty by providing cheap electricity to poor countries and the people can then help themselves to a prosperous future .
        All countries with a high standard of living have low birth rates and it is poor countries that have high birth rates and low life expectancy .
        Do you Loydo want us all to drop our living standard to that of the poor countries of Africa and Asia ?
        Global warming is a scam and if warmists get their way and push energy prices higher and higher the majority of the people in any country are disadvantaged and the elite still live well .
        That is not what most people want but if those in power have their way only hardship will ensue for most .
        It is basic economics that the cost of energy flows into everything grown or manufactured.
        Something for you to think about Loydo.
        Graham
        Proud to be growing food for a hungry world

    • Having manned a mass spec as a lab technician in the ’60s this strikes me as nothing more than intellectual masturbation on steroids.

  7. The use of high resolution mass spec instrumentation raises many questions. The first of these is the sample itself. The greatest bugbear in the resource industry is the ensuring the sample being analysed is not compromised. Samples taken from sea bed unless taken into an undisturbed collection facility must considered to be compromised. I have in the past done heaps of sea floor sampling using air lift in the early 70s. A compromised sample for sure but adequate. Today ICP MS places huge demands on the accuracy of the sample. Chemists are fortunate to have access to such instruments and as an end user most grateful. However, it is the sampler that we must turn to ensuring accuracy of the sample in the first place. QA/QC.

    • This is a valid point. The original articles indicate how the samples were collected and stored. The samples generally were handled by standard procedures for studying the materials but these always require careful following of the procedures.

  8. Hoo boy, aerosols again. That’s going to be a tough sell. Sure, they probably have some influence, but I highly doubt they are much of a driver, one way or the other.

  9. Hello,

    What is the confidence intervalle of the measurements from such proxy ? Does somebody knows ?

    Thanks in advance.

    • Thanks for asking. Figure 1 does show confidence intervals. The other articles state that in their texts but not always in the figures.

  10. The introduction to mass spectrometry use is the best I can recall, my history going back to when carbon and oxygen were the main ones. It is important in marine ecology, for example, because isotopes have become a proxy for so many things from dating hypoxic areas to food habits. Caveats with uncertainties range from excellent to poor. Poor students nowadays must learn so many things across all the real sciences. And, of course, mastery of statistics and computer models. And getting away from the screen and checking on the world.

  11. I’m sure this is all very interesting but those charts are more difficult to read than a prescription from my doctor.

  12. Has anyone done oxygen isotope studies on tree-ring samples for comparison purposes?

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