CSIRO 2020 10 28 Cross Exam / archived / read-only

28 October 2020 Senator Malcolm Roberts PO Box 6100 Senate Parliament House Canberra ACT 2600

Dear Senator Roberts CSIRO acknowledges your letter received by email on 19 October 2020 regarding Senate Budget Estimates questions. Your questions are addressed below.

• In relation to claims made in blog posts regarding the integrity of the Marcott study, and the questions raised regarding this research, it should be noted that there are currently 265 [>640, as of October 2020] published papers in the peer-reviewed literature citing Marcott et aI (2013),
• Citations in no way validate a reference - Appeal to the Majority - Argumentum ad populum
• and there is no published study that draws the temperature reconstruction into question for the period for which sufficient proxies are available (~11,300 BP to 1800 CE).
• Marcott 2013 did not support your statement and it is irrelevant (and entirely expected) that you can't find studies that you like that contradict your stated opinions.
• We further note that reference [1] derives a 12,000-year record of Arctic temperatures that extends to the year 2009 CE, with 25-year resolution, and concludes that the recent rate of Arctic temperature change is unprecedented in the entire Holocene.
• Study 1 Lecavalier 2017 was reviewed by us in???. CSIRO has not responded to the detailed points that were raised, so we include our detailed points again here.
  • Only one location on the Agassiz ice cap at 80 deg north was sampled which can hardly claim global significance.
  • The short core, that was spliced on to the end of the long cores, was able to detect changes that were undetectable in the long cores. This is not good for unprecedented claims.
  • Comparison of Lecavalier 1960 and 1985 temperatures with the four major global thermometer series shows that the two most recent points are wildly and obviously wrong. Any rate of change derived from these two points will be even more obviously wrong. [img: Lecavalier.png]
  • The major plot shows a final one point uptick on a steadily declining temperature.
    • [img: Lecavalierfig3.png] The past 10,000 year temperatures (Plot A) have been passed through a low pass filter (parameters unspecified) and a further Gaussian filter (sigma 50 years). These processes will reduce the ability to detect fast temperature changes so affecting unprecedented claims. We would like to examine the unfiltered data.
  • The 2 long cores and the short additional core are shown at one year resolution. As claimed there is enough agreement in the 35 years of overlap to align the time scales. However the disagreement between the 2 long cores sometimes exceeds the unprecedented amount of the final uptick. The difference in variance between the long cores and the short core is obvious. They are not measuring the same quantity to the same quality. The full one year datasets for all cores was requested from the authors but not provided.
    • [img: Lecavalierfig4.png]
  • Here the 2 long cores have been combined to their mean. The difference in variance is now very obvious. We are getting a glimpse of the missing Gain Function plot. The long cores are incapable of measuring the rapid changes detected in the short core, so the paper cannot claim unprecedented rates of change .
    • [img: Lecavalier__Extracted.png]
  • The short core does not correlate very well with 3 modern temperature series from high arctic This means the short core is not representative of what is actually happening in the Arctic, let alone the whole planet..
    • [img: Lecavalier_Comparison.png]
  • Using two differing sets of instruments and claiming one result being unprecedented is suspect. It's bad enough combining data from two different instruments yet this becomes even worse when differentiating the data to asses rate of change. To assess rate of change both instruments must have the same variance. The researchers should have measured the same section of ice cores with the old instruments and the new instruments. Without this, comparing rate of change is highly suspect.
• CSIRO reaffirms the scientific rigour of the Marcott et al. (2013) study and the conclusion that the rate of recent warming of global mean temperature is unprecedented in the past 10,000 years.
• Marcott 2013 did not contain the conclusion that the rate of recent warming of global mean temperature is unprecedented in the past 10,000 years. It did not contain any "conclusions" at all.
• To support a statement about unprecedented centennial rate of temperature change, Marcott 2013 would have to have measured centennial rates of temperature change during the 10,000 years which it did not (and indeed could not) do. This is obvious to any reader who understands the paper.
• Marcott 2013 did have "our results indicate" but nothing about measured centennial rates of temperature change during the 10,000 years
  • Our results indicate that global mean temperature for the decade 2000–2009 (34) has not yet exceeded the warmest temperatures of the early Holocene (5000 to 10,000 yr B.P.).
  • So current temperatures are not unprecedentedly high.
  • These temperatures are, however, warmer than 82% of the Holocene distribution as represented by the Standard5×5 stack, or 72% after making plausible corrections for inherent smoothing of the high frequencies in the stack (6) (Fig. 3).
    • Marcott 2013 5x5 series
    • Because the relatively low resolution and time uncertainty of our data sets should generally suppress higher-frequency temperature variability, an important question is whether the Holocene stack adequately represents centennial- or millennial scale variability.
    • We composited a Standard5x5 global stack from these synthetic records and calculated the ratio between the variances of the stack and the input white noise as a function of frequency to derive a gain function. The Gain Function plots from Marcott 2013 SI [img: screenshot-science.sciencemag.org-2018-02-21-17-26-04.png]
    • The results suggest that at longer periods, more variability is preserved, with essentially no variability preserved at periods shorter than 300 years, ~50% preserved at 1000-year periods, and nearly all of the variability preserved for periods longer than 2000 years (figs. S17 and S18).
    • Without filling data gaps, our Standard5×5 reconstruction (Fig. 1A) exhibits 0.6°C greater warming over the past ~60 yr B.P. (1890 to 1950 CE) than our equivalent infilled 5° × 5° area-weighted mean stack (Fig. 1, C and D). However, considering the temporal resolution of our data set and the small number of records that cover this interval (Fig. 1G), this difference is probably not robust.
  • Assume today's Canberra 6am temperature was 10°C and at 6pm 30°C. Can we determine if today's rate of temperature change is unprecedented by comparing it to the yearly average temperatures of Australia from 1900 to 2000?
  • In contrast, the decadal mean global temperature of the early 20th century (1900–1909) was cooler than >95% of the Holocene distribution under both the Standard5×5 and high-frequency corrected scenarios.
  • Global temperature, therefore, has risen from near the coldest to the warmest levels of the Holocene within the past century, reversing the long-term cooling trend that began ~5000 yr B.P.
  • Similar changes may have occurred hundreds of times over the last 10,000 years as the Marcott process cannot measure any changes that occurred within a few centuries.
  • Strategies to better resolve the full range of global temperature variability during the Holocene, particularly with regard to decadal to centennial time scales, will require better chronologic constraints through increased dating control. Higher resolution sampling and improvements in proxy calibration also play an important role, but our analysis (fig. S18) suggests that improvements in chronology are most important.
  • Well done Marcott for indicating shortcoming of this process and suggestions for improvements.
• Studies published after Marcott et al. (2013), using a variety of data sets and analysis methods and covering various time periods, support the conclusion that recent rates of warming are unprecedented [e.g. 1-5].
• Study 1 Lecavalier 2017 has been discussed above. CSIRO is asserting that studies 2-5 support the conclusion that recent rates of warming are unprecedented which is not the point under discussion. This point is: the rate of recent warming of global mean temperature is unprecedented in the past 10,000 years.
• Study 4 - North Report 2006 - states on p118 **Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900* because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.*
• Study 2 IPCC AR5 WG1 whose Summary for Policy Makers contains no reference to rates of temperature change in 10,000 years
• Studies 3 PAGES 2k Consortium (2013) and 5 PAGES 2k Consortium (2017) contain PAGES 2k in their titles which is the give away - they only go back 2,000 years.
• The conclusion drawn by CSIRO and by the Marcott study is based on a comparison of recent temperatures, as measured by instruments, to past temperatures inferred from proxy data.
• Marcott drew no conclusions. CSIRO drew conclusions about centennial rates of temperature change from a paper that never claimed to be able to measure centennial rates of temperature change.
• Neither Marcott, nor CSIRO, make any conclusions based on the "uptick" part of the proxy temperature record.
• Not surprising, as the uptick was apparently created by undocumented changes to core top dates. Some would consider this to be deliberate deception.
• This approach is used because the best information we have about recent temperatures are those made by instruments measuring temperature (thermometers measure temperature more accurately than tree rings, ice cores, or plankton preserved in sediments).
• Agree. Study 1 Lecavalier 2017 used a short recent ice core to bring the ice core temperatures up to the present. However there were three thermometer series of the high Arctic that should have been used instead. They are included below.
• [img: Lecavalier_Comparison.png]
• There is no scientific evidence in any other climate variable to support the supposition that there may have been periods of rapid warming and cooling in the past that were missed by Marcott's reconstruction method
• We supplied you with 4 time series that do so. Here they are again below.

• Comparing Marcott 2013 with other time series covering -2,000 to -1,000 BCE shows that the Marcott process is almost unable to detect any of the variation in temperature at all. No wonder the recent changes appear unprecedented.

  

• nor has a plausible physical mechanism been identified that could have driven such spikes in warming and cooling.
• This is not surprising considering the state of knowledge about the non-linear chaotic climate system
• In addition, it can be demonstrated that the Marcott method could have detected periods of rapid warming/cooling in the past, had they occurred.
• Without Logical Points this is just another Baseless Assertion.

• The state of the science in an Australian context was provided by the volume Greenhouse: Planning for the Future, published by CSIRO in 1988 (https://ebooks.publish.csiro.au/content/greenhouse-planning-climate-change). It was already evident in the 1980s that anthropogenic emissions of carbon dioxide were altering the chemical composition of the atmosphere (e.g. increasing the concentration of carbon dioxide and other greenhouse gases). There was already substantial evidence that this increase in greenhouse gases would alter regional and global climate. The state of the science in the 1980s was summarised in the first global assessment of climate science, published by the IPCC in 1990.

• CSIRO has always provided scientific advice to government on issues of national significance. That is part of our remit. For more than 60 years our scientists have been contributing to scientific knowledge about climate change and its impacts.

• As discussed at multiple briefings (September 2016, May 2017 and July 2017), numerous correspondence through Estimates Committee processes, as well as direct correspondence with your office there are many lines of evidence that show the recent changes in the climate system lie outside the range of natural variability. Further studies demonstrate that the observed record cannot be explained by natural factors alone. The statistical analyses used in the 1000s of published studies that provide this evidence cannot be summarised simply but are described in full in the peer-reviewed literature.
  • As stated in prior briefings, the direct empirical evidence that human activities are causing climate change includes:
    • a) Carbon dioxide is a greenhouse gas (i.e. absorbs and emits infrared radiation), as shown by direct measurement and the laws of physics.
    • b) Carbon dioxide concentrations in the atmosphere have increased by more than 45% since 1850, as shown by direct measurements of atmospheric samples and air trapped in ice cores.
    • c) The extra carbon dioxide in the atmosphere comes from human activities. Isotopic measurements show the source of the extra carbon dioxide is fossil fuel burning and land clearing.
    • Without Logical Points this is a Baseless Assertion.
    • d) The additional carbon dioxide added to the atmosphere by human activities has enhanced the greenhouse effect: measurements show that less energy is leaving the top of the atmosphere, and more energy is reaching the earth surface, in the wavelengths absorbed and emitted by carbon dioxide and other greenhouse gases.
    • Without Logical Points this is a Baseless Assertion.
    • e) The earth has warmed as a result of the enhanced greenhouse effect.
    • Without Logical Points this is a Baseless Assertion.
    • Surface and lower troposphere temperatures have increased, ocean heat content has increased, sea level has risen, and ice (sea ice, glaciers and ice sheets) has melted.
    • Without Logical Points this is a Baseless Assertion.
    • f) Observed changes in the climate system are consistent with an enhanced greenhouse effect.
    • Other forcings (e.g. volcanoes, the sun, internal variability) cannot explain the magnitude, timing and distribution of observed trends.
    • For example, enhanced greenhouse forcing causes warming of the lower atmosphere, as observed.
    • Without Logical Points this is a Baseless Assertion.
    • For example, enhanced greenhouse forcing causes cooling of the upper atmosphere, as observed.
    • Without Logical Points this is a Baseless Assertion.
    • We have previously provided you with published papers supporting each of these points.

• Science provides a firm foundation for evidence-based policy.
• Pseudo science provides a firm foundation for policy-based evidence.

• It is not possible to attribute changes in carbon dioxide concentrations to individual emitters. This is because carbon dioxide is a well-mixed gas in the atmosphere. The annual Global Carbon Project produces a comprehensive global analysis of sources and sinks of carbon dioxide. The research relies on the self-reported and global energy data stored by UN Statistics and more recently by the International Energy Agency (IEA), along with observations of greenhouse gas levels and carbon cycle models.

• The relationship between emissions and carbon dioxide concentrations in the atmosphere can be evaluated using analyses from the Global Carbon Project, (see above).
• In summary, the science - based on empirical evidence and physical understanding - provides a clear and compelling case that the climate has changed, and human activities are the principal driver.