From: rparson@spot.Colorado.EDU (Robert Parson) Subject: Dixy Lee Ray and Ozone Message-ID: Date: Fri, 10 Jun 1994 20:44:13 GMT A critical analysis of two chapters from: _Environmental Overkill_, by Dixy Lee Ray with Lou Guzzo. Regnery Gateway Press, 1993. Chapter 3 - Stratospheric Ozone and the "Hole" Chapter 4 - The Ozone and Ultraviolet Rays ------------------------------------------------------------------ This article Copyright 1994, 1995 by Robert Parson. Readers are | permitted to download, save, and print a single copy for personal| use. Any other reproduction requires permission from the author. | ------------------------------------------------------------------ These chapters display serious misunderstandings of atmospheric chemistry and dynamics, they either ignore or misrepresent scientific evidence, and they are based upon poor scholarship, in particular the uncritical use of exceedingly unreliable sources. To analyze all of the errors would result in a document considerably longer than the original, since in many cases it takes a paragraph or more to explain why a given brief remark is wrong. Also, I am interested not only in pointing out errors, but also in showing how these errors have arisen. Instead of providing a litany, therefore, I will examine nine points in detail. I have grouped these into four categories: A. Basic Misconceptions about the atmospheric sciences These are assertions which could only be made by someone unfamiliar with fundamental principles and procedures, as found in basic textbooks. This category includes: 1. The claim that CFC's cannot rise to the stratosphere in significant quantities because they are heavier than air. 2. The implication that CFC's are unlikely to be involved in antarctic ozone depletion because most of them are emitted in the northern hemisphere. 3. The claim that salt spray, passively degassing volcanoes, and other sea-level emissions are likely sources of stratospheric chlorine. 4. The claim that soil bacteria consume a major proportion of the CFC's emitted into the atmosphere. In the second category I put false assertions that require a more detailed knowledge of the technical literature to refute. This category includes: 5. The claim that decay products of CFC's have not been observed in the stratosphere. 6. The claim that the ozone hole was first seen in 1956. 7. The claim that explosive volcanic eruptions are a major source of stratospheric chlorine. In the third category I include statements that are not wholly false, but which are presented in a misleading context and surrounded with false information. These include: 8. The suggestion that decreases in sulfur dioxide have been interpreted as ozone losses. 9. The assertion that UV-B radiation has not increased. Finally, I discuss the book's scholarship, its massive neglect of the relevant scientific literature and its uncritical reliance on such bizarre sources as publications by Lyndon LaRouche's associates. A. Misconceptions about basic principles and procedures of the atmospheric sciences 1.: Vertical distribution of atmospheric gases p. 35: "How does CFC rise when its molecules are four to eight times heavier than air? All experience with freon and related CFCs shows that they are non-volatile and so heavy that you can pour CFCs from a container and if some of them spill, they will collect at the lowest point on the ground where soil bacteria will decompose them. Of course, some molecules will be caught in upward air eddies or otherwise carried upwards, but this is a very small fraction of the total." This seemingly plausible objection merely demonstrates that the authors do not understand the mechanisms of vertical transport in the atmosphere. It has long been known [Wallace and Hobbs] that gases do not segregate by weight in the first 80 km of the atmosphere, an altitude range that extends well above the ozone layer. Molecular weight is entirely irrelevant for determining the chemical composition in the troposphere and stratosphere. The mixing of atmospheric gases takes place by turbulent processes that do not distinguish molecular masses - the rare heavy particles are carried along by the much more numerous light ones. Thus, for example, the ratio of oxygen to nitrogen is constant up to ~100 km (the ozone layer lies between 15 and 50 km.) Now one might argue that CFC's are quite a bit heavier than most molecules in the atmosphere; perhaps the mixing mechanisms are strong enough to keep the O2/N2 ratio constant, but not to sustain the heavier CFC molecules. Rowland and Molina considered this point carefully in their 1975 review [Rowland and Molina]. At that time CFC's had not yet been measured in the stratosphere, so they examined data on atmospheric concentrations of heavy inert gases. These data showed that the relative proportions of Krypton (mass 84), Argon (mass 40) and Neon (mass 20) between 40 and 60 km were within 0.5% of those measured at ground level. Shortly thereafter, direct measurements of CFC's themselves as a function of altitude began; the very first such measurements showed that the CFC mole fraction is virtually independent of altitude up through the troposphere and lower stratosphere, then drops off suddenly at altitudes in which the molecules are exposed to UV radiation. It is a molecule's UV absorption spectrum, not its weight, that determines its distribution in the atmosphere. Even more revealing are measurements of the fluorocarbon CF4. This extraordinarily persistent molecule is not dissociated by the UV wavelengths that are abundant in the stratosphere, and thus serves as a tracer for vertical motion. The mole fraction of CF4 has been measured and found to be essentially independent of altitude all the way up to the top of the stratosphere at 55 km. [Fabian et al.] [Zander et al. 1992] 2. Geographical distribution of atmospheric trace gases p. 35: "We do not know how these heavier-than-air molecules cross the equatorial counter currents to accumulate at the South Pole and do the most ozone destruction there." First of all, the CFC's do not "accumulate" at the south pole. Rather, they are distributed almost uniformly with latitude [Singh et al.] [Elkins et al.]. Exchange of air between the hemispheres takes about two years, but this is short compared to the atmospheric lifetime of the CFC's (more than 50 years). This time scale for transport across the equator is demonstrated very nicely by the measured increase in CO2 concentrations in Hawaii and at the South Pole [Wayne, p. 20] [IPCC, p. 14], as well as by the CFC's themselves. The quoted sentence also demonstrates unfamiliarity with the history of this subject. CFC's were measured in the South Atlantic in 1973, *before* Rowland and Molina suggested that they might contribute to ozone depletion [Lovelock et al.]. Indeed, it was these measurements, and the long atmospheric lifetimes that they suggested, that motivated Rowland and Molina's work. 3. Sources of Stratospheric Chlorine The entire discussion of stratospheric chlorine sources demonstrates ignorance of the enormous body of research that has addressed these questions. For example, the book cites rough estimates of the amounts of HCl produced at sea level by such natural sources as sea salt spray and volcanoes: p. 34: "Chloride is one of nature's most abundant ions. Sea water evaporation provides the atmosphere with 600 million tons of chloride per year. Volcanic eruptions emit millions of tons of chloride .... At this rate there would be roughly 750,000 tons of chloride available from CFCs annually." The apparent implication is that even if most of this natural chlorine is removed from the atmosphere by natural processes, surely some of it must reach the stratosphere. This is nothing more than an "argument from personal incredulity", and it collapses when one looks at the actual *concentrations* of various chlorine-containing species in the atmosphere. These concentrations have been measured as a function of latitude, altitude, and time. From such data and some knowledge of atmospheric rate processes one can infer estimates of natural emissions, which may be compared with whatever direct emission measurements are available. Nevertheless the concentrations are the most reliable data, and they lead directly to the conclusion that the natural chlorine is rapidly removed and that the bulk of the chlorine in the stratosphere is anthropogenic. Let us look at sea salt spray. The mechanism here involves the conversion of chloride ions to gaseous HCl by reaction with airborne nitric and sulfuric acids. So, what are the concentrations of HCl in the atmosphere? Measurements close to sea level show that the mole fraction of HCl over open water is about 0.25-0.45 parts per billion [Harris et al] [Vierkorn-Rudolf et al.] Over dry land it is much less, down to 0.05 ppb. At 7 km over the ocean the concentration has fallen below 0.1 ppb, and at 13.7 km, at the top of the troposphere, it is down to 0.04 ppb. From this, together with some estimates of removal rates by rain, etc., one can infer a very large rate of HCl production. If we were to find that the removal rate was much smaller than we think, then we would have to conclude that the production rate was smaller as well; such revisions do not affect the measured concentrations. Now when we compare the actual concentrations of HCl and of CFC's in the atmosphere, we are led to a very different conclusion than a naive comparison of estimated emission rates suggests. At sea level, the total mole fraction of Cl in manmade halocarbons (CFC's, together with related compounds such as CCl4 and CH3CCl3) comes to 3.0 ppb! So irrespective of production and removal rates, *there is more chlorine in the lower atmosphere in the form of halocarbons than in HCl*. At higher altitudes the halocarbons dominate overwhelmingly, since their mole fraction is almost independent of altitude whereas that of HCl drops off rapidly. All claims that HCl produced *at sea level* is more important than CFC emissions collapse when this simple point is considered. (*Explosive* volcanic eruptions cannot be rejected on these grounds, since they can in principle inject HCl directly into the stratosphere - as discussed below, direct measurements show that they are not important sources of stratospheric chlorine.) 4. Removal mechanisms for atmospheric halocarbons A similar misunderstanding underlies the discussion of CFC removal processes. On p. 47 we read: "...now it has been discovered that soil bacteria destroy CFCs very effectively. This fact has not been taken into account in calculating the persistence of CFCs, whose _estimated_ lifetimes range from 20 years to 1000 years. For freons, the estimates are 75 to 120 years, or an average of 100 years, which is the figure most often quoted. These estimates are all based on the assumption that nothing disintegrates the CFC molecules. Enter the microbes. As already pointed out, CFC molecules are ... four to eight times heavier than air molecules; most CFC that escapes into the atmosphere falls to the earth. There, soil bacteria decompose CFC's within a few days or weeks....Khalil and Rasmussen reported on the microbial removal of CFCs in 1989; their research has been substantiated by field work in China's rice fields and by considerable laboratory experimentation." Citations are given to [Khalil and Rasmussen 1989] and to [Khalil et al. 1990], who did indeed show that some halocarbons are taken up in soils. I will discuss these papers below, but first I want to argue that the overall thrust of the paragraph is wrong. Atmospheric lifetimes are *not* merely estimated from calculations, they are firmly rooted in observation and experiment. As stated earlier, it was Lovelock's observations of CFC's in the South Atlantic that first suggested their long atmospheric lifetimes. Soon thereafter, extensive measurements of halocarbons in the atmosphere began, culminating in the "Atmospheric Lifetime Experiment" that began in the late 1970's. The results of this project were published in a series of six long papers in 1983 [Prinn et al] with an update in 1986 [Cunnold et al.], and they demonstrate clearly that the halocarbon concentrations are steadily increasing. Similar results have been obtained by researchers all over the world [WMO 1991] It is _experiments_, not a priori theoretical estimates, that lead to the quoted lifetimes for atmospheric halocarbons. Both the older and the more recent measurements have been summarised by [Elkins et al.]: Growth Rate, parts per trillion per year Year CFC-12 CFC-11 1977-84 17 9 1985-88 19.5 11 1993 10.5 2.7 (Note the dramatic decrease in the observed growth rate since the imposition of CFC restrictions in 1988.) From such observations, together with industry production figures, we can establish the absence of major terrestrial sinks. In particular, from observations of CFC's and of their decay products *directly in the stratosphere*, we can establish that the stratosphere is the principal sink. The discussion in _Environmental Overkill_ completely ignores nearly 20 years' worth of observations, leaving the false impression that these conclusions are wholly theoretical. With this general picture in mind let us now turn to the first of the papers cited to support the claims made in _Environmental Overkill [Khalil and Rasmussen 1989]. It states: "The rates of removal are greatest for CCl4 followed by CH3CCl3 and F-11. Very little F-12 and probably no F-113 is removed by soils. ... If the rate of removal of these gases was the same all over the world as in our experiments, every year soils would remove about half of the CCl4 compared to all other processes, about 15% of the F-11 and 5% of the CH3CCl3 and F-12." (note: F-12 = CFC-12 = CF2Cl2; F-11 = CFC-11 = CFCl3) In other words, only for CCl4 (which is not a CFC although it behaves like one in many ways) are the soils a major sink. In the later paper, thesame workers [Khalil et al. 1990] give estimates of the global flux of halocarbons into rice fields. We can combine these with emission estimates from the Chemical Manufacturers Association and the lifetime measurements of [Cunnold et al.]: CFC-12 CFC-11 Total Emissions, 337 265 [Cunnold et al.] Gg/yr (1980-81) Total Atmospheric 6000 3960 " " Burden, Gg (1981) Lifetime, years 111 74 " " Total Destruction 54 53.5 (Rate = Burden/Lifetime) Rate, Gg/yr Soil Uptake, Gg/yr 0.6 1.0 [Khalil et al. 1990] We see that uptake by rice fields, extrapolated by [Khalil et al.] to provide a rough estimate of the global loss rate by this mechanism, accounts for 1-2% of the total loss rate. The work of Khalil and Rasmussen simply does not support the assertions made about it in _Environmental Overkill_. For completeness, I note that the same workers [Khalil and Rasmussen 1993] have more recently estimated that out of a total production of 9152 Gg of CFC-11, only *one* Gg has been taken up in soils and 33 Gg in the oceans. 1709 Gg have been destroyed in the stratosphere (to release Cl that can destroy ozone), 741 kt are now in the stratosphere, and 5360 kt are still in the lower atmosphere. The remainder is still trapped in foams, refrigerators, etc. B. More specialized factual errors So far I have considered erroneous conclusions that arise from a misunderstanding of the fundamentals of this subject. I now consider some more specific factual errors, of which there are many. Some are relatively minor, such as repeated references to stratospheric "chloride ions" (should be neutral chlorine radicals), a claim that the marine environment produces CFC's (marine algae produce halocarbons - methyl chloride and methyl bromide in particular - but _not_ CFC's), and a statement that Suva is an HCFC and will come under the Montreal ban in the year 2000 (Suva is an HFC, not an HCFC, and is therefore not covered by the Montreal Protocol, which in any event does not ban HCFC's until 2030.) Other points, however, have been widely repeated and are important enough to merit detailed discussion. 5. Decay products of CFC's in the stratosphere: p. 34: " The assumption that it comes from CFCs is based on hypothesis only. No breakdown products of freon have been identified in the stratosphere." Well, this is wrong because both the CFCs and their breakdown products _have_ been identified in the stratosphere. [Zander et al.] Let us consider CFC-12, CF2Cl2, as an example. Laboratory studies show that UV photolysis at wavelengths below 240 nm breaks this into a Cl atom and a CF2Cl radical. The radical reacts very rapidly with oxygen, initiating a sequence that ends with the Cl atoms incorporated in HCl and the F atoms in HF. One of the intermediates in this chain is COF2. This molecule is reasonably stable (it is essentially a fluorinated formaldehyde) and survives long enough to be detected. Now what do measurements in the stratosphere find? a.) the mole fraction of the CFC's _decreases_ with altitude; b.) the mole fraction of HCl and HF _increases_ with altitude; c.) the mole fraction of COF2 increases and then decreases, peaking in just the region where the CFC's are dropping off rapidly. [Zander et al.] We thus have direct evidence of CFC photolysis in the stratosphere. In addition, the long-term trends in stratospheric HCl and HF show that both are increasing, in the proportion expected if CFC photolysis is the major source for each. [Rinsland et al.] [Zander et al. 1992] 6. The myth of the 1956 ozone hole p. 32: "By convention, a decrease in the amount of ozone of 50 percent or more is called a 'hole', even though there is no ozone 'gap'. The regular, annual 'hole' that appears over Antarctica was first measured in 1956-57, long before CFCs were in common use." p. 37: "...Dobson was the first scientist to measure and describe the late winter formation of the Antarctic ozone 'hole' and its sharp recovery with the onset of spring." This false claim has been refuted many times, beginning with the 1989 World Meteorological Organization report [WMO 1989], so I will be brief. (It is very easy to refute - one need only look up the original papers.) During the years 1928-1958, Gordon Dobson laid the foundations of atmospheric ozone research by showing how the "ozone column", the total amount of ozone in a column over a spot on the earth, varies with latitude and season. Dobson showed that the ozone column was smallest in the tropics, ~260 milliatmosphere-cm, almost independent of season (milliatmosphere-cm are often called "Dobson Units" (DU) in his honor.) At higher latitudes there is more ozone overall with a significant seasonal variation, highest in the spring and lowest in the fall. At Spitsbergen, in the Arctic Ocean, the ozone column varies smoothly between a minimum of ~280 DU in September and a maximum of ~470 DU in March. When the first Antarctic ozone station was set up at Halley Bay in 1956, Dobson naturally expected to see similar behavior, shifted by six months. Instead, his coworkers noted that the ozone column stayed low throughout the winter, at about 300 DU (a little above the fall minimum), and then suddenly jumped up to above 350 DU in November. Dobson was naturally surprised to see that the Antarctic and Arctic ozone behaved so differently. This pattern was followed throughout the period 1956-1975, and is explained by the formation and breakup of the antarctic polar vortex.[WMO 1989] The Antarctic ozone hole, which began to form in the late 1970's, is *qualitatively* different. In late August and September the ozone column does not merely stay low, it plunges downwards by about 50% (mean october ozone in 1993 was 117 DU, as compared to 320 DU in 1957). The British Antarctic survey discovered this phenomenon by comparing their results for the period 1978-84 with their own long term record going back to 1956. Their 1985 paper [Farman et al.] presented this long term record; the first three points on their principal figure are the same measurements to which Dobson referred! Here is how springtime antarctic ozone has developed from 1956 to 1991: ------------------------------------------------------------- Halley Bay Antarctic Ozone Data Mean October ozone column thickness, Dobson Units From J. D. Shanklin, personal communication, 1993. For graphical representations see [Farman et al.], [Hamill and Toon], [Solomon], or [WMO 1991], p. 4.6. 1956 321 1969 282 1982 234 1957 330 1970 282 1983 210 1958 314 1971 299 1984 201 1959 311 1972 304 1985 196 1960 301 1973 289 1986 248 1961 317 1974 274 1987 163 1962 332 1975 308 1988 232 1963 309 1976 283 1989 164 1964 318 1977 251 1990 179 1965 281 1978 284 1991 155 1966 316 1979 261 1992 142 1967 323 1980 227 1993 117 1968 301 1981 237 1994 124 ------------------------------------------------------- 7. Volcanoes and Stratospheric Chlorine We now come to the notorious claim that volcanic eruptions are major sources of stratospheric chlorine. Fifteen years ago this was a defensible hypothesis. Volcanic gases _are_ rich in Hydrogen Chloride, HCl, and very large eruptions can in principle inject these gases directly into the stratosphere. It is well known that they do inject large quantities of sulfur dioxide; whether they inject chlorine as well is a question that must be resolved by observation. Such observations have been carried out for El Chichon, the largest eruption between 1956 and 1991, and for Pinatubo, the largest eruption since 1912, and in both cases large increases in stratospheric chlorine were not found. El Chichon injected ~40 ktons of HCl into the stratosphere [Mankin and Coffey], while Pinatubo produced considerably less [Mankin et al.] CFC emissions, on the other hand, result in an annual flux of 300 ktons of Cl into the stratosphere. The long-term record of total stratospheric chlorine shows a steady increase with time, rather than a series of steps following major volcanic eruptions [Rinsland et al.] Finally, major volcanic eruptions can be detected as sulfur spikes in ice core records. These same cores show no corresponding chlorine spikes, not even for the enormous eruption of Tambora in 1815 [Delmas]. Indeed, the scientific question is not whether volcanoes deliver large amounts of chlorine to the stratosphere, but rather why they do not do so. Model calculations suggest that the HCl is dissolved in condensing water vapor (there is ~10,000 times as much water as HCl in a volcanic plume) and removed in the heavy rains that usually follow an eruption before it can be dispersed in the stratosphere [Pinto et al] [Tabazadeh and Turco]. Whatever the explanation, direct measurement has shown that *volcanoes are not major sources of stratospheric chlorine*. Turning to _Environmental Overkill_, we find that none of the recent work is even mentioned. Only a single paper, published in 1980, is cited, and this one is blatantly misrepresented: p. 35: "...David A. Johnston (who died at Mt. St. Helens), in a posthumously published paper (Science, July, 1980), brought many previous estimates up to date and refined the measuring techniques for chloride in volcanic emissions. He pointed out that a single eruption of Mount Augustine in Alaska in 1976 put more chlorine into the stratosphere than was contained in the worldwide production of CFCs for the entire year 1975." Johnston says no such thing. From the abstract of his paper: "Degassing of ash erupted during 1976 by Augustine Volcano in Alaska released 525 x 10^6 kilograms of chlorine (+- 40%), of which 82x10^6 to 175x10^6 kilograms may have been ejected into the stratosphere as hydrogen chloride. This stratospheric contribution is equivalent to 17 to 36 percent of the 1975 world industrial production of chlorine in fluorocarbons." [Johnston] Two things to note: first, Johnston did not measure the chlorine contribution _in the stratosphere_; rather, he estimated it from the total chlorine production. Many such estimates were published during the 1970's, and because different workers made different assumptions about what fraction of the chlorine produced actually reached the stratosphere, the results varied widely. Johnston was one of those who believed that the fraction was large. Direct measurements, cited above and ignored in _Environmental Overkill_, have shown him to be wrong. Second, even Johnston's overestimate does not support the claim that the volcano's contribution to stratospheric chlorine amounted to *more* than a year's worth of CFC production - instead, Johnston said 17- 36%. As I will discuss below, it is very likely that the authors never examined Johnston's paper, relying instead on an unreliable secondary source. Similar criticism applies to the statements about Mt. Erebus: p. 34: "...Mt. Erebus in Antarctica has been producing 1000 tons of chloride daily since 1972. Mt. Erebus is located 10 kilometers upwind of McMurdo Sound, where ozone measurements are made. The volcano pumps out 50 times more chlorine annually than an entire year's production of CFCs." To begin with, Mt. Erebus has _not_ been producing 1000 tons of chloride daily since 1972. Measurements in 1986 indicated that it was producing about 100 tons per day; the researchers then estimated that during a more active period between 1976 and 1983 the volcano's output did reach 1000 tons per day. [Kyle et al.] Let us, however, proceed on the assumption that the quoted figure is correct. 1000 tons/day is 365 kton/year, which is nowhere near 50 times the chlorine contained in a year's CFC production; it's more like about 50% [Wayne, p. 167]. Oddly enough the book gives an approximately correct figure for industrial production, ~750,000 tons Cl, on the very same page; the authors appear to have lost a factor of 1000 in their arithmetic. But more importantly, Erebus is _not_ an explosively erupting volcano. Even in the active period it was about 4 orders of magnitude weaker than Mt. Pinatubo, and the plume never came near the stratosphere; most of the time it just crawls over the crater rim (where the chlorine measurements were made.) It is just one more source of water-soluble HCl, and is ruled out by the arguments given previously for sea salt spray (which in fact is a much larger source than all volcanoes put together). Furthermore, if chlorine from Mt. Erebus were responsible for the antarctic ozone hole one would expect that the *total* amount of chlorine over antarctica would be much higher than elsewhere in the stratosphere. This is not observed. Rather, during the Antarctic Spring all of the chlorine is in the form of radicals that can destroy ozone. Elsewhere, most of the chlorine is bound up in "reservoir compounds" such as HCl and ClONO2. (Note: It has recently been found that the 1986 measurements were too large [Zreda-Gostynska et al]; the true figure for 1986 should be 19 tons/day (or 7 ktons/year) and the estimate for 1976-83 is now 167 tons/day (61 ktons/year.) This paper was published after _Environmental Overkill_, so the authors cannot be held responsible for it; nevertheless they did misrepresent the information that was available at the time of writing.) C. Information Presented in a Misleading Context The book makes a number of claims which are not wholly false in themselves, but which lead to false conclusions when the original context is left out. 8. Sulfate aerosols interfering with ozone measurements p. 51: "...two Belgian meterologists, D. DeMuer and H. DeBacker (published in the _Journal of Geophysical Research_), who contend that all ground-based measurements of stratospheric ozone concentration are influenced by changing amounts of sulfur dioxide (SO2) in the atmosphere. They conclude that the presence of SO2 - from volcanos and from industry - produces a 'fictitious' ozone depletion and point out that when the data for the past 30 years are corrected for SO2 interference, all evidence of ozone depletion disappears." De Muer and De Backer do make such a claim - but only for a *single* station, located near Brussels. They also say "It should be clearly noted that we do not want to infer any conclusion about regional ozone trends from this single station analysis." [De Muer and De Backer] The situation in Brussels is highly unusual - it suffered from extraordinarily high levels of SO2 pollution during the early 1970's, which has since been cleaned up to a remarkable degree. The mean SO2 concentration dropped by a factor of 5, from 160 micrograms/m^3 in 1969 to 30 micrograms/m^3 in 1989. Most of the ozone-monitoring stations in the ground-based Dobson network are located in remote areas where this kind of contamination is not an issue. Satellite data are not affected at all, nor are chemical measurement techniques such as balloon-borne ozonesonde. Interestingly, the correction brings the ground-based Brussels data into agreement with the satellite data for the same region for the period 1978-89; the uncorrected data had indicated a larger depletion. 9. Ultraviolet Radiation at the Earth's Surface p. 39: "The problem with this theory is that ultraviolet radiation levels at the earth's surface are going down, not up... "Measuring instruments set up across the U.S. in 1974 by the National Cancer Institute show that over two test periods - 1974-79 and 1980-85 - the amount of ultraviolet 'B' (UVB) reaching the earth actually decreased by an average of 0.7 percent per year since 1974. In an article in _Science_ (1988) the institute also reports that data from Mauna Loa, Hawaii show no increase in UVB radiation from 1974 to 1985. Similar results were obtained by Penkett in East Anglia, England and Bavaria, Germany. Measurements taken between 1968 and 1982 show UV decreases of from 0.5 to 0.9 percent." There is a lot of confusion in this paragraph. There were no measurements in "East Anglia" or in Bavaria. Rather, radiative transfer _calculations_ by [Bruehl and Crutzen] which include the effects of both ozone depletion and tropospheric ozone increases suggest that there _should_ have been an overall UV decrease at Hohenpeissenberg, Bavaria over this period. These calculations were described by Penkett, who is an atmospheric scientist *at the University* of East Anglia, in a "News and Views" article in _Nature_. As for the Mauna Loa results, they are real but entirely unsurprising, as all of the data indicates that there was no ozone depletion in the tropics in that period [Stolarski et al.][WMO 1991]. This leaves us with the National Cancer Institute study [Scotto et al.] which did indeed find slight decreases (not significant in all cases), in surface UV in eight *urban areas* for the period 1974-1985. This surprising result stimulated the theoretical work of Bruehl and Crutzen and others, and from this work it seems likely that increases in tropospheric ozone and sulfate aerosol pollution compensated for decreases in stratospheric ozone over that period. Note that the first clear evidence for ozone depletion itself at middle latitudes came in 1988 [WMO 1988]. Total UV measurements are much more difficult than ozone measurements, and far more sensitive to confounding factors such as local pollution, and it is not surprising that in a period when ozone decreases were just emerging from the noise, a single study of surface UV failed to find an increasing trend. On the other hand, there *is* evidence for UV increases in unpolluted regions, such as the Swiss Alps [Blumthaler and Ambach] and New Zealand [Seckmeyer and McKenzie], and large increases have been found in Antarctica [Frederick and Alberts] and in Argentina [Frederick et al.]. D. Flawed Scholarship and Unreliable Source Material I have given numerous examples of the misconceptions, misrepresentations, and outright fallacies that permeate these two chapters from end to end. The reader should now be able to draw some general conclusions - for example, it should be clear that ozone depletion is *not* based on cooked-up computer models, it is firmly anchored in observation and experiment. I will now try to show just where all this misinformation came from. To an outsider this book may appear to be impressively documented. Closer examination shows that this is merely the appearance of scholarship, not the reality. No modern textbooks on atmospheric sciences are mentioned, nor are the many scientific review articles, or the comprehensive reports from the World Meteorological Organization [WMO 1985, 1988, 1989, 1991] . A single overview by Rowland is cited, that is all, and it seems that the authors did not pay close attention to it. A few technical papers on highly specialized subjects are mentioned, but as I have shown above, the conclusions drawn in _Environmental Overkill_ are in most cases simply not supported by the cited source. There are a number of references to articles in the popular media, or in the journals of political organizations such as the Cato Institute. Some of these non-peer-reviewed articles are written by atmospheric scientists, although not by people presently engaged in research in this area. There are also a number of references to articles published in what can fairly described as "fringe media", such as _New American_, an organ of the John Birch Society, and _21st Century Science and Technology_ and _Executive Intelligence Review_, two magazines edited by the associates of political extremist Lyndon LaRouche. Indeed, the major source for these two chapters is a book, _The Holes in the Ozone Scare_, by Rogelio Maduro and Ralf Schauerhammer (21st Century Science Associates, Washington, DC 1992). The endpapers tell us that Maduro, who holds an undergraduate geology degree, was a researcher for the Schiller Institute, a well-known LaRouche organization [King], while Schauerhammer has worked on "the simulation of economic development according to the LaRouche-Riemann model." The authors of _Environmental Overkill_ cite this book, together with other articles by Maduro, frequently; moreover, even where they cite primary literature, it seems likely that they actually relied only on the summaries in Maduro and Schauerhammer. Consider, for example, Johnston's estimates of chlorine emissions from Augustine volcano, discussed above in section B.3 above. Johnston wrote: "Degassing of ash erupted during 1976 by Augustine Volcano in Alaska released 525 x 10^6 kilograms of chlorine (+- 40%), of which 82x10^6 to 175x10^6 kilograms may have been ejected into the stratosphere as hydrogen chloride. This stratospheric contribution is equivalent to 17 to 36 percent of the 1975 world industrial production of chlorine in fluorocarbons." [Johnston] Maduro and Schauerhammer write: (p. 17) "Specifically, he says, one single volcanic eruption in 1976 put more chlorine into the atmosphere than the entire amount of chlorine contained in the CFCs manufactured in 1975." And _Environmental Overkill_ says (p. 35) "He pointed out that a single eruption of Mount Augustine in Alaska in 1976 put more chlorine into the stratosphere than was contained in the worldwide production of CFCs for the entire year 1975." Notice that Maduro and Schauerhammer say "atmosphere", not "stratosphere". Their statement is a misleading, but not literally incorrect, description of Johnston's conclusions. Johnston's estimate of the _total_ chlorine release from the volcano comes to 1.07 times the 1957 world industrial production in fluorocarbons. (This is the overall strategy of their book - they try to make statements that are not literally false, but that are likely to mislead. Since they do not in fact understand the subject very well they do not always succeed in avoiding literal error.) _Environmental Overkill_ takes the bait and confuses total emissions with the stratospheric contribution, a mistake that would be difficult to make if the authors had read Johnston's very explicit statement. A similar analysis could be made of the discussions of soils as sinks for CFC's, of surface UVB measurements, and of Dobson's early ozone measurements. In each case a direct comparison of the texts strongly suggests that the authors of _Environmental Overkill_ relied solely on Maduro and Schauerhammer, and did not consult the original literature. To put it bluntly, these two chapters consist largely of recycled LaRouchian propaganda. In view of this, it is somewhat ironic to read these sentences at the beginning of Chapter 3, p. 29: "My only advice is this: Look for evidence, not for arguments; discount any unsupported assertions, even if they come from an eminent authority, and then make up your own mind based on what facts you can assemble and on your own common sense." What _Environmental Overkill_ has actually done is to ignore the evidence, to repeat uncritically the unsupported assertions of utterly unreliable 'authorities', and to make a string of what are purported to be 'common sense' arguments that have no foundation in the facts. -------------------------------------------------------------------------- _References_ [Blumthaler and Ambach] M. Blumthaler and W. Ambach, "Indication of increasing solar ultraviolet-B radiation flux in alpine regions", _Science_ _248_, 206, 1990. [Bruehl and Crutzen] C. Bruehl and P. 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