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Joshua P. Howe Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019 This Is Nature; This Is Un-Nature: Reading the

Data images make odd cultural artifacts. On one hand, scientists pre- sent their data in images as a form of visual communication, intended, like other forms of visual culture, to convey both specific information and larger culturally coded messages. On the other hand, scientists typically hew to methods of measurement and math- ematical analysis intended to ensure that the data they present reflect some objective reality that transcends the cultural. To the extent that the data tell a cultural story, it is supposed to “speak for itself.” Such is the case with the Keeling Curve, the oscillating upward- sloping graph of measured atmospheric (CO2) that has come to stand as one of the most important and powerful scien- tific symbols of anthropogenic . To a lay reader, it may seem odd to read a simple measure of atmospheric gas through the many-sided prism of modern American life the way you might read a historical photograph or piece of art. And yet the Keeling Curve func- tions as much as a symbol in our collective cultural understanding of climate change as it does a representation of data about CO2. The Keeling Curve faithfully represents something quite real—the accumulation of CO2 in the atmosphere since 1958, expressed in parts per million (ppm)—but it is also a constructed image ripe for reading, similar to a painting, a photograph, a landscape, or a written document. The Keeling Curve conveys information about CO2, but it

VC The Author 2015. Published by Oxford University Press on behalf of the American Society for Environmental History and the Forest History Society. All rights reserved. For permissions, please e-mail: [email protected]

Joshua P. Howe, “This Is Nature; This Is Un-Nature: Reading the Keeling Curve,” Environmental History 20 (2015): 286–293 doi: 10.1093/envhis/emv005 This Is Nature; This Is Un-Nature 287 Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019

Figure 1. Atmospheric CO2 at Observatory. The oscillating red line of the Keeling Curve tracks the actual monthly average of measured atmospheric CO2 over time while the solid, upward sloping black line represents the same data corrected for the seasonal cycles that cause the oscillations. Credit: Dr. Pieter Tans, NOAA/ESRL and Dr. , Scripps Institution of Oceanography, 2014. Pieter Tans and Ralph Keeling, Trends in Atmospheric Carbon Dioxide, Earth Systems Research Laboratory Global Greenhouse Network, http://www.esrl.noaa.gov/gmd/ccgg/trends. also makes a set of culturally specific and politically salient claims about nature and historical time that we ought to take seriously as we think about the intractable riddle of climate change.

CONSTRUCTING THE CURVE At its heart, the Keeling Curve is a scientific image with scientific objectives in mind, and any reading of the Keeling Curve as a cultural symbol necessarily starts with the scientific construction of the im- age. In figure 1, for example, the curve measures a single variable, CO2, over time. But the graph is not a plot of raw data. Rather, the oscillating upward sloping line from 1958 to 2014 runs through points representing the average monthly mean of the daily averages of measured atmospheric CO2 at the , as cor- roborated by measurements at other observing stations around the world. Figure 2, an interactive image of the Keeling Curve from the Earth Systems Research Laboratory of the National Oceanographic and Atmospheric Administration (NOAA), helps to demonstrate this construction process. In the image, individual measurements, ag- gregated and averaged over increasing increments of time, constitute recognizable trends. In figure 1—the most recognizable version of the curve—NOAA portrays these trends in lines that smooth out 288 Environmental History 20 (April 2015) Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019

Figure 2. Mauna Loa Daily, Monthly and Weekly Averages for Two Years. Recorded daily averages from multiple measurements (in blue) provide the basis for weekly averages (in green), which in turn are used to construct the monthly averages (in red) that constitute the familiar Keeling Curve. Credit: Dr. Pieter Tans, NOAA/ESRL and Dr. Ralph Keeling, Scripps Institution of Oceanography, 2014. Tans and Keeling, “Interactive Plots,” Trends in Atmospheric Carbon Dioxide, Earth Systems Research Laboratory Global Greenhouse Network, http://www.esrl.noaa.gov/gmd/ccgg/trends/graph.html.

variations and irregularities in individual measurements and short- term averages—that is, outliers among the dots—in order to make meaning out of changes in CO2 over months and years. In most versions of the Keeling Curve, this aggregating and averag- ing stop at the monthly mean; we recognize the Keeling Curve not just by its upward slope, but also by its peculiar wavelike shape. Frequently, depictions of the curve like the one in figure 1 include both the oscillating line of monthly means (in red) and a straighter, more direct line of seasonally corrected data that roughly approxi- 1 mate the annual average measured CO2 over time (in black). Rarely, however, do we see this straight line alone; if we do, we do not recog- nize it as the “Keeling Curve.” In a few important respects, we need both lines to interpret the curve. The Keeling Curve of figure 1 is a form of storytelling, and it actually tells two mutually instructive stories. The line of annual average tells a long-term story of change, depicting a troublingly per- sistent rise in atmospheric CO2 over the past half century that most scientists recognize as a consequence of humans’ collective burning of fossil fuels. Embedded within that long story, however, is an This Is Nature; This Is Un-Nature 289

important story of annual oscillation operating independently of human influence. Across the globe, fix atmospheric carbon in the form of new shoots, leaves, blossoms, and flowers during the Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019 spring and summer months—the growing season—and then release that carbon back into the atmosphere in the fall and winter months as they die or drop their leaves. Because the Northern Hemisphere contains the majority of the earth’s continental landmasses—and a corresponding majority of its seasonal plants—measurements of atmospheric CO2 reflect the annual uptake and release of CO2 as an artifact of the Northern Hemisphere’s seasonal cycles. The annual os- cillations depicted in the Keeling Curve reflect this cycle of growth and decay. The Keeling Curve thus also uses scientific data to tell the story of the earth “breathing.”2 There are two good reasons to tell these stories together. First, the two stories—one of cyclical planetary respiration and the other of sec- ular atmospheric change—reflect the two major important insights of the curve’s namesake, . In 1956 Keeling was a postdoctoral fellow in geochemistry at Cal Tech with Harrison Brown, who encouraged Keeling to begin investigating the transfer of carbon between water, rock, and air over time. In taking control samples for the highly sensitive gas manometer that he had designed for the carbon project, Keeling noted a consistency in the “back- ground” concentrations of CO2 that he took from places as different and disparate as the lab in Pasadena and the forests of the Olympic Peninsula in State.3 In 1957 Roger Revelle of the Scripps Institute of Oceanography and Harry Wexler of the US Weather Bureau secured funding for Keeling to conduct continuous CO2 mea- surements at the Mauna Loa Observatory, and by 1960 Keeling had both identified the cyclical variations of atmospheric CO2 as an arti- fact of seasonal growth and decay and noted a consistent year-to-year increase of about 1 ppm in background measures of atmospheric 4 CO2. To portray the two phenomena together consolidates Keeling’s career into a form of well-deserved data-driven scientific hagiography.

THIS IS NATURE; THIS IS UN-NATURE There is a second, more important way to read these two phenom- ena together, however. The upward-sloping oscillations of the Keeling Curve embed a cyclical story about the processes of nature— seasonal growth and decay—within a larger story about the “un- nature” of anthropogenic climate change. In figure 1, the red line of monthly means oscillating up and down within the curve represents the earth breathing. This is nature. The cycle is annual, but the organic process is timeless—influenced 290 Environmental History 20 (April 2015)

by human activities, perhaps, but ultimately independent of any- thing short of tectonic change. And yet the Keeling Curve as a whole

is not timeless. The oscillating curve of monthly means does not run Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019 straight across the page; it slopes upward and to the right along the black line of corrected averages as it follows the half-century human time scale demarcated by the numbers at the bottom of the graph. The earth continues to inhale and exhale as it has for millions of years, but humans have changed the air that it breathes. This is un- nature, or nature that humans have tipped on its side. Scientists don’t have to make an explicit normative judgment about rising CO2 when they present the two lines of the curve together. The Keeling Curve puts rising anthropogenic CO2 in tension with a timeless natu- ral process of planetary respiration, and extra-scientific cultural ideas about the duality of the natural and the human do the work to make that image meaningful. The tension between the natural and the unnatural embedded in the two lines of the Keeling Curve has informed the recent emphasis in climate change discourse on the concept of the anthropocene. First popularized by Paul Crutzen and E. F. Stoermer, the term anthro- pocene describes the current geologic epoch, in which humans have begun to act as agents of geophysical change.5 The core insight be- hind the term is that in our intensive burning of fossil fuels, humans have collectively affected geophysical changes on human timescales.6 Few images convey this concept more clearly and effectively than the simple upward-sloping oscillations of the Keeling Curve. Repeating cycles of planetary respiration (the oscillating red line on the curve) reveal secular planetary change (the straighter black line running from the lower left to the upper right), plotted in human time. In fact, understood in the context of a world in which human activ- ity has collapsed the distinction between the human and the natural (however artificial that distinction may have been), the Keeling Curve becomes a new form of historical time marker. As Dipesh Chakrabarty writes, the idea of the anthropocene requires that we reevaluate narratives of modernity, especially insofar as climate change complicates the benefits of a “modernity” achieved through the burning of fossil fuels.7 The Keeling Curve offers an anthro- pogenic timeline, a new chronological background for contemplating both personal and collective histories. To say that Lee Harvey Oswald shot JFK at 317 ppm, near the lower left of figure 1; that Nixon launched the Cambodian incursion somewhere around 327 ppm; that Reagan fired Secretary of the Interior James Watt at 341.5 ppm, near the middle of the curve; and that the invaded Iraq once at 353 ppm and again at 376.5 ppm, closer to the top right, is to trace historical events onto a geophysical timeline that gives those events new historical and environmental meaning. Where were you at 400 ppm? Will you be around at 450 ppm? This Is Nature; This Is Un-Nature 291

THE RIDDLE OF THE KEELING CURVE In tracking history in anthropogenic time via measurements of Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019 CO2, we also track a history of scientific knowledge that makes CO2 meaningful. Much of that knowledge is not new; scientists have understood anthropogenic climate change as an important environ- mental and human problem for at least three decades, and the international political community has officially recognized the importance of climate change for more than twenty years through hybrid science-to-policy mechanisms like the Intergovernmental Panel on Climate Change and political mechanisms like the United Nations Framework Convention on Climate Change. In fact, Keeling himself had to know enough to look for a change in background atmospheric CO2 to begin his measurements, and in that sense the

Figure 3. An image of the Keeling Curve from a 1971 conference on inadvertent climate modification reveals gaps in Keeling’s monthly measurements, inscribing Keeling’s difficulties in finding funding onto the image of the record of CO2 itself. Mean monthly values of CO2 concentration at Mauna Loa, , for the period 1958–1971. Credit: William H. Matthews, William W. Kellogg, and G. D. Robinson, eds., Inadvertent Climate Modification: Report on the Study of Man’s Impact on Climate, Stockholm (Boston: MIT Press, 1971), figure 8.11, p. 234. VC 1971 Massachusetts Institute of Technology, by permission of the MIT Press. 292 Environmental History 20 (April 2015)

Keeling Curve is an artifact of scientific knowledge from the 1950s as much as it is a driver of knowledge about climate change in the

twenty-first century. Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019 There have been short-term downturns in public and scientific in- terest in CO2, of course, and at least one of these downturns is inscribed in a 1971 image of the curve itself. A gap in the oscillating line of monthly means near the middle of figure 3, which comes from the Study of Man’s Impact on Climate, reflects a three-month period in the spring of 1964 when Keeling lost his funding. The gap functions at once as a historical time marker of budgetary problems in 1963 and a rhetorical argument for continued funding—avoiding future gaps— in 1971. Here, in a very real way, an image of the Keeling Curve depicts not only measured atmospheric CO2, but also the scientific politics of its measurement at a particular time in history.8 But that gap is an anomaly, and herein lies the riddle of the more recent images of the curve. As you follow the Keeling Curve for- ward in time toward the present, our collective knowledge of and concern about climate change increases on imaginary curves with slopes that far outstrip that of CO2. We know and care much more about climate change in 2015 than we did in 1958. Climate scientists and global warming advocates have self-consciously used that knowl- edge and concern to try to mitigate global CO2—that is, to reduce the slope of the Keeling Curve. And yet the Keeling Curve itself persists in its upward trajectory. In fact, the slope has only increased, from around 1 ppm per year to closer to 2 ppm per year. We know more and we care more, but half a century in, the problem is not getting better; it is getting worse. How can this be? And how can it be changed? This is the riddle of the Keeling Curve—a riddle of the past, certainly, but perhaps more importantly a riddle for our collective global future.

Joshua Howe is assistant professor of history and environmental studies at Reed College and the author of Behind the Curve: Science and the Politics of Global Warming (University of Washington Press, 2014).

Notes 1 Pieter Tans and Ralph Keeling, Trends in Atmospheric Carbon Dioxide,Earth Systems Research Laboratory Global Greenhouse Network, http://www.esrl.noaa. gov/gmd/ccgg/trends. 2 See Scripps Institution of Oceanography, “The Keeling Curve: A Daily Record of Atmospheric Carbon Dioxide from the Scripps Institution of Oceanography at UC San Diego,” accessed May 9, 2014, http://keelingcurve.ucsd.edu. 3 Scripps Institution of Oceanography, “Keeling Curve History,” accessed May 9, 2014, http://keelingcurve.ucsd.edu/the-history-of-the-keeling-curve. This Is Nature; This Is Un-Nature 293

4 See also Spencer Weart, The Discovery of Global Warming (Cambridge: Harvard University Press, 2003), 36; Gale E. Christiansen, Greenhouse: The 200 Year Story

of Global Warming (New York: Penguin Books, 1999), 151–57. Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019 5 P. J. Crutzen and E. F. Stoermer, “The ‘Anthropocene,’” Global Change Newsletter 41 (2000): 17–18. 6 See Dipesh Chakrabarty, “The Climate of History: Four Theses,” Critical Inquiry (Winter 2009): 197–222. 7 Chakrabarty, 207–8. 8 The gap was short lived, and CO2 would land on President Johnson’s desk in a report on the state of the environment just a year later. US President’s Science Advisory Committee. Environmental Pollution Panel, Restoring the Quality of Our Environment. Report of the Pollution Panel, President’s Science Advisory Committee (Washington, DC: US Government Printing Office, 1965).