When climate change predictions are right for the wrong reasons
Just over 40 years ago, I wrote a paper entitled “Climate change: Are we on the brink of a pronounced global warming?” In it, I attempted to explain why despite a rise in the atmosphere’s CO2 content there had been no significant warming. I predicted that a natural cooling was about to give way to a warming, and that industrial emissions of CO2 would amplify this warming. The paper published in Science in 1975. Warming did follow in 1976–1977. However, a retrospective look shows that my analysis was flawed. What is more—and to my chagrin—based on the words “global warming” in my Science paper, I was given the title “Father of Global Warming.” Not only did I not like this title, I had done little to merit it.
1 Dumb luck
My Science paper made use of the oxygen isotope record from the northern Greenland Camp Century ice core, the only available well-dated and highly detailed record. The oxygen isotope record was thought to serve as a proxy for local air temperature. Willi Dansgaard, the pioneer of such studies, had shown that over the last 800 years, much of the variance in his 18O record could be explained by a combination of 180- and 80-year cycles (Dansgaard et al. 1971).
However, over the next couple of decades, it became clear that my use of the Camp Century record as a stand-in for global temperature was flawed. As other records including those for ice cores from southern and central Greenland appeared, none showed Dansgaard’s 180- and 80-year cycles. Because of this, I became convinced that my analysis was faulty and that my prediction, although correct, was the product of dumb luck.
2 I am not the father!
My Science paper circulated widely; given the paper’s title, some popular media sites unfortunately started referring to me as the “Father of Global Warming.” This credit was misplaced. If there has to be such a person, it should be the late Charles David Keeling, whose tireless work unequivocally demonstrated that atmospheric CO2 concentrations are rising in lock-step with fossil fuel use.
In 2001, I offered a $200 reward to anyone who could find an earlier use of the two words “global warming.” For a long time, I received no claim. But finally, one appeared. David McGee, then a colleague here at Lamont-Doherty, found a 3-in.-long column in Indiana’s The Hammond Times (6 November 1957) which used these words. Its subject was a claim by unnamed scientists in Southern California that CO2 released by industry was going to lead to global warming. The 1957 date for this piece was close to the time when Keeling was gearing up for his CO2 measurements at the Mauna Loa Observatory on the island of Hawaii. I suspect the unnamed scientists were Keeling and Roger Revelle, the director of Scripps.
I promptly gave David McGee the promised reward. Since then, other uses of “global warming” prior to my 1975 publication have come to my attention. Two scientific papers in the 1960s used the phrase, one by. JM Mitchell in 1961 and the other by NR Malkin in 1968. It is my hope that the title “Father of Global Warming” does not appear on my tombstone. Were it to, I would be faced with a restless afterlife.
3 What happened in 1976–1977?
Although this change occurred at the time of an important El Niño event, the actual physics of what happened remains unclear. Perhaps in the new circulation regimen, the ocean absorbed less of the heat generated by the atmosphere’s growing CO2 content.
This reorganization had repercussions elsewhere. McGowan et al. (2003) show that the frequency of warm events along the California Current underwent a dramatic increase in 1977 creating important biologic responses. Further, it also came at the time when the Pacific Decadal Oscillation (PDO) was undergoing an unusually large negative to positive transition (Henley et al. 2015) and a pronounced 18O increase recorded in Tonga and Fiji corals (Linsley et al. 2015). It was also a time that a large increase in rainfall occurred in the Argentine Pampas (Troin et al. 2010).
4 A signal and noise problem
There was in hindsight another problem with my 1975 analysis. It had to do with magnitude of the noise in the temperature record. Between 1959 and 1975, CO2 rose from 315 to about 330 ppm. Based on the best match between the CO2 record and the temperature record (see Fig. 1), the temperature is expected to have risen by about 0.1 °C. Considering that inter-annual temperature changes of up to about 0.3 °C occurred, it is not surprising that prior to 1975, no significant temperature increase could be identified. Also, it is possible that cooling caused by Anthropocene CO2 emissions had been counter balancing the CO2 warming.
5 Why 1976–1977 warming remains important
Those who choose not to accept that the warming produced by fossil fuel CO2 poses a serious threat, point to what they view as a cessation of warming during the first decade of this century (see Trenberth 2015). This observation has been used to strengthen the position of those who oppose tough legislation designed to reduce CO2 emissions. This plateau could be interpreted as an undoing of what happened in 1976–1977. Hence, it is of great importance to gain an understanding of these reorganizations and whether similar ones will punctuate the ongoing warming.
- Dansgaard W, Johnson SJ, Clausen HB, Langway CC Jr (1971) Climatic record revealed by Camp Century ice core. In: Turekian KK (ed) The late Cenozoic glacial ages. Yale University Press, New Haven, pp 37–56Google Scholar
- Linsley BK, Wu HC, Dassié EP, Schrag DP (2015) Decadal changes in South Pacific sea surface temperatures and the relationship to the Pacific decadal oscillation and upper ocean heat content. Geophys Res Lett 42. doi: 10.1002/2015GL063045
- Malkin NR (1968) The retreat of the North American ice sheet and shifts in cyclone tracks. Sov Geogr 9. doi: 10.1080/00385417.1968.10771051
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