The first scientific paper using the terminology of ‘scenario’ to describe the possible future evolution of climate was published in 1977 by the German meteorologist Hermann Flohn. It appeared as the first paper in the very first issue of the new journal Climatic Change, published by Springer and edited by the ambitious young American climatologist, Stephen Schneider. In this short essay I look back at this paper from the perspective of more than 40 years of ‘climate scenarios’ and find in Flohn’s presentation some important lessons for thinking about and using scenarios today.

Flohn framed his analysis of future climate in the context of the 1970s energy crisis and took inspiration from the Club of Rome’s 1972 report The Limits to Growth. Although in the mid-1970s it was very far from agreed amongst scientists that the world was warming, let alone that the prognosis was for future warming (NDU, 1978), in a series of bold moves Flohn brought together concerns about future energy, economic and population growth and the presumed human influences on climate to speculate about the climatic future.

“It is intended to ventilate here some possibilities of near-future climatic evolution based on the most recent state of knowledge. This can never be a forecast – rather it is a perspective, a scenario outlined after many discussions among many leading experts …” [p.10].

There are several notable qualities to the reasoning and style of scenario presentation that Flohn adopted back in 1977. First, he was very clear about the synthetic and subjective qualities of the future he was creating. Flohn assimilated evidence and reasoning from different domains of knowledge—energy projections, energy technology, demography, paleoclimate science, the nascent field of climate modelling, etc.—to create “a perspective” on future climate, certainly not a forecast or a prediction. It was fully acknowledged as a subjective assessment, eschewing any claims to special or privileged knowledge of the future: “… the author, however, takes the responsibility for its wording alone” [p.10].

Second, he explicitly worked with the original dramaturgical meaning of the Italian word ‘scenario’, meaning a sketch of the plot of a stage play. Flohn presented his climate scenario “in three acts”. Act 1 was to be the beginning of the twenty-first century (i.e., now!) in which world climate had warmed to resemble the warm climate of the 1920s and 1930s (cf. Kincer, 1933). Act 2 was set in the middle decades of our present century–the 2040s and 2050s–which would more resemble the “warm epoch” of the Earth between 800 and 1200 AD. Arctic sea-ice would be in retreat and desert margins destabilised. The third and final Act of Flohn’s drama—by the end of our century—would witness global conditions warmer than the last inter-glacial 200,000 years ago, and possibly warmer than any time in the last 1-2 million years. In Act 3, the Arctic was largely ice-free in summer, with attendant changes in mid-latitude and tropical weather circulations.

The third notable feature of his analysis was how he used his creative scenario to pose questions about the energy future: “What does this three-act [climate] scenario with its alarming inferences mean for the energy problem?” [p.17]. This contrasts with much subsequent scenario work in the field which inverted Flohn’s question: what do different energy futures mean for climate? Flohn drew two conclusions from his climate drama: a reduction in economic growth and a future powered by solar energy, ahead of nuclear and fossil fuels. He concluded using the voice of the prophet calling a society to heed its covenant values (cf. Walsh, 2013) … “It is our generation which bears responsibility for a global scale problem facing our grandchildren – let us take care to match it” [p.18].

In the 40 years since Flohn’s publication, climate scenarios have gained great salience, but they have also taken on very different forms to that presented by Flohn. A clutch of climate scenario papers followed around 1980—Kellogg (1978), Williams (1980), Wigley et al. (1980)—all of them using past climates as analogues for the future. But through the 1980s and 1990s the growing dominance of global climate models in the study of climate change meant that by the time the IPCC reviewed the whole field of climate scenario production in 2001 (Mearns & Hulme, 2001), the ‘art’ of scenario creation had been largely superseded by technical considerations and an excess of numerical objectivity. Confusions between the language of climate ‘scenarios’, ‘forecasts’, ‘projections’ and ‘predictions’ abounded (Bray and von Storch, 2009).

And we are still today in a place of ambivalence. Is a climate scenario an imaginative provocation to think imaginatively, but seriously, about the relationship between present actions and the future? Or is a climate scenario revealing objective and (implied) authoritative knowledge of the future? Is a climate scenario a scientific technical accomplishment to be admired or a prophetic call to re-think and react based on a moral vision? Reno Knutti recently lamented the scientisation of climate scenarios associated with the speculative geoengineering technologies of carbon dioxide removal and (especially) solar radiation management, “computer modellers using scenarios a Trojan horses to drive a geoengineering agenda” (Knutti, 2018: 214). Scenarios should never offer what is ‘most likely to happen’ and they should caution against implied objectivity. The ambiguity of scenarios works in different ways. Will Steffen and colleagues’ recent invocation of a ‘hothouse earth’ (Steffen et al., 2018) has echoes of Act 3 in Flohn’s 1977 scenario. Yet while Steffen et al. describe this outcome as “an extreme scenario”, its narrative lacks the explicitly subjective and exploratory qualities offered by Flohn.

Scenarios are not coercive devices to corral subjects into a determined course of action; like any art form they are provocations to its audience to reflect and to see the world differently. The consequence of such reflection is beyond determining. “Scenarios help us explore options rather than [focus] narrowly on what is most likely to happen” (Knutti, 2018: 214).

References
Bray,D. and von Storch,H. (2009) ‘Prediction’ or ‘projection’? The nomenclature of climate science Science Communication 30(4), 534-543

Flohn,H. (1977) Climate and energy: a scenario to a 21st century problem Climatic Change 1, 5-20

Kellogg,W.W. (1978) Is mankind warming the Earth? Bulletin of the Atomic Scientists 34(2), 10-19

Kincer,J.B. (1933) Is our climate changing? A study of long-term temperature trends Monthly Weather Review 61, 251-259Knutti,R. (2018) A wider role for climate scenarios Nature Sustainability 1(5), 214-215

Mearns,L.O. and Hulme,M. (2001) Climate scenario development pp.739-768 in, Climate change 2001: the scientific basis (eds.) Houghton,J.T., Ding,Y., Griggs,D.J., Noguer,M., van der Linden,P.J., Dai,X., Maskell,K. and Johnson,C.A. (eds.) (2001), Cambridge University Press, Cambridge, UK, 944pp.National Defense University (1978) Climate change to the year 2000 National Defense University, Washington DC

Steffen,W. and co-authors (2018) Trajectories of the Earth System in the Anthropocene Proceedings of the National Academy of Science 115 (33) 8252-8259

Walsh,L. (2013) Scientists as prophets: a rhetorical genealogy Oxford University Press, New York, 264pp.

Wigley,T.M.L., Jones,P.D. and Kelly,P.M. (1980) Scenario for a warm, high CO2 world Nature, 283, 17-21

Williams,J. (1980) Anomalies in temperature and rainfall during warm Arctic seasons as a guide to the formulation of climate scenarios Climatic Change 2(3), 249-266

Mike Hulme, August 2018

To appear in ‘Culture and Climate Change: Scenarios‘, edited by Renate Tyszczuk and Joe Smith