Indeed, our journey through the annals of scientific progress brings us to 1956, a year that, though perhaps less heralded in popular discourse than other milestones, represents a quiet yet profound leap forward in our understanding of Earth’s intricate climate system. It was in this year that Ewing and Donn presented their feedback model for abrupt climate change, and Plass further refined his calculations regarding the significant effect of carbon dioxide on the planet’s radiation balance. These developments were not isolated incidents but were deeply embedded within a rapidly evolving scientific landscape, particularly benefiting from the burgeoning capabilities of early computing and a growing appreciation for systemic thinking.
Let us first consider the contribution of Ewing and Donn, who offered a feedback model for abrupt climate change in 1956. This was categorized as a “simple model”, yet its conceptual power lay in its recognition of feedback mechanisms within the climate system. In essence, a feedback model acknowledges that changes in one part of a system can either amplify (positive feedback) or diminish (negative feedback) initial shifts. For instance, the melting of ice due to warming can lead to further warming because less reflective ice means more sunlight is absorbed by the Earth’s surface – an “ice-albedo feedback”. The very notion that climate change could be abrupt and driven by such internal system dynamics was a significant conceptual advance at the time. Later scientific inquiry would indeed reveal drastic temperature oscillations over short periods, as seen in Greenland ice cores in 1982, and the possibility of great climate changes occurring within a single decade by 1993. This early modeling effort by Ewing and Donn thus foreshadowed a critical area of modern climate science, contributing to what would eventually be recognized as a “paradigm shift” in the scientific community’s understanding of abrupt climate change by 2001.
Concurrently, Gilbert Plass continued his groundbreaking work on the infrared absorption of atmospheric gases. In 1956, Plass calculated that the addition of carbon dioxide to the atmosphere would have a “significant effect on the radiation balance”. This built upon his earlier, equally pivotal work in 1955, where, utilizing “early computers,” he had already concluded that a doubling of CO2 concentrations could lead to a temperature increase of 3-4°C. This deeper dive into the radiation balance was crucial because it provided more detailed physical underpinnings for the “greenhouse effect,” a concept first articulated by Joseph Fourier in 1824 and further demonstrated by John Tyndall in 1861, who showed that water vapor and other gases create this effect. Svante Arrhenius, in 1896, had already calculated that industrial coal burning would enhance this effect, with his estimates of a few degrees Celsius for doubled CO2 being remarkably consistent with modern climate models. Knut Angstrom’s discovery in 1900, that even tiny concentrations of CO2 strongly absorb parts of the infrared spectrum, further underscored this. Plass’s work, enhanced by “a new generation of equipment including early computers” and advances in radiative transfer theory and measurements spurred by military applications of radar and infrared radiation, provided a more rigorous quantitative basis for these earlier insights.
The ability to perform such complex calculations on emerging digital computers was truly transformative. The 1950s were a period when electronic computers, still in their nascent stages, began to “affect many fields including the calculation of radiation transfer in the atmosphere, and [made] it possible to model weather processes”. This era saw the development of new statistical tools and an increased focus on empirical work, fueled by “enormous advances in computer power”. The very idea of simulating complex natural systems on machines, as seen with Phillips’s “convincing computer model of the global atmosphere” in 1955, was still relatively new. These early computational successes fostered a growing confidence in the potential of machines to unlock previously intractable scientific problems.
The insights from Plass and Ewing and Donn laid fundamental groundwork for later discoveries. Roger Revelle and Hans Suess, just a year later in 1957, showed that the oceans would not absorb all the additional CO2, famously describing human activity as “carrying out a large scale geophysical experiment”. This was swiftly followed by Charles David Keeling’s systematic measurements of atmospheric CO2 starting in 1958, which within four years provided the “first unequivocal proof that CO2 concentrations are rising”. Indeed, subsequent climate models, building on these foundational efforts, would later provide robust evidence that observed warming could only be explained by human influence, not natural causes. Even ExxonMobil’s own scientists, in the 1980s, produced climate forecasts that were “very accurate,” demonstrating a “very good handle” on future climate change, which underscores the validity of the scientific principles established by pioneers like Plass.
In sum, 1956 was a year where theoretical understanding of Earth’s climate, coupled with emerging computational power, moved from generalized concepts to more concrete, quantifiable models. The contributions of Ewing and Donn, and Plass, were vital steps in solidifying the scientific understanding that human activities could indeed lead to significant and potentially abrupt changes in the global climate, setting the stage for the comprehensive climate science that would follow in subsequent decades.