A Conversation With Steve Running on Teaching Climate Change
by John Roach
As lead author on our new interactive chapter on Climate Change, I spent much of the past year researching climate science and how a changing climate is likely to impact—indeed, already has impacted—the ecology of our planet. One of the privileges of this work was the excuse to talk with a number of experts in the field.
This fall I sat down with Steve Running, who was part of the Nobel-prize winning board of the Intergovernmental Panel on Climate Change (IPCC), and who happens to live Missoula, MT, my own home city. I showed him our completed interactive chapter on Climate Change and then we discussed some of the common issues that Steve encounters as he talks with lay audiences about climate change. With his wide experience, I thought his insights were valuable and with his permission am sharing some of the themes he emphasizes, especially regarding climate modeling.
Acceptance of Warming vs. Acknowledgement of Human Impact
Over the past few years, Steve has noticed that an increasing proportion of people have become convinced Earth’s climate is changing. Particularly in more northern regions like Montana, where winters have become shorter and milder, the evidence of a warming climate and its impact on places like Glacier National Park has become increasingly difficult to dismiss and the general public is increasingly willing to acknowledge that “Yes, it is getting warmer”.
Nevertheless, many of these same people remain reluctant to accept that observed changes are human caused, arguing that the observed warming is due solely to natural variation. This is where the role of climate models comes in, and Steve attempts to counter the skepticism with three observations about climate models.
Attribution Models Show the Role of Anthropogenic Forcing
The attribution studies of Peter Stott and his colleagues have shown that models could only reproduce the observed 20th century global mean temperature changes if anthropogenic forcings were included. This work was most notably reported in a 2001 paper and later updated in two papers published in June and July of 2006, both of which are freely available on line. These studies provided the foundation for one of the more famous figures in the IPCC report (right), which shows that Earth would be much cooler than it is today were it not for the forcings of greenhouse gasses. In short, we cannot explain the observed warming without CO2.
Models are Based on Well Established Science
Many people, even some scientists, have an innate aversion to models. They simply do not trust them. So a second thing Steve emphasizes is that much of the science behind these models is extremely well established. He begins by noting that the greenhouse effect was first described over a century ago by a Swedish scientist named Svante Arrhenius, a Nobel Prize winner in Chemistry (1903). In work unrelated to his Nobel prize, Arrhenius wanted to explain the ice ages. This pursuit led him to realize the how changes in the concentration of carbonic acid (CO2) in the atmosphere could affect climate. In a paper published in 1896, Arrhenius postulated that changes in atmospheric CO2 could substantially alter the surface temperature of the Earth through a process called the greenhouse effect. About a decade later in his book, Worlds in the Making, he suggested that changes in atmospheric CO2 concentrations resulting from fossil fuel burning would not only prevent the next ice age, but would create a warmer Earth.
The broader scientific community was relatively slow to accept this theory and many of the details, including the climate sensitivity, have since been refined. Nevertheless, as Steve emphasizes, the basic thrust of the theory—that energy radiated from Earth's surface is absorbed by CO2 in the atmosphere before it can escape into space—was worked out over a century ago. When climatologists model the effects of CO2 on Earth's climate, they are relying on scientific principles that have been rigorously scrutinized for 100 years.
Orbital Variation is Well Understood
Orbital variations are one of the most important drivers of long-term climate variations, and again Steve emphasizes that cycles have been known since World War I. While he was imprisoned by the Austro-Hungarian army in Budapest, Milutin Milankovich, a Serbian geophysicist and civil engineer, began working out equations describing how solar isolation at Earth's surface varied with changes in eccentricity, obliquity (axial tilt), and precession. In 1920 Milankovich estimated how Earth's climate varied over the last 600,000 years. James Hays and colleagues used deep-sea sediment cores several decades later to produce a 450,000 year record of Earth's temperate change that demonstrated Milankovich's theory was largely correct. Just as the greenhouse effect has been scrutinized for nearly 100 years, so too has the way in which models incorporate orbital variations effect on climate.
Bottom Line: Models Synthesize Understanding of Complex Climate Science
The sum of all these arguments is that the models we rely on are not so much operating at the edge of our understanding as allowing us to explore the consequences of what we already know. Certainly, Global Climate Models (GCMs) are complex, using millions of lines of code to synthesize scientists’ current understanding of the climate system. The result is a complex systems modeling triumph! We now have models that present a balanced, coherent representation of Earth’s climate that simply was not possible a decade ago. Of course given their complexity, many of these models will have to be tweaked as our understanding improves. Nevertheless, it is extremely unlikely that future discoveries will undermine the importance of the model’s critical climatic drivers—drivers like greenhouse gasses and orbital variations.
Check Out Real Climate
While Steve was happy to discuss the themes from his own talks, he also strongly recommended (and I strongly concur) that educators visit the Real Climate website for more information on common misconceptions around climate change. Real Climate is run by climate scientists working in the field and seeks to help both the general public and journalists understand climate science. It is a truly superb resource.