By David Emory Stooksbury
The most important thing to know about the terms “global warming” and “climate change” is that among atmospheric scientists, these two terms refer to the same phenomenon. In this use of the terms, the reference is to atmospheric changes over the past century or so due to introduction of additional carbon-dioxide and other compounds to the atmosphere. The climate has changed over time on the decadal to thousands of years scale. But the common use of the term “climate change” refers to recent changes in the climate.
In the late 1960s, the first generation of computer models of the climate were developed. These models used basic physics and mathematics to model the behavior of the earth’s atmospheric temperature. Because of the limited computing power available in the late 1960s, these early models were relatively simple.
These early models were able to calculate atmospheric temperature changes as the amount of carbon-dioxide in the atmosphere changed. These early models indicated that an increase in carbon-dioxide would lead to a warming of the atmosphere. Since these early models indicated global temperature changes, the term “global warming” was commonly used. While simple, these early models have done a good job of modeling the rise in global temperature since the late 1960s.
In the 1960s, atmospheric scientists knew that the earth acts as a system with the atmosphere, oceans, ice, land, vegetation and other components interacting with each other. It was known that changing any of these components would change ocean currents, temperature patterns, and importantly, precipitation patterns. Changing precipitation patterns would change agricultural patterns which could lead to food shortages and famine. Thus, it is better to think of the “earth system” rather than just the individual components. However, the early computer models did not have the computing power to model these interactions.
The best know atmosphere-ocean interaction in the southeastern United States is the El Niño – Southern Oscillation (ENSO) climate pattern. Atmospheric pressure pattern changes cause changes in the sea surface temperatures in the equatorial Pacific Ocean which leads to different cool season climate patterns across the southeast. Typically, and El Niño climate pattern gives Georgia a cool, wet winters while the La Niña pattern typically gives Georgia warm, dry winters. There are other atmosphere-ocean interactions that also impact Georgia and can modify the typical El Niño or La Niña patterns.
As the computing power increased through the 1970s, ‘80s, and ‘90s, more realistic and thus complex features of the atmosphere, such as clouds of multiple types and layers, were added to the climate computer models. Additionally, other realistic aspects of the earth system were added such more realistic ocean circulation patterns, ice, and vegetation. Importantly, the models allowed interactions between the various components of the land-ocean-atmosphere system.
By the early 2000s, climate models had developed into earth systems models. While these models could not give detailed local predictions, they could predict regional pattern changes in temperature and precipitation. With these much more complex models, earth systems scientists (atmospheric scientists, oceanographers, etc.) were able to run scenarios showing how changes in carbon-dioxide (and other gases such as methane) would not only change the atmospheric temperature but also how melting of ice could change ocean currents which would change regional temperature and precipitation patterns. Over the past 20 years, the climate (or better the earth systems) models have continued to improve in details and their ability to give more localized predictions.
Since the late 1960s, computer climate models had gone from very simple models that model changes in temperature to very complex models that model changes not only in temperature, but changes in sea ice coverage, in ocean currents, in precipitation patterns, in vegetation patterns, and more. The models have gone from modeling “global warming” to modeling “climate change.”
In 2001, the George W. Bush administration came into office. The Bush administration did some polling and found that the public found the term “climate change” was less scary than the term “global warming.” Thus, the Bush administration started using the term “climate change.” This meant that federal granting agencies also started using the term climate change. Climatologist and other earth system scientists had no problem with the term since “climate change” is a better descriptor than “global warming.”
Thus, around the turn of the century, better computer models of the earth system and decisions from a Republican lead administration lead to the term “climate change” being used more commonly than the term “global warming.” That is how we got from “global warming” to “climate change.”
David Emory Stooksbury is on the engineering and atmospheric sciences faculties at the University of Georgia. He is chair of the Commission on Environmental Stewardship for the Episcopal Dioceses of Atlanta. While a student at UGA, he majored in plant genetics (B.S.A.), physics and astronomy (B.S.P.A.) and agronomy (M.S.). He completed additional graduate work in applied statistics (M.A.S. Penn State) and environmental sciences (Ph.D. Virginia).