The Climate Change Skeptic’s Argument: Natural Solar Cycles or Human Activity?
The complexity of the climate system and the conceptual challenges associated with understanding climate change contribute to some of the skepticism of Americans who have been subjected to unintentionally misleading as well as occasional deliberately inaccurate reporting of climate change science for the past three decades.
One misconception often seen in the media is the belief that scientists are attributing all of the climate change to human factors. However, the computerized climate models used to understand the interactions that generate climate (General or Global Circulation Models—GCMs) have long included algorithms that represent solar forcing, as well as other natural environmental variables that play a role in our dynamic climate.
How accurate are these models and how are they used? Explore “Accuracy and Uncertainty in Climate Models.” Uncertainty exists about what the climate will “do” in the future due to the forcings and feedbacks between different parts of the Earth. Can models help in understanding more about these uncertainties?
In an early climate modeling experiment reported by Hansen et al. (1981), the scientists conducted several GCM experiments to evaluate how well the model was able to replicate historical climate data under different experimental scenarios.
Just like in a laboratory experiments you may be familiar with, computer modeling experiments are conducted using a “control” so that the analyst can determine the effect of the different variables in the experiment. In this famous experiment, the scientists were trying to understand the importance of several different variables on climate, including the amount of CO2 in the atmosphere, the role of volcanic aerosols (dust and gases from eruptions), and solar variability by comparing the computer model experiments (dark line) to the historical data (dashed line). In the Hansen graph you can see plots of the data from three model runs.
Reporting on computer modeling experiments, the experimental run that calculated the combined effect of atmospheric CO2 concentrations, volcanic aerosols, and solar variability had the greatest fidelity. Comparing the three graphs in the Hansen graph, you can see correspondence between the simulated temperature in the model run (dark line) and the historical temperature record (dashed line) under the scenario CO2 + volcanoes + sun.
The role of our variable Sun is mentioned frequently by climate change skeptics as the alternative argument to explain the Earth’s warming temperature. Many of your students, and perhaps you yourself, may have heard this argument:
Over the past few hundred years, there has been a steady increase in the numbers of sunspots, at the time when the Earth has been getting warmer. The data suggests solar activity is influencing the global climate causing the world to get warmer.
- BBC News Online (2004)
You have seen from the data activity in this lesson that this position is not supported by the scientific data. So why do these statements continue to be reported in the media?
Naomi Oreskes and Erik Conway, in their book Merchants of Doubt (2010), trace the history of research and reporting about global warming over the past four decades. They recognize that the media strives for balanced reporting, but note:
In an active scientific debate, there can be many sides. But once a scientific issue is closed, there is only one “side”. Imagine providing “balance” to the issue of whether the Earth orbits the Sun, whether continents move, or whether DNA carries genetic information. These matters were long ago settled in scientists’ minds. Nobody can publish an article in a scientific journal claiming that the Sun orbits the Earth, and for the same reason, you can’t publish an article in a peer-reviewed journal claiming there’s no global warming.
Oreskes and Conway conclude that news articles that gave equal time to the majority view among climate scientists, as well as to deniers of global warming, is a form of “informational bias” and that the ethic of balanced reporting has resulted in minority views getting more visibility and credence than they warrant.
Consider how you could effectively teach your students about the role of CO2 enrichment of the atmosphere by human activity as the best explanation of the data behind global climate change over time.
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