When we see the increase in global temperatures, there is always that conspicuous absence of warming from 1940s – 1970s. Scientists have since discovered that there was a decline of sunlight reaching the earth during this period; they called it “Global Dimming”. Since there is no direct correlation with CO2 during this period, some climate deniers use this data to refute the impact of CO2 on the global temperature.
However, many factors affect warming, including changes in incoming solar radiation and the reflective properties of sulfate aerosols that are released with the burning of fossil fuels. Only when combining all these factors together can we account for the rise in global temperature across all the different decades – and even the lack of warming in the mid-20th century. This movie provides a detailed explanation as to how the release of sulfate aerosols led to reduced incoming solar radiation that ironically kept the globe from warming. It wasn’t until the clean air act in 1970 that global warming resumed. Even today, it is not clear how much the current pollutant haze may be offsetting the total warming that would ensue in the absence of air pollution. Hence, we need to tackle both the release of CO2 resulting in global warming and the pollutant emissions – both factors that result from the burning of fossil fuels.
Watch the movie “Global Dimming” and read the following arguments at skeptical science.com as to why there was no mid-20th Century warming. https://www.skepticalscience.com/global-cooling-mid-20th-century-advanced.htmLinks to an external site.
Combine what you learn from this movie with the arguments to create a Personal Movie Discussion Board Essay/Blog for others to read. Use separate paragraphs for each item and keep your responses organized. As part of your essay/blog, include the following:
- Describe four different data sets from the movie that led scientists to the discovery of global dimming, and explain how the Clean Air Act helped to eliminate this dimming.
- Explain how the 3 day period after 9/11 and the related airplane contrails were a factor in the discovery of global dimming. Also describe how they determined the temperature rise during this 3 day period?
- Explain how the global radiation budget is affected by sulfate aerosols compared to CO2. In your response describe how CO2 affects outgoing infrared radiation, describe how sulfate aerosols affect the incoming solar radiation, and explain the process of what happens when we reduce pollution emissions and airplane contrails.
- Discuss the three most interesting things that struck you the most while watching the film. Explore your thoughts in depth on these three things. (100-200 words total minimum)