1980 · Monthly Weather Review
Trends in atmospheric transmission at three locations in the United States, 1940–1977
Hoyt, Turner, and Evans
What was measured. Transmission of sunlight at three U.S. stations over 37 years. Aerosol optical depth inferred from that record.
What it does to the budget. They concluded the trend was very small, perhaps nonexistent, and not statistically significant. Using a 6 percent anthropogenic share of aerosol, they got about a 0.02 percent loss of global insolation and “no more than a few hundredths of a degree.” Their sentence: mankind is having no perceptible influence on the global climate through anthropogenic aerosols, and such aerosols “have not been a serious climatic threat in the past nor will they be one in the immediate future.” That was a mainstream measurement paper. The aerosol budget was later rewritten. Particle surface area is also how stratospheric chlorine is supposed to become chemically active. The term was treated as settled, then replaced.
Aerosol optical-depth growth they reported
percent per year
From their conclusions, not a redraw of the station transmission curves, which were not released as a table. The three stations together were about 0.85 percent per year in urban optical depth. Scaled to the globe, they estimated about 0.05 percent per year, close to their lower limit of 0.06 percent per year, and about 1,400 years to double.