Final answer:
Without specific model output data correlating CO₂ levels to temperature changes in Fahrenheit by the year 2020, it's not possible to conclusively determine the temperature from the provided options.
Step-by-step explanation:
In Scenario One, where carbon dioxide emissions are kept constant at 9.8 gigatons, we would expect to see a specific temperature change. Although the exact temperature in Fahrenheit for the year 2020 is not explicitly detailed in the materials provided, we can infer from the provided information about temperature increases and associated CO₂ levels. For instance, for a CO₂ rise that stabilizes at today's levels, we expect a temperature increase of 3.4°C over pre-industrial levels by 2100. If the global temperature increase is already about 1.0°C above pre-industrial levels, and we're about 55% through the warming process, then the temperature in 2020 would likely be slightly above the current increase, yet not as high as the ultimate 1.7°C increase that was expected in a stable scenario.
However, to give a specific answer in the Fahrenheit scale to the question at hand would require direct information from such a projection or data that explains the relationship between CO₂ levels, time, and temperature in Fahrenheit for the given scenario. This information is not present in the materials provided, and thus, the predicted temperature for 2020 in Fahrenheit cannot be conclusively given from the options a. 58.2, b. 58.4, c. 58.6, or d. 58.8 without additional context or a specific model output from the climatology data given. To remain factual, I cannot confirm which option is correct.