No Climate Change Under The Faint Early Sun Analysis

In No Climate Change Under the Faint Early Sun, Rosing makes an argument about the climate during Earth's early life. Rosing's main focus and motivation of the paper is to explain why the Earth was warmer than expected. He does this by having different scenarios and for some of them, finding a counterargument that contradicts them. In the paper, he contradicts that there was an extremely high level of carbon dioxide and that the greenhouse gases alone were not sufficient to compensate for the faint early sun. Instead Rosing turns to the idea that in Earth's early history, the low albedo was what kept the planet warm along with little help of the greenhouse gases. The paper's findings have given a proper explanation as to why the Earth was
The greenhouse gases alone didn't compensate for the faint early sun because of the band saturation, which demonstrates that adding more and more carbon dioxide will eventually be weak for it to warm up the planet. Since the sun's luminosity was not as strong as it is now, Rosing discovered that the combination of low albedo, droplets in the clouds and greenhouse gases kept the Earth warm. The low albedo came from the proposition that the ratio of continents, compared to the ocean, was so much smaller than it is now. In figure 2, (graph a) the continent fraction of the Earth's surface as a function of time shows that the continents at first were a small ratio compared to the ocean. It also reveals that as time progressed, the continents began to grow and so did the albedo. Graph b shows the surface albedo of the earth as a function of time, which verifies that the albedo indeed does increase as the continent fraction also begins to increase. Rosing also concluded that droplets in the clouds would have had a larger size. He comes to this reasoning by figuring out that the Earth would have had so much more less cloud condensation nuclei (CCN) than present day. The
Rosing explains that one obstacle they faced was that they did not know exactly when the continents started to emerge or at what rate they emerged. Using the continental growth models, they know that between 3.5 and 1.5 billion years ago the continents had its fastest growth rate. The time interval is huge because they cannot pin point exactly when the continents began to have their fastest growing rate therefore causing an uncertainty in the data. Rosing only found a time interval as close as he could get to the actual fastest growing rate. In figure a, the fraction of continent as a function of time, uses present day area/volume relationship of the ratio of continent, which therefore may overestimate the continental area and hence overestimate the Earth's albedo. Since there are uncertainties in the continental fraction and Earth's albedo during this time, there was also uncertainties in the data about the surface