There was significantly less sunlight, we are told, due to planet-forming detritus floating around (like a smoke-filled room, sort of):
Not much is known about what was happening on Earth at that time, but what little we do know suggests that there was some amount of liquid water present at or near the surface starting in the Hadean, and there is evidence that life itself began in the Archean (4.0–2.5 billion years ago). If modern Earth were suddenly to receive 25% less sunlight today, it would quickly freeze over, so how did early Earth manage to avoid it for 2 billion years?Kimberly M. S. Cartier, “The Young Earth Under the Cool Sun” at Eos (February 22, 2022)
The only thing current researchers are sure of is that they do not like the term “paradox.” That said, they do not have a clear answer, just a number of evidence-based speculations:
Beyond a boost in geophysical data, there is an almost unanimous call for better and faster 3D models of the interconnected Earth system: mantle and crust, sea ice and lower atmosphere, solar radiation and upper atmosphere. Each component of the system plays a key role in solving this early Earth puzzle. Arriving at a consensus solution will require a holistic and interdisciplinary approach that leverages the strengths of each field—paleoclimatology, geochronology, astronomy.
“Whenever there is a paradox or a problem of this type, people look for that one glorious solution which does it all,” Feulner mused. “But there’s probably no silver bullet. [The solution] is probably a mixture of many factors contributing to the warming…just a mix of more CO2, less clouds, you name it. It’s probably messier than many people think.”Kimberly M. S. Cartier, “The Young Earth Under the Cool Sun” at Eos (February 22, 2022)
So it’s still a paradox until the word itself gets Cancelled.
You may also wish to read: Did giant mountain ranges provide nutrients in early Earth’s history? According to the new thesis, the erosion of mountains provided nutrients that were hitherto unavailable, that helped life forms get started. Sounds like a rollout, actually.
Researchers: Poisonous cyanide may have been a harbinger of life 4 billion years ago Note the “may have” and “could have been.” That’s where a lot of origin of life studies are, really. Nothing wrong with that, of course, as long as it is not mistaken for “the findings of science.” It’s speculation, pure and simple. It would be a great hard sci-fi novel, maybe a flick. And fun for chemistry students!