Faint Young Sun, Warm Dark Earth

Early Earth absorbed more sunlight — no extreme greenhouse needed to keep water wet.

Researcher unravels one of geology’s great mysteries.

The two news pieces discuss a single PreCambrian conundrum – the puzzle of liquid water on an Earth illuminated by a Sun at just 70-75% of today’s luminosity. The solution was previously thought to be lots and lots of carbon dioxide, but new chemical evidence has nixed that idea. Now the solution might be that Earth was, on average, darker because it had fewer and less reflective clouds than it presently does. The single study that spawned the two news-bites suggests different cloud chemistry – but what if the triggering factor for cloud formation was reduced?

Christoffer Karoff at the University of Birmingham suggests that Galactic Cosmic Rays were reduced to the much higher frequency and severity of Coronal Mass Ejections by the early Sun…

A Solution to the Faint Young Sun

…a scenario ably discussed at TechReview’s arXiv blog. As odd as it seems, but that “faint young sun” was incredibly violent and active, producing up to 1000 times more extreme UV and solar wind than it does in its warmer, but more sedate middle-age.

Of course the two effects could have operated in parallel and amplified each other. Coupled with possibly higher levels of nitrogen, thus a more effective CO2 greenhouse, and the conundrum isn’t so puzzling anymore.