When our sun first got going, some 4.5 billion years ago, it wasn't the same blazing star we know today--its warmth and brightness grew gradually as more and more of its fuel ignited. So, for Earth's first two billion years, our planet was bathed in a light 25 percent dimmer than it receives today.
If the sun dropped back down to that magnitude today, our planet would plunge into an ice age dramatic enough to bury the continents in miles-thick ice sheets and freeze the oceans solid. But according to the geological evidence, ancient Earth was not frozen: It was covered in vast liquid oceans and dotted over with arcs of island chains that sprouted up from undersea volcanoes and then wore back down again in the rain.
Scientists have been working to resolve this troubling paradox for decades: how, they have asked, could a faint young sun have kept Earth out of an ice age for two billion years, when several ice ages have come and gone in more recent times, under a much brighter star?
The answer, they reasoned, must lie in the planet's early atmosphere--the air must have been packed with enough heat-trapping greenhouse gas to compensate for the lack of sunlight. But which greenhouse gas was it? Evidence from ancient soils suggested that carbon dioxide levels weren't high enough to do the job alone, and theories pointing to methane as ancient Earth's chief atmospheric insulator fell apart under close scientific scrutiny. (Water vapor--today's biggest greenhouse gas--was out from the beginning, because air needs to be warm to begin with to hold large amounts of the stuff).
Now, researchers at the University of Chicago have come up with a new theory: the greenhouse gases that provided Earth with extra warmth weren't CO2 or methane or any of the usual suspects--they were nitrogen and hydrogen. Though H2 and N2 don't normally soak up the sun's light, collisions between the molecules can energize them, prompting them to absorb infrared energy.
Based on computer simulations, the researchers found that, if the early atmosphere were composed of 10 percent hydrogen, the warming effect from those molecular collisions could have been enough to raise the planet's temperature by as much as 60 degrees fahrenheit--enough to keep liquid water falling on the young, dimly-lit planet during the first part of its life.
The picture is kind of a reverse of reality. The mountain ridges are clear of ice and everything else is covered with snow. I would snow and ice would cover all in a snow ball Earth, if a snow ball Earth hypothetically actually ever would happen.
Santa would have loved it.
@robot, if you pay attention where the snow is in the picture is where the deserts are, roughly speaking anyways, i think there would be more snow on the plains of North America but that's just a small tidbit...
as for the concept itself, i could actually understand that, i truly believe that nature itself has a feedback system that gives our earth's temperature a bit of an inertia when it comes to change.
to mars or bust!
Could earth itself have been warmer? Radioactive decay must have been greater at that time. There was at least one natural nuclear reactor ( in Gaboon). The earths crust could have been thinner.
Typically, mountaintops are cold and covered with snow and ice. For me, I imagine a snowball Earth being in a colder state and the mountaintops being even colder, more snow and ice covered.
I suppose you are entitled to your opinion, but I just cannot envision your point. Take care. ;)
Well, with the entire planet covered in ice being pulled down by gravity, the mountains wouldn't have ice/glaciers on them. Furthermore, with all water frozen, and 25% less heat radiation from Sol, not much would be evaporating, meaning not much snow would be falling on the mountaintops. Plausible?
What ifs, what ifs.
The easiest most believable solution to the paradox (and also fixed a number of issues between observation and theory). Is to drop the billions of years religious crap.
Things ain't that old, observation says so.
You can't fix it by a computer simulation that will always give the results you wanted it to.