It’s 2020, and it’s impossible to know what new terrible thing is going to make Murder Hornets and squirrels with the bubonic plague look normal. Showing us that things could indeed be worse is a new paper in the Proceedings of the Royal Society A by Constantin W. Arnscheidt and Daniel H. Rothman. These two Massachusetts Institute of Technology (MIT) researchers have shown that we are just one massive volcanic ash cloud away from global glaciation.
To those of you with Yellowstone, Katla, and Naples all erupting on your 2020 Bingo Card, you really don’t want that to happen. Now, to be fair, any one supervolcano or massive eruption probably can do in the climate, but widespread eruptions or some kind of biologically induced cloud formation could reflect enough sunlight back to space to bring back a terrible ice age.
It turns out that a sudden drop in the amount of sunlight hitting the surface of the Earth can cause the ice caps to expand, which sets up a feedback loop such that as the ice expands, it reflects more sunlight, further dropping the amount of energy warming our world, and thus allowing the ice to further expand, reflecting more light, and eventually turning our planet into a giant ice ball that is called a Snowball Earth.
This kind of global glaciation isn’t permanent. When ice covers the landscape, vegetation dies back, algae get iced under, and carbon dioxide is able to build up in the atmosphere until the greenhouse effect causes the Earth to warm up enough that the snow retreats and forests and grasslands can return. This has already happened multiple times in Earth’s past, and according to this new research, this phenomenon may be common to otherwise habitable worlds orbiting other stars.
For those keeping score, this means that life can die both by fire and ice even on a planet in a star’s habitable zone. We see how runaway greenhouse effects can ruin environments like that of Venus. This is a permanent death worlds can’t return from. We now understand how the global ice ages in our own history may have occurred, and we see in our own existence and in the fossil record that life can and does rebound after ice ages. It just may be different life than was around before the ice age.
This teaches us two really important things. First off, finding a world in a star’s habitable zone does not make it habitable. It could either be a greenhouse baked death world like Venus or a snowball like our Earth has periodically been. Second, while Robert Frost thought death by fire was something he might desire, I’d like to state, there is no coming back from that less-traveled path. Ice is nice – pick the ice.
“Routes to global glaciation,” Constantin W. Arnscheidt and Daniel H. Rothman, 2020 July 29, Proceedings of the Royal Society A