How Life on Our Planet Made It Through Snowball Earth

@Bruce1253, "This set up the conditions, along with the removal of the dinosaurs, which led to the explosion of mammal development and humans. If you want evidence of the Divine, this is it." I guess God prefers mammals to the dinosaurs? You kinda have to wonder why he made them, then, if he was just going to kill them off later. Whenever anyone claims that Earth is just so perfect for life, I'm reminded of the allegory of the puddle who exclaims "oh, how amazing it is that this hole fits me so well! It must have been made for me!"

@Benjamin Winchester Perhaps dinosaurs had become an evolutionary dead end? They had been the dominate species for 160 million years and seemed to be doing 'more of the same, but bigger!' Time to start over. When you look at the series of evolutions, then extinctions and rebirths, it seems to indicate to me that life itself is the goal, with a bias towards more complexity and greater capacity. We view ourselves as the crowning achievement of evolution, that may be so far. But we are not the end point. If we wipe ourselves out, Earth/Gaia/The Force/God seems perfectly willing to start over again. A million years or so to a planet that is 4.5 billion years old is really no big deal.

@Bruce1253 I see no evidence of "the Divine". Why do folks still need this crutch? Can't things just be as they are? Wouldn't that be divine?

@Mark Dobias Which makes what difference to whom? You wait long enough and you'll see it sink into the dying sun. The ultimate in cleansing. And also won't make any difference to humankind.

@Aurora The Earth isn't conscious. Nor can it magically break the laws of physics at a whim.

@David Weintraub - I disagree. The Earth has it's own way of living. It responds to things that are happening everyday. We've had ice ages before. Why did they occur? Nobody knows for certain, so my thoughts can't be summarily discarded. Not to mention, the Earth itself breaks the law of physics by moving constantly.

@Penn Towers - it might help to think of scientific progress as more of watching CSPAN rather than watching a local news program. The plot doesn't resolve between the commercial break and the weather, it takes as long as it takes, with bits of information throughout, and sorting and consideration of the new information happening after it comes by on the screen. So when the NYTimes is reporting on a new paper that was just published December 2, it's dealing with a bit of new research that's been written up, reviewed, revised, published - and NOW is when other researchers get to mull it over and decide if it's a new brick for the wall, or if it isn't. Tough for modern commercial journalism, but useful. Knowledge and understanding and what can be done with it is exciting. The process of accumulating the stuff is less so (for the watcher, at least), but is the basis for what we eventually understand about something tricky, like what the climate was like hundreds of millions of years ago, and the implications of it.

@bill Life will go on regardless of humans. That does not make it any less of a tragedy that we've doomed biodiversity as long as we exist, and it will take millions of years to recover after we're gone.

@richard cheverton -- Take a deep breath, richard, rapid changes in greenhouse gas concentrations dramatically changed things before it was us rapidly increasing the concentrations. So we're in for a very bumpy ride. The people who are being real about it don't like that we're creating a rapidly-changing climate, moving out of the range that was "normal" when we did things like develop agriculture, civilization, and plop great big cities along every coast and river. But tell me, things made of wood and other common household materials burn, because they're made of stuff that's always burned, right? So if, for example, someone's house caught fire from a gas line break, or downed power lines, would you stand outside and tell the fleeing residents to take a deep breath and just relax, because things have burned before? The scientists you believe about this snowball earth are people who will tell you that the initial cooling, the overall freezing and the eventual thaws were all happening largely because of changes in the concentration of greenhouse gases. We're rapidly increasing concentrations of greenhouse gas. Explain how nature is supposed to ignore that just this once.

@richard cheverton Our global population grew from a few million to several billion, during the 10,000 years of relatively stable global temperatures since the end of the last "ice age". Our cities are built, our staple crops produced, in areas that have had the 'right' climate for millennia. Now mean global surface temperature is rising faster than at any time in at least 2000 years. Droughts are longer and dryer, wildfires bigger and hotter, tropical cyclones stronger, and rising sea levels are flooding coastal cities (public.wmo.int/en/media/press-release/global-climate-2015-2019-climate-change-accelerates). The ensuing human cost is already immense, in money and tragedy, and will mount as long as we keep pumping fossil carbon into the atmosphere. You can be sure we've only begun to pay. That's all "settled" science, Mr. Cheverton, even if not proven to your satisfaction. Do you think you are somehow exempt from the laws of physics? Believe it or not, everyone connected to the global economy, including you, is responsible for the cost of climate change due to anthropogenic global warming, in proportion to the amount of fossil carbon they personally burn or cause to be burned. Just as everyone now living or yet to live will have to pay for it, one way or another: if not in the price of energy, then in taxes for disaster relief and border defense; or with their own homes, livelihoods and lives. What makes you think only 'Greens' care? Do you call yourself a 'Brown'?

@richard cheverton At the time the events discussed here occurred the human population of the planet was 0. You're right that dramatic, relatively rapd changes in the earth's climate have occurred - just none in the presence of human 'civilization'. But, what the heck, there are far too many people anyway. I just regret that I won't be around for the aftermath when I can finally enjoy Yosemite or Mt. Whitney in peace and solitude.

Why is it odd? We are here. What is odd is that despite the odds of life evolving here, we insist on mucking up our planet

@Ambrose Who worked out those odds? There's organic matter all over the universe. There's more planets in the universe than we can fathom. Even having observed the tiniest fraction of them, humans have located other planets in the zone we know to support life similar to Earth. What makes you think it's so unlikely another one exists?

@Saul RP I hike the Rockies with an artist who decided he wanted to paint a glacier that lies beyond Helen Lake. He wanted to update a picture that he had taken 5 years earlier. We hiked beyond Helen Lake and came upon a most unusual landscape. My artist friend looked and looked for the glacier but we found none. He thought that perhaps he had been mistaken about the location. He wasn’t. It turned out that the very unusual landscape was the dead carcass of the glacier. I was stunned as I had never thought that I would see what a dead glacier would look like in my lifetime. Is the physical world like the stock market? I can only assume you that you move from house to car to building to car and so on.

@Saul RP - if you live another 200 years then you'd be convinced? Why not go like Mel Brooks and shoot for 2,000? Or how about a decade of careful measurements recently that validate science done about 150 years ago? John Tyndall measured the ability of the different greenhouse gases to trap and re-radiate infrared (IR) in the 1860s in laboratory experiments. The IR is heat radiating from the surface towards space, which is how Earth (or any object orbiting the sun) dumps the excess heat, so sunlight doesn't melt the place. Each greenhouse gas traps and re-emits in specific wavelengths of the IR spectrum. Now the same effect has been measured, with observed changes in greenhouse concentration tracked right along the temperature changes at sites in Alaska and Oklahoma over the course of two ten-year experiments. Our Department of Energy's Lawrence Berkeley National Lab ran the experiments for CO2 and methane. Here's a writeup of each. Note that the methane-linked radiation didn't increase during the years in the experiment when methane wasn't increasing. https://newscenter.lbl.gov/2015/02/25/co2-greenhouse-effect-increase/ https://newscenter.lbl.gov/2018/04/02/methane-greenhouse-effect/ By the way, it's been 200 years since Joseph Fourier finished his second paper that showed the Earth was warmer than it should be at our distance from the sun, and he proposed that there was something in our atmosphere that was slowing the escape of heat.

@Saul RP Are you under a delusion that you are going to be around to reflect on 200 years of evidence? That is some pretty amazing denial right there.

@mountainone Single-cell stromatolites and oncolites and phytoplankton are suggested from a fairly quick check of https://en.wikipedia.org/wiki/Snowball_Earth#Survival_of_life_through_frozen_periods. Good question.

@Bob -- The sun was somewhat dimmer back then, but different researchers had different suggestions about the actual cause. The hypothesis from the Paul Hoffman paper linked at the end of this article is that the amount of CO2 in the atmosphere dropped below critical levels when the supercontinent Rodinia split into smaller masses with a great deal more shallow coasts, and that the increase in coastal life increased rapidly, (think shallow, swampy waters) consuming so much of the available CO2 that the lessened greenhouse effect allowed ice to spread to the equator. They also note that during the millions of years of ice cover, CO2 from volcanoes accumulated to extremely high concentrations, eventually warming ice near the equator enough to expose the surface. Once some dark ocean and land was exposed, sunlight added some warming and the overall result was a very rapid (geologically) collapse of the ice and then a swing into extremely warm conditions. It's one of the extreme lessons from the past about climate reaching tipping points. When that happens, often the result has been overshoot in the opposite direction until things eventually stabilize again at some new point.

@b fagan So are you saying ice melting allows for more CO2 sequestration in liquid water? Interesting.

@HS - I wasn't saying that, no, but read Hoffman's paper because he goes into a lot of detail about carbonates and isotopic shifts and carbon chemistry in the oceans while they were essentially unable to exchange gases with the atmosphere. According to it, the CO2 buildup during the millions of years iced over was staggeringly high before it plus sunlight finally began overcoming albedo and got the melting underway. Once the melt swung to hothouse, rain started rapid weathering (geologically speaking) and resumption of surface biology started reducing CO2 back down. Worthwhile paper.

@CR Uhh... no, CR. Fish do not convert H2O to hydrogen. Free Oxygen dissolves into the water from the surface and from underwater photosynthesis... and apparently also from the air bubbles in snow and ice.

@CR Except the oxygen is locked up in the water molecule, so it's not available for undersea organisms to breath.

@CR Dissolved oxygen.