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Early Plants May Have Caused Massive Glaciation
sciencehabit writes with this excerpt from Science: "The first plants to colonize land didn't merely supply a dash of green to a drab landscape. They dramatically accelerated the natural breakdown of exposed rocks, according to a new study, drawing so much planet-warming carbon dioxide (CO2) from the atmosphere that they sent Earth's climate spiraling into a major ice age."
The Medea hypothesis is the mirror of the Gaia hypotheis. Gaia says life is in ecological balance and self-balancing.
.025% now. (Human activity has temporarily raised it to .04%.) When CO2 falls below .01% then plants cannot survive and neither animals. Just bacteria. This is predicted in few hundred million years. Life consumes CO2 and buries in hydrocarbons and limestone. Unless some imbalance like humans come along, the trend is to pretty much lock up carbon for good.
Part 1 of the Medea hypothesis says that life isnt necessarily in ecological balance and sometimes overruns resources nearly killing itself off. Several past mass extinctions, particularly the Permian may have been caused by this.
Part 2 says the ultimate end of life on Earth may be running out of CO2. CO2 has been falling from tens of percent on the early Earth to about one percent in the Phanerozoic to
Geo-engineering CO2 increase is straight forward. Burn limestone to release CO2. There is 100x more carbon in limestone than hydrocarbons.
The phrase "at the height of" means "the beginning of the end."
I'd be more interested in knowing what the deepest cores show, from the beginning of the last ice age. If they were similarly high, then your question is insightful.
If however the co2 peeked sometime within the ice age, and that was followed by the decline of the ice age we have an interesting coincidence, but still no causation.
The question then becomes where did this co2 come from. Did it come from the much reduced plant intake of co2 due to having significant areas of the planet in a deep freeze? Were the oceans chilled enough such that marine organisms ceased sequestering co2 into reefs?
Or was there some as yet undocumented sources of co2 that were ramping up production?
Or was the output of the sun reduced during this period and any suggestion about co2 merely mistaking the effect for the cause?
Sig Battery depleted. Reverting to safe mode.
From the article:
About 460 million years ago, the concentration of CO2 in the atmosphere ranged somewhere between 14 and 22 times the current level, and the average global temperature was about 5C higher than it is now.
From www.globalchange.gov:
Based on scenarios that do not assume explicit climate policies to reduce greenhouse gas emissions, global average temperature is projected to rise by 2 to 11.5F by the end of this century
Taking the data on trends in carbon dioxide measured at Mauna Loa, the 1960 concentration of CO2 was 320ppm. Taking an extreme value for annual increase in CO2 from their data of 2 ppm, doubling the CO2 concentration from the 1960 value wuold take 150 years, and increasing it to fourteen times the 1960 value -- a (low estimate) CO2 concentration at which the average global temperature was 5C higher -- would take almost 2000 years. But we're expected to believe the AGW doomcriers that, according to their tight, rigid, and scientifically-accurate climate models, we might see an increase of 6.4C by the end of the century with a tenth the amount of CO2 in the atmosphere?
And everyone running down the AGW skeptics wonders why we find it difficult to believe the reports 'proving' AGW and painting doomsday scenarios if we don't pour trillions of dollars into reducing CO2 emissions. Or even if we do pour trillions of dollars into reducing CO2 emissions, if you believe the reports that say we've already passed a tipping point.
And this is why the AGW deniers aren't taken seriously: you cherry-pick your facts. Besides the fact that the rest of the paragraph that you quoted explains why your assumptions are wrong, you also ignored that the rate of CO2 growth is increasingly linearly, which means that the actual CO2 output is increasing exponentially, thereby making your calculations way, way off.
An irrelevant observation since the original poster's argument is not dependent on people never dying from starvation, but rather that the species is not so vulnerable. It's also worth noting that famine now is due to societal and infrastructure problems in a few countries rather than some flaw of humanity to adapt to changing circumstances.
It's irrelevant to point out that when a human population is denied its primary food source, it doesn't just instantly adapt to a new food source and carry on but rather suffers and dies in large numbers? When refuting the idea that if humanity's primary food sources go away we can just switch to another one no problem? Yeah, I think it's very relevant.
Aren't societal and infrastructure problems in countries that used to be able to feed themselves just changes that they should be able to adapt to? Why are these changes beyond human adaptability, but anything climate-related is assumed not to be?
Because surely, climate change won't result in any social or infrastructure problems. Nope. If coastal cities flood and a significant percentage of the world's population has to move inland that's going to be easy-breezy. It's not like there's any important infrastructure on the coasts. If the location of arable land shifts from a nice convenient place like the Midwest to the Middle East, no problems. No wars, no upheaval, nothing to deal with but some minor climate problems.
Don't get me wrong -- humans are very adaptable. That's for sure. Our adaptability isn't "flawed". But it also isn't perfect. Being able to survive in a wider range of environments than most other species does not mean we can survive anywhere close to anything.
In particular in our modern world, most of us depend on the rest of civilization for our survival. In many ways, we are less adaptable today than in the past. Which is fine -- specialization and the pyramid of technology we depend on makes our lives better and supports a larger population of humans than in the days when our entire technology stack could be created in a day with access to rocks and sticks.
Doesn't sound to me like you do either. What's the "easy" event that kicks over modern civilization and drives humanity to extinction?
Ha! Please. Your city is about one to four weeks from the last delivery of food, fuel, electricity, or water from anarchy.
Think about everything it takes for you to get a sandwich on your table. Crops grown in the midwest are brought to your city by a truck where they're kept fresh in the grocery store with refrigeration. Oh but the crops need artificial fertilizers, made in a factory. That factory needs a huge swath of input chemicals, including petroleum. Which the truck also needs. One hurricane hitting one region where drilling platforms and refineries are located caused skyrocketing fuel prices and even shortages. If a bigger hurricane, or more than one, knocked out those same pieces of infrastructure for longer, then the shortage would have become severe. The truck might not show up. The factory might not be able to make the fertilizer for the next season's crops. Your grocery store is empty.
And that's just one of the more obvious branches in the system. If you really trace out what goes into everything you take for granted that enables your survival, you'll find there are a great many things where any one of them taken out for a significant period of time can bring the whole thing down. Is that, or any one thing, irrecoverable? No. But when we're talking about Global Climate Change, we will never be talking about any one thing. There will be many changes, many things that go wrong, many upheavals.
Believing we don't need to worry because humanity is just so awesome (I mean look at our technology!) is naive and foolish.
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