Continuous ice core records from Antarctica & Greenland are great. They contain trapped pockets of air containing ancient CO2, & the ice can be geochemically analyzed to reconstruct temps. But they "only" go back 800,000 years. (efforts are underway to retrieve older ice cores)
Beyond that, you need different proxies. And that's where the most important organism in paleoclimate research comes in: foramenifera.
Something I think a lot of Silicon Valley-type space enthusiasts really don’t appreciate is that there is nothing we could do, nuclear war-wise or climate change-wise that would make the Earth more uninhabitable than Mars.
Like, even after an End-Permian-style climate catastrophe, or all-out nuclear war, there would still be oxygen and a magnetic field
I know this isn't some new insight, but I still hear people talking about Mars as an "insurance policy" and it's idiotic
Paleoclimatology, is the study of Earth's ancient climates. Taking the extreme long view it becomes unsettlingly apparent that Earth's climate is "an angry beast," as Columbia climate scientist Wally Broecker used to say, "And we are poking it with sticks" theatlantic.com/magazine/archi…
Within recorded history, climate changes have been linked with the faltering of the Hongshan & Yangshao cultures, the Akkadian Empire, the Bronze Age, the Roman Empire, the Ptolemaic Empire, Ancestral Puebloans, the Khmer Empire, Classic Maya... But recorded history is nothing.
This is our immediate climate context: In red is the span of time that covers recorded history. Stable. But at the bottom of the slope is the depths of last ice age, when sea level was +400 feet lower, an Antarctica's-worth of ice covered North America & icebergs listed off Miami
PART 2 Over huge area of Siberia, enough lava erupted in a few thousand years to cover the lower 48 United States A KILOMETER DEEP. But as mindblowing as eruptions were, they only covered part of Russia--so lava itself couldn't have killed almost everything on the planet.
It had to be the volcanic gases that came up out of the earth, especially CARBON DIOXIDE. Most ominously, these volcanoes had the misfortune of burning through one of the largest coal basins in the world, the Tunguska Basin.
By burning through this coal, the eruptions released something like 10,000 to 40,000 gigatons of carbon over thousands of years--a truly mind-boggling amount--and raised global temperatures an estimated 10-12 degrees C, acidified the oceans and starved them of oxygen
It seems like people are into MASS EXTINCTIONS these days and I wrote a book on them so here's a 2-Part ⚡️MEGATHREAD⚡️ on the worst things that have ever happened
EXTINCTION 1: The first major mass extinction was 445 million years ago, the End-Ordovician. It happened on a planet that as alien as any in science fiction.
N. America was mostly south of the equator and on its side, eastern New England had just rifted off of a supercontinent straddling the South Pole--and wouldn't crash into N. America for almost 100 million years. The midwest was a shallow ocean.