800 years ago the West was stricken with a mega-drought, like it is today. As a result, huge swathes of the Sand Hills of Nebraska weren't grass-covered hills and wetlands, like today, but were instead mobile, Sahara-style sand dunes--the largest in the Western Hemisphere
Around the same time, from Rocky Mountains to California, the record of charcoal in lake sediments indicates widespread forest fires. But "the magnitude of variation in climate & fire" was "still smaller than those projected to occur over the next century" pnas.org/content/109/9/…
This 13th century megadrought "is thought to have contributed to the depopulation of Mesa Verde and the Four Corners region by Ancestral Pueblo societies." digitalcommons.unl.edu/cgi/viewconten…
Megadroughts like the one 800 yrs ago show the natural variability of the climate in what has been an extremely stable Holocene. We're well on our way out of that comfortable little window though & into climate regimes that only have analogs millions of years ago in Earth history

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More from @PeterBrannen1

25 Feb
One (very important) topic I didn't get to address in this story is: how do we know what the temperature, or the co2 level in the atmosphere was millions of years ago? 1/x
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.
Read 24 tweets
21 Feb
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
Read 4 tweets
4 Feb
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 Image
Read 32 tweets
7 Jul 19
Things (I think) humanity can Survive v Not Survive

Not Survive:
Sufficiently large Large Igneous Province
Sufficiently large asteroid
Vacuum decay
Burn-it-ALL (12k GtC)

Survive but not very fun:
RCP 8.5
Nuclear war
Yellowstone-style eruption
Gamma-ray burst
Bad AI
Geomag storm
NB: I think "civilization" would collapse in every one of these scenarios with possible exceptions of bad AI and big geomagnetic storm
My reasons for "survive"
-RCP 8.5: Scattered, roving bands of hunter-gatherers living at high latitudes a few centuries from now seems like an adequate adaptation to Bad Climate Change
Read 12 tweets
14 Dec 18
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
Read 28 tweets
14 Dec 18
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.
Read 25 tweets

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