Hot Earth Dreams
The Trap of Binary Logic
We apparently can't live in this enormous biosphere that we evolved in, this incredible planet that provides us with notionally free air, water, gravity, and meteor and radiation shielding, therefore our only hope is to pack ourselves into cans where all elements have to be totally recycled, where we hope our radiation and meteor shields are good enough, and where we're spun up to provide a centrifugal simulacrum of gravity, because, of course, we can more easily live packed in a can for 1,000 years traveling to Alpha Centauri B than we can for 1,000 years on this planet. Once we arrive at Our New Home, either we wil colonize a totally alien biosphere after 1,000 years of living in a tightly confined, very simple ecosystem, or we'll terraform some planet or other to be just like the Earth we couldn't live on before, only simpler. The alternative is that we'll all go extinct, because we "obviously" can't live here.
Yes, that was very sarcastic, but it's incredibly easy to fall into these kinds of false dichotomies when we speculate about the future: Progress or extinction. People or the environment. Civilization or nature. Singularity or apocalypse.
As the wildlands get broken into smaller and smaller fragments, as the critical connections between them become more tenuous, they become more fragile. Our conservation plans, with their connectivity patterns, richness studies, and core habitats surrounded by development, now these all have to contend with a climate that's changing all the habitat parameters. Will the migration corridors work, or will they break?
Apocalypse or Singularity or ???
The most fragile thing is our global civilization. Our species is less fragile than civilization, the biosphere is less fragile than our species, and the planet is less fragile than the biosphere. While many people are justifiably horrified by how much destruction we can cause at present, the best we can now do is to destroy civilization, or possibly our species if we go for something extra-special, super-duper, inhumanly stupid.
The Fart That Broke Civilization
This is our civilization's most enduring contribution to the future of life on Earth: 1,000 to 1,400 gigatonnes of carbon (henceforth abbreviated GtC) breaking into the wind over the next 100 to 1,000 years. If you remember your unit prefixes, 1 tera is 1,000 gigas, so we're going to emit 1 to 1.4 teratonnes of carbon.
Let's call it the terafart. [...] Unlike a far, [...] the remnants of our outgasses carbon will be airborne for up to 400,000 years.
The ocean will take up about half the carbon in 1,000 to 1,500 years, becoming acid enough to kill off coral reefs. Carbonate reactions will then take up to 40,000 years to take our about half of the carbon that's left, dissolving some really lovely islands and reefs. It will take up to 400,000 years for non-carbonate rocks to take the last of our fart out of the atmosphere.
To begin with, the terafart will most likely raise the global average temperature about 3-5°C (5-9°F) by 2100, a degree or three above the 2°C (3.5°F) that experts and politicians have compromised on as our safe upper limit for climate change.
Hot air can, of course, make deserts hotter and lead to longer and deeper droughts. But hot air can also absorb more water vapor than cold air can. This leads to greater humidity and long, hot, humid summers, and it can also lead to bigger storms, which occur when hot air cools enough that the water condenses out. Climate scientists currently believe there won't be more storms, but the storms that will occur will likely be bigger and slower moving. The combination of giant storms and deep droughts leads to things like massive flash floods and heavy erosion, since dry soil can't immediately absorb massive amounts of water.
[Footnote:] I know that the terafart won't "cause" each storm, because storms happen regardless. Similarly, steroids don't cause home runs in baseball, because there were home runs before the steroids era of the 1990s. Nonetheless, both the number and distance of the home runs during the steroids era are larger than seen before or (hopefully) since. In baseball terms, our terafart is juicing our weather, and unlike baseball, the CO2 will stay in our system for a long time after we stop injecting it.
High humidity at high temperature can kill humans and other large mammals. At a "wet bulb temperature" above about 35°C (95°F), humans stop being able to shed heat from our bodies by sweating, which means that, basically, we can't live under those conditions without air conditioning. I'll call this condition "black flag weather," as that is the color of the flag the US Marine Corps flies when wet bulb temperature gets around 32°C (90°F). Since, among large mammals, humans are actually among the best at getting rid of waste heat through sweating, black flag weather represents a death zone for us, our livestock, and many wild mammals. [...] Under the extreme climate change we're talking about here, there will be extended episodes of black flag weather over much of the western Sahara, much of the Middle East, Red Sea, and Persian Gulf, the Australian Outback, much of India, much of China, much of central Brazil, part of Spain, and much of the southeastern US. These places may be habitable seasonally in the cooler and drier months, but humans and other large mammals will have to migrate away from these zones during the hottest and most humid months. Black flag weather has the potential to displace more people than sea level rise, and unfortunately, it's much less studied.
History seems to show that changes in global average temperatures cause chaos. For example, about 1 to 2°C of cooling in the 17th Century, during the heart of the Little Ice Age, coincided with a period historians call the "General Crisis," which marked the chaotic era between the end of the Renaissance and the beginning of the Enlightenment in Europe (with civil wars, revolts, and famines across the continent), the fall of the Ming dynasty to the Qing dynasty in China, the Mughal Civil War in Asia Minor, the fall of the Kongo kingdom in West Africa, and colonial wars throughout the Americas.
If we're very lucky, East Antarctica won't melt. This rather large patch of Antarctica, which includes the South Pole, averages something like 4,800 m (15,700 feet) in elavation. Roughly 3,000 meters (years, 3 kilometers, or about 10,000 feet) of that is ice. East Antarctica has an annual temperature of -57°C (-70°F), and a high recorded temperature at the South Pole of -12.3°C (9.9°F). The East Antarctic ice sheet is currently increasing in size, not decreasing, due to increased snowfall, and even 16°C of terafart-added temperature increase will rarely bring it above freezing, especially since most of the increase is modeled to occur in the winter, when it is at its coldest.
This is definitely not the case for West Antarctica nor for Greenland, which is why these smaller ice sheets will melt into the ocean over the next century or three.
If all the glaciers melt, they will add about 70 meters (230 feet) to mean sea level, according to David Archer.
As the West Antarctic Ice Sheet disintegrates over the next 200-300 years or so, sea levels will rise by perhaps 4.8 meters (16 feet), with 3.3 meters (11 feet) of rise happening in spurts in the weeks and months after catastrophic ice sheet failures. [...] The already-melting Greenland ice sheet will contribute another 6 to 7 meters (20 to 23 feet) of sea level over the coming centuries. Finally, the East Antarctic ice sheet will contribute perhaps 55 meters (180 feet) to sea level rise if it melts. This is why I earnestly hope that East Antarctica stays frozen, although I assume it will not here.
Global civilization, even the primitive global civilization pioneered by the Romans and later by the Muslim Indian Ocean trade, depends on shipping between ports, and those ports are going to be repeatedly destroyed by rising sea levels for the next century.
Coasts rise and fall on their own due to continental drift, independent of what the ocean is doing. A few coasts are rising so fast they can stay ahead of of the ocean's thermal expansion. Some are subsiding so fast that they'll be over a meter underwater in a century even without sea level rise. These are natural processes. It means that some places, like the subsiding Tacloban City in the Philippines, which was destroyed by super-typhoon Haiyan, are even more at risk than the averages suggest.
Long Tails, Dragon Kings, and Black Swans
A dragon king even is one that is much bigger than predicted. [...] The king "is an 'outlier', with a wealth many times larger than predicted by the extrapolation of the Pareto distribution" of the rest of the population.
Because culture mutates so fast, it moderates the impacts of environment on DNA, thereby weakening environmental selective forces on our genes. Where our genes seem to be evolving is in areas related to culture, for instance dealing with processing culturally relevant chemicals such as lactose, gluten, sucrose, and capsaicin, or with surviving epidemic diseases.
In a weird way, milk is the food of freedom, because it gives nomadic herders a way to get away from oppressive regimes based on controlling farmers, and their herds allow them to flee beyond any pursuer's ability to forage for supplies. As one nomad poem has it: "Do not cultivate the vineyard; you'll be bound/ Do not cultivate grains; you'll be ground/ Pull the camel, herd the sheep/ A day will come, you'll be crowned".
Tissues in the human body have different energy requirements, and two of the most energy-intensive organ systems are our brains and our guts. Some scientists suggest that there's a trade-off between the two. The idea is that an organism can attain a limited amount of food resources, and this limits how many resources can go to brains or guts. Guts are a good thing, because they allow animals to digest difficult food but common sources, while brains are good because they allow animals to find rare but easy and valuable food sources. Given the energy constraints in food, the theorists believe that you can't have both large guts and large brains.
The 2,000 "calories" a day we're said to need is a gross underestimate. We've got to count the fuel we burn to cook our food and keep us warm, something no nutritionist does.
The Difficult Problems
Dunbar's number limits the size of non-hierarchical groups. [...] [Groupthink mental modeling] is a way to get around the limits of Dunbar's number. It's a model for how the members of a group behave in common situations, how you are supposed to behave as a member of a group. People don't have to have mental models of every individual in the group, if everyone follows the norms of the group they all belong to. All they have to do is know those norms and follow them.
Fish Traps and the Theory of Competitive Control
[David Kilcullen's] Theory of Competitive Control states, "In irregular conflicts, [...] the local armed actor that a given population perceives as best able to establish a predictable, consistent, wide-spectrum normative system of control is most likely to dominate that population and its residential area".
Greenhouse, Icehouse, PETM
According to geologists, the Earth has spent something like four-fifths of the last 400,000,000 years in greenhouse mode, rather than in icehouse mode. According to the modelers, this has to do quite a lot with the clumping of continents to limit coastline and coastal erosion, and to the absence of big, highly erodible young mountain ranges like the Himalayas. Icehouse Earths like our own tend to have smaller continents that are relatively spread out, with long, erodible coasts, and big, rapidly growing, quickly eroding mountain ranges that can weather carbon out of the air as the wind and rain chew them down.
The PETM [Paleocene-Eocene Thermal Maximum] ended the Paleocene epoch and started the Eocene epoch about 55,800,000 years ago, and lasted for 100,000 to 200,000 years. Yes, that interval should look hauntingly familiar, because it's about how long the coming Altithermal is likely to last unless we get 1,400 GtC airborne, in which case it will last 400,000.
The problem with the PETM as a model is that both the Paleocene that preceded it and the Eocene that succeeded it were greenhouse worlds
One could imagine a future Arctic city, perhaps at the mouth of the Mackenzie River, in a landscape that looked a bit like New York's Central Park, a bit like an old-timey town on the upper Mississippi River.
California gets most of its rain in the winter and is mostly dry in the summer, while the Carolinas at exactly the same latitude get rain in the summer. The major difference is ocean currents.
The Trap of Cyclic Thinking
It took over 1,000 years for iron to become an everyday item and not a precious metal. The interesting thing is that Europe went through a Dark Age at the end of the Bronze Age, right as knowledge of ironsmithing and everyday iron objects and weapons spread out of the Middle East. It's possible that that terrible early Dark Age was exacerbated by the spread of ironsmithing through the trading networks that had sustained the European Bronze Age. After all, if ironwork is everywhere, why trade Baltic amber and slave girls for bronze? And if your local god-kings no longer monopolize the tool and weapon trade, why not defy them instead of deifying them? [...] Ironsmithing is a ratchet technology, one of many. If and when our civilization collapses, I don't think we'll forget how to smelt or work iron and steel. We just won't build skyscrapers out of them, because we won't have the fuel to create such colossal ironworks.
Five Extinction Events
A rather heterodox theory [about the end of the Devonian] posits that the previously unprecedented great forests would have sucked CO2 out of the air, lowering temperatures and promoting glaciers (for which there is evidence). It's also possible tha the tree roots weathered rocks into soil faster, freeing nutrients that flowed into the ocean and thereby produced anoxic zones in the ocean (for which there is also evidence). Finally, there were no wood-rotting fungi or termites around at the time, so most of the carbon locked into the wood was buried as coal, rather than getting cycled back into the biosphere by something that produced the enzyne cellulase.
If the Deccan Traps and the Siberian Traps could cause or exacerbate mass extinctions, the CAMP [Central Atlantic Magmatic Province] is at least a candidate for dumping huge amounts of CO2 into the ocean and atmosphere and causing trouble.
Neither of the largest LIPs [Large Igneous Province] in Earth's history was associated with a big spike in extinctions, nor do they begin or end geologic periods. Both of them were apparently slower and mostly underwater, and that might have made all the difference.
Assuming we survive the mess we're making, everything that survives along with us will be well-adapted to surviving around, with, on, in, or in spite of us. This should not be a comforting thought.
Extinction, Fragmentation, and Invasion
Enemy release was used for centuries before it because a scientific theory. From 1492 on, Europeans transported crops around the world, finding new places where they could grow without the enemies that killed the crops in their native range. This is why the great colonial powers transferred rubber to Malaysia from Brazil, and chocolate, coffee, and sugar cane around the world. It's a great trick, so long as the enemies don't get transferred too.
Many invasive species are actually quite genetically uniform, for in expanding from a small immigrant population they have only a small proportion of the genetic diversity that the ancestral population has. This uniformity makes invaders quite vulnerable to any enemy that can kill them efficiently. As a result, invasive species can vanish as quickly as they explode, as happened with the prickly pears in Australia. Enemy release is a temporary phenomena, but a released invader can cause tremendous changes before its enemies find it.
Climate change affects invasibility. Remember that an invasion is an process of colonization and establishment beyond a former range? Climate change is going to change every habitat, and most species that survive the coming changes will have to colonize and establish beyond their present ranges. This means that they will have to transport themselves (or get transported) to suitable habitats, and establish new populations there, until they spread to another place.
Politics can wipe out agricultural diversity. When the US occupied Iraq in 2004, Paul Bremer, the head of the US Provisional Authority, signed Order 81, which prohibited Iraqi farmers from saving their own seed to sow in their fields, as they had done for over 7,000 years. Irqi agriculture was supposed to become dependent on patented crops brought from the US and controlled by US agribusiness. This strategy was originally devised by Henry Kissinger in the 1970s as a way of pacifying occupied areas through making them utterly dependent on US agribusiness. Since Order 81 went into effect, Iraq has gone from being a net exporter of food to being a net importer, as left the land to find jobs that pay enough to support their families.
What we do now will matter for the next 10,000,000 years.
Why 10,000,000 years? That's about how long the paleontologists believe it took the Earth to recover after four of the five mass extinctions. After a mass extinction, recovery is through evolution, not through a diverse mix of species migrating out of refugia. Mass extinctions are not the end of all species, but re-evolving the survivors to something like our current diversity will take something like 10,000,000 years. This is a very, very, very, very long time.
It's better to not lose that diversity in the first place.
The Trap of Collapse
China's story emphasizes transformation and continuity, while Europe's story emphasizes collapse and fragmentation. Is either story more useful for modern civilization?
Demand hardening can affect any peaking resource. If we use efficiency to support more people rather than banking surpluses, we harden demand to the point where a supply system has to work all the time, and any shortfall is an emergency.
Hohokam 2.0/Anasazi 2.0/Atlantis 2.0
Modern buildings are built with steel, copper, and all sorts of useful stuff. Given how hard it is to mine these elements even today, we can expet that modern and future skyscrapers will be broken up for srap, rather than repurposed, especially as disintegrating concrete makes them unsafe to occupy.
[Quoting Stewart Brand:] "Digital information lasts forever—or five years, whichever comes first"
[On the Seuss effect:] Because plants prefer ^12C and because ^14C decays, fossil fuels [...] are extraordinarily rich in ^12C. When we burn large amounts of fossil fuels as we are doing now, we enrich the air with ^12C, thereby diluting the amount of ^13C and ^14C in the air, thereby throwing off every study that uncritically uses the ratio of ^12C to these other two isotopes as a chronological marker. [...] Nuclear weapon explosions produce a lot of ^14C, and during that time, atmospheric ^14C concentrations roughly doubled. If people know about this, it forms a great label, for all plant material that grew during the atomic era has elevated levels of ^14C slowly decaying away, whether it's now wine, leather, or wood. Because it contains too much ^14C, carbon from this time appears anomalously young. For example, someone born in 1956 CE has the ^14C profile of a person born around 5300 CE. Still, all that ^14C was absorbed into the biosphere and deposited in sediments pretty quickly. Bomb carbon effect currently overrides the Seuss effect. [...] In between bomb carbon and the Seuss effect, the 20th and 21st Centuries will be largely invisible to simple carbon-14 dating. ^14C speciments from the first half of the 20th century and all the 21st Century will seem centuries too old, specimens from the last half of the 20th century will seem centuries too young.
Connections and Local Technology
Gill also notes that back in the 18th Century the relative cost ratios for transportation were 1 if by sea (the baseline), 4.4 if by river, or 22.6 if over land, so that land transport was considered under five percent as efficient as maritime transport. In the 17th Century, it took about as long to get from London to Edinburgh by carriage as it took to get from London to South Africa by sea.
Polar Seesaws, Black Flags, and Dead Zones
Remember all those stories of how cold the snow was when your grandparents were children, the ones you blew off as tall tales, irrelevant to your life? The weather experiences that formed you as a child will be even more irrelevant to your children and grandchildren, just as their experience will be irrelevant to their offspring, and so on for [the] next ten generations or so of their descendants. Assuming they have any.
After 200 years, with the Greenland and West Antarctic sheets melted, the sea will have invaded many of the major rivers, sometimes for hundreds of miles. Salt water may reach Manaus on the Amazon, Boma on the Congo, Cairo on the Nile, Baton Rouge on the Mississippi, Nanjing on the Yangtze, past the Tonle Sap in Cambodia on the Mekong, to Sacramento and Portland on the US west coast, and upstream past London to Bracknell on the Thomas. Low lying coasts will also be flooded, including most of the Netherlands, the Yangtze Delta well past Shanghai, the Nile Delta, the Mississippi Delta, over half of Bangladesh, eastern Iraq on the Persian Gulf, and much of southern Vietnam and Cambodia, including Ho Chi Minh City.
Some, like the paleontologist Peter Ward, believe that deep anoxic waters are perhaps too good a carbon trap, but only in the short term. Ward is a proponent of a theory that methane-producing bacteria built up in the waters of the late Permian ocean, and that a gigantic belch of methane caused the P-T mass extinction. There's some evidence to say it happened, with the Siberian Traps perhaps aiding and abetting the bacteria.
Jellyfish are distant relatives of coral, so there's a certain symmetry to going from cnidarians that secrete limestone (corals) to cnidarians that do not (jellyfish). Unfortunately, swarms of jellies won't support quite the biodiversity of coral reefs
Fern Spike Earth
Now it would be wonderful is all the modern descendants of those plants could just spontaneously grow in their new climatic regions, but the sad truth is that the species will have to move something like 2,000 miles (3,000 kilometers) to go from where they are growing now to where they need to be growing during the high Altithermal. [...] In reality, few plants other than leptosporangiate ferns and some weeds are capable of migrating this fast on their own, and ferns can only pull it off because they reproduce via airborne spores that can survive in the stratosphere.
[Childs] spent two days hiking through the corn and identifying every life form he saw. He came up with about 25 species, including him and his uncomfortable traveling companion, the corn, a few deer tracks on the edge of the field, a few birds that flew overhead, over a dozen tiny invertebrates (spiders, an ant, a mite, and similar) and a few fungi. [...] That corn field [in Iowa] is full of food for a few weeks out of the year and a nutritional desert otherwise. [...] Just for comparison, the tallgrass prairie replaced by that corn field probably had over 1,000 species and was one of the champion ecosystems for sequestering carbon in the soil.
Ultimately, any species that survives has to pass through two great filters: peak humanity in this century, and the heat-up of the High Altithermal.
There's no reason to think that the High Altithermal won't cause shrinkage of many animals, and this will probably include humans. To provide a reference, the average US male and female, age 20-29, weighed 88.7 kg (195.5 lb) and 75.4 kg (166.2 lb) from 2007-2010. Yeah, we're fat. Shrink us 30% and the average American man and woman would weigh 62.09 kg (136.6 lb) and 52.8 kg (116.1 lb), or about what people now weigh on average in much of Asia. Shrink modern Asians by 30% and people start getting into the body range of modern pygmies, groups where the men are five feet tall and under.
State Prophecies and Barbarians by Design
Barbarian societies in rich environments can be in danger, for they are tempting targets for slaving raids, invasion, and conquest, because their riches can be exploited to feed a control system. Sometimes barbarians stay in resource-poor areas deliberately, simply to avoid this danger.
Many barbarians living near states actively adapt their cultures to become as useless as possible to states, following the example of the shrine oak in the Taoist classic Zhuangzi (Chuang-tzu), which grew ancient and enormous because every bit of it was perfectly useless to humans, except for the shade it cast. Barbarians within reach of states can do many things to be more useless. First and foremost, they can flee, especially into places like dense forests, mountains, deep deserts, swamps, and the like, where organized raiding is difficult and the terrain is the primary defense. They can adapt to moving, have few material possessions, live in small groups and simple settlements that are easy to abandon and rebuild, but hard to conquer and rule. They can adopt pastoral herding, for herds and especially horses can make it easy to outrun raiders. Slash-and-burn (swidden) agriculture is another good option, especially if they favor root crops like potatoes, yams, and cassava that are hard for the raiding soldiers to steal. Unlike a granary that can be rapidly emptied, a militia confiscating a potato field has to dig up every potato themselves. Barbarians can be not just multicultural but cultural shapeshifters, people who have family connections to many groups, some perhaps even civilized, who can pass as members of multiple groups at need, people who have multiple names and nicknames, multiple religions, multiple outward identities. Each of these adaptations serves two purposes: it allows people to adapt in often unpredictable environments, and it makes them as useless as possible to anyone who wants to systematize their lives, control them, and extract surplus resources from them.
Swiddening is labor-efficient, maximizing food production per hour worked, while something like paddy-rice is land-efficient, maximizing food produced per acre. There are good reasons to practice each one, but if we're talking about practices that minimize soil nutrient depletion, sequester carbon in the soil, and so forth, swiddening and practices like it appear to win.The key problem faced by civilized agriculture is that a lot of nutrients leave the farm to feed other people. Unless those nutrients come back in the form of composted garbage and night soil, civilized extractive agriculture degrades farmland. Worse, as civilizations grow, the people in charge generally try to get as much out of their farms as possible, so the farms are often run close to, or past, peak production.
The are four basic responses to a warming climate: moving to the coast, moving poleward, moving into the mountains, and sheltering in place on the rest of the globe.
On the coasts, the problem is the ever-encroaching sea, which doesn't just chew up land, it invades the groundwater first, making it impossible to grow salt intolerant plants long before it floods.
Survival in mountains depends on creating a network of farms, foragers, and herders at many elevations, and often the best network is based on kinship.
Absent a herd of ruminants to eat these inedible species and support herders with their milk, much High Altithermal vegetation will be challenging simply to survive in. The situation is analogous to parts of modern Papua New Guinea, where hunters often take food with them. No matter how skillful they are, there simply isn't enough human food in some Papuan forests for people to survive without gardening.
Hell Then High Water
There will be superficially "primitive foragers." They may wel be like the 1940s Sirionó tribe in eastern Bolivia, profiled by Allan Holmberg in his 1950 anthropology classic, Nomads of the Long Bow. Holmberg documented the lives of a tribe of about 150 people who had "no clothes, no domestic animals, little art, no design, no musical instruments, and no religion." Holmberg didn't even observe tools for making fire. A woman in each family carried coals between camps. He saw the Sirionó as timeless primitives, but later research found that they were the remnants of a group of about 3,000 people who'd been farmers, in contact with westerners since the 1690s. They'd had to abandon their homes and fields due to violence from cattle ranchers abetted by soldiers, along with epidemics of smallpox and influenza. Holmberg's "timeless primitives" were refugees, their culture shattered, making a meagre living while hiding on the edge of the Amazon rainforest. They lived atop a system of mounds and causeways that had supported an enigmatic society (their ancestors?) 1,000 years before.
In herd scattering, people transfer some of their animals to relatives' and friends' herds. The people herding animals they don't own may keep the milk the animals produce and possibly the offspring, but since animals are wealth (they store perishable vegetation as less-perishable live meat that can move under its own power), scattering animals among the allies' herds is a great way to make sure they're not all wiped out by disease or disaster.
The evidence suggests that the classic Maya civilization, a time when millions of people lived on the peninsula, collapsed during extended droughts, after they'd spent centuries adapting to drought. The problem was not just that they had hardened their demand for water, it was that, even with all the terraforming of the Yucatan peninsula, they were totally dependent on rain water, and could only store about an 18 month water supply.
The Earth Inhales
At the beginning of the Deep Altithermal, around 3,600 CE, humans will face what is, for the first time in 1,500 years, a strangely stable world. The Deep Altithermal still starts at [at] least 5°C (9°F) hotter than today's global average, so normal weather will include giant, slow-moving storms, cyclones any month of the year, black flag weather here and there for at least the first 11,000 years or so, and the other inconveniences of a hot Earth.
The Great Cycles
The idea of big climatic cycles may sound bizarre, but we're very privileged to live in a time of medium sunlight and high stability that has lasted about 5,000 years, and the last 12,000 years have actually been fairly calm. The last big swing happened about 12,000 years ago, when the last Ice Age ended. Truly large climatic swings won't start for about another 70,700 years.
Epochs of Empire and Fallow
The sunlight samba has a fairly regular beat to it. The climate swings back and forth with a period of about 9,200 years between peak and trough, and the peaks and troughs, when the climate is relatively constant, last about 2,000 years before reversing direction and heading the other way. [...] The period from around 3,000 BCE to the present is actually wonderfully flat, one of those long epochs where the isolation wobbles but doesn't change a lot. If you know anything about history, well, that's when we have history. [...] It's foolish to assume that something changed in our genes that enabled civilization to happen spontaneously across the globe. The rather better bet is that the climate stabilized long enough to enable civilization, with its centralized control systems that depend on predictable surpluses from farmers and herders, to exist in the first place.
A Flight of Drunken Swans
Normally, atmospheric particles are about 0.2 microns (µm). Pinatubo boosted this up to 0.5 µm. However, the critical value is 2.0 µm. Above that size, the particles act to trap heat in the atmosphere and warm it. Below that size, the particles scatter light back into space and cool the atmosphere.
At their worst, diseases might have climatic effects. [...] Some link the General Crisis of the 17th Century to the virgin ground plagues that hit the New World in the 16th Century. The idea is that the mass die-off of the New World peoples caused New World forests to massively expand. This sucked carbon out of the air, lowered the Earth's temperature, and caused the General Crisis in the next century, as well as arguably marking the beginning of the Anthropocene, the time when human activities affect the entire globe.
The Limits of Knowing
It's probably easier to think of the world of scientific disciplines as a global world of stateless tribes, most of which are small, with only a few to a few thousand people who share a specific scientific language, culture, and conventions. The language of each of these scientific subdisciplines can be as easily threatened as the language of an uncontacted forest tribe. It only takes a funding downturn, as happened in the US in the last decade, to drive people out of smaller fields and threaten the transmission of their fields' languages, cultures, and knowledge.
Of Guns, Bows, and Limited Resources
A few centuries ago in Europe, particularly in Britain and France, saltpeter deposits quickly became depleted as the kings' oft-despised "saltpeter-men" (or petermen, a term later applied to safecrackers) dug out saltpeter wherever they found it, even if they destroyed someone's outhouse, barn, or grave in the process. Still, mining saltpeter was insufficient to keep the guns fed, so they developed "saltpeter plantations." These were basically piles of manure watered with urine and kept out of the rain. There are a number of methods, but over the course of a year or two, you can get a few pounds of saltpeter per cubic yard of manure in a plantation. [...] The British Empire temporarily solved their saltpeter shortage when the British East India Company found that the mudflats at the mouth of the Ganges were the natural equivalents of saltpeter plantations. Ganges saltpeter was the Company's major trade item, easy to ship back to Britain because it retarded decay, including rot in the hulls of the wooden ships carrying it. So long as Britain controlled India, the British Empire could afford to feed a lot of guns and people. [...] Other countries were less lucky, forced to rely on things like saltpeter plantations and guano deposits all around the world. The 19th Century even saw "guano wars" over control of tiny islands that hosted seabird colonies. Much of this guano ended upon farmer's fields, but it also fed the guns. These struggles ended with the invention of artificial nitrogen fixation in the early 20th Century.
The Syms of Humanity
Artificial selection is fast, but it's not significantly faster than natural cases of rapid selection, like evolution of pesticide resistance in insects. The difference between artificial and natural selection appears to be the intensity of the selective pressures, and nature does occasionally create similarly intense pressures through change.
Some, like apples, never breed true, so controlling their reproduction involves cloning individuals that have desirable traits.
Only the [dogs] who crack our social codes will be able to parasitize us, take food and care form us, and they can only do that when we actively help them coevolve with us.
If you think about Altithermal history as a piece of music, the fundamental beat is the passage of years, all 400,000 of them. They pass, one second per second, whatever happens. That's the metronome of time. Start here. History happens when it happens, and it takes as long as it needs to, no less and no more.
On top of that basic beat, lay the Milankovitch cycles. They are the result of the gravity of the Sun, Moon, Jupiter, and Saturn. There's nothing we can do to affect them, but they'll affect our history over the coming millennia. [...] On top of that, layer on the story of the terafart, how we will release greenhouse gases over the next 100 years, and how those gases are slowly absorbed, in stages, over the next 400,000 years. By itself, it's pretty easy to talk about how the terafart heats up the climate and how things cool down aain. However, the Milankovitch cycles also affect temperature regionally. Temperature changes around the Arctic and Antarctic circles control when the glaciers start reforming, and finally they blend with the concentration of atmospheric CO2 to determine when we get another ice age. [...] On top of the terafart and the Milankovitch cycles, add ice. During the High Altithermal and for probably 100,000 years thereafter, ice won't matter much. But once glaciers start forming, things get weird, because ice forming and melting takes a lot of energy. Ice accumulations put a hitch into the way Earth's climates follow the steady, slow beats of the Milankovitch cycle, making rapid change possible. [...] On top of all that, lay the cycles of vegetation and oceanic change. The shifting forest biomes, the masses of water in the global thermohaline circulation take centuries to move. They're sort of tracking the first two tracks, but they're also lagging by up to 500 years and being influenced by subsequent swings as they change. These lags add chaos to the climate. [...] On top of all that, lay the vibrant, busy back-and-forth of coevolution across the landscapes. [...] A world where civilization has collapsed, climate is abruptly changing, and there are few humans across large swathes of low diversity weed-lands, is very different than one that's had ten thousand years of relative stability for relationships to, quite literally, evolve, but the relationships are critical.
You might say that humans are prone to outbreaks when and where environmental conditions are right. We call these outbreaks civilization, and even without people using fossil fuels, such outbreaks will recur and will have major impacts on the world.
The Ice Age Double-Tap
Over the 100,000 year glacial cycle, basically there are 10,000 years when the Earth is so cold that even a Heinrich [Event] can't get the thermohaline circulation up to northern Europe. It's stuck in its coldest mode, and it's pretty stable. Then there are the interglacials or interstadials, like we're in now, when Hudson Bay isn't freezing solid, so Heinrich Events and Bond Cycles aren't possible. This climate is also stable. Then there's the rest of the time going from one to the other. During this time, apparently, the Bond Cycles, D-O Oscillation, and Heinrich Events happen, when climate jumps at least 5-10°C (10-20°F) rapidly and repeatedly.
How Long the Anthropocene?
In perhaps 5,000,000 years new coral reefs, or their equivalents, will start popping up in the tropics, as water chemistry returns to 20th Century conditions. This will be seen as a major environmental crisis by people who've lived for millions of years without coral reefs, as the reefs clog their harbors, render tropical shores impassable to ships, even raise the tops of submerged volcanos to the surface and above for the first time in millions of years.
We could attempt to dominate the planet, try to suppress eveything but our domestic species, rule tyrannically. We would then become the best host on the planet for pathogens and parasites, the next virgin, untapped frontier for whatever can evolve to take advantage of us.
If it's going to hurt either way, why not work towards a path of life for the future. [...] If you want a positive goal to live for, consider this: instead of thinking of life as a game where you win by dying with the most toys, I'd simply suggest playing life as an infinite game, where the point of the game isn't winning, but keeping the game going with as many players as possible. Those players aren't just your fellow humans. They include animals, plants, fungi, protists, bacteria, ideas, cities, landscapes, and cultures. All will eventually disappear, but you don't have to be the one to exterminate any of them.