Climate Only Sends the Bill; Institutions Decide Who Pays

During the Holocene warm period the African monsoon belt sat further north, and today's desert was savanna and lakes. Nabta Playa in southern Egypt held seasonal cattle-herding camps from about 7500 BCE, and around 4800 BCE acquired aligned stone slabs and cattle burials. Rudolph Kuper and Stefan Kröpelin (Science, 2006) used more than a hundred radiocarbon dates to map human settlement retreating southward in step with the rain belt.

From roughly 5300 BCE the eastern Sahara dried fast, and herders moved south into Sudan or east into the Nile valley. The valley was not the preferred address: the floodplain was marsh, full of hippos and crocodiles, and living there meant first building dykes, draining land and organizing labour. But once people were squeezed into a narrow corridor, settlement density and extractable surplus rose together, and around 3100 BCE Narmer unified Upper and Lower Egypt. Fekri Hassan put it most economically: the Nile did not pull people in, the desert pushed them.

Sahel rainfall variability and the runaway growth of Lagos and Kinshasa. Climate migration rarely looks like a refugee column; it is decades of household-level decisions accumulating.

In 985 Erik the Red led a fleet west from Iceland and founded the Eastern and Western Settlements in southwest Greenland, peaking at perhaps two to three thousand people. They lived by European-style stock-raising plus seal hunting, and their hard currency was walrus ivory — traded for the iron and timber the island lacked. Around 1250 the North Atlantic cooled, sea ice increased and the sailing season shortened. When the Dano-Norwegian missionary Hans Egede arrived in 1721, he found only ruins.

Jared Diamond's account in Collapse (2005) is the best known: they clung to a European identity, kept cattle and refused fish, and would not learn Inuit ice hunting or the kayak. Later evidence overturned it — Jette Arneborg and Thomas McGovern measured carbon isotopes in human bone and found that marine sources made up 50–80% of the late population's diet. They had switched to seal long before the end. Andrew Dugmore and colleagues (PNAS, 2012) offer a combined explanation: crusader routes brought African elephant ivory back into Europe, walrus ivory collapsed in price, and the colony's only export income vanished; the Black Death then removed buyers; sea ice merely made resupply less certain. The Western Settlement was empty by about 1360 and the Eastern by about 1450, with no archaeological layer of warfare or mass starvation — it reads more like departure by boat, in batches.

The fragility of a single-export economy when demand substitutes away: output is fine, the buyer simply found another source. Lithium, rare earths, and any supplier with one dominant customer sit on the same curve.

Zhu Kezhen's 1972 reconstruction of five thousand years of Chinese climate, built from phenological records and local gazetteers, identified the seventeenth century as one of the coldest troughs in that span. Geoffrey Parker's Global Crisis (2013) folds it into the "general crisis of the seventeenth century" — the same decades brought the English Civil War, the Fronde and Ottoman upheaval. North China suffered consecutive droughts from 1637 to 1643, with drought and locusts arriving together in Henan in 1640.

The treasury was already failing when Chongzhen took the throne. In 1629 the censor Liu Mao proposed abolishing the imperial post-station network, saving roughly 680,000 taels of silver a year; the proposal passed, and Li Zicheng, a post courier at Yinchuan in Shaanxi, was among those laid off (the details are disputed in the sources, but the mass layoffs are not). Meanwhile, to fund the Liaodong front and suppress rebellion, three successive surtaxes were levied, totalling some 20 million taels by 1639 — and their weight fell precisely on the driest north. The 680,000 taels were saved at the price of a cohort of unemployed young men who knew the roads and the courier network intimately. On 25 April 1644 Li Zicheng entered Beijing and Chongzhen hanged himself on Coal Hill.

Austerity cuts low-unit-cost, high-coverage frontline roles first: the accounting gain lands on one ledger, the risk exposure on another, and different people sign each.

1876–78 saw one of the strongest El Niño events on record, with the monsoon failing simultaneously across the Indian Deccan, North China and northeastern Brazil. China calls it the Dingwu Famine; Shanxi and Henan were worst hit, with deaths estimated at 9.5 to 13 million, against 5.5 to 10 million in India. One sea-surface anomaly, and mortality rates that differed several-fold between regions.

Viceroy Lytton staged the Delhi Durbar in January 1877 to proclaim Victoria Empress of India, a week of banquets. In the same months he insisted on non-interference in grain markets, opposed "excessive" relief, and imposed the Temple Wage — about a pound of grain a day on relief works, a ration whose calorie content Mike Davis compared to concentration-camp issue. Indian wheat continued to be exported through both years. In China, Shanxi's governor Zeng Guoquan and the British missionary Timothy Richard ran relief separately, Richard pressing for work-for-relief with published accounts; the Qing treasury was empty, but a gentry-merchant "righteous relief" network raising silver through Shanghai mobilized cross-provincial donations — the starting point of modern Chinese civil disaster relief.

Through the 2023–24 El Niño, several countries restricted rice exports in turn. Price signals travel far faster than grain, so the shortfall usually erupts somewhere else.