Drought Causes Cultural Breakdown

What happened to the Hittites, and the late Bronze Age?

Climate change is already causing wars and migration, misery on a vast scale. The global South takes the heat, while the global North keeps making it, pumping out the CO2. Can we adapt, or is the human population going to decrease, either gently or not so gently, as conditions deteriorate? The answer is not at all clear. The adaptation measures taken by the rich world involve highly contentious politics, and uncertain technology that, at best, requires a great deal more resource extraction. The poor, on the other hand, are left to either try developing (if they can maintain good political and economic governance) to join the rich in their extractive ways, (China, India), or migrate en masse to rich countries (Africa, Central America). All this is going to get worse, not better, since we are still at peak CO2 emissions and only beginning the process of global heating.

Our emissions of CO2 are still going up, not down. Therefore climate change will be getting worse, faster. Conflict is one likely outcome.

Well, migrations and dislocation have happened before. Over the last millennium, it was cold temperatures, not hot, that have correlated with conflict. Epic migrations occurred in the declining days of the Roman Empire, when the Huns drove a domino series of migrations of Germanic tribes that fought their way throughout Europe. What prompted the Huns out of the Asian steppe is unknown, however. Jared Diamond wrote of several other cultures that met their end after exhausing their resources and technologies. A recent paper added one more such case- the Hittites of late Bronze Age.

The Hittites were a big deal in their time (1700 to 1200 BCE, very roughly), running what is now Eastern and Southern Turkey, and occasionally Syria and points South. They were an early offshoot of the Indo-European migrations, and had a convulsive (though not very well understood) history of rises and falls, mostly due to their political dynamics. At the height of Hittite power, they fought Egypt directy at the battle of Kadesh, (1274 BCE), which occured just a little north of current-day Lebanon. This was the complex frontier between Assyria / Babylon, the Hittites, and Egypt. Egyptian history is full of expeditions- military, economic, and diplomatic- through the Levant.

The Hittites were artists as well as warriors.

The Hittites were also one of several communities around the Mediterranean that shared in the late Bronze Age collapse. This is the epic time that saw the Greek siege of Troy, (~1200 BCE), and the "Sea People's" invasion of Egypt. Its causes and details remain a long-standing historical mystery. But its scale was vast. Greece entered its dark age that lasted from 1200 to the 800's BCE. North Africa, the Balkans, Turkey, Levant, and the Caucaus all declined. Assyria and Egypt were weakened, but did not collapse. The latest paper uses tree-ring data from junipers from around the former Hittite capital in what is now central Turkey to more precisely date a severe drought that may have caused this collapse. Drought is just the kind of cause that would have been wide-spread enough and foundational enough to destroy the regional economies and prompt migrations and wars. Wars.. there are always wars, but no single war would have caused the collapse of cultures on such a wide scale, including a weakening of Egypt. Plagues are also not a great candidate, since they do not harm a society's resource base, but only its population. Such population reductions typically benefit the survivors, who rebuild in short order.

Moisture levels inferred from tree ring data, with lower values dryer. There are three consecutive catastrophic years dated to 1198-1196 BCE in this region, which is around the ancient Hittite capital. The ensuing decade was also unusually dry and likely poor for agriculture. The 20% and 6.25% levels of drought are by comparison to wider sampling, including modern data.

The drought these authors identified and located with precision was extraordinary. They note that, using modern data for indexing, the 20% level (representing about 30 cm of annual rain) is the minimum viable threshold for growing wheat. The 6.25% level is far below that and represents widespread crop failure. They developed two types of data from the tree rings, drawn from 18 individual trees whose rings spanned about a thousand years across the second millenium BCE. First is the size of the rings themselves, whose data are shown above. Second is the carbon 13 isotope ratio, which is a separate index of dryness, based on the isotopic discrimination that plants exercise over CO2 respiration under different climatic conditions. 

The same tree rings that provided the inferences above from their geometry (width) also here provided carbon 13 isotope data that lead to a similar conclusion, though with much less precision. High proportions of C13 indicate drier climate, here continuous around 1200 BCE.

The paper shows three consecutive years at the 6.25% level of rainfall, starting at 1198 BC. The ensuing decade was also harshly dry. All this correlates with cuneiform texts found in the Levant that were letters from the Hittites, bemoaning their drought and begging for assistance. But everyone in the region was in a similar position. The Hittite culture never recovered. 

So drought is now a leading hypothesis for the ultimate cause of the late Bronze Age collapse around many parts of the Mediterranean, with Greece and Anatolia particularly affected. While it is reasonable to imagine that such conditions would lead to desperation, migration, and war, there is no direct link yet. The nature and origin of the Sea Peoples who attacked Egypt remain unknown, for instance. The reasons for the seige of Troy are lost to myth. The Illiad never mentions drought, nor would Troy have been in a much better position than Mycenaean Greece, climatically speaking. But the consequences of geopolitical shifts in alignment can be unpredictable, as we continue to experience today. It is exciting (as well as sobering) to get a glimpse into this cloudy history- into a vast swath of human experience that built great cultures and suffered epic defeats.

• The planet can just go to hell.
• And so can our political system and media.
• The next Mein Kampf.
• Maybe governments should really do things themselves.