Gary sent in the link www.dailymail.co.uk/sciencetech/article-9052229/ … climate change was responsible for the collapse of farming cultures in central Asia in the 12th and 13th centuries AD, rather than the real culprit, Genghis Khan. This is the new science it would seem. The Medieval Warm Period toppled long established agricultural communities around the Aral Sea basin and the delta of the Amu Darya etc. This is a projection back into history if the headlines in the Daily Mail are to be believed. What they do not say is that the Medieval Warm Period had come to an end with the onset of cool weather in the late 12th century which is what set the Mongols into motion. They attacked central Asian countries that had suffered dry weather and drought for a couple of hundred years and more or less finished them off by slaughtering the farmers. As pastoralists they had a contempt for farmers. This is an age old cycle. It all has to do with the rainfall belt. The jet stream moves south during cooling episodes and the Little Ice Age from the 13th to 17th centuries was one such occasion. It therefore greens central Asia and rivers and lakes increase very quickly. Too late for the farmers around the Aral Sea. They were wiped out before the rains became beneficial to their activities. In warm periods of climate, such as the Medieval era and the Roman warm period, and in the modern world, the jet stream is more northerly, and there is a reduction of river flow into the Caspian and Aral seas. All fairly simple and cyclic in nature. Nothing exceptional. In fact, there is a wealth of studies out there explaining all this but catastrophic global warming is the big number one doom mongering scare story to frighten everyone out of their shoes. The original article was probably just pointing out that the central Asian zone was hit by environmental factors such as prolonged drought prior to the arrival of the Mongols, and Mr Genghis, but by adding the nod to global warming/ climate change, they had a guaranteed route to publication. Then, when the media become involved, well ….
Over at https://phys.org/news/2020-12-ancient-dna-rewrite-corn-year.html … ancient dna rewrites maize/corn's 9000 year old history. Around 4000 years ago Maize/corn profited form an injection of genetic diversity with an origin in farming in South America, as revealed by the discovery of some cobs in a cave in Honduras. Maize/ corn is thought to have originated in Mexico and was taken to South America where it became a staple as well. The interesting point here is that around 4000 to 4500 years ago there were some spectacular migrations of people around the world, and the DNA of maize/ corn appears to show this occurring in the Americas as well. Now, this is one story that may have benefited from the employment of climate change as the period was also one of cooling, with wetter weather in some places and drier weather in others, a switch involving not just the jet streams but the monsoon track. See also www.pnas.org/cgi/doi/10.1073/pnas.2015560117