Evidence for widespread droughts ~4.2 ka, lasting for several centuries in some regions, has been tentatively linked to declines of the Akkadian Empire , the Indus Valley , and the Egyptian Old Kingdom and Yangtze River Valley . Deteriorating climates often exacerbate accumulating weaknesses in social systems to which population growth and urban expansion contribute . The rather narrow climatic niche favoured by human societies over the last 6000 years is poised to move on the Earth's surface at speeds unprecedented in this time span , with consequences for human well-being and migration that could be profound under high-emission scenarios . This will overturn the long-lasting stability of interactions between humans and domesticated plants and animals as well as challenge the habitability for humans in several world regions  .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report