14 DAY TRIAL // A civilization that occupied areas of modern-day Pakistan and India may have declined, at least in part, due to an extreme bout of climate change, researchers at the University of Cambridge argue in a study.
This is not to say that the event was brought on by global, or even localized, warming, but by an abrupt weakening of the summer monsoon, which occurred 4,100 years ago. The traces left behind by this event are visible even now, the research team reveals in a paper published in the journal Geology.
The weak summer monsoon affected northwest India the most, and led to significant droughts that most likely created widespread famine. Even if a direct causal link is not found between this event and the decline of the Indus Civilization, the fact remains that the two phenomena coincide remarkably well.
Unlike other cultures, the Indus Civilization was capable of building metropolises, and spanned parts of northern India and most of modern-day Pakistan. The conclusions in this new study may suggest that climate change is one of the main reasons why many large, ancient cities fell into ruin.
The presence of the weak monsoon was determined through an in-depth analysis of snail shells found inside sediments at the bottom of an ancient lake. Cambridge investigators analyzed the amount and type of oxygen isotopes in these shells in order establish weather conditions at the time.
This is one of the first pieces of evidence supporting the older hypothesis that climate change may have had a hand in the decline of the Indus Civilization and its major cities. Furthermore, the work supports an idea which argues that a global climate change event occurred on Earth during the Bronze Age.
Scientists say that this event had repercussions in other places as well, including the Old Kingdom in Egypt, the Greek and Cretan Bronze Age-era civilizations and the famous Mesopotamian Akkadian Empire. The latter has been proven to have declined due to climate change a few years ago.
“We think that we now have a really strong indication that a major climate event occurred in the area where a large number of Indus settlements were situated,” says David Hodell, who holds an appointment as a professor with the Department of Earth Sciences at Cambridge.
“Taken together with other evidence from Meghalaya in northeast India, Oman and the Arabian Sea, our results provide strong evidence for a widespread weakening of the Indian summer monsoon across large parts of India 4,100 years ago,” the investigator adds.
“We know that there was a clear shift away from large populations living in megacities. But precisely what happened to the Indus Civilisation has remained a mystery. It is unlikely that there was a single cause, but a climate change event would have induced a whole host of knock-on effects,” concludes team member and Cambridge archaeologist, Dr. Cameron Petrie.