Our monsoon almost 40 million years old
An international research team has now found that the Asian monsoon already existed 40 million years ago during a period of high atmospheric carbon dioxide and warmer temperatures.Updated: Sep 15, 2014, 16:07 IST
Asian monsoon, one of the largest and crucial climate system in the world, existed 40 million years ago - much earlier than previous estimates, according to a new study.
Scientists believed the climate pattern known as the Asian monsoon began 22-25 million years ago as a result of the uplift of the Tibetan Plateau and the Himalaya Mountains.
An international research team has now found that the Asian monsoon already existed 40 million years ago during a period of high atmospheric carbon dioxide and warmer temperatures.
"It is surprising. People thought the monsoon started much later," said lead author Alexis Licht, a research associate in the University of Arizona geoscientist department of geosciences.
The monsoon, the largest climate system in the world, governs the climate in much of mainland Asia, bringing torrential summer rains and dry winters.
"This research compellingly shows that a strong Asian monsoon system was in place at least by 35-40 million years ago," co-author Jay Quade, a UA professor of geosciences, said.
The research by Licht and his colleagues shows the earlier start of the monsoon occurred at a time when atmospheric CO2 was three to four times greater than it is now.
The monsoon then weakened 34 million years ago when atmospheric CO2 decreased by 50% and an ice age occurred.
Licht said the study is the first to show the rise of the monsoon is as much a result of global climate as it is a result of topography.
"This finding has major consequences for the ongoing global warming. It suggests increasing the atmospheric CO2 will increase the monsoonal precipitation significantly," he said.
Unravelling the monsoon's origins required contributions from three different teams of scientists that were independently studying the environment of 40 million years ago.
All three investigations showed the monsoon climate pattern occurred 15 million years earlier than previously thought.
Due to its effect on agriculture, flora and fauna and the general weather of India, Bangladesh, Bhutan, Pakistan, Sri Lanka, among other economic, social and environmental effects, monsoon is one of the most anticipated, followed and studied weather phenomena of the Indian subcontinent.
The study was published in the journal Nature.