Rainfall from the Asian summer monsoon, which influences water availability, ecosystems and agriculture in India, has been decreasing over the past 80 years, according to a study.
Man-made atmospheric pollutants are likely the reason for the decline unprecedented in the last 448 years, said researchers from the University of Arizona in the U.S.
The study, published in the journal Geophysical Research Letters, used tree ring records to reconstruct the Asian summer monsoon back to 1566.
The study found the monsoon has been weakening since the 1940s, resulting in regional droughts and hardships.
Previous studies have looked at tree ring chronologies from this region but the new study, “surpasses in terms of the timespan covered and the number of trees involved”, scientist Steve Leavitt. “We were able to gather nearly 450 years worth of tree ring data with clear annual resolution,” Mr. Leavitt said.