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The trends studied by Teri’s Environment Status Report for the Mumbai Metropolitan Region were taken from 42 years of data from four stations—Santacruz, Colaba, Dahanu, and Alibaug—and are largely in line with other studies.

The study found that humidity levels have increased slightly—by 2% during the day. On the other hand, evening humidity levels are falling. “Atlhough humidity has not increased hugely, any increase does add to thermal discomfort,” said Anjali Parasnis, associate director of TERI’s western region office.

The study also looked at rainfall, finding that while annual rainfall had not changed much, the number of heavy rainfall days have increased. The number of days with 124-244mm rainfall rose by 26.9% from the 1970s to the 2000s, for instance. In the same period, light rain days—with just 2.5-7.5mm rainfall—declined by 6.5%.

In fact, only 13 of 42 years had seen rainfall below the long-term average, the analysis showed. The study also found some data to suggest that wind speeds had declined from 12km per hour in 1970 to 7km per hour in 2012, but more research was needed to verify the trend, researchers said.

Climatic trends have huge impacts not only on the health of humans and wildlife, but also on infrastructure and economy. For instance, higher temperatures affects the service life of asphalt and increases the use of electricity. Humidity, meanwhile, can affect agriculture as well as human health, the study warned.