Mumbai is becoming warmer, facing increased extreme rainfall events: WRI study

The plan will focus on climate resilience with mitigation and adaptation strategies by focusing on six areas – sustainable waste management, urban greening and biodiversity, urban flooding and water resource management, building energy efficiency, air quality and sustainable mobility.

The process of preparing a climate plan also involves creating a climate profile of the city with vulnerability assessment due to climate change and greenhouse gas inventory.

Analysis of the Indian Meteorological Department (IMD) data a steady rise in air temperature over the past 50 years, with uneven increase in night time temperatures, and seasonally, faster warming of the winter months – from November to February – compared to the summer months.

Also, the number of extreme caution days is increasing, the report said. As per the data, on an average, Mumbai sees 174 caution days and 187 extreme caution days per year. As per the guidelines adopted by National Weather Service, USA, caution days mean days with temperature between 26-32 degree Celsius, while it is considered an extreme caution day if the temperature is between 32 and 42 degrees Celsius. Officials said temperatures above 35 degrees Celsius can impact human health and productivity.

“Since 2007, the city has seen a constant rise in temperature. Across years, cumulative numbers are the same but the general temperature trend is moving towards the warmer side. We are observing an increase in the number of extreme caution days,” said Rubaina Rangwala, associate director, WRI India.

However, the study on data regarding specific numbers of extreme cautions days is under process. The rise in temperature has been attributed to concretisation, lack of green cover and housing density. From 2007, the average rise in temperature is up to 1 degree Celsius.

According to the reports, satellite imagery tools show that in March-May, between 2005 and 2010, the land surface temperatures in Sakinaka was average 33.64 degrees Celsius, but this increased to 38.83 degrees Celsius between 2015 and 2020 in March-May. The data also added that slums are hotter than housing societies.

Meanwhile, rainfall trends for the past 10 years show an increase in extreme-rainfall events, resulting in frequent conditions of water logging and flooding. Data collected from the BMC’s automatic weather stations (AWS) suggested that Mumbai has seen, on an average, six heavy (64.5 – 115.5 mm), five very heavy (115.6 – 204.4 mm) and four extremely heavy (> 204.5 mm) rain events per year.

From 2017 to 2020, there is a steady increase in the number of extremely heavy rainfall events. Vulnerability assessment report shows that areas like Worli, Dadar, Kurla and Andheri are prone to localised extreme rainfall events.

The report warned that coastal risks due to storm surge, coastal inundation, and sea intrusion are also exacerbated during the monsoon months. Landslide prone areas become particularly more vulnerable during extreme rainfall.

“Mumbai faces two major climate challenges – urban flooding and increasing heat. As part of gathering data to build the plan, a greenhouse gas inventory for Mumbai was developed using a global standard tool to identify emission reduction strategies for 2030 and 2050. For Mumbai to adapt to changing climatic scenarios, a vulnerability assessment using satellite imagery has been completed to identify critical risk factors,” said Dr Sanjeev Kumar, additional municipal commissioner.

The data showed that Mumbai’s greenhouse gas emission was 34.3 million tonnes in 2019, of which, 71 per cent came from the energy sector, which is mainly based on coal.