Mumbai’s Climate Action Plan is a document prepared by the Mumbai Metropolitan Area Development Authority (MMRDA) and published by the BruhanMumbai Corporation (BMC). The main purpose of the document is to identify the risks from climate change to the city, the vulnerabilities of the population to these risks, come up with mitigations for these risks, and identify a pathway to zero carbon emissions.

The report identifies the following risks for Mumbai from climate change in the coming decades. Many of them are already being seen in increasing frequency and the report warns that it is only going to get worse.

Urban Heat

According to the report, Mumbai has been seeing a warming trend over the past 47 years (1973-2020) with an average increase of 0.25°C per decade, which has led to an increase of more than 1°C from the baseline average air temperature. In this 47-year period, 10 heatwave and 2 extreme heatwave events have been recorded.

Low-income households and informal settlements bear the brunt of this increasing temperature due to poor light and ventilation inside their houses. In fact, in higher density informal settlements, like slums, with very poor vegetation cover, temperatures were recorded to be 6-8°C warmer than surrounding areas!

The fifth assessment report of the IPCC projects Asia to experience more frequent and intense heat waves resulting in increased heat-related mortalities by the end of the century. For Mumbai, the projections from the IPCC sixth assessment report from 2021 are that:

• Mean temperatures are expected to rise by 1.5-2°C as per RCP 2.6 (Representative Concentration Pathway, a greenhouse gas concentration trajectory), and by 4.5-5.0°C under the RCP 8.5 projections.
  (RCP 2.6 is a “stringent” trajectory where the temperature rise is limited to 2°C by the end of the century, and RCP 8.5 models business-as-usual emissions.)
• Number of extremely hot days, with maximum temperature above 35°C are expected to increase by 20-30 days per annum under RCP 2.6 and 40 days as per RCP 8.5.

Projections from the NOAA (National Oceanic and Atmospheric Administration, Govt of USA) and ClimateLab, however, expect that 60% of the days in a year will comprise high-heat days (over 32°C). Such high temperatures combined with humidity would increase heat exhaustion and can result in increases in heat-related mortalities and illnesses.

Urban Flooding

Data for the last decade (2011-2020) assessed from 37 weather stations around the city show that Mumbai, on average, experienced six heavy (64.5 – 115.5 mm in a 24 hour period), five very heavy (115.6 – 204.4 mm in a 24 hour period) and four extremely heavy rainfall (> 204.5 mm in 24 hours) events per year. Most worryingly, the number of extremely heavy rainfall events have been increasing steadily since 2017.

The report finds that 35% of Mumbai’s population is exposed to the risk of flooding and wards H/E, H/W and F/N are the most vulnerable with more than 60% of their population at risk. Populations living in informal settlements are the most vulnerable to flooding, and they are particularly at risk during storm surges and cyclonic events when the sea level rises. Studies rank Mumbai at 5th amongst cities around the world most at risk of flooding.

The sixth assessment of IPCC predicts that South Asia will witness increased annual and monsoon precipitation with large variation year-to-year. For Mumbai the projections from the report are:

• By 2080, the frequency of 2005-like events, which led to more than 900 deaths, will more than double.
• With increased rainfall events, the number of flooding events in general are predicted to go up.
• The analysis recommends strengthening the city’s storm water drains network which can reduce losses by more than 70%.

Coastal Risk

IMD (Indian Meteorological Department) data shows that between January 2011 and June 2021, Mumbai and other areas along the Arabian Sea experienced 18 cyclones, of which 2019 saw the highest number of cyclones(4). Coinciding with high tide events cyclonic events are likely to contribute to higher sea level rise.

Sea-level rise (SLR) projections for 2050 predict that the Arabian Sea could flood Mumbai at least once every year. This puts the at-risk population at three times what was estimated!

The report identifies the need to address the risk from storm surges and sea intrusion by conserving mudflats and mangrove forests. However, satellite imagery shows that from 2008 to 2021, 325 ha of dense mangrove cover degraded to sparse mangrove cover or has been converted to mudflats due to excessive erosion and sedimentation. Meanwhile, in 305 ha the density of mangrove cover has increased.

The IPCC Sixth Assessment report says, on the topic of coastal risk:

• Sea levels in India are expected to rise, along with coastal floods, coastal erosion and coastal heatwaves.
• In fact, the assessment report finds that around Asia the sea level rise has been higher than the global average.
• In the next three decades, Mumbai, along with 11 other Indian coastal cities, will witness sea level rise of 0.1-0.3m.

However, lack of data on Mumbai’s coast makes it difficult to establish sea-level rise as a current risk to the city, according to the report, even though global projections sound a strong warning on the need for mitigation/adaptation strategies.

Landslides

The report identifies locations around Sanjay Gandhi National Park, in central Mumbai around the Ghatkopar area and in south-western coastal areas around Malabar hills, as being at increased risk from landslides during rainfall. The Disaster Management Department of the BMC has identified 287 locations as prone to landslides, 209 of which fall in informal settlements. These areas are especially vulnerable given the poor building conditions and temporary nature of buildings and houses.

According to the IPCC sixth assessment, given the projected trends for extreme rainfall in Mumbai, landslides have the potential of becoming a major threat if adequate investments are not made for mitigation.

Air Pollution

According to a World Bank report, 670,000 premature deaths occurred in India in 2017 due to poor air quality. Studies by BMC and SAFAR Mumbai from 2015 to 2021 have analysed the pollution levels and trends in Mumbai and this is what they have found:

PM 10 and PM 2.5:

The positive news is that annual concentrations of PM2.5 and PM10 have been showing a declining trend in Mumbai. However, they still remain above National Ambient Air Quality (NAAQ) standards. Areas around Bandra-Kurla complex, Mazgaon, Andheri and Malad have emerged as pollution hotspots. These pollutants are majorly generated from construction and roadside dust, and vehicular emissions.

NO2:

NO2 (Nitrogen Oxide) is a major pollutant and is mainly emitted by industries. Between 2010 and 2020, monitors have shown a high concentration of this pollutant beyond the permissible limit of 40 µg/m3 (micrograms per cubic meter), and this concentration has been increasing steadily over the years.

Small and medium scale industries, petroleum refineries and dumpsites are the major emitters of NO2. Areas near the Tata thermal power plant, the refineries in Trombay, Deonar landfill site and areas such as Khar, Andheri and Maravli have emerged major pollutant hotspots for NO2.

Indoor Air Pollution:

Indoor air pollution is a poorly researched area when it comes to impacts of air pollution. Burning of fossil fuels and domestic activities like cooking and heating water are major sources of this form of pollution. According to data from the 2011 Census, firewood is used in only 2% of the households as the primary fuel in Mumbai, while the rest have switched to Kerosene or LPG. Studies show that these households are exposed to twice the concentration of PM2.5 as compared to those that use Kerosene or LPG.

The Way Forward

The report identifies the vulnerabilities faced by the population in terms of access to housing, electricity, sanitation, information, recreational facilities and mass transit among others. Having access to these amenities helps mitigate the risks of climate change to a large extent. For the civic agencies trying to help, these are vital gaps that can help them target long-term mitigation measures better.

The report also identifies the main sources of Greenhouse Gases (GHGs) and their carbon sinks. It lays out a roadmap to decarbonise the city by investing in energy efficient and climate resilient infrastructure, sustainable mobility with a strong focus on non-motorized transport, better waste management, improving biodiversity in the city, water conservation and flood-risk management, and finally, reducing air pollution through better monitoring and regulation.

You can read the report to know more about Mumbai’s plan to tackle climate change. Climate Action plans for Chennai and Delhi are also on our site. Plans for other major cities – Bengaluru, Hyderabad, Ahmedabad, Pune, Kolkata are still awaited.