Climate change is impacting the water cycle and the rainfall patterns, resulting in intense rainfall and associated flooding in some areas and drought in other regions of Karnataka. Extreme weather events have increased both in terms of frequency and intensity across Karnataka in the last decades.
The State’s normal annual rainfall is 1,153 mm, 74% of which is received during the south-west monsoon, 16% during the north-east monsoon, and 10% during the pre-monsoon.
During the south-west monsoon, rainfall is higher in coastal locations on the windward side of the Western Ghats (3,350 mm), which drops sharply on the leeward side (600-700 mm). Northern-interior regions, by contrast, have markedly semi-arid climates with low annual precipitation (500–600 mm).
Variability of the south-west monsoon rainfall has increased significantly since 1960. Several districts are seeing an increase in long dry periods with low or no rainfall, or intermittent with short, intense spells of rainfall. The large-scale secular changes in monsoon rainfall are attributed to the increase in global emissions of greenhouse gases and air pollutants. At the same time, urbanisation, land-use changes, and deforestation at local levels have brought in a non-uniform response in these rainfall trends.
A long-term climate change scenario study for Karnataka, which deciphers variations in climate factors in the past, found that a significant shift in climatic factors has been observed around the year 1990. The long-term climate data series for the 58 years (1960 to 2017) was considered for the study. Thus by taking 1990 as the major change point, the data series has been divided into two sub-series: Period 1 (1960-1990) and Period 2 (1991 to 2017), for further parametric analysis.
The variations in the amount of rainfall, rainy days, frequency of rainfall events, the occurrence of dry spells (>= 3 weeks), number of below-normal rainfall years, fluctuations in temperature and relative humidity were examined, and there is a considerable shift in rainfall pattern over Karnataka.
The quantum, intensity, and distribution of rainfall has varied across the regions in the State from Period 1 to Period 2. While the number of rainy days and amount of annual rainfall has increased in south-interior Karnataka and the Malnad region, there is a reduction in the amount of annual rainfall and marginal increase in the number of rainy days observed in north-interior Karnataka and the coastal region from Period 1 to Period 2.
Parts of Vijayapura, Bagalkot, Raichur, Koppal, Ballari, Gadag, Dharwad, Belagavi, Haveri, Davangere, Chitradurga, Chikkamgaluru, Bengaluru, and Ramanagaram districts showed higher inter-annual variability (CV %) in rainfall. The remaining districts showed less variability (CV) from Period 1 to Period 2. Very light and light rainfall events have increased in all the regions. Moderate and heavy rainfall events did not show any distinct pattern.
In the last two decades, extreme rainfall events have occurred in different regions of the State. Also, the number of years with below normal rainfall has increased in north-interior Karnataka, whereas it has decreased in other regions from Period 1 and Period 2.
An analysis of temperature and relative humidity data series for the period 2002 to 2018 shows a steady increasing trend in average temperature, while the relative humidity showed a decreasing trend commonly in most of the regions in the State.
Hydro-meteorological disasters in the State such as flood, drought, cyclone, hailstorm, lightening, heatwave, and thunderstorm events have become more frequent in recent years
Between 2001 and 2020, the State has experienced a drought of varying severity for 15 years. Some talukas have been drought-affected consecutively for more than five years. A majority of districts in the north-interior Karnataka region were subjected to severe drought conditions.
Karnataka also experienced severe floods in 2005, 2009, 2018, 2019, 2020 and 2021. For the fourth consecutive year since 2018, it has been affected by flooding and landslips. Flooding and landslips have become new normal during the south-west and the north-east monsoon seasons, which hitherto was most vulnerable for drought, obviously indicating the effect of changing climatological conditions.
The recurrence of droughts and floods because of changing rainfall patterns caused by climate change would be detrimental to the surface and groundwater recharge and also pose a great challenge to water security.
Response to climate change in cities falls into two broad categories: mitigating emissions that drive climate change and adapting to effects that can’t be stopped. Cities produce more than 70% of global greenhouse gas emissions, mainly from heating and cooling buildings and powering cars, trucks and other vehicles. Urbanisation also makes people more vulnerable to climate change impacts.
Bengaluru Urban district rainfall has increased from 836 mm in Period 1 to 943 mm in Period 2. The average temperature for Bengaluru Urban district has significantly increased at 0.1°C/year in the last 16 years, while the minimum temperature has risen at 0.19°C/year. Extreme weather events have caused the loss of human life, livestock, and critical infrastructure, private and public property. The Government has already taken several steps to mitigate the impact of climate change.
This includes agriculture and livelihood by providing scientific information, customised weather forecasts and weather information and natural hazard information in time to the public and farmers to monitor and manage their daily crops and activities.
Yet, the community still has far to go in showing increased ambition on mitigation, adaptation, and other ways to challenge climate change.
(Dr. Manoj Rajan is Commissioner, Karnataka, State Disaster Management Authority)
