Extreme weather events: Imprints of changes in climatic conditions

Ahead of World Environment Day on June 5, a look at how Karnataka has witnessed an increase in severe weather patterns in both frequency and intensity in the last decades

Last month, even as parts of north India were reeling under heat wave, many places in Karnataka, including Bengaluru, were suffered large-scale destruction caused by heavy pre-monsoon showers. In fact, the quantum of rainfall recorded in the State from March 1 to May 31 was 105% above normal.

Climate change is here to stay, and the imprints of changes in climatic conditions, says the Karnataka State Disaster Management Authority (KSDMA), are in the form of high-impact weather events. The State has witnessed an increase in such events in both frequency and intensity in the last decades, as also hydro-meteorological disasters such as drought, flood, hailstorm, cyclone and heatwave. 

“During the past few years, the entire State witnessed extreme events in the Western Ghats and parts of the interior district. A significant increase in the rainfall is observed in Kolar for the pre-monsoon season, and a decreasing trend is observed in northeast monsoon for the north interior Karnataka (NIK) region. The main reason for these extreme events can be attributed to the active phase of monsoon season coupled with La Nina and positive / Neutral Indian Ocean Dipole (IDL) conditions over the State,” explained Manoj Rajan, Commissioner, KSDMA.

At the same time, there is a reduction in the amount of annual rainfall and a marginal increase in the number of rainy days in NIK and coastal regions, he said. The KSDMA Commissioner also said there has been a continuous change in temperature and relative humidity (RH) data from 2002 to 2018.

“The average temperature has shown an increasing trend, whereas the RH had a decreasing trend in most regions,” he said. Thunderstorms and lighting events have occurred more frequently in recent years, while the variability of south-west monsoon rainfall has increased significantly since 1960. Several districts are seeing an increase in prolonged dry periods with low or no rainfall or intermittent with short, intense spells of rainfall.

“The analysis of the temperature and relative humidity data series for 2002 to 2020 shows an increasing trend in average temperature, while the relative humidity showed a decreasing trend. The State has experienced drought for 15 years in the last two decades. Karnataka also experienced severe floods, and the last four years have been consecutive flood years for the State. The recurrence of droughts and changing rainfall patterns are detrimental to the surface and groundwater recharge and pose a significant challenge to water security,” said Mr. Rajan. 

Bharath Setturu, Post-Doctoral Fellow, EWRG, CES, IISc, said their study of changes in land surface temperature across agro-climatic zones of Karnataka from 2006 to 2019 using spatial data highlights increase in temperature across the agroclimatic regions of Karnataka due to large-scale deforestation, urbanisation and loss of wetlands. The districts of hot dry semi-arid and hot moist semi-arid regions, such as Bidar, Yadgir, Kalaburagi, Vijayapura, Raichur and Ballari depict an increase in temperature mostly deprived of forest cover, he added.