Karnataka - Climate
The climate of Karnataka is basically tropical and determined largely by the physiographic and geographic location with respect to the sea and monsoon. The state enjoys the benefit of two monsoons and hence it will be called the land of two monsoons because both southwest and northeast monsoons account for major part of the rainfall. Temperature is lowest in the month of January and increases thereafter gradually at first and then, rapidly after the middle of February or beginning of March. Temperature varies between 18° to 40°C during summer and between 14° – 32°C during winters.
Karnataka’s annual rainfall is 1,151 mm on average. Around 80% of it is received during the southwest monsoon, 12% in the post monsoon period, 7% during summer and 1% in winter. Within the state there are considerable variations. During the southwest mon-soon rainfall is much 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 precipi-tation (500–600 mm). A recent study observed a declining trend in rainfall during the southwest monsoon: -1 mm per day per 100 years or 6% in 50 years. India Meteorologi-cal Department (IMD) by contrast holds that its own data is indicative of a slight rise in annual precipitation. Projections made for the period 2021 to 2050 under a SRES A1B scenario predict a decline in annual rainfall for the south-western and north-eastern re-gions of the state. A wide region from the north-western part of the state including the coastal districts to the south-east is projected to see significant increases.
A warming trend in Karnataka has been observed for the period June to September in northern interior Karnataka. Both minimum and maximum temperature were found to have risen by up to 0.6°C over the last 100 years. According to projections made (SRES A1B scenario), average temperatures may rise further by 1.7°C to 2.2°C by the 2030s. Projected increases are more pronounced in the northern districts.
It was inferred from a recent study that overall reduced precipitation and continuous warming is a possible, perhaps probable scenario for Karnataka. It is predicted that regions that already witness less rainfall and higher temperatures, such as northern Kar-nataka, will further experience lesser rainfall and increases in average temperatures.
Groundwater provides for 45% of irrigation in the state and GoK places emphasis on its expansion. Karnataka experienced a decline in net annual groundwater availability by 3.2% between 2004 and 2009, attributed to groundwater extraction beyond replenish-ment. There are 8.6 lakh irrigation wells, 94% of which are equipped with electric pumps. Groundwater development stands at 68%. As much as 64 watersheds covering 35 of the 176 taluks of the state are over-exploited.
About 20% of Karnataka’s geographical area is under forest cover. Forests declined by about 2% between 2001 and 2007, especially dense forests were affected (-16%). The Western Ghats are among the 25 global biodiversity hotspots. Likewise the coastal area has a rich and diverse biodiversity. A large number of species are identified as rare, endemic or threatened in both biota.
It is widely accepted that higher CO2 levels will stimulate carbon sequestration by plants and increase net uptake. Nevertheless, the prediction that climatic changes will impact existing vegetation and forests in particular is a concern. A recent study finds that about 38% of the present forest area, mostly in the central and northern parts of the Western Ghats, is predicted to experience shifts in respect of the forest type. Though the coastal hinterland has an average height of 70 to 75 meters, studies have es-timated that, if the present tend continues sea levels could rise by 25 cm in 100 years, inundating around 461 km2 of coastal wetlands. Exacerbated by sand mining, erosion has been found to be significant. Likewise, encroachments and coastal pollution are notable.
Human health is vulnerable to climatic changes in multiple ways: Increases in the tem-perature can increase thermal stress. Increased incidence of floods and droughts would reduce crop productivity, affecting nutrition and consequently resistance to infections. Floods could contaminate drinking water causing outbursts of water borne diseases. Warming trends could also favour the spread of vector borne diseases (malaria, kala azar, dengue). The transmission window for malaria in the state is already 10-12 months though and hence further increase is impossible.
A changing weather pattern could severely impact the overall wellbeing of the state. The projected increase in rainfall and temperature is expected to cause changes in the cropping pattern and production, affect the availability of water and cause changes in the biodiversity profile of the state. It would possibly also reduce carbon sinks, affect the coastal zone due to sea level rises and higher water temperatures and lead to unemployment and migration of coastal communities. The transmission window for vector borne disease may widen. It is thus imperative to carefully analyse potential impacts of climatic changes, identify the most vulnerable sectors and increase preparedness and enhance resilience of the state to cope with changes.
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