Channel: Down To Earth

Category: Science & Technology

Tags: la ninaheat wavehealth mobilityindian summercivil service preparationsjammu and kashmirhimachal pradeshias coachingsustainable developmentenvironmentwarmest marchglobal warmingcsedroughtdown to earthscienceclimate crisiswater crisisupscuttarakhandcentre for science and environmentclimate change

Description: Heat waves on land and depressions in the sea have started early in India this year because of an unexpected climatic anomaly which could be linked to global warming. In the plains, a heatwave is declared when the maximum temperature reaches 40 degree celsius and at least 4.5 notches above normal. On April 9, the temperature was 42.4 degree celsius, the highest in April in the last five years. This is also the first time in 72 years that the first half of April has seen this kind of heat. Parts of northwest and central India are expected to see more frequent heat waves in April from now on. India also saw the warmest March in 122 years this time around. The reason behind an early heat wave in North India is the continued persistence of a north-south low-pressure pattern that forms over India in winters when the La Nina phenomenon is occurring. The temperatures over western Russia, down to Kazakhstan and over Pakistan, Afghanistan, all the way into Spain and Portugal were more than 10 degree Celsius warmer during February. The last time La Niña persisted for three years(1998-2000) there was a cyclone in March 2000. An interesting aspect of the heat waves this season has been their occurrence in Himachal Pradesh, Uttarakhand and Jammu and Kashmir. This fastens the melting of snow and glaciers in these regions which, in turn, would affect the availability of water for the people. Heat waves can impact crop yields as they can often lead to drought. And drought or lack of moisture leads to forest fires. There have been over 1,141 large forest fires recorded across the country in between April 3 and 11 2022. North India has faced a heat wave for about a fortnight now. According to the IMD, there is going to be a temporary respite on 12th April. In the pre-monsoon season which began on March 1st, India has already faced a 46% deficiency in rainfall this year. Normally a 4-5 day heatwave is succeeded by short pre-monsoon showers which has not happened yet. This is attributed to the absence of western disturbances over North India and the peninsular region. Two western disturbances from April 12-14 and 18-20 are likely to cause rainfall over the higher reaches of the Himalayas. Maximum temperatures were above normal by about 5 degrees in most northern states last week.