Climate Change

Hotter than normal: trends show that it is true for both summer and winter temperature

Interestingly, Himalayan states such as Himachal Pradesh and Sikkim have seen the highest increase in annual mean minimum and maximum temperature over the last few decades

 
By Kiran Pandey
Last Updated: Tuesday 01 May 2018
States such as Haryana have registered a 4.8°C departure from normal. Credit: Swaminathan / Flickr
States such as Haryana have registered a 4.8°C departure from normal. Credit: Swaminathan / Flickr States such as Haryana have registered a 4.8°C departure from normal. Credit: Swaminathan / Flickr

By the end of April 2018, a large swathe of north-western and central India is under the grip of heat wave. According to the latest forecast issued by the India Meteorological Department (IMD), “Maximum temperatures were appreciably above normal (3.1°C to 5.0°C) at many parts of Rajasthan; at some parts of Jammu & Kashmir, Assam & Meghalaya and at one or two pockets of and Arunachal Pradesh, West Madhya Pradesh, Madhya Maharashtra and Haryana.”

On April 20, highest maximum temperature (45.9°C) was recorded in Chandrapur of Vidarbha region. This temperature was surpassed by Churu (West Rajasthan) on April 28, when it registered a maximum temperature of 46.5°C. States such as Haryana and Himachal Pradesh have registered a 4.8°C and 4.5°C departure from normal. The current heat wave conditions fall in the line with the historical trend.

Departure from normal temperature. Credit: IMD

Summer temperature trend

When it comes to number of heat waves in India between 1970 and 2016, Maharashtra tops the list with 87 heat wave incidents. It is followed by Rajasthan (81), West Bengal (77) and Odisha (67). The number of deaths due to heat wave has increased manifold. For example, during the five-year period from 1970-74, 2029 deaths were reported. However, in 2015, alone, death toll reached 2081.

India has witnessed hottest summers in the last 15 years. In nine out of 15 years, the seasonal maximum temperature was over 31°C on an average. 2017 was the fourth consecutive hottest year after 2016, 2015, and 2014 and 2018, too, seems to be joining the league of hottest years.

 

2018 recorded the fourth warmest winter since 1901

As predicted by IMD, the winter was warmer in 2018, in fact, the fourth warmest in the last 117 years. With an average annual temperature of 21.84°C, the warmest ever winter was recorded in 2017. Winters are, in fact, becoming warmer as evident from the rise in minimum temperature from Jan-Feb during 2001-2017.

In 10 out of 17 years, minimum temperature was over 15°C on an average during these two months. In 2009, winter months were the warmest when the minimum temperature was over 16 degrees (16.25°C). Following this, 2006 and 2016 had the warmest winters.

How the states have been heating up all this while

Although the rise in both minimum and maximum temperatures has become more pronounced between 2001 and 2016, the temperature has been on rise since the beginning of the 20th century. The mean minimum and maximum temperatures have increased by 1.07°C and 1.18°C respectively, since 1901.

Going by the state-level climate change trends released by the IMD, the highest increase in annual mean maximum temperatures during 1951-2010 was observed in Himachal Pradesh (+0.06°C/year) followed by Goa (+0.04°C/year), Manipur, Mizoram and Tamil Nadu (+0.03°C /year). Simply put, the Himalayan state has seen 3.54°C rise in just six decades.

Worryingly, the highest increase in annual mean minimum temperature was observed in another Himalayan state: Sikkim. With 0.07°C every year, the state’s mean minimum temperature is now 4.13°C higher than what was there in 1951. In fact, Sikkim has surpassed all other states when it comes to experiencing highest increase in both winter and summer mean minimum temperature, which is 0.08°C and 0.07°C respectively, every year.

What to expect in the coming months?

May 2018 could be even worse considering IMD issuing a warning of a possible severe summer with temperatures 0.5 to 1°C higher than the long-term average. According to IMD projections, Jammu & Kashmir, Punjab, Haryana, Chandigarh & Delhi and Himachal Pradesh are likely to be warmer than normal by ≥1 °C.

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  • From the map it is clear that there is no uniform rise in maximum temperature over different parts of India. Some areas show below normal [negative] and some above normal [positive] with large number of stations showing close to normal. Only in pockets they show high deviations. These are associated with localised/regional circulation patterns. The main driving force is western disturbances from northwest and low pressure rainy condition in Bay of Bengal, etc.

    2002 and 2009 were drought years wherein the temperature rose by 0.7 and 0.9 oC at all India average with rainfall below the average at 81 % and 79 %.

    Dr. S. Jeevananda Reddy

    Posted by: Dr. S. Jeevananda Reddy | 6 months ago | Reply