India's 2nd Deadliest Heat Wave in History Ends as the Monsoon Arrives

The monsoon has arrived in India. The India Meteorological Department (IMD) announced that the monsoon arrived on Friday, June 5 at the southern tip of the country--four days later than the usual June 1 arrival. Although the monsoonal rains have not yet reached the province hardest hit by the heat wave--Andhra Prahesh in Southeast India--the atmospheric circulation associated with the monsoon has caused temperatures to drop significantly in this region in recent days, ending the heat wave. India's deadly May 2015 heat wave claimed approximately 2,500 lives, ranking as the second deadliest heat wave in India's recorded history--and the fifth deadliest in world history. According to statistics from EM-DAT, the International Disaster Database, India's only deadlier heat wave was in 1998, when 2,541 died. Below is the list of top ten deadliest heat waves in world history as compiled by EM-DAT (which uses direct deaths for their statistics, and not excess mortality):

The 10 Deadliest Heat Waves in World History
1) Europe, 2003: 71,310
2) Russia, 2010: 55,736
3) Europe, 2006: 3,418
4) India, 1998: 2,541
5) India, 2015: 2,500
6) U.S. and Canada, 1936: 1,693
7) U.S., 1980: 1,260
8) India, 2003: 1,210
9) India, 2002: 1,030
9) Greece and Turkey, 1987: 1,030


Figure 1. Temperatures in Machilipatnam, Andhra Prahesh, India from May 14 - June 8, 2015 show that the heat wave peaked between May 22 - May 26, with high temperatures rising as high as 118°F (47.8°C.)

Death toll from the 2015 India heat wave questioned
As I discussed in more detail in my May 29 post on the heat wave, death tolls from heat waves are very difficult to estimate, since excess heat is typically just one factor contributing to a death. For example, the U.S. National Climatic Data Center (NCDC) lists the total direct deaths from the U.S. heat wave of 1980 at 1,260, but estimates that the combined direct and indirect deaths (i.e., excess mortality) due to heat stress was 10,000. According to an article in The Indian Express, the death toll from this year's heat wave in India may be much lower than 2,500. Of the 1,636 heat wave deaths reported between May 15 and May 30 in the hardest-hit province of Andhra Pradesh, only 511 were certified to have been caused by heat; the number of reported heat deaths soared when officials offered monetary compensation to relatives of heat victims. "The number of deaths being reported to mandal officers, Andhra Disaster Management Authority officials say, almost doubled after Chief Minister N Chandrababu Naidu announced ex-gratia of Rs 1 lakh to the kin of each person who dies in the heat wave," The Indian Express reported. However, even if the number of deaths in the heat wave were 1,000 less than officially reported, it still would rank as the second deadliest in India's history, and seventh deadliest in world history.


Figure 2. Progress of the monsoon towards India as of June 8, 2015 (green line) has lagged by about 4 - 9 days compared to its usual pace. The province hardest hit by this year's heat wave, Andhra Prahesh (shaded in yellow), should see the monsoon move through late this week and early next week. The province recorded 1,735 heat deaths as of June 3, 2015. Image credit: India Meteorological Department .

A deficient monsoon predicted
Although the heat wave of 2015 has ended, India's weather troubles are not over this year. The problem: the atmospheric circulation patterns brought on by an El Niño event usually cause much reduced monsoon rains. The current moderate El Niño event is forecast to intensify this summer, and this is likely to cause a significant reduction in monsoon rainfall over India. IMD is forecasting only a 7% chance of near-average rains during the 2015 summer monsoon period, and a 93% chance of below average or well below average rains. IMD's best estimate is that 12% less rain than usual fall, which would cause severe stress on agriculture and the power grid, which relies heavily on hydroelectric power. However, a 12% reduction in rains would not rank in the top five for worst monsoons on record. The five worst Indian monsoons for rainfall deficit were:

1) 1877, -33%
2) 1899, -29%
3) 1918, -25%
4) 1972, -24%
5) 2009, -22%

Climate change and India
This year's deadly heat wave in India was made much more probable by the fact that Earth is experiencing its hottest temperatures on record--the past twelve months were the warmest twelve-month period in recorded history, and so was the January - April 2015 period. According to the India Meteorological Department, a warming climate increased heat waves in India by a third between 1961 to 2010. As the planet continues to warm due to human-caused global warming, heat waves will become more frequent and more intense, and heat-related deaths will soar unless we take strong measures to adapt. An April 2015 paper published in Regional Environmental Change, Intensification of future severe heat waves in India and their effect on heat stress and mortality, warned that "heat waves are projected to be more intense, have longer durations and occur at a higher frequency and earlier in the year. Southern India, currently not influenced by heat waves, is expected to be severely affected by the end of the twenty-first century." Perhaps a bigger concern for India with climate change is drought, though. Many climate models show that climate change might increase the average rainfall in India from the monsoon, but when dry years occur, the hotter temperatures accompanying the dry years will drive much more intense droughts capable of causing significant challenges to growing food in India.


Figure 3. Tropical Cyclone Ashobaa as seen from the International Space Station at 3 pm EDT Sunday June 7, 2015. At the time, the storm had top winds of 45 mph. Image credit: Terry Virts.

Tropical Cyclone Ashobaa forms in the Arabian Sea
The ocean regions surrounding India have two tropical cyclone seasons, one from May to early June before the monsoon arrives, and one beginning in late October after the monsoon departs. During the June - October peak of the monsoon season, the monsoon dominates the atmospheric circulation in the Bay of Bengal and Arabian Sea, and only rarely allows a tropical cyclone to form. The only tropical cyclone so far this year in the North Indian Ocean, Tropical Cyclone Ashobaa, formed on Sunday just north of the advancing monsoon in the waters of the Arabian Sea to the west of India. Ashobaa is predicted to attain Category 1 strength before hitting cooler water and dryer air this weekend, which should weaken it to a tropical storm.

Jeff Masters