Heat wave in India? It will only get worse in years to come: Study

With more than 2300 dead in extremely hot weather across India a recent Indian Institute of TechnologyBombay IITB study predicts more intense and longer heat waves more often and earlier in the year in futureIn a changing climate newer areas including large swathes of southern India and both coastsndashhitherto unaffectedndashwill be severely hit resulting in more heat stress and deaths said the study published in the journal Regional Environmental ChangeA traffic police woman in Chandigarh trying to get some relief from the heat with a drink of water ldquoFrom climate model projections we have pointed out that there is a possibility of high occurrences of heat waves in South India in futurerdquo Subimal Ghosh associate professor at the Department of Civil Engineering IITB and one of the paperrsquos authors told IndiaSpend Heat waves in a warming world Such a forecast is in line with global and Indian studies Other recent assessments have predicted that intense heat waves will grow with rising global temperatures up by 09 degC since the start of the 20th century The Intergovernmental Panel on Climate Change IPCC records that from 1906 to 2005 the mean annual global surfaceair temperature increased by about 074 degC landsurface air temperature increases more than seasurface temperature As a result there will be significant changes in the frequency and intensity of extreme weather events including heat waves as IPCCrsquos 2014 report warns ldquoIt is difficult to directly link this present singleyear high heatwave occurrence to climate changerdquo said Ghosh ldquoHowever there is a good possibility that such heat waves may indicate the adverse impacts of global warmingrdquo A rise in the frequency and intensity of heat waves would increase the risk of heat stroke and heat exhaustion and even deaths from hot weather the IITB team predicted echoing concerns raised by IPCC scientists With a large proportion of people without sufficient access to water electricity and primary healthcare facilities India could be very vulnerable to heat waves the study noted ldquoHeat waves are an important class of climate hazard that may have serious consequences on health and ecosystem keeping existing vulnerabilities of population in mindrdquo says Kamal Kumar Murari the lead author of the study and an IITB doctoral candidate ldquoOur findings highlight the need to better understand the direct temperaturerelated consequences in order to develop better adaptation strategiesrdquo Multiple data sources one result Heatrsquos coming The IITB study is important because it is particularly exhaustive Murari and his colleagues used daily temperature data over 40 years 19692009 from 395 weather stations across India They also used climatechange simulations of seven Earth System Models ESM which combine the interactions of atmosphere ocean land ice and biosphere under a wide variety of conditions In addition they used US National Center for Atmospheric Research data on daily relative humidity and data on heatstress analysis Based on these datasets the IITB team estimated the potential impact of future heat waves on mortality using historical data from Indiarsquos Ministry of Home Affairs The team projected intensity duration and frequency of severe heat waves for low middle and high range rates of climate change as shown in longterm projections called representative concentration pathways RCPs RCPs are four greenhouse gas concentration trajectories that climate modellers use to describe possible climate futures see table Each pathway notes how much the planet has heated up and the concentration of greenhouse gases doing the heatingSource IPCC 2014 Climate Change 2014 Impacts Adaptation and Vulnerability Summary for policy makersThe IITB team took RCP26 a projection consistent with the goal to hold global warming to 2 degC showing a peak and a decline in warming RCP45 considered the most probable case and RCP85 possibly the worstcase scenario Future hot zones South India and both coasts Under the most probablecase and the worstcase scenarios 2070 onward there could be an increase in intensity duration and frequency of severe heat waves In particular a large part of southern India east and west coasts which have been unaffected by heat waves are projected to be severely affected after 2070Intensification of severe heat waves for different emission scenarios Graphic Kamal Kumar MurariSevere heat waves are expected to appear early in future years starting in early April under the worstcase scenario A sizeable part of India is also projected to be exposed to extreme heatstress conditions intensification of heat wave and heatstress leading to increased mortality Heatstress is a condition in which the body cannot cool off to maintain a healthy temperaturendashresulting in rashes cramps dizziness or fainting exhaustion heat stroke and a worsening of existing medical conditions Other studies similar conclusion The IITB study follows other studies that have also shown an increasing trend in heat waves Dr D S Pai who heads the Long Range Forecasting division at the National Climate Centre Pune and his colleagues at the India Meteorological Department IMD have shown a noticeable increase in the heat wave and severe heatwave days over the country during 20012010 ndashthe warmest decade recordedndash compared to the previous four decades The IMD team used heatwave information from 103 stations on the Indian mainland during the hotweather season of March to July over the past 50 years 19612010 They examined various statistical aspects of heat waves and severe heat waves such as longterm climatology decadal variation and longterm trends Pai and colleagues also found heat waves linked with El NintildeoSouthern Oscillation ENSO denoting fluctuating ocean temperatures in the equatorial Pacific known for its global impact The study indicates the complexity of future weather predictions They found that heat waves of eight or more days peak a year after the El Nino warm phase of this cycle and are at a minimum a year after the La Nina cool phaseThe year to year variation of all India averaged over all the stations a HW days and b SHW days during the hot weather season March ndash July for the period 19612010 The red green markers correspond to El Nino La Nina yearsSource D S Pai Smitha Anil Nair and A N Ramanathan 2013 Long term climatology and trends of heat waves over India during the recent 50 years 19612010The IMD team found other factors linked to heatwave dynamics including the annual path of the sun moisture distribution across India and how it is influenced by seas on its either side and the arrival of the monsoon Arrival of the monsoon over north India marks the end of the hot weather season In 1998 and 2002 when the monsoon was delayed long heatwave conditions prevailed hereAn Indiaspendorg storyAs the geographic spread of heat waves and trends change weather scientists stress the need for better forecasts and more rigorous research ldquoThe present assessment could be a good starting point for considering heat waves as a disaster even though they do not yet appears in the priorities of disastermanagement plans of the Government of Indiardquo said MurariIndiaspendorg is a datadriven publicinterest journalism nonprofit