NEW DELHI: As the death toll in the current heat wave crossed the 2,000 mark, this has become the fifth deadliest ever heatwave in the world and the second deadliest in India , according to an international database of disasters.Weathermen are predicting that there are a few more days left in the ongoing heatwave which has killed the most number of people in Andhra Pradesh and Telengana, while affecting large parts of the rest of the country.The deadliest heatwave on record in India is the 1998 one in which 2,541 people died. The most lethal heatwave in the world was the one that crippled Europe in 2003, killing 71,310 people. These figures are maintained in the Emergency Events Database (EM-DAT) maintained by the Centre for Research on the Epidemiology of Disasters (CRED) based in Brussels, Belgium.Weather expert and founder of Weather Underground Jeff Masters writes that "death tolls from heatwaves are very difficult to estimate, since excess heat is typically not listed as the primary cause of death in cases where the victim has a pre-existing condition such as heart or lung disease." This means that in most cases, especially in India, the actual death toll will be much higher in all the listed events, including the current one.Researchers of the Ahmedabad Heat Climate Study Group analysed all deaths in Ahmedabad in the 2010 heatwave and compared it to all deaths in the previous year (2009) and the subsequent year (2011) to find out the real number of excess deaths attributable to a heatwave. Their results, published in the journal PLOS-ONE in March 2014 were stunning. While the official death toll due to heatwave conditions was recorded as 50, the study found an excess of 1,344 deaths in 2010 over other years. That's a 43% spike in deaths due to heatwave conditions, and that too in a city which is used to high temperatures. The group of researchers in this study have since collaborated with civic authorities in Ahmedabad to put in place a system for saving people's lives in heatwave conditions.In the list of top ten deadliest disasters, Indian heatwaves figure four times — 1998, 2002, 2003 and 2015. Unsurprisingly, six of the top ten heatwaves in terms of deaths have occurred in the 21st century, which has also recorded eight of the ten warmest years ever since records of global temperatures were started being kept. 2014 was tied at the warmest year on record with 1998, and the first quarter of 2015 has already been declared the warmest on record. So, global warming and increasing population are contributing to the increasing ferocity of heatwaves.According to a study done by researchers from IIT Bombay, TISS and Monash University, Australia, the frequency and intensity of heatwaves is going to increase in the future. In a paper published in the April 2015 issue of the journal Regional Environmental Change, they write "heatwaves are projected to be more intense, have longer durations and occur at a higher frequency and earlier in the year." Apart from predicting that heatwaves will become more common in south India, the scientists say that "in northern India, the average number of days with extreme heat stress condition during pre-monsoon hot season will reach 30. The intensification of heatwaves might lead to severe heat stress and increased mortality."