Climate change made the extreme temperatures that baked north-west India and Pakistan in April and May over 100 times more likely and also increased the chances that such heat waves will occur more frequently by the end of the century.
Without accounting for climate change, a heat wave exceeding the 2010's average temperature could happen once in every 312 years, according to an attribution study by the UK's Met Office published on Wednesday. Taking climate change into account, the probabilities increase to once in every 3.1 years in the current climate, and to once in every 1.15 years by the end of the century.
"Spells of heat have always been a feature of the region's pre-monsoon climate during April and May," Nikos Christidis, the scientist who produced the report, said in a statement. "However, our study shows that climate change is driving the heat intensity of these spells."
Climate change is already making extreme weather events such as heat waves more intense and more frequent, and will continue to do so in the future. India and Pakistan's heatwave is also extraordinary in its duration -- extremely high temperatures started in March and the heat looks likely to build again this week, according to the Met Office.
Attribution studies, which determine the influence of climate change on a particular weather event, can take months to complete as each study must be individually peer reviewed. To speed up the process, the Met Office said it has come up with a peer-reviewed methodology that can be re-applied to every major event that occurs.
Scientists will have to wait until the end of the month, when all records for April and May have been collated, to see whether this year's heatwave exceeds the levels experienced in 2010.
In recent days, temperatures in some parts of India have exceeded 50 degrees Celsius (122 Fahrenheit), while some parts of Pakistan reached 51 degrees Celsius last Sunday. The extreme pre-monsoon heatwave has eased for now, but maximum temperatures are likely to reach 50 degrees Celsius again in some places, said Paul Hutcheon of the Met Office's Global Guidance Unit.