India and Pakistan in particular have been moaning under an unprecedented heat wave since early March. Climate change has made these extreme temperatures about 30 times more likely, climate researchers now believewho have come together in the “World Weather Attribution” initiative.
It is difficult to determine precisely how often such events, which are still rare, are to be expected, especially since many data series date back only a few decades. However, based on the available data, the researchers assume that a heat wave like the one currently plaguing the current climate is likely to occur approximately every hundred years. Without the previous warming of around 1.2 degrees Celsius, this would have been virtually impossible. However, as warming progresses, such events are likely to occur more frequently, the scientists point out. If the climate warmed about two degrees above pre-industrial levels, such heat waves would be two to 20 times more likely. However, these numbers may underestimate the current and future likelihood of such heat.
The analysis focuses on daily maximum temperatures in March and April in northwest India and southeast Pakistan, the hardest hit regions. March was the hottest in India since records began 122 years ago, and April was even hotter.
Wheat yields have dropped significantly in some Indian states
Pre-monsoon heat waves are not uncommon in the region. In this case, however, the temperatures were extreme very early in the year and the precipitation was well below average. The two together have had serious consequences for public health and agriculture. Early estimates indicate that wheat yields in the Indian states of Haryana, Uttar Pradesh and Punjab have fallen by 10-35%. It is not yet possible to say what excess mortality the heat has caused.
“In the states for which we have data, heat waves are the deadliest extreme weather events,” says Friederike Otto of Imperial College London, who helped with the analysis. “At the same time, they are increasing the most in a warming world.”
