The summer of 2003 struck Western Europe with extremely high temperatures and reportedly contributed to around 70.000 deaths in the region. It was crowned the hottest summer since 1540 and caused a lot of trouble not only to urban dwellers, but also to farmers and rural populations, who saw a significant drop in yields and a higher incidence of forest fires.
According to studies carried out the following year, the summer of 2003 was the first extreme weather event that can firmly be chalked up to human activities – the pollution we let out into the atmosphere has made such events more than twice as likely.
Now, a group of three scientists from the Met Office, the British weather agency, found that our increasing impact on the environment made the probability of unusually hot summers ten times more likely than it was just a decade ago.
Their findings, published yesterday in the online journal Nature Climate Change, suggest that every five years Europe is likely to experience “a very hot summer” with temperatures exceeding the 1961-1990 average by 1.6 degrees Celsius. In 2003, this was thought to occur only once every 52 years, which means that the likelihood has increased ten-fold.
To predict how global warming will play out in the future, Nikolaos Christidis and his colleagues ran their computer models twice: first, with both natural climate fluctuations and human-caused warming included, and secondly with only natural influences on the climate. This method, called “climate attribution”, lets scientists assign responsibility for weather events to natural or manmade factors.
The researchers pored over historical data on Western European and Mediterranean summers during the periods from 1990 to 1999 and from 2003 to 2012. They found that the likelihood of temperature increasing as sharply as during the heat wave of the last decade has gone from less than once a millennium to roughly once every 127 years.
The study also looked at how the odds of extremely hot weather are likely to change in the future as temperatures continue to climb. Results indicate that if carbon emissions continue to increase, heat waves of the magnitude experienced in 2003 will become “very common” by 2040. Dr. Christidis et. al. even suggest that if appropriate measures will fail to be implemented, by 2100 such events may actually be considered “extremely cold”.
This means that our conception of what hot summers are may change dramatically in the near future. In the words of Mr. Christidis himself: “[A]s summer temperatures continue to increase, the perception of extremely hot summers is set to change drastically over the next few decades.”
The paper concludes by saying that even though no one can say with certainty when will extreme weather hit, European governments should take their study seriously and make increasing society’s resilience to such events a priority.
Original research article: Nikolaos Christidis, Gareth S. Jones and Peter A. Stott, 8 December 2014, Dramatically increasing chance of extremely hot summers since the 2003 European heatwave. DOI: 10,1038/NCLIMATE2468.