Peter A. Stott, D. A. Stone, M. R. Allen


Published date December 2, 2004

Human contribution to the European heatwave of 2003

  • States that the summer of 2003 was probably the hottest in Europe since at latest AD 1500, and unusually large numbers of heat-related deaths were reported in France, Germany and Italy
  • States that it is an ill-posed question whether the 2003 heatwave was caused, in a simple deterministic sense, by a modification of the external influences on climate—for example, increasing concentrations of greenhouse gases in the atmosphere—because almost any such weather event might have occurred by chance in an unmodified climate
  • States, however, it is possible to estimate by how much human activities may have increased the risk of the occurrence of such a heatwave
  • Uses this conceptual framework to estimate the contribution of human-induced increases in atmospheric concentrations of greenhouse gases and other pollutants to the risk of the occurrence of unusually high mean summer temperatures throughout a large region of continental Europe
  • Estimates it is very likely (confidence level >90%) that human influence has at least doubled the risk of a heatwave exceeding this threshold magnitude, using a threshold for mean summer temperature that was exceeded in 2003, but in no other year since the start of the instrumental record in 1851
  • Finds the best estimate is that climate change in made such an extreme heat event 4 times as likely