Climate change and natural hazards

Since the late 19th century, the global surface temperature has risen by 0.6°C. Since the beginning of systematic recordings in 1864, the annual mean temperature has increased in Northern Switzerland by between 1.2°C and 1.5°C and in Southern Switzerland by approx. 0.9°C. The climate had, and still has, a vide variability and this will not change in future.

Incidence and intensity of extreme events, therefore, highly vary – independent of recent global warming. Due to the increasing sensitive and latent energy in the atmosphere, caused by the green house effect, natural hazards are likely to happen more often.
Depending on region and season the development of natural hazards in Switzerland is estimated as follows:

• Hazards caused by thunder and other storms:
  Due to the green house effect, the energy and water content of the atmosphere increases. This raises the potential of foehn and thunderstorms. Besides, climate change influences courses of winterstorms considerably. The courses of Atlantic depressions appreciably alter to North. Consequently, the core pressure of those air masses decreases. This means that several disasters now can be more devastating than hitherto.
  Foehn and thunderstorms will occur more frequently and have more disastrous consequences in future. Climatic warming causes less winterstorms in Switzerland, due to the shift of their courses, but if they hit, they rage more furiously.
  
  
• Flood hazard:
  Due to the generally higher temperatures, climatic extremes increase. On the one hand, more intense rain fall is to be expected. On the other hand, the more frequent rains during winter cause a regional and seasonal shift of drainage. Floods occur more frequently and storm season prolongs to late winter and late autumn.
  
  
• Hazards caused by mass movements:
  The expected warmer and more humid winter could increase the hazard of mass movements, as water is the important factor in moving masses. Geologically unfavourable regions are particularly affected, when flysch, molasse, alpine slate or fine-grained debris are dominant. Additionally, glaciers disappear and permafrost starts melting, which has a negative effect on slope stability.
  
  
• Hazards caused by cold waves:
  Fewer cold spells and frost days in Switzerland.
  
  
• Hazards caused by heat waves and droughts:
  More frequent heat waves and droughts in the summer.