Since measurements began, some of which date as far back as 1864, marked changes in a number of climate variables have been observed:
A warmer atmosphere can store more humidity, which makes for heavier precipitation. This does not necessarily mean an increase in total precipitation, though. In fact, there has been no significant change in total summer precipitation since measurements began. At the same time, the higher temperatures lead to increased evaporation, which is, in turn, conducive to drought.
Drought occurs when there is no precipitation for an extended period of time. Combined with hot days and high levels of evaporation, this dryness leads to drought in summer. This can put pressure on agriculture and forests.
Dry winters lack the snow and rain needed to fill the reservoirs for spring and summer, as well as presenting a challenge for snow sports.
There are various climate indices for drought. One commonly used indicator is the maximum number of consecutive dry days per year on which less than 1 mm of precipitation is measured. For other indicators, see “Drought indicators” below.
In Switzerland, an increase in drought can be seen for the period of 1981–2020, especially in the summer. This is due on the one hand to a slight decrease in precipitation and on the other hand to increased evaporation caused by climate warming in recent decades.
Without climate change mitigation, the average precipitation amount in the summer months will shrink, and evaporation will increase. The ground will become drier, there will be fewer rainy days, and the longest precipitation-free periods will last longer.
Relevant information and data on drought are available online in a centralized location on a dedicated platform. Information on the current situation and current warnings can be found on the drought platform.
Evapotranspiration – the combination of evaporation and transpiration in plants – plays a central role in the occurrence of drought. Explanations of this and its influence on drought can be found on the page “Drought indicators”.
These publications contain detailed analyses and annual summaries of climate and weather phenomena, including drought.