Another important characteristic is the prevailing climate during the glacials and interglacials because it determines living conditions for humans directly above, or in the vicinity of, the repository.
Following the Köppen climate classification scheme (Köppen 1918), a typical climate at the start of a glaciation is a polar climate, followed by continental and temperate climates. Polar, continental and temperate climates have all occurred in the past and are well documented using proxy data and simulations (Nagra 2024j), and it is reasonable to assume that they are also representative for future glacial/interglacial cycles. At the height of an interglacial period, Switzerland may also experience a warmer-drier climate, especially if high carbon emissions are assumed. Simulations of the IPCC using Scenario RCP8.5, which is approximately equivalent to the 3'000 PgC scenario, predict warm-temperate climates for Switzerland by 2100. These climates are defined as having a mean temperature during the coldest month above 0 °C and above 22 °C for the warmest months, while 8 months have mean temperatures above 10 °C (IPCC 2023). A dry climate is defined as having very little precipitation and very high average monthly temperatures throughout the year. Currently, most of Spain experiences temperate to dry climates. According to Beck et al. (2018), the dry climate will advance north-eastwards in the next 100 yr and reach the Pyrenees while arid conditions are expected in parts of Spain. Under normal low or natural emission scenarios, a dry climate is not to be expected in Switzerland during a glacial/interglacial cycle. However, with continued carbon emissions and subsequent climate change a warmer-drier climate cannot be ruled out that, at least in the high-emission scenarios, such a dry climate may occur even in Switzerland in the future.