Lotta Andersson (Sweden) 1; Lars Bärring (Sweden) 1; Torben Koenigk (Sweden) 1; Grigory Nikulin (Sweden) 1; Gustav Strandberg (Sweden) 1; Shiyu Wang (Sweden) 1; Renate Wilcke (Sweden) 1
1 - SMHI
Many actors in Sweden, including municipalities and county administrative boards, have requested political guidance at the national level regarding choice of climate scenarios, time perspective and levels of risk taking. However, other question that the designation of fixed values would benefit climate adaptation efforts, not the least due to natural variability.
Within the Swedish project ‘REGTREND’ large ensembles of global climate model simulations are investigated to assess ranges of possible regional climate trends and provide a probabilistic assessment of future climate trends. The results clearly demonstrate that large ensembles of climate model simulations provide a wide range of probabilities. For instance, according to our results, winter temperature trends to the year 2050 can vary between –2º and + 5º in Southern Sweden. Natural climate variability was shown to be important for changes also in the perspective of the year 2100.
Together with dedicated users, strategies are developed to communicate these uncertainties. The Swedish National Climate Adaptation Portal will be updated with guidelines related to the handling of natural variability, as well as model and scenario uncertainties, and how this information can be combined with already available information.
In order to develop such guidelines, a set of workshops have been arranged with national, regional and local authorities. During these workshops, it has been discussed how climate information is used today, and if there are potentials to work with risk management, based on probabilities and locally determined consequences, rather than on ‘fixed’ levels of future change.
Preliminary results from the workshops indicate that it might be constructive to use a risk approach, based on probabilities and consequences, rather than to talk about uncertainties due to natural variability. Uncertainties caused by natural variability might otherwise be taken as an argument to not take action. Another reflection was that climate adaptation mainly is based on re-active actions after the occurrence of extreme events. Comparing experienced extreme weather with probabilities for occurrence in the future was seen as a powerful illustration that makes information tangible and possible to act on. Use of terms similar to what is used in the IPCC reports (e.g., ‘likely’, ‘extremely likely’) was seen as often more helpful than maps and diagrams that could be difficult to interpret. However, it was emphasized that guidelines need to be customized, with selections of indicators (or combination of indicators) and thresholds for which probabilities are provided linked to specified types of sector-relevant decisions.