Spatial characteristics of gridded Swiss temperature trends: local and large-scale influences

Temperature is an essential variable in monitoring the impact of global climate change. Here we perform a detailed regional trend analysis of Swiss Alpine temperatures in the period 1959 to 2008 using a newly available gridded data set based on homogenised observations from 91 MeteoSwiss stations. The aim is to quantify possible large-scale and local-scale contributions to the local trends. It is shown that the annual trends are all positive and highly significant, with an average warming rate of 0.35°C/decade, consistent with results from earlier studies. The values show fairly little spatial variability, with 90% of all gridpoint trends between 0.30 and 0.39°C/decade. This indicates that the warming in Switzerland has exceeded the NH extratropical mean trend by a factor of 1.6 over the last 50 years.