How to trigger people : Weather service decision aid for everyone

In recent years the thermal extremes have become increasingly severe, and it is expected that hot extremes will become twice as frequent if we are unable to limit global warming. The global warming will increase the available energy in certain weather systems making hurricanes more easily reach the development threshold and the increased displacement of precipitation will cause longer and more intense droughts which in turn promotes wildfires. To adapt and to mitigate the risks of these extremes, thermal health warning systems can increase the resilience of our societies.This thesis explores the concept of integrating human thermal models which predict thermophysiological responses based on the environment into weather forecasting and early warning systems. By integrating the models, the weather forecasts may provide detailed information about the risks of exposure for individuals based on their activity and clothing. The thesis further discusses possibilities of integrating the concept on different spatial scales where both local and regional early warning systems can benefit from the integration.Paper I evaluates the concept behind ClimApp, a smartphone app which can provide individualized thermal stress predictions based on the weather forecast and the user input of clothing and activity. The possibilities and limitations are discussed where the underlying models and indices each have their strengths and limitations.In paper II, the developed smartphone app was tested for its usability aspects by first-time users in both a controlled laboratory setting and in a field test. The first iteration of the app was evaluated using a pre-determined set of tasks where the user actions were recorded and followed by a semi-open interview. Several improvements were made, and the second iteration was tested in the field in cold environments. A post-exposure survey and follow-up interview concluded that the ClimApp concept is viable, usable, and relevant particularly during extreme events.In paper III, the validity of the ClimApp prediction was evaluated based on the root mean square deviation of the prediction compared to the standard deviation of the observed prediction. The evaluation concluded that the ClimApp prediction was valid for the field test. Similarly, ClimApp provides the Universal Thermal Climate Index (UTCI) alongside the ClimApp index, and it was found that UTCI overpredicted the cold stress sensation compared to users perception. The reason for overprediction was most probably due to the low activity and clothing insulation in UTCI where activity is a fixed value and clothing insulation is derived from the air temperature. The Early Warnings For All (EW4All) action plan by the United Nations and the World Meteorological Organization aims to have every person on the globe to be covered by an early warning system by 2027. Therefore, paper IV explored the association between the El Niño Southern Oscillation (ENSO) and thermal stress for the Asia-Pacific region. By understanding the association between global weather phenomenon such as ENSO and the regional thermal stress exposure, regional early warning systems can be developed to increase preparedness and response capacity in the region.The thesis concludes with key findings of the ClimApp concept, with feasible development possibilities to promote both individual resilience and that of vulnerable groups such as the elderly and occupational groups such as firefighters who are exposed to a multitude of risks, including heat stress.