Midwestern Climate Modelling and Analysis: An Examination of Climate Patterns, Trends, and Sensitivities

In recent years, global climate change has been at the forefront of scientific research. While the global perspective gives the most comprehensive understanding of our changing climate system, it is more practical to downscale the perspective to a regional view to better illustrate to our communities and policy makers the changes in our local climate that may occur in our not-so-distant future. The Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC-AR5) outlines four Representative Concentration Pathways (RCPs) that represent greenhouse gas (GHG) emissions scenarios. RCP8.5 was chosen and examined in this study, as it represents the “business-as-usual” scenario, in which the anthropogenic emissions of GHGs, continue at the current rate. This study was conducted by using a 20-year historical period from 1981-2000 and a 20-year future period from 2081-2100 under the “business-as-usual” RCP8.5 scenario. Monthly surface air temperature data from 30 Global Climate Models (GCMs) was investigated to determine the potential warming in the surface atmosphere by the end of the 21st century. The continental United States, particularly the Midwest is focused. This study revealed the ensemble-mean annual-mean Midwest US temperature change to be 5.39 °C compared to the global-mean 4.65 °C, illustrating that the Midwest is more sensitive to future warming than the global average. There is substantial spread across GCMs; the most sensitive GCM projects 7.35 °C in Midwest while least sensitive projects 3.37 °C, representing model-to-model uncertainties. The projected warming is also dependent on seasons. Summer and fall are found to witness more warming than winter and spring, suggesting hot-seasons will be even hotter and implying more frequent and elongated heat waves in the future under the “business-as-usual” GHG emissions scenario. A potential “mitigation” scenario is discussed and will be examined in a future study.