High-resolution projections of climate-related risks for the Midwestern USA

Abstract

We use output from a suite of Regional Climate Models (RCMs) applied under the North American Regional Climate Change Assessment Program (NARCCAP) to quantify possible changes in metrics of climate impacts in the Midwest for the middle 21st century (2041-2062). RCM simulations of the historical period indicate a large positive bias in growing season length, but generally good agreement with observationally derived estimates of metrics such as the mean summertime maximum and apparent temperatures and number of cooling degree days. There is a tendency towards intensification of thermal extremes by 2041-2062 that is equal to or exceeds the bias in the ensemble mean during the historical period (1979-2000). For example, the number of days in the Chicago region each year with temperatures in excess of 32.2°C (90°F) is doubled by the mid-century. The ensemble average estimates for 1979-2000 from the RCMs is negatively biased in terms of annual, spring and summer precipitation (the wettest pentad) and mean dry day duration, but is positively biased in terms of total precipitation accumulated on the 10 wettest days of the year. The RCM simulations indicate an increased likelihood of extreme hydroclimate events that again are equal to or exceed the historical biases. For example, the wettest pentad and total accumulation on the top 10 wettest days of the year are projected to increase by ~10%. Preliminary results for icing and extreme wind events indicate no change in the magnitude of extreme wind events, and perhaps slight reductions in icing risk.

Downscaling of Climate Information

“…The high spatial variability in the response in warm season precipitation evident for the Great Plains and Midwest as shown in Figs. 5.2 and 5.3 is consistent, at least in part, with other downscaling analyses that have indicated enhanced precipitation during the spring transition months, coupled with drying of the summer proper (Patricola and Cook 2013;Pryor et al 2013) (see further discussion below).…”

“…The ESD scenarios indicated increases of approximately 2 weeks (15.8 days) in the duration of the frost-free period by 2046-2065 and by almost one month by 2081-2100 (both relative to (Schoof 2009). This is consistent with the average increase in duration of the growing season for the Midwest by 2041-2062 of approximately 3 weeks derived based on an ensemble of the North American Regional Climate Change Assessment Program (NARCCAP) models (Pryor et al 2013).…”

“…The results indicate that the frequency of heat days, which has increased by over a factor of two during the last four decades, is projected to increase by 2.1-2.4, 3.4-3.6 and 4.0-5.1 times by 2020s, 2050s and 2080s respectively relative to the average for 1961-1990 based on the B2 and A2 SRES (Garcia Cueto et al 2010). Other ESD analyses of heat-wave intensity have included the additional influence on apparent temperature of humidity, and have indicated apparent temperature and hence heat stress in the Midwest increased across all SRES scenarios considered, with the 90th percentile apparent temperature increasing by between 3 and 6°C between 1961-1990and 2081-2100(Schoof 2013. This tendency towards intensification of thermal extremes is also manifest in the NARCCAP RCM simulations.…”

“…This tendency towards intensification of thermal extremes is also manifest in the NARCCAP RCM simulations. For example, the number of days in the Chicago region each year with temperatures in excess of 32.2°C (90°F) is doubled by the mid-century based on an 8-member ensemble mean (Pryor et al 2013).…”

Developing a shared understanding of the Upper Mississippi River: the foundation of an ecological resilience assessment

“…Levees, navigation infrastructure, extensive channel modifications of streams and rivers throughout the basin, and basin-wide land use changes, e.g., extensive tile drainage, have further modified flow regimes through increased discharge and water level variability (Sparks et al 1998, Raymond et al 2008, Schilling et al 2010, Watson et al 2013). Projections of increased precipitation and increased frequency of storm events and droughts will likely further influence flow regime (Pryor et al 2013). For subsequent purposes, we classify these changes as external drivers that influence controlling variables, yet are ultimately external to, or operate at a larger scale, i.e., watershed and jurisdictional boundaries, than our focal scale, the riverfloodplain reach.…”