Assessment of Anticipated Changes in Extreme Temperature and Precipitation Under 1.5°C and 2°C Warming Over the Mississippi River Basin

ABSTRACT Extreme precipitation and temperature have large socioeconomic and human health impacts. This study aims to analyse the projected changes of extreme precipitation and temperature indices at 1.5°C and 2°C of warming over the Mississippi River Basin (MRB) under Shared Socio‐economic pathways (SSP) 2‐4.5 and SSP5‐8.5. We used a technique named bias correction constructed analogues with quantiles mapping reordering (BCCAQ) to downscale daily precipitation, minimum and maximum temperature from a set of 12 Coupled Models Intercomparison Project phase 6 (CMIP6) over MRB. The changes in extreme precipitation and temperature indices such as very heavy rainfall (R95p), warm days (TX90p), and warm spell duration (WSDI) are sensitive to warming targets and emission scenarios. Results indicate that both warming targets are expected to exacerbate R95p whilst intensifying extreme precipitation and temperature as a whole except for cumulative wet days (CWD) (many parts of MRB are experiencing reduced CWD at both warming targets and scenarios). However, the rainfall intensity (SDII) is more reduced under SSP5‐8.5 compared to SSP2‐4.5 with an additional 0.5°C highlighting the sensitivity of SDII to the emission scenario. An additional 0.5°C (from 1.5°C to 2°C) climate warming is expected to: (1) increase TX90p and WSDI by 50% under SSP2‐4.5 and nearly 100% under SSP5‐8.5 over much of the MRB subregions, (2) reduce extreme precipitation in the centre of the MRB. Uncertainty superimposes on the magnitude of changes with more than 75% contribution from internal climate variability to total variance, nearly 20% from climate models, and marginal contribution from climate scenarios. The predominance of natural climate variability underscores a decreased predictability in future extreme precipitation and extreme temperature due to anthropogenic forcings, particularly at the regional scale. So, a deep understanding of what drives climate and its variability on a local and regional scale is critical for future generations of climate models and climate projections assessment. However, climate warming will pose serious challenges to water availability over the MRB, with consequences for agriculture, crop yields, and ecosystems.