Response of Global Mesoscale Convective Systems to Increased CO₂ and Uniform SST Warming in a Global Storm-Resolving Model

Mesoscale convective systems (MCSs) are critical components of global energy and water cycles and significantly contribute to extreme weather events. However, projecting future MCS behavior remains challenging due to the limitations of regional models and the inadequate representation of MCSs in coarser climate models. In this study, we use GFDL's global storm-resolving model (GSRM), X-SHiELD, to explore the response of global MCSs to both increased sea surface temperatures (SST) and elevated CO₂ levels using three sets of unique two-year-long warming simulations. We find that SST warming leads to an increase in MCS occurrence over ocean regions while reducing it over land, whereas elevated CO₂ results in an overall increase over ocean and land. When SST and CO₂ increases are combined, their impacts on MCS changes are generally additive. Using stepwise multiple linear regression, we identify the key environmental drivers of these changes across five MCS hotspots, highlighting the regional variability in MCS responses. Furthermore, MCS-associated precipitation and its contribution to total rainfall are shaped by changes in both MCS frequency and the precipitation intensity within each event. By utilizing the explicit MCS-resolving capabilities of GSRMs, this study provides critical insights into future changes in MCS characteristics and their implications for global precipitation patterns.