Assessing Surface Temperature and Precipitation Extremes Across Climate Scenarios Using an Integrated Human-Earth Systems Model with CESM

Climate extremes are intensifying worldwide, impacting both humanity and the environment. This study investigates future global climate extremes using a newly developed computational framework that links the Integrated Global System Model (IGSM) with the CESM1. The IGSM's emission driven projections generate greenhouse gas concentrations that drive CESM1, which is used to assess the impact of resolution on projected changes in climate extremes. The IGSM-CESM1 connected system has been used to generate two feasible futures: Current Trends (CT) and Accelerated Actions (AA). The analysis evaluates extreme diagnostics for temperature and precipitation over two future periods—Near (2021–2040) and Far (2081–2100)—compared to the baseline period of 1986–2005. The investigation finds that the IGSM-CESM1 simulations of widespread warming also carry important regional changes to extremes by the end of the 21^st century. Projections of summer days increase by 30 days under the AA scenario and 60 days under the CT scenario, with the most severe increases affecting South America. Precipitation indices, such as consecutive dry days, are expected to increase in the Amazon, Central America, and Southern Africa, while slightly decreasing in the Central Pacific (CP), Central Africa (CA), and northwest SA. Conversely, maximum daily precipitation is projected to increase by the end of the century, with the strongest increases seen across the western US, CA, CP, Australia, and northern SA, while weakening in dry areas such as the South Pacific, the South Atlantic, and northern Africa. Our analysis shows that the IGSM-CESM1 at 2° resolution is comparable to its simulation results at 1° resolution across many regions of the world such as Europe, Australia, the Amazon, Southern Africa, India, US, major ocean basins, and Antarctica. This suggests that the IGSM-CESM1 projections at 2° resolution can capture important climate-change patterns while reducing computational expenses and maintaining key interpretations of human-forced climate change on extremes. CESM1 was modified to adjust climate sensitivity via a cloud radiative approach. Higher computation efficiency of CESM1 version with 2° resolution let us to perform ensembles of simulations for estimating uncertainty in future climate under different emission scenarios.