Global drought changes and attribution under carbon neutrality scenario

As the carbon-neutral target has been set, it is of great importance to investigate and attribute dry-wet climate response for which CO₂ emission is increasing, decreasing, and remaining stable over time. Therefore, our study utilize data from five models of the CMIP6 to analyze the spatiotemporal variations and attribution of global drought as presented by the Standardized Precipitation Evapotranspiration Index (SPEI) during periods of CO₂ increasing by 1% per year, decreasing by 1% per year, and remaining stable. During the CO₂ ramp-up period, potential evapotranspiration (PET) increases faster than precipitation (P), causing a decrease in SPEI. Conversely, a faster PET decrease than P leads to increased SPEI during the CO₂ ramp-down period. Spatially, low and mid-latitudes exhibit opposite trends to high latitudes, with the most pronounced responses observed in the Amazon, southern Africa, and Australia. After CO₂ returns to pre-industrial (PI) concentration, global P and PET do not recover, remaining ~2% higher compared to PI levels. However, SPEI shows a recovery in the global average, yet fails to reach PI levels in specific regions. Furthermore, extreme drought and wetness events persist with increased frequency and severity compared to PI levels despite the recovery of CO₂ concentration. Finally, based on the attribution analysis, the contribution of precipitation (~35%) to drought changes is secondary to that of PET (~65%), which is primarily promoted by air temperature (~50%), followed by net radiation (~10%) and relative humidity (~6%) with negligible effect of wind speed.