Distinct response of Northern Hemisphere land monsoon precipitation to transient and stablized warming scenarios

Abstract

To better understand the climate response under stabilized, overshoot, and transient global warming, four types of ensemble experiments on 1.5 °C/2 °C global warming scenarios (i.e., stabilized 1.5 °C, 1.5 °C overshoot, stabilized 2 °C, and transient 2 °C) are elaborately designed using the Nanjing University Information Science and Technology Earth System Model (NESM). Compared with the modern climate (1985–2014), the projected surface air temperature (SAT) change is characterized by a robust ‘Northern Hemisphere (NH)-warmer than-Southern Hemisphere (SH)’ and ‘land-warmer than-ocean’ patterns. The projected precipitation change exhibits ‘NH-wetter than-SH’ pattern in the tropics. Although the response of SAT and precipitation climatology show similar pattern between stabilized and overshoot scenarios, some significant differences are still found. The projected change in the Northern Hemisphere land monsoon precipitation (NHLMP) is 30% larger in the transient 2 °C experiment compared with that in the stabilized 2 °C experiment. The more vigorous NHLMP in the transient global warming scenario is mainly due to the enhanced land–sea thermal contrast and interhemispheric temperature difference. The enlarged land–sea thermal contrast increases the surface pressure gradient between the NH continents and its adjacent oceans, thus enhancing the NH monsoon circulation and moisture convergence. The enhanced interhemispheric temperature difference shifts the Hadley circulation and intertropical convergence zone northward, leading to the enhanced moisture convergence and the shifts of tropical rain band over the NH monsoon region. This result highlights that climate responses may depend on different warming trajectories and, which could facilitate the strategic planning of governments.