Simulated terrestrial climate and carbon cycle response to cloud albedo enhancement over ocean and land

[Geoengineering News]

https://www.sciencedirect.com/science/article/pii/S1674927825001224

Authors

Yu FANG, Long CAO

12 June 2025

https://doi.org/10.1016/j.accre.2025.06.003

Abstract

Marine cloud brightening (MCB) has been proposed as a backup method to mitigate some impacts of global warming. Cloud albedo can be increased over ocean or land either intentionally or unintentionally. Our understanding of how the climate response differs between cloud albedo enhancement over ocean and land remains limited. In this study, we use the Community Earth System Model (CESM) to explore the impact of cloud albedo enhancement over either ocean or land on the terrestrial climate and carbon cycle. In our simulation design, both MCB and land cloud brightening (LCB) are applied over the latitude bands of 30ºS‒30ºN under atmospheric CO2 concentration of 800 × 10−6 to achieve a net negative radiative forcing of about −1 W/m2. Over large parts of the low latitude land, MCB increases precipitation by enhancing upward atmospheric motion, resulting in increased soil moisture. In contrast, LCB decreases precipitation by inducing subsidence, resulting in decreased soil moisture. Changes in climatic factors affect land gross primary production (GPP). Relative to the high CO2 world, LCB reduces GPP by 3.80 ± 0.09 GtC per year, which is about three times the reduction caused by MCB (1.34 ± 0.10 GtC per year). These differences in GPP responses are closely linked to changes in the hydrological cycle. In large parts of low-latitude regions, MCB increases soil moisture, which acts to enhance GPP. Conversely, LCB reduces soil moisture, which acts to suppress GPP. MCB and LCB-induced changes in temperature, sunlight, and vapor pressure deficit also play important roles in regulating GPP change. This study would help us to better understand terrestrial climate and carbon cycle consequences resulting from large-scale cloud albedo change over either ocean or land, as well as large-scale albedo change over ocean and land surface.

Source: ScienceDirect