Marine Cloud Brightening and Subseasonal-to-Seasonal Northern Hemisphere Weather Control

Abstract:

As global mean temperatures and associated climate risks rise in response to greenhouse gas forcing, research on the engineered management of incoming solar radiation is increasingly pertinent. Marine cloud brightening (MCB), the introduction of sea salt aerosols into the lower marine troposphere, is one such strategy. By increasing the albedo of both stratocumulus cloud decks and the clear-sky atmospheric column, MCB is expected to counteract some fraction of anthropogenic climate change through a reduction in net radiative forcing. Previous studies demonstrate a capacity for MCB to alter global and regional temperature, precipitation, and circulation patterns on interdecadal timescales, but leave open questions regarding impacts on subseasonal-to-seasonal weather. We explore the potential for MCB to significantly alter atmospheric drivers of Northern Hemisphere weather on shorter timescales than have yet been examined, with implications for controllability of climate-induced extremes. Put simply: would large-scale MCB enable a degree of weather control? We quantify the impacts of MCB in three mesoscale ocean regions on Northern Hemisphere 500hPa geopotential height and atmospheric standing wave structure, which are known to predict key features of subseasonal to seasonal weather, including precursor conditions for heat waves and other hazardous weather extremes. Cloud droplet number concentration (CDNC) is modified over the selected regions to simulate MCB in the Community Atmosphere Model (CAM) component of Community Earth System Model (CESM) version 2.1.3, fully coupled with CESM land and ocean components. CDNC perturbations are applied to each region individually and in combination. Results yield preliminary insights into the predictability of Northern Hemisphere weather in response to the MCB schemes considered here, and associated possibilities for control.