Abstract
Abstract. Plants primarily conduct photosynthesis in the daytime, offering an opportunity to increase photosynthesis and carbon sink by providing light at night. We used a fully coupled Earth system model to quantify the carbon sequestration and climate effects of a novel carbon removal proposal: lighting up tropical forests at night via lamp networks above the forest canopy. Simulation results show that additional light increased the tropical forest carbon sink by 10.4±0.05 Pg of carbon per year during a 16-year lighting experiment, resulting in a decrease in atmospheric CO2 and suppression of global warming. In addition, local temperature and precipitation increased. The energy requirement for capturing 1 t of carbon is lower than that of direct air carbon capture. When the lighting experiment was terminated, tropical forests started to release carbon slowly. This study suggests that lighting up tropical forests at night could be an emergency solution to climate change, and carbon removal actions focused on enhancing ecosystem productivity by altering environmental factors in the short term could induce post-action CO2 outgassing.
Highlights
Anthropogenic greenhouse gas (GHG) emissions have led the global mean temperature to increase by approximately 1.1 ◦C since the industrial revolution (IPCC, 2013, 2018; IPCC AR6 WGI, 2021)
Physiological responses of tropical trees to longer photoperiods at the ecosystem level remain among the biggest uncertainties in model simulations
Some field experiments indicate that higher CO2 did not increase carbon sequestration of forests without added nutrients (Oren et al, 2001), suggesting tree growth might be limited by nutrient supply
Summary
Anthropogenic greenhouse gas (GHG) emissions have led the global mean temperature to increase by approximately 1.1 ◦C since the industrial revolution (IPCC, 2013, 2018; IPCC AR6 WGI, 2021). Greenhouse experiments either lengthen or shorten photoperiods, and results suggest that short photoperiods reduce plant growth rate and lead to thinner leaves and lower chlorophyll content (Djerrab et al, 2021; Luo et al, 2021), while long photoperiods increase stem growth rate and stimulate tree growth (Dixit and Singh, 2014; Stubblebine et al, 1978) These studies are more focused on specific tropical plant species and tend to agree that longer photoperiods might have a positive effect on vegetative growth in tropical forests. Each simulation has a spatial resolution of 1◦ and has two members (created from small perturbations to initial conditions) to provide uncertainty estimation. (See Methods for detailed experimental design.)
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