Small global effect on terrestrial net primary production due to increased fossil fuel aerosol emissions from East Asia since the turn of the century

Abstract

The global terrestrial carbon sink has increased since the start of this century at a time of growing carbon emissions from fossil fuel burning. Here we test the hypothesis that increases in atmospheric aerosols from fossil fuel burning enhanced the diffuse light fraction and the efficiency of plant carbon uptake. Using a combination of models, we estimate that at global scale changes in light regimes from fossil fuel aerosol emissions had only a small negative effect on the increase in terrestrial net primary production over the period 1998–2010. Hereby, the substantial increases in fossil fuel aerosol emissions and plant carbon uptake over East Asia were effectively canceled by opposing trends across Europe and North America. This suggests that if the recent increase in the land carbon sink would be causally linked to fossil fuel emissions, it is unlikely via the effect of aerosols but due to other factors such as nitrogen deposition or nitrogen‐carbon interactions.

Have Synergies Between Nitrogen Deposition and Atmospheric CO2 Driven the Recent Enhancement of the Terrestrial Carbon Sink?

“…Hansen et al () speculated that the parallel increase in global fossil fuel emission and the land carbon sink since the turn of this century may be a result of carbon uptake mechanisms that are controlled by the emissions themselves, namely a larger fraction of diffuse solar radiation from increased sulfate aerosol emissions and increased nitrogen deposition. However, the diffuse radiation mechanism has been shown to play only a minor role at global scale (O'Sullivan et al, ). Alternatively, the concurrent rise in both anthropogenic carbon and nitrogen emissions (predominantly from East Asia) could have worked in tandem to fertilize the terrestrial biosphere via a combination of direct fertilization by increased nitrogen deposition along with an increased CO 2 fertilization effect due to alleviation of nitrogen limitation.…”

Estimated spatiotemporal variability of total, direct and diffuse solar radiation across China during 1958–2016

“…Existing studies have revealed the long‐term variations of total radiation, however, knowledge of total solar radiation is not sufficient (Karakoti et al, ) since total radiation passing through the atmosphere comprises both direct and diffuse components (Qian et al, ). It has been proved that more diffuse light can increase the efficiency of plant photosynthesis (Mercado et al, ; O'Sullivan et al, ) and that canopy photosynthetic capacity co‐varies with diffuse radiation at a given solar irradiance (Williams et al, ). In this sense, variations of direct and diffuse radiation are equally important for energy utilization and agricultural activities.…”

Characterization of the radiative impact of aerosols on CO<sub>2</sub> and energy fluxes in the Amazon deforestation arch using artificial neural networks

“…The spatial distribution and nature of the shortwave radiation is critical for the productivity of terrestrial ecosystems and further studies on the impacts of light limitation on vegetation productivity are needed. In light-limited ecosystems such as rainforests and temperate forests, the radiative impact of aerosols on vegetation productivity must be evaluated in combination with other environmental factors, such as temperature and water (O'Sullivan et al, 2016). With fieldwork and numerical studies in the Australian savannah, Whitley et al (2011) suggested that vegetation productivity was more influenced by light limitation than by water limitation.…”