• Energy Research

Abstract Recent increases in vegetation cover, observed over much of the world, reflect increasing CO2 globally and warming in cold areas. However, the strength of the response to both CO2 and warming appears to be declining. Here we examine changes in vegetation cover on the Tibetan Plateau over the past 35 years. Although the climate trends are similar across the Plateau, drier regions have become greener by 0.31±0.14% yr−1 while wetter regions have become browner by 0.12±0.08% yr–1. This divergent response is predicted by a universal model of primary production accounting for optimal carbon allocation to leaves, subject to constraint by water availability. Rising CO2 stimulates production in both greening and browning areas; increased precipitation enhances growth in dry regions, but growth is reduced in wetter regions because warming increases below-ground allocation costs. The declining sensitivity of vegetation to climate change reflects a shift from water to energy limitation.

Net radiation plays an essential role in determining the thermal conditions of the Earth’s surface and is an important parameter for the study of land-surface processes and global climate change. In this paper, an improved satellite-based approach to estimate the daily net radiation is presented, in which sunshine duration were derived from the geostationary meteorological satellite (FY-2D) cloud classification product, the monthly empirical as and bs Angstrom coefficients for net shortwave radiation were calibrated by spatial fitting of the ground data from 1997 to 2006, and the daily net longwave radiation was calibrated with ground data from 2007 to 2010 over the Heihe River Basin in China. The estimated daily net radiation values were validated against ground data for 12 months in 2008 at four stations with different underlying surface types. The average coefficient of determination (R2) was 0.8489, and the averaged Nash-Sutcliffe equation (NSE) was 0.8356. The close agreement between the estimated daily net radiation and observations indicates that the proposed method is promising, especially given the comparison between the spatial distribution and the interpolation of sunshine duration. Potential applications include climate research, energy balance studies and the estimation of global evapotranspiration.

Abstract The seasonal peak of vegetation photosynthesis is a key indicator of terrestrial ecosystem productivity, bearing significant impacts on atmospheric CO2 concentrations. Recent remote sensing observations have indicated an escalating trend in peak photosynthesis, yet the sustained trajectory of this increase under warming remains uncertain. Notably, water availability and temperature emerge as paramount limiting factors governing vegetation photosynthesis. To probe these constraints, here we employ solar-induced chlorophyll fluorescence as a surrogate for photosynthesis, focusing on the examination of temperature and water-related restrictions on peak photosynthesis for northern ecosystems. Our findings unveil a discernible expansion of water-constrained zones in northern ecosystems over the past two decades. A general relationship is identified between mean annual temperature and precipitation that effectively distinguishes temperature-constrained and water-constrained ecosystems, which can be used to predict future changes in the constraint status in various climate change scenarios. Our results show that water-constrained regions will further expand by 4.51% and 11.13% by 2100 under the SSP245 and SSP585 scenarios.