China’s goal to achieve carbon (C) neutrality by 2060 requires scaling up photovoltaic (PV) and wind power from 1 to 10–15 PWh year⁻¹(refs. ^1–5). Following the historical rates of renewable installation¹, a recent high-resolution energy-system model⁶and forecasts based on China’s 14th Five-year Energy Development (CFED)⁷, however, only indicate that the capacity will reach 5–9.5 PWh year⁻¹by 2060. Here we show that, by individually optimizing the deployment of 3,844 new utility-scale PV and wind power plants coordinated with ultra-high-voltage (UHV) transmission and energy storage and accounting for power-load flexibility and learning dynamics, the capacity of PV and wind power can be increased from 9 PWh year⁻¹(corresponding to the CFED path) to 15 PWh year⁻¹, accompanied by a reduction in the average abatement cost from US$97 to US$6 per tonne of carbon dioxide (tCO₂). To achieve this, annualized investment in PV and wind power should ramp up from US$77 billion in 2020 (current level) to US$127 billion in the 2020s and further to US$426 billion year⁻¹in the 2050s. The large-scale deployment of PV and wind power increases income for residents in the poorest regions as co-benefits. Our results highlight the importance of upgrading power systems by building energy storage, expanding transmission capacity and adjusting power load at the demand side to reduce the economic cost of deploying PV and wind power to achieve carbon neutrality in China.

A decline in the carbon fertilization effect: One source of uncertainty in climate science is how the carbon fertilization effect (CFE) will contribute to mitigation of anthropogenic climate change. Wang et al. explored the temporal dynamics of CFE on vegetation photosynthesis at the global scale. There has been a decline over recent decades in the contribution of CFE to vegetation photosynthesis, perhaps owing to the limiting effects of plant nutrients such as nitrogen and phosphorus. This declining trend has not been adequately accounted for in carbon cycle models. CFE thus has limitations for long-term mitigation of climate change, and future warming might currently be underestimated. Science , this issue p. 1295

Spatial patterns and temporal trends of nitrogen (N) and phosphorus (P) deposition are important for quantifying their impact on forest carbon (C) uptake. In a first step, we modeled historical and future change in the global distributions of the atmospheric deposition of N and P from the dry and wet deposition of aerosols and gases containing N and P. Future projections were compared between two scenarios with contrasting aerosol emissions. Modeled fields of N and P deposition and P concentration were evaluated using globally distributed in situ measurements. N deposition peaked around 1990 in European forests and around 2010 in East Asian forests, and both increased sevenfold relative to 1850. P deposition peaked around 2010 in South Asian forests and increased 3.5‐fold relative to 1850. In a second step, we estimated the change in C storage in forests due to the fertilization by deposited N and P (∆C_{ν dep}), based on the retention of deposited nutrients, their allocation within plants, and C:N and C:P stoichiometry. ∆C_{ν dep} for 1997–2013 was estimated to be 0.27 ± 0.13 Pg C year⁻¹ from N and 0.054 ± 0.10 Pg C year⁻¹ from P, contributing 9% and 2% of the terrestrial C sink, respectively. Sensitivity tests show that uncertainty of ∆C_{ν dep} was larger from P than from N, mainly due to uncertainty in the fraction of deposited P that is fixed by soil. ∆C_{P dep} was exceeded by ∆C_{N dep} over 1960–2007 in a large area of East Asian and West European forests due to a faster growth in N deposition than P. Our results suggest a significant contribution of anthropogenic P deposition to C storage, and additional sources of N are needed to support C storage by P in some Asian tropical forests where the deposition rate increased even faster for P than for N.

High-resolution mapping of fuel combustion and CO₂ emission provides valuable information for modeling pollutant transport, developing mitigation policy, and for inverse modeling of CO₂ fluxes. Previous global emission maps included only few fuel types, and emissions were estimated on a grid by distributing national fuel data on an equal per capita basis, using population density maps. This process distorts the geographical distribution of emissions within countries. In this study, a sub-national disaggregation method (SDM) of fuel data is applied to establish a global 0.1° × 0.1° geo-referenced inventory of fuel combustion (PKU-FUEL) and corresponding CO₂ emissions (PKU-CO₂) based upon 64 fuel sub-types for the year 2007. Uncertainties of the emission maps are evaluated using a Monte Carlo method. It is estimated that CO₂ emission from combustion sources including fossil fuel, biomass, and solid wastes in 2007 was 11.2 Pg C yr⁻¹ (9.1 Pg C yr⁻¹ and 13.3 Pg C yr⁻¹ as 5th and 95th percentiles). Of this, emission from fossil fuel combustion is 7.83 Pg C yr⁻¹, which is very close to the estimate of the International Energy Agency (7.87 Pg C yr⁻¹). By replacing national data disaggregation with sub-national data in this study, the average 95th minus 5th percentile ranges of CO₂ emission for all grid points can be reduced from 417 to 68.2 Mg km⁻² yr⁻¹. The spread is reduced because the uneven distribution of per capita fuel consumptions within countries is better taken into account by using sub-national fuel consumption data directly. Significant difference in per capita CO₂ emissions between urban and rural areas was found in developing countries (2.08 vs. 0.598 Mg C/(cap. × yr)), but not in developed countries (3.55 vs. 3.41 Mg C/(cap. × yr)). This implies that rapid urbanization of developing countries is very likely to drive up their emissions in the future.