Constrained future brightening of solar radiation and its implication for China's solar power

As Earth's primary energy source, surface downward solar radiation (Rs) determines the solar power potential and usage for climate change mitigation. Future projections of Rs based on climate models have large uncertainties that interfere with the efficient deployment of solar energy to achieve China's carbon-neutrality goal. Here we assess 24 models in the latest Coupled Model Intercomparison Project Phase 6 with historical observations in China and find systematic biases in simulating historical Rs values likely due to model biases in cloud cover and clear-sky radiation, resulting in largely uncertain projections for future changes in Rs. Based on emergent constraints, we obtain credible Rs with narrowed uncertainties by ∼56% in the mid-twenty-first century and show that the mean Rs change during 2050-2069 relative to 1995-2014 is 30% more brightening than the raw projections. Particularly in North China and Southeast China with higher power demand, the constrained projections present more significant brightening, highlighting the importance of considering the spatial changes in future Rs when locating new solar energy infrastructures.