Abstract
Assessing potential impacts of 1.5 °C and 2 °C global warming and identifying the risks of further 0.5 °C warming are crucial for climate adaptation and disaster risk management. Four earth system models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and a process-based ecosystem model are used in this study to assess the impacts and potential risks of the two warming targets on the carbon cycle of China’s terrestrial ecosystems. Results show that warming generally stimulates the increase of net primary productivity (NPP) and net ecosystem productivity (NEP) under both representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios. The projected increments of NPP are higher at 2 °C warming than that at 1.5 °C warming for both RCP4.5 and RCP8.5 scenarios; approximately 13% and 19% under RCP4.5, and 12.5% and 20% under RCP8.5 at 1.5 °C and 2 °C warming, respectively. However, the increasing rate of NPP was projected to decline at 2 °C warming under the RCP4.5 scenario, and the further 0.5 °C temperature rising induces the decreased NPP linear slopes in more than 81% areas of China’s ecosystems. The total NEP is projected to be increased by 53% at 1.5 °C, and by 81% at 2 °C warming. NEP was projected to increase approximately by 28% with the additional 0.5 °C warming. Furthermore, the increasing rate of NEP weakens at 2 °C warming, especially under the RCP8.5 scenario. In summary, China’s total NPP and NEP were projected to increase under both 1.5 °C and 2 °C warming scenarios, although adverse effects (i.e., the drop of NPP growth and the reduction of carbon sequestration capacity) would occur in some regions such as northern China in the process of global warming.
Highlights
Since the threshold of 2 ◦C warming was first proposed by Nordhaus [1], it has gradually been accepted as the important greenhouse gas reduction target
Our results indicate the annual net primary productivity (NPP) averaged over China’s terrestrial ecosystem is about 518.8 ± 29.0 g C m−2 yr−1 of the two scenarios during the reference period
The fluctuation of annual NPP in the 2 ◦C warming period is greater under the RCP4.5 scenario than that under the RCP8.5 scenario, and the standard deviation of the former is 1.5 times higher than that of the latter
Summary
Since the threshold of 2 ◦C warming was first proposed by Nordhaus [1], it has gradually been accepted as the important greenhouse gas reduction target. The enhanced global warming target has been proposed, the assessment of associated impacts on terrestrial ecosystems is very rare in China. Previous modeling studies have shown that the net primary productivity (NPP) will increase in response to future global warming [9,10]. Recent studies using the Coupled Model Intercomparison Project Phase 5 (CMIP5) model projections suggested that the rate of net terrestrial carbon uptake would decrease during the 21st century in most scenarios due to enhanced soil organic matter decomposition, water deficit, climatic extreme events, land use change, etc. We averaged results of the CEVSA2 model and the ESMs to an ensemble, which was used to provide a comprehensive assessment of impacts and risks of 1.5 ◦C and 2 ◦C global warming on the carbon cycle of China’s terrestrial ecosystems. Our results would be helpful for defining management options for the regional carbon cycle, and provide evidence for assessing the risks of 1.5 ◦C and 2 ◦C warming globally
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