Paper Published in Environmental Pollution

Title: CO2 emissions patterns of 26 cities in the Yangtze River Delta in 2015: Evidence and implications

Journal: Environmental Pollution


Abstract: As a country with the highest CO2 emissions and at the turning point of socio-economic transition, China’s effort to reduce CO2 emissions will be crucial for climate change mitigation. Yet, due to geospatial variations of CO2 emissions in different cities, it is important to develop city-specific policies and tools to help control and reduce CO2 emissions. The key question is how to identify and quantify these variations so as to provide reference for the formulation of the corresponding mitigation policies. This paper attempts to answer this question through a case study of 26 cities in the Yangtze River Delta. The CO2 emissions pattern of each city is measured by two statistics: Gini coefficient to describe its quantitative pattern and Global Moran’s I index to capture its spatial pattern. It is found that Gini coefficients in all these cities are all greater than 0.94, implying a highly polarized pattern in terms of quantity; and the maximum value for Global Moran’s I index is 0.071 with a standard deviation of 0.021, indicating a weak spatial clustering trend but strong difference among these cities. So, it would be more efficient for these cities at current stage to reduce CO2 emissions by focusing on the large emission sources at certain small localities, particularly the very built-up areas rather than covering all the emission sources on every plot of the urban prefectures. And by a combination of these two metrics, the 26 cities are regrouped into nine types with most of them are subject to type HL and ML. These reclassification results then can serve as reference for customizing mitigation policies accordingly and positioning these policies in a more accurate way in each city.

Paper Published in Earth’s Future

Title: Drought Occurring With Hot Extremes: Changes Under Future Climate Change on Loess Plateau, China

Journal: Earth’s Future


Abstract: Drought is one of the most widespread and destructive hazards over the Loess Plateau (LP) of China. Due to climate change, extremely high temperature accompanied with drought (expressed as hot drought) may lead to intensive losses of both properties and human deaths in future. A hot drought probabilistic recognition system is developed to investigate how potential future climate changes will impact the simultaneous occurrence of drought and hot extremes (hot days exceeding certain values) on the LP. Two regional climate models, coupled with multiple bias‐correction techniques and multivariate probabilistic inference, are innovative integrated into the hot drought probabilistic recognition system to reveal the concurrence risk of droughts and hot extremes under different Representative Concentration Pathway (RCP) scenarios. The hot-day index, TX90p, indicating the number of days with daily maximum temperature (Tmax) exceeding the 90th percentile threshold, and the Standardized Precipitation Index are applied to identify the joint risks on the LP using copula-based methods. The results show that precipitation will increase throughout most of the LP under both RCP4.5 and RCP8.5 scenarios of 2036–2095, while Tmax may increase significantly all over the LP (1.8–2.7 °C for RCP4.5 and 2.7–3.6 °C for RCP8.5). The joint return periods of Standardized Precipitation Index and TX90p show that fewer stations will experience severe drought with long-term hot extremes in two future scenarios. However, some stations may experience hot droughts that are more frequent and extreme, particularly certain stations in the southwest and south-central regions of the LP with recurrence period less than 10 years.

Paper Published in Climate Dynamics

Title: Climate warming will not decrease perceived low-temperature extremes in China

Journal: Climate Dynamics


Abstract: Temperature-related health metrics are often determined not only by temperatures but also by multiple climate variables. Temperatures compounded by other climate variables are of significant concern in the assessment of climate change impacts on public health. Temperatures, wind speeds and their combined effects are investigated here for a comprehensive study of how measured temperatures, perceived temperature, and their related extremes will change in China under climate change conditions. Future projections of combined temperatures and wind speeds over China are generated through the PRECIS regional climate modeling system. Results indicate that temperatures can increase nearly 6 °C over China by the end of the twenty-first century from the baseline period (1976–2005) without considering the wind speed changes. However, by considering the combined effect of temperature and wind speed, the perceived temperatures over China are projected to decrease by 4.8 °C relative to the observed values in the baseline period. This unexpected drop in the future perceived temperatures suggests the projected warming is likely to be offset to a large extent by a potential increase in wind speed. This may be related to the RCM’s high-resolution making the thermal contrast distribute at finer scales. The mechanism behind this result needs to be further investigated to help understand the related physical processes and the associated uncertainties at regional scales. As for low-temperature extremes, China is projected to experience an apparent decrease in the frequency and duration of extreme cold events in the future compared to the baseline period without considering the combined wind chill effect. Considering the wind chill effect, an opposite trend for extreme cold events is detected, with an increase by 21% in the frequency of temperatures below − 20 °C.

Paper Accepted by Earth’s Future

The following paper about drought projections over Loess Plateau, China under future climate change has recently been accepted for publication by Earth’s Future:

Sun, C., G. Huang, Y. Fan, X. Zhou, C. Lu, and X. Wang. Drought occurring with hot extremes: changes under future climate change on Loess Plateau, China, Earth’s Future (AGU, SCI IF = 4.59), accepted on April, 2019.

More details will come soon once the paper is published.

Paper Published in Journal of Hydrometeorology

Title: Hydrologic Impacts of Ensemble-RCM-Projected Climate Changes in the Athabasca River Basin, Canada

Journal: Journal of Hydrometeorology


Abstract: In this study, the Providing Regional Climates for Impacts Studies (PRECIS) and the Regional Climate Model (RegCM) system as well as the Variable Infiltration Capacity (VIC) macroscale hydrologic model were integrated into a general framework to investigate impacts of future climates on the hydrologic regime of the Athabasca River basin. Regional climate models (RCMs) including PRECIS and RegCM were used to develop ensemble high-resolution climate projections for 1979–2099. RCMs were driven by the boundary conditions from the Hadley Centre Global Environment Model, version 2 with Earth system configurations (HadGEM2-ES); the Second Generation Canadian Earth System Model (CanESM2); and the Geophysical Fluid Dynamics Laboratory Earth System Model with MOM (GFDL-ESM2M) under the representative concentration pathways (RCPs). The ensemble climate simulations were validated through comparison with observations for 1984–2003. The RCMs project increases in temperature, precipitation, and wind speed under RCPs across most of the Athabasca River basin. Meanwhile, VIC was calibrated using the University of Arizona Shuffled Complex Evolution method (SCE-UA). The performance of the VIC model in replicating the characteristics of the observed streamflow was validated for 1994–2003. Changes in runoff and streamflow under RCPs were then simulated by the validated VIC model. The validation results demonstrate that the ensemble-RCM-driven VIC model can effectively reproduce historical climatological and hydrological patterns in the Athabasca River basin. The ensemble-RCM-driven VIC model shows that monthly streamflow is projected to increase in the 2050s and 2080s under RCPs, with notably higher flows expected in the spring for the 2080s. This will have substantial impacts on water balance on the Athabasca River basin, thus affecting the surrounding industry and ecosystems. The developed framework can be applied to other regions for exploration of hydrologic impacts under climate change.