A copy of Guangbo jiemu bao [Broadcast Program Report] was being passed from hand to hand among a group of young people eager to be the first to read the article introducing the program "What Is Revolutionary Love?" It said: "… Young friends, you are certainly very concerned about this problem'. So, we would like you to meet the young women workers Meng Xiaoyu and Meng Yamei and the older cadre Miss Feng. They are the three leading characters in the short story ‘The Place of Love.’ Through the description of the love lives of these three, the story induces us to think deeply about two questions that merit further examination.

This is How the Discussion Started

Recent Mediterranean droughts have highlighted concerns that climate change may be contributing to observed drying trends, but natural climate variability in the region is still poorly understood. We analyze 900 years (1100-2012) of Mediterranean drought variability in the Old World Drought Atlas (OWDA), a spatiotemporal tree-ring reconstruction of the June-July-August self calibrating Palmer Drought Severity Index. In the Mediterranean, the OWDA is highly correlated with spring precipitation (April-June), the North Atlantic Oscillation (January-April), the Scandinavian Pattern (January-March), and the East Atlantic Pattern (April-June). Drought variability displays significant east-west coherence across the basin on multi-decadal to centennial time scales and north-south anti-phasing in the eastern Mediterranean, with a tendency for wet anomalies in the Black Sea region (e.g., Greece, Anatolia, the Balkans, etc) when coastal Libya, the southern Levant, and the Middle East are dry, possibly related to the North Atlantic Oscillation. Recent droughts are centered in the Western Mediterranean, Greece, and the Levant. Events of similar magnitude in the Western Mediterranean and Greece occur in the OWDA, but the recent 15-year drought in the Levant (1998-2012) is the driest in the record. Estimating uncertainties using a resampling approach, we conclude there is an 89% likelihood this drought is drier than any comparable period of the last 900 years and a 98% likelihood it is drier than the last 500 years. These results confirm the exceptional nature of this drought relative to natural variability in recent centuries, consistent with studies that have found evidence for anthropogenically forced drying in the region.

Spatiotemporal drought variability in the Mediterranean over the last 900 years

Traditionally, for the planning and assessment of solar energy systems, the amount of solar radiation (sunlight) incident on the Earth’s surface is assumed to be constant over the years. However, with changing climate and air pollution levels, solar resources may no longer be stable over time and undergo substantial decadal changes. Observational records covering the past decades confirm long-term changes in this quantity. Here we examine how the latest generation of climate models used for the 5th IPCC report projects potential changes in surface solar radiation over the coming decades, and how this may affect, in combination with the expected greenhouse warming, solar power output from photovoltaic (PV) systems. For this purpose, projections up to the mid 21st century from 39 state of the art climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are analysed globally and for selected key regions with major solar power production capacity. The large model ensemble allows to assess the degree of consistency of their projections. Models are largely consistent in the sign of the projected changes in solar radiation under cloud-free conditions as well as surface temperatures over most of the globe, while still reasonably consistent over a considerable part of the globe in the sign of changes in cloudiness and associated changes in solar radiation. A first order estimate of the impact of solar radiation and temperature changes on energy yields of PV systems under the RPC8.5 scenario indicates statistically significant decreases in PV outputs in large parts of the world, but notable exceptions with positive trends in large parts of Europe, South-East of North America and the South-East of China. Projected changes between 2006 and 2049 under the RCP8.5 scenario overall are on the order of 1%/decade for horizontal planes, but may be larger for tilted or tracked planes as well as on shorter (decadal) timescales.

Projections of long-term changes in solar radiation based on CMIP5 climate models and their influence on energy yields of photovoltaic systems

The Qinghai–Tibetan Plateau (QTP) is one of the most sensitive areas to climate change, and fully understanding the impacts of climate on the hydrological process in this region is desired. This study explores the impacts of climate change on the hydrological processes of the Lhasa River Basin (LRB) in QTP based on the Soil and Water Assessment Tool (SWAT). The model is fed with bias-corrected future climatic data derived from three global circulation models (ACCESS1.3, MRI-CGCM3, and MPI-ESM-MR) under two emission scenarios (RCPs 4.5 and 8.5) within two periods (mid-century and end-century). The results indicate that the sediment load and streamflow of LRB would significantly decrease, and the reduction of former is consistently higher than the that of latter in all scenarios and periods. Changes in streamflow and sediment load are mainly caused by temperature increase. The findings provide additional insights into the impacts of climate change on the hydrologic processes of typical basins in QTP and assist decision-makers in developing watershed management plans.

Large decrease in streamflow and sediment load of Qinghai–Tibetan Plateau driven by future climate change: A case study in Lhasa River Basin

Portugal, which is located in the west limit of the Mediterranean subtropics, is a small region with a complex orography with large precipitation gradients and interannual variability. In this study, the newer and higher resolution regional climate simulations, covering Portugal, are evaluated in present climate and used to investigate the rainfall projections for the end of the twenty-first century, following the RCP4.5 and RCP8.5 emission scenarios. The EURO-CORDEX historical simulations, at 0.11° and at 0.44° resolution, are evaluated against gridded observations of precipitation, which allows the assembly of four multi-model ensembles. An extra simulation, at even higher resolution (9 km) with WRF is also analysed. In present climate, the models are able to describe the precipitation temporal and spatial patterns as well its distributions, although there is a large spread and an overestimation of larger rainfall quantiles. The multi-model ensembles show that selecting the best performing models adds quality to the overall representation of rainfall. The high-resolution simulations augment the spatial details of precipitation, but objectively do not seem to add value with respect to the coarse resolution. Regarding the RCP8.5 scenario, WRF and the multi-model ensembles consistently predict important losses of precipitation in Portugal in spring, summer and autumn, ranging from −10% and −50%. For all seasons, the changes are more severe in the southern basins. The precipitation distributions show, for all models, important reductions of the contribution from low to moderate/high precipitation bins and augments of days with strong rainfall. Furthermore, a prominent growth of high-ranking percentiles is predicted reaching values over 70% in some regions. Generally, the changes associated with the RCP4.5 scenario have the same signal and features, but with smaller magnitudes.

Future precipitation in Portugal: high-resolution projections using WRF model and EURO-CORDEX multi-model ensembles

A sustainable water-food-energy plan to confront climatic and socioeconomic changes using simulation-optimization approach

The impact of global warming on the characteristics of mean and extreme precipitations over China is investigated by using the Providing REgional Climate Impacts for Studies (PRECIS) model. The PRECIS model was driven by the Hadley Centre Global Environment Model version 2 with Earth System components and coupling (HadGEM2-ES). The results of both models are analyzed in terms of mean precipitation and indices of precipitation extremes (R95p, R99p, SDII, WDF, and CWD) over China at the resolution of 25 km under the Representative Concentration Pathways 4.5 and 8.5 (RCP4.5 and RCP8.5) scenarios for the baseline period (1976–2005) and two future periods (2036–2065 and 2070–2099). With improved resolution, the PRECIS model is able to better represent the fine-scale physical process than HadGEM2-ES. It can provide reliable spatial patterns of precipitation and its related extremes with high correlations to observations. Moreover, there is a notable improvement in temporal patterns simulation through the PRECIS model. The PRECIS model better reproduces the regional annual cycle and frequencies of daily precipitation intensity than its driving GCM. Under RCP4.5 and RCP8.5, both the HadGEM2-ES and the precis project increasing annual precipitation over the entire country for two future periods. Precipitation increase in winter is greater than the increase in summer. The results suggest that increased radiative forcing from RCP4.5 to RCP8.5 would further intensify the magnitude of projected precipitation changes by both PRECIS and HadGEM2-ES. For example, some parts of south China with decreased precipitation under RCP4.5 would expect even less precipitation under RCP8.5; regions (northwest, northcentral and northeast China) with increased precipitation under RCP4.5 would expect more precipitation under RCP8.5. Apart from the projected increase in annual total precipitation, the results also suggest that there will be an increase in the days with precipitation higher than 15 mm and a decrease in the days with precipitation less than 5 mm. Under both RCPs, there would be an increasing trend in the magnitude of changes in precipitation extremes indices (R95p, R99p, and SDII) over China, while an opposite trend is projected for CWD and no apparent trend is projected for WDF from 2036–2065 to 2070–2099. Increased extreme precipitation amounts accompanied with decreased frequencies of extreme precipitation suggest that the future daily extreme precipitation intensity is likely to become large in northeast China and south China.

High-resolution projections of mean and extreme precipitations over China through PRECIS under RCPs

Assessing Climate Change Impacts on Human-Perceived Temperature Extremes and Underlying Uncertainties

Projected Changes in Abrupt Shifts Between Dry and Wet Extremes Over China Through an Ensemble of Regional Climate Model Simulations

Impacts of climate change relating to public health are often determined by multiple climate variables. The health-related metrics combining high-temperature and relative humidity are most concerned. Temperatures, relative humidity and relationship among them are investigated here for a comprehensive assessment of climate change impacts over China. A projection of combined temperatures and humidity through the PRECIS model is addressed. The PRECIS model's skill in reproducing the historical climate over China was first gauged through validating its historical simulation with the observation dataset in terms of the two contributing variables. With good results of validation, a plausible range of combined temperatures and relative humidity were generated under RCPs. The results suggested that the annual mean temperature of China will increase up to 6 °C at the end of 21st century. Opposite to the significantly change in the temperature, the maximum magnitude of changes in relative humidity is only 8% from the value in the baseline period. The dew point temperature is projected to be 14.9 °C (within the comfortable interval) over the whole nation under high radiative forcing scenario at the end of this century. Therefore, the combination effects of high-temperatures and relative humidity are substantially smaller than generally anticipated for China. Even though the impact-relevant metric like the dew point temperature is not projected as bad as the generally anticipated, we found that the frequency of high-temperature extremes increases up to 40% and the duration increases up to 150% in China. China is still expected to have more number of extremely hot days, more frequent high-temperature extremes, and longer duration of warm spell than before. Regionally, South China has the smallest changes in the mean, maximum and minimum temperatures while the largest increases in all five high-temperature indices. Consequently, the climate over South China for two future periods will be changing more drastically than the baseline period. Extra cautions need to be given to South China in the future.

Jinxin Zhu

Papers

A sustainable water-food-energy plan to confront climatic and socioeconomic changes using simulation-optimization approach

High-resolution projections of mean and extreme precipitations over China through PRECIS under RCPs

Assessing Climate Change Impacts on Human-Perceived Temperature Extremes and Underlying Uncertainties

Projected Changes in Abrupt Shifts Between Dry and Wet Extremes Over China Through an Ensemble of Regional Climate Model Simulations

Investigation of Changes in Extreme Temperature and Humidity Over China Through a Dynamical Downscaling Approach