Future Emission Scenarios Research Articles

Variability in Projected North American Mean and Extreme Temperature and Precipitation Trends for the 21st Century: Model‐To‐Model Differences Versus Internal Variability

AbstractWhile climate change is expected to alter mean and extreme temperature and precipitation over the 21st century, regional changes in these fields remain difficult to project. For a given future emissions scenario, the uncertainty in future projections can be attributed to either model‐to‐model differences, which can presumably be reduced if models are improved, or internal variability, which cannot be constrained to a single outcome but can be used to quantify a range of plausible outcomes. This study examines the range of possible trends in North American mean and extreme temperature and precipitation across phase 6 of the Coupled Model Intercomparison Project models under the SSP3‐7.0 emissions scenario. While model‐to‐model differences primarily govern the spread in mean and extreme temperature trends across these model simulations, the spread in mean and extreme precipitation trends is dominated by internal variability in many regions. A storylines approach—a type of regression‐based analysis—is used to identify key dynamical drivers that explain the variance in future trends across model simulations. The dynamical drivers considered include trends in global mean surface temperature (GMST) and four common modes of climate variability. Combinations of these drivers can reinforce each other to create high‐impact storylines. For example, model simulations with large positive GMST and El Niño‐Southern Oscillation trends are associated with a large reduction in the annual maximum number of consecutive dry days in the American Southwest. However, limiting these storylines to only models with climate sensitivities consistent with observational constraints reduces the likelihood of a large reduction of consecutive dry days in this region.

Spatio-temporal characteristics and driving factors of the meteorological drought across China based on CMIP6

Abstract The characteristics of meteorological drought in different river basins in China have clear spatio-temporal differences and the difference between watersheds is also reflected in the influence mechanism of meteorological drought. This study investigated the meteorological drought risk under different future emission scenarios, based on the Coupled Model Intercomparison Project 6 (CMIP6). Furthermore, we explored the influence of precipitation and temperature on meteorological drought in different basins of China in the future. Meanwhile, the uncertainty associated with CMIP6 in different watersheds is also considered. In the future, the frequency of meteorological drought events mainly shows a decreasing trend, but the drought intensity and duration increase. In China, the rate of probability change in drought's intensity was greater than drought duration and the probability distribution of drought characteristics is significantly different between the historical and the future periods. Under the low and medium emission scenarios (SSP126 and SSP245), the Joint Recurrence Period of future drought intensity and duration increases and the Recurrence Period decreases in the western and north-eastern basins. Precipitation plays a major role in the meteorological drought, especially in the northeast and southeast basins of China.

The influence of future weather pattern changes and projected sea-level rise on coastal flood impacts around the UK

When local extreme water levels surpass defences, the consequences can be devastating. We assess the importance of sea-level rise and future weather pattern changes on UK coastal flood impacts. Historical weather pattern classifications are matched with the observed skew surges and significant wave heights. Coastal-risk weather patterns are then defined as ≥ 1% of events in the distribution exceeding the local warning threshold. We combine this methodology with projections of sea-level rise and weather pattern frequency occurrences, to determine the relative importance of each on future coastal risk. A deep low-pressure system situated to the west of Ireland (WP29) has the highest probability (6.3%) of exceeding Newlyn’s present-day warning threshold; this is projected to increase under climate change to 46.2% by 2050 under RCP2.6. This work found that weather patterns associated with storm surges are increasing and decreasing in frequency; a synoptic situation causing windy conditions in the north of the UK (WP23) will increase by > 40% under RCP8.5 by the end of the century (2079–2090). When combining the impact of sea-level rise and changing frequency of weather patterns, this study found that sea-level rise dominates future coastal risk and is highly linked to the future emission scenarios. The need for successful adaptation, such as coastal defence improvements and early warning systems, will become even more important under the higher emission pathway. The most significant increases in coastal risk are found along the east coast, through the English Channel to the north Devon coastline.

Vulnerability of California roadways to post-wildfire debris flows

Post-wildfire debris flows represent a significant hazard for transportation infrastructure. The location and intensity of post-fire debris movements are difficult to predict, and threats can persist for several years until the watershed is restored to pre-fire conditions. This situation might worsen as climate change forecasts predict increasing numbers of wildfire burned areas and extreme precipitation intensity. New insights are needed to improve understanding of how roadways are vulnerable to post-fire flows and how to prioritize protective efforts. Using California as a case study, the vulnerability of transportation infrastructure to post-fire debris flow was assessed considering geologic conditions, vegetation conditions, precipitation, fire risk, and roadway importance under current and future climate scenarios. The results showed significant but uneven statewide increases in the number of vulnerable roadways from the present to future emission scenarios. Under current climate conditions, 0.97% of roadways are highly vulnerable. In the future, the ratio of vulnerable roadways is expected to increase 1.9–2.3 times in the representative concentration pathways (RCPs) 4.5 emission scenarios, and 3.5–4.2 times in the RCP 8.5 emission scenarios. The threat of post-fire debris flow varies across the state, as precipitation changes are uneven. The vulnerability assessment is positioned to (a) identify, reinforce, and fortify highly vulnerable roadways, (b) prioritize watershed fire mitigation, and (c) guide future infrastructure site selection.

Effect of Climate Change on the Potentially Suitable Distribution Pattern of Castanopsis hystrix Miq. in China.

Climate warming poses a great threat to ecosystems worldwide, which significantly affects the geographical distribution and suitable growth area of species. Taking Castanopsis hystrix Miq. as the research object, the potentially suitable cultivation regions under present and future climatic emission scenarios in China were predicted based on the MaxEnt model with 360 effective individual distributions and eight environmental variables. The min temperature of coldest month (bio6), precipitation of driest month (bio14), and precipitation of warmest quarter (bio18) are three leading factors affecting the geographical distribution area of C. hystrix Miq. The suitable cultivation regions of C. hystrix Miq. range from 18°-34° N, 89°-122° E in central and southern China and cover an area of 261.95 × 104 km2. The spatial pattern of C. hystrix Miq. will migrate to the southern region of low latitudes with a decreasing suitable area when in ssp1-2.6, and to the southwestern region of low latitudes or expand to the northeast region at high latitudes in ssp5-8.5, with an increasing suitable area; no significant change on the spatial pattern in ssp2-2.4. For ssp1-2.6 or ssp2-4.5 climate scenarios, the southern region of high latitudes will be appropriate for introducing and cultivating C. hystrix Miq., and the cultivation area will increase. For ssp5-8.5, its cultivation will increase and expand to the northeast of high-latitude areas slightly.

Basin Runoff Responses to Climate Change Using a Rainfall-Runoff Hydrological Model in Southeast Australia

The effects of climate change have been observed in the Murrumbidgee River basin, which is one of the main river basins in the southeast region of Australia. The study area is the largest and most important agricultural production area within the Murray Darling Basin (MDB). It produces more than AUD 1.9 billion of agricultural products annually and accounts for about 46% of Australia’s total agricultural production. Since Australia’s economy largely depends on its natural resources, climate change adversely impacts the economy in various ways. According to the Intergovernmental Panel on Climate Change’s fifth assessment report (IPCC, AR5), the adaptive capacity and adaptation processes have increased in Australia. The country has implemented policies and management changes in both rural and urban water systems to adapt to future drought, unexpected floods, and other climatic changes. In this study, future catchment runoff has been estimated using the hydrological model, Simplified Hydrolog (SIMHYD), which is integrated with data from three different General Circulation Models (GCMs) and future emission scenarios. Two different representative concentration pathway (RCP) emission scenarios, RCP 4.5 and RCP 8.5, have been used to obtain downscaled future precipitation and evapotranspiration data for the period of 2016 to 2100. Modeling results from the two emission scenarios showed an anticipated warmer and drier climate for the Murrumbidgee River catchment. Runoff in the Murrumbidgee catchment is affected by various dams and weirs, which yields positive results in runoff even when the monthly rainfall trend decreases. The overall runoff simulation result indicated that the impact of climate change is short and intense. The result of the Simplified Hydrolog (SIMHYD) modeling tool used in this study under the RCP 4.5 scenario for the period 2016 to 2045 indicates a significant future impact from climate change on the volumes of runoff in the Murrumbidgee River catchment. For the same period, the climate change prediction showed a decrease in total annual rainfall within the range of 2% to 62%. This reduction in rainfall is projected to decrease river runoff in the upper catchments (e.g., Tharwa, and Yass) by 17% to 58% over the projected periods. However, the runoff trends in the lower sub-catchments (e.g., Borambola) have increased by 137% to 87% under RCP 4.5 and RCP 8.5, respectively. This increasing potential runoff trend in the lower Murrumbidgee catchments gives an indication to build irrigation dams for dry season irrigation management.

Non-persistent chemicals in polymer and non-polymer products can cause persistent environmental contamination: evidence with DEHP in Europe.

Bis(2-ethylhexyl) phthalate (DEHP) is a plasticizer that has been massively used since the second part of the twentieth century by the plastic industry to provide softness properties to PVC. This chemical is considered as toxic to reproduction and endocrine disrupting, and a wide range of uses are now forbidden by the EU. Despite these regulations, DEHP is still found to be a widespread contaminant in watersheds in the EU. In this study, we calculate retrospective and prospective scenarios of past and future emissions of DEHP in the environment (water, soil, air) in the EU 28, taking into account the entire lifecycle of the substance, from its production and its inclusion in polymer (mainly PVC) and non-polymer products (adhesive and sealant, ceramic and printing ink) to the recycling and end of life of these products. We develop a stock and flow model based on dynamically estimating the stocks of DEHP present in products on the market. Our results show that the introduction of recent regulations to limit the use of DEHP (that bring a 70% reduction of DEHP contained in products placed on the market in 2020 and 75% in 2040) will not reduce significantly future emissions. This persistence of emissions is explained by the high stocks built in the economy and the long-term presence of soft PVC waste in landfills. Our results suggest that DEHP will remain a cause of environmental contamination many decades after uses have declined and even ceased, and it appears to be too late for market regulation at the market stage to offset the effect of past stock buildup and landfilling. It is likely that several chemicals that are not considered as persistent and therefore not the focus of international regulations could exhibit the same characteristics. Regulations should avoid possible use patterns that make hazardous chemicals persistent in products, because they have the potential to create long-term and almost irreversible environmental pollution and impacts.

Decadal Application of WRF/Chem under Future Climate and Emission Scenarios: Impacts of Technology-Driven Climate and Emission Changes on Regional Meteorology and Air Quality

This work presents new climate and emissions scenarios to investigate changes on future meteorology and air quality in the U.S. Here, we employ a dynamically downscaled Weather Research and Forecasting model coupled with chemistry (WRF/Chem) simulations that use two Intergovernmental Panel on Climate Change scenarios (i.e., A1B and B2) integrated with explicitly projected emissions from a novel Technology Driver Model (TDM). The projected 2046–2055 emissions show widespread reductions in most gas and aerosol species under both TDM/A1B and TDM/B2 scenarios over the U.S. The WRF/Chem simulations show that under the combined effects of the TDM/A1B climate and emission changes, the maximum daily average 8-h ozone (MDA8 h O3) increases by ~3 ppb across the U.S. mainly due to widespread increases in near-surface temperature and background methane concentrations, with some contributions from localized TDM emission changes near urban centers. For the TDM/B2 climate and emission changes, however, the MDA8 h O3 is widely decreased, except near urban centers where the relative TDM emission changes and O3 formation regimes leads to increased O3. The number of O3 exceedance days (i.e., MDA8 h O3 > 70 ppb) for the entire domain is significantly reduced by a grid cell maximum of up to 43 days (domain average ~0.5 days) and 62 days (domain average ~2 days) for the TDM/A1B and TDM/B2 scenarios, respectively, while in the western U.S., larger O3 increases lead to increases in nonattainment areas, especially for the TDM/A1B scenario. The combined effects of climate and emissions (for both A1B and B2 scenarios) will lead to widespread decreases in the daily 24-h average (DA24 h) PM2.5 concentrations, especially in the eastern U.S. (max decrease up to 93 µg m−3). The PM2.5 changes are dominated by decreases in anthropogenic emissions for both the TDM/A1B and TDM/B2 scenarios, with secondary effects on decreasing PM2.5 from climate change. The number of PM2.5 exceedance days (i.e., DA24 h PM2.5 > 35 µg m−3) is significantly reduced over the eastern U.S. under both TDM/A1B and B2 scenarios, which suggests that both climate and emission changes may synergistically lead to decreases in PM2.5 nonattainment areas in the future.

Future global debris flow susceptibility considering climate change, wildfire probability, and glacier retreat

The present-day impact of climate changes on debris flow magnitude, frequency, and susceptibility has been demonstrated in North and South America, Europe, Asia, and New Zealand. Such impacts are expected to increase under future emission scenarios. Future global debris flow susceptibility models provide an international perspective on areas worthy of further, more detailed analyses with regard to geographic changes in global debris flow susceptibility. In this study, future global debris flow susceptibility models are developed under RCP 2.6 and 8.5 IPCC Climate Change Scenarios. These models were further augmented with wildfire probability, and areas of potential glacier retreat, both of which can act as amplifiers to debris flow susceptibility. The results are projected against future urban centers, for a spatial view on potential human vulnerability. Key findings are (1) wildfire acts as a significant amplifier in area and magnitude of debris flow susceptibility in all modeling scenarios, (2) greater than 50% of the studied glaciers reside within higher susceptibility zones when wildfire is not considered, and greater than 75% when wildfire probability is considered, (3) 76 of the studied glaciers are within 5 km of eleven urban centers, (4) 11% of these “urban” glaciers are in higher susceptibility zones when wildfire probability is not considered, and 51% are in higher susceptibility zones when wildfire is considered, (5) about 12% of future urban centers will reside within higher susceptibility zones under both future climate change scenarios. Consideration of these factors, together with traditional environmental factors and triggers, and findings by local and regional glacier-related debris flow researchers, suggests a new paradigm in modeling debris flow susceptibility, at any scale.

Terrestrial Net Ecosystem Productivity in China during 1900–2100

Terrestrial ecosystems are a critical carbon dioxide (CO 2 ) sink for achieving carbon (C) neutrality before 2060 in China. Here, we used the Coupled Model Intercomparison Project phase 6 (CMIP6) model outputs to quantify the spatiotemporal patterns of net ecosystem productivity (NEP) and its major environmental controls, as well as the dominant C pools for NEP during 1900–2100. We found that (a) according to CMIP6 NEP spatiotemporal characteristics, terrestrial ecosystems in China sequestered 0.310 ± 0.058 Pg C·year –1 during 1980–2014 and will act as a strong C sink [from 0.515 ± 0.075 Pg C·year –1 under Shared Socioeconomic Pathway 126 (SSP126) to 0.631 ± 0.089 Pg C·year –1 under SSP585] in the future (2015–2100). Pronounced turning points were found for the temporal trends of NEP during the historical (1984) and under 4 future emissions scenarios (2057 for SSP126, 2053 for SSP245, 2038 for SSP370, and 2044 for SSP585). (b) The positive effect of temperature on NEP appears to weaken after each turning point of future scenarios. (c) The enlarged vegetation C pool size dominates the growing terrestrial ecosystem C storage. The CMIP6 projection shows that the total C storage in Chinese terrestrial ecosystems increases continuously and peaks in the 2040s to 2050s under each scenario. Future afforestation in the northeast, southeast, and southwestern regions, as well as soil C pool management in the northwest and middle north regions, will greatly contribute to achieving C neutrality in China, particularly under low emission scenario (SSP126).

Projected values of thermal and precipitation climate indices for the broader Carpathian region based on EURO-CORDEX simulations

Since our climate is in a rapid changing phase, it is crucial to get information about the regional patterns of basic climatic parameters and indices. The EURO-CORDEX project provides high quality regional climate model outputs, but these raw datasets are not convenient for the application in wider geoscience studies. According to the authors’ knowledge, there is a lack in published spatial information about basic climate parameters and indices in Central-Europe and especially in the broader Carpathian region therefore the basic aim of this study to fill this gap. The study presents the future trends in daily air temperature and precipitation and various climatic indices in the broader Carpathian Basin region during the 21st century. The indices are calculated using multi-model average temperature and precipitation data from EURO-CORDEX model simulations for the future time periods (2021–2050, 2071–2100) and emission scenarios (RCP4.5, RCP8.5). The indices present the future trends of the heat load, energy demand as well as extreme precipitation and drought characteristics. Based on the results the temperature increase is obvious and the heat load and energy demand quantifying indices follow the temperature trend. However, the trend is difficult to evaluate in case of precipitation. The changes in the precipitation and the related indices can be considered small and appear within the regions. The future changes are the most considerable in the Carpathian Basin, but the entire examined region faces crucial changes in the following decades.

Daily precipitation and temperature for 2021–2050 over China: Multiple RCMs and emission scenarios corrected by a trend‐preserving method

AbstractDaily climate data are extremely important to drive ecological models, but the outputs of climate models are often deviated from the observations. The bias correction methods mostly highlight the target statistical parameters (e.g., mean and variance) for a target period, but perturb the simulated change trend and variability. In this study, we utilize a trend‐preserving bias correction method that can simultaneously consider the frequency and intensity of climatic variables to adjust the daily maximum and minimum temperature, and precipitation (Tmax, Tmin, and Pre) from CORDEX‐EA regional climate models for the period of 2021–2050 over China. Results show that: (a) the bias correction method greatly improves the spatial patterns of simulated Tmax, Tmin, and Pre since the corrected data has higher correlation and smaller differences across the whole domain. The differences in mean Tmax, Tmin, and Pre between climate models and observations have been reduced from −4.5 ± 6.41°C, −2.06 ± 0.58°C, 177.25 ± 51.55 mm before correction to 0.01 ± 0.02°C, −0.01 ± 0.02°C, −26.22 ± 6.39 mm after correction, respectively. In addition, the simulated change trend and climate variability at all time scales are well preserved. (b) Spatially, the warming rates in the west would be higher than in the east, and they are larger under the most severe future emissions scenario (RCP8.5) relative to the low‐mid emissions scenario (RCP4.5). The Pre change would mainly occur over east China with the significant upward trend. The dataset presented in this article has been published in the Network Common Data Form (NetCDF) File Format at https://doi.org/10.5281/zenodo.5058620.

Effects of Climate Change and Environmental Factors on Bamboo (Ferrocalamus strictus), a PSESP Unique to China

Bamboo is a plant that may replace plastics and wood as a new green environmental protection material that can be developed. Ferrocalamus strictus is a very special and rare bamboo which is a plant species with extremely small populations (PSESP) endemic to Yunnan, China, and it is listed as a China key national first-class protected wild plant. To explore the effects of extreme climate and environmental changes on this PSESP, we conducted a case study on the response of F. strictus to climate under two extreme future emission scenarios. We combined 29 environmental variables, including the temperature, precipitation, altitude, slope, aspect, soil pH, soil organic carbon content, and mean UV-B radiation of the highest month, to analyze the important environmental factors limiting the distribution of F. strictus and identified the priority conservation areas (PCAs) of F. strictus. Under the two future extreme climate scenarios, the core potential suitable distribution area of F. strictus would decrease by 26%–34% in 2040, 44%–46% in 2060, and 23%–58% in 2080, respectively. Bio18 (precipitation in the warmest quarter) and Bio3 (isotherm) were the two key factors limiting the geographical distribution of F. strictus (the contribution rates were 40.1% and 18.45%, respectively). The results of this study show that F. strictus is in urgent need of protection and PSESPs require more attention.

Future trends in atmospheric circulation patterns over Africa south of the equator

Abstract The impact of climate change on the frequency of occurrence of atmospheric circulation patterns can have a wide range of consequences ranging from weather extremes to the modification of pollutant transport. This study uses 11 CMIP6 global climate models (GCMs) to investigate the impact of future climate change on the frequency of occurrence of atmospheric circulation patterns, in Africa south of the equator. Here it is shown from the historical analysis that there are statistically significant trends in the frequency of occurrence of some of the classified circulation types (CTs) in the study region. Further, under the SSP5-8.5 and SSP2-4.5 emission scenarios, the historical CTs were reproduced, suggesting that future climate change will not constrain the existence of the CTs. However, for future emission scenarios, the ensemble of the GCMs projects notable changes in the spatial structure of the CTs and statistically significant trends in the frequency of occurrence of most of the CTs, towards the end of the 21st century. The intensity of the projected changes in the spatial structure and linear trends in the frequency of occurrence of the CTs are relatively stronger under the higher emission scenario. As regards changes in synoptic circulations in the study region, the ensemble of the GCMs project, (i) a positive trend in the frequency of occurrence of austral summer dominant CTs associated with atmospheric blocking of the Southern Hemisphere mid-latitude cyclones, adjacent to South Africa; (ii) alternating frequent periods of enhanced (suppressed) anticyclonic circulation at the western branch of the Mascarene high possibly due to a more positive phase of the Southern Annular Mode (warmer southwest Indian Ocean); (iii) possible weakening of the Angola low. The aforementioned changes can be expected to have direct impacts on the regional climates in the study region.

Emulation of a Chemical Transport Model to Assess Air Quality under Future Emission Scenarios for the Southwest of Western Australia

Simulation outputs from chemical transport models (CTMs) are essential to plan effective air quality policies. A key strength of these models is their ability to separate out source-specific components which facilitate the simulation of the potential impact of policy on future air quality. However, configuring and running these models is complex and computationally intensive, making the evaluation of multiple scenarios less accessible to many researchers and policy experts. The aim of this work is to present how Gaussian process emulation can provide a top-down approach to interrogating and interpreting the outputs from CTMs at minimal computational cost. A case study is presented (based on fine particle sources in the southwest of Western Australia) to illustrate how an emulator can be constructed to simultaneously evaluate changes in emissions from on-road transport and electricity sectors. This study demonstrates how emulation provides a flexible way of exploring local impacts of electric vehicles and wider regional effects of emissions from electricity generation. The potential for emulators to be applied to other settings involving air quality research is discussed.

An ensemble-based assessment of bias adjustment performance, changes in hydrometeorological predictors and compound extreme events in EAS-CORDEX

The effectiveness of adaptive measures tackling the effects of climate change is dependent on robust climate projections. This becomes even more important in the face of intensifying extreme events. One example of these events is flooding, which embodies a major threat to highly vulnerable coastal urban areas. This includes eastern Asia, where multiple coastal megacities are located, e.g. Shanghai and Shenzhen. While the ability of general circulation models (GCMs) and regional climate models (RCMs) to project atmospheric changes associated with these events has improved, systematic errors (biases) remain. This study therefore assess capabilities of improving the quality of regional climate projections for eastern Asia. This is performed by evaluating an ensemble consisting of bias adjustment methods, GCM-RCM model runs and future emission scenarios based on representative concentration pathways (RCP) obtained from EAS-CORDEX. We show that bias adjustment significantly improves the quality of model output and best results are obtained by applying quantile delta mapping. Based on these results we evaluate potential future changes in crucial hydrometeorological predictors, univariate extreme events and compound extreme events, focusing on high wind speeds and extreme precipitation. Key findings include an increase in daily maximum temperature of 1.5 to nearly 4 °C, depending on the scenario, as well as increased levels of precipitation under RCP 8.5. Furthermore, a distinct intensification of extreme events including high temperatures and heavy precipitation is detected and this increase exceeds the increase of the overall mean of these predictors. The annual number of compound events including heavy precipitation and extreme wind speeds shows a significant increase of up to 50% for RCP 8.5 in the South China Sea as well as the adjacent coastal areas.

Spatially Varying in CO2 Concentrations Regulates Carbon Uptake in the Northern Hemisphere

AbstractAgainst the current climate change background, the mid–high latitudes (>23.7°N) of the Northern Hemisphere have experienced an increase in atmospheric CO2 concentrations, which is higher than the global average. An Beijing Normal University–Earth System Model was used in this study to estimate the carbon uptake in the mid–high latitudes from 2031 to 2060 under the SSP5‐8.5 future emissions scenario. Results showed that, in the high latitudes, non‐uniform CO2 led to a reduction in net ecosystem productivity (NEP) by −0.1 Pg C yr−1. This mainly resulted from a 1.5‐fold greater increase in heterotrophic respiration than in net primary productivity (NPP). In the mid‐latitudes, meanwhile, the decrease in carbon uptake was generally due to a two‐fold greater decrease in NPP than heterotrophic respiration. The decrease in precipitation was closely correlated with local carbon uptake, which could explain this decrease in NPP. It was further found that, in East Asia, changes in atmospheric circulation induced by the non‐uniform CO2 might have reduced the amount of large‐scale precipitation by −9 mm yr−1. This reduction was the primary contributor (98%) to the decrease in overall precipitation, possibly strengthening the limitation of water on plant growth, which would cause a decline in NEP. In the future, it is suggested that such spatially varying CO2 concentrations should be assessed for possible impacts on local carbon uptake.

Future Emission Scenario Effects on Melon Cultivars (Cucumis melo L.) in the Brazilian Semi-Arid Region

Future emission scenarios can interfere with the yield of major crops. In this study, we investigated the future impact of increased air temperature and relative humidity on melon phenology and water demand in the Brazilian semi-arid region. We applied the PRECIS (Providing Regional Climates for Impact Studies) climatological model to develop the Intergovernmental Panel on Climate Change emission scenarios—B2 optimistic emission scenario and A2 pessimistic emission scenario—and we assessed the climate change effects on the phenology and water demand of two melon cultivars. The “Orange County” hybrid, the Honeydew melon, grew from 2006–2007, and the “Néctar” hybrid, the Galia melon, grew in 2008. These cultivars were also considered using the actual emission scenario. We found that the B2 and A2 emission scenarios will cause a cycle decrease of 15.49 and 25.35% for the “Orange County” hybrid and a 9.84 and 18.03% decrease for the “Néctar” hybrid. Future changes to the climate will increase the melon crop coefficient and daily rate of evapotranspiration. Regarding the “Orange County” hybrid, the cycle shortening overcomes the daily water demand increases, decreasing water demand by 13.7–18.3%. Regarding the “Néctar” hybrid, cycle shortening will be proportional to the increase in water demand. The Honeydew melon will be more sensitive to air temperature and relative humidity increases than the Galia melon.

Prediction of Future Spatial and Temporal Evolution Trends of Reference Evapotranspiration in the Yellow River Basin, China

Reference evapotranspiration (ET0) is an integral part of the regional hydrological cycle and energy balance and is extremely sensitive to climate change. Based on temperature data from 24 global climate models (GCMs) in the Coupled Model Intercomparison Project Phase 6 (CMIP6), this study developed a multi-model ensemble based on delta statistical downscaling with multiple interpolation methods and evaluation indicators to predict the spatial and temporal evolution trends of ET0 in the Yellow River Basin (YRB) under four emission scenarios (SSP126, SSP245, SSP370, and SSP585) for the near- (2022–2040), mid- (2041–2060), and long- (2081–2100) term future. Results demonstrate that regional data generated based on delta statistical downscaling had good simulation performance for the monthly mean, maximum, and minimum temperatures in the YRB, and the developed multi-model ensemble had better simulation capability than any single model. Compared to the historical period (1901–2014), the annual ET0 showed a highly significant increase for different future emission scenarios, and the increase is faster with increasing radiative forcing. The first main cycle of ET0 change was 52, 53, 60, and 48 years for the SSP126, SSP245, SSP370, and SSP585, respectively. ET0 in the YRB had positive values for EOF1 under all four emission scenarios, responding to a spatially consistent trend across the region. Compared to the historical period, the spatial distribution of ET0 under different future emission scenarios was characterized by being larger in the west and smaller in the east. As the radiative forcing scenario increased and time extended, ET0 significantly increased, with a maximum variation of 112.91% occurring in the western part of the YRB in the long-term future under the SSP585 scenario. This study can provide insight into the water cycle patterns of watersheds and scientific decision support for relevant departments to address the challenges of climate change.

Predicting the Geographical Distribution Shift of Medicinal Plants in South Africa Due to Climate Change

There has been a recent rise in the number of medicinal plant users in Southern Africa, with approximately a million users reported to utilize these plants for various health conditions. Unfortunately, some of these plants are reportedly endangered and facing extinction due to harvesting pressure. In addition, climate change is likely to negatively affect the geographical distribution of these medicinal plants. In the current study, future greenhouse gas emission scenarios of the representative concentration pathways, RCP2.6 and RCP8.5, for future projections to 2050 and 2080 were used to simulate the effect of climate change on three medicinal plants’ (Aloe ferox, Bowiea volubilis, and Dioscorea elephantipes) distribution in South Africa. We studied these plant species as the International Union for Conservation of Nature stated that A. ferox is currently of least concern in South Africa, while B. volubilis and D. elephantipes are categorised as declining and vulnerable, respectively. Specifically, we utilised a species distribution model (i.e., the maximum entropy: MaxEnt) to investigate the effect of climate change on the future spatial distribution of medicinal plants in South Africa. In 2050 and 2080, under both RCP scenarios, the suitable habitat of the studied plant species will reduce in the country’s northern parts. Specifically, the habitat for D. elephantipes will totally disappear in the country’s northern parts. However, there will be slight additions of suitable habitats for the species in the country’s southern parts. Model validation indicated that the area under curve (AUC) for A. ferox was 0.924 ± 0.004, while for B. volubilis and D. elephantipes it was 0.884 ± 0.050 and 0.944 ± 0.030, respectively. Using the results from this study, there is a need for the long-term in situ and ex situ conservation of these medicinal plants. The results of the present study could guide the development of effective and efficient policies and strategies for managing and conserving medicinal plants in South Africa.